Patent Application
20090104177
The invention relates to nucleic acid sequences encoding peptides which inhibit the interaction of protein kinase A (PKA) and protein kinase A anchor proteins (AKAP), to a host organism comprising said nucleic acid sequences and expressing the peptides of the invention, to the use of said peptides and of said host organism in therapy and experimental investigation of diseases associated with a modified AKAP-PKA interaction, and to the use of said peptides as pharmaceutical agents for the treatment of such diseases, specifically insipid diabetes, duodenal ulcer, hypertony and pancreatic diabetes.
The biological activity of hormones and neurotransmitters is mediated via activation of signal cascades altering the phosphorylation state of effector proteins. Two classes of enzymes are involved in this reversible process: protein kinases and phosphoprotein phosphatases. Phosphorylation is effected by kinases catalyzing the transfer of the terminal phosphate group of ATP on specific serine or threonine residues, and dephosphorylation is mediated by phosphoprotein phosphatases. One mechanism of controlling and regulating such enzyme activities is compartmentation of these enzymes by association with anchor proteins located near their substrates. Protein kinase A (PKA) is one of the multifunctional kinases with broad substrate specificity, which is anchored on subcellular structures by so-called protein kinase A anchoring proteins (AKAPs).
In many essential cellular processes such as contraction, secretion, metabolism, gene transcription, cell growth and division, the transduction of extracellular signals proceeds via G protein-coupled receptors, G protein Gs, activation of an adenyl cyclase, and formation of the second messenger cyclic adenosine monophosphate (cAMP). The effects of cAMP are mediated by the cAMP-dependent PKA.
The protein kinase A (PKA) holoenzyme consists of a dimer of regulatory (R) subunits, each of which has a catalytic (C) subunit bound thereto. Activation of the kinase by binding of two cAMP molecules to each R subunit induces dissociation of the C subunits which phosphorylate substrates in the proximity thereof. Corresponding to the existence of type I (RI) or type II (RII) regulatory subunits, the PKA holoenzyme is referred to as type I or type II PKA. The RI subunits have RIα and RIβ, the RII subunits have RIIα and RIIβ and the C subunits Cα, Cβ and Cγ. The different PKA subunits are encoded by different genes (Klussmann, 2004; Tasken and Aandahl, 2004).
The regulatory subunits show varying expression patterns. While RIα and RIIα are ubiquitous in tissues, the regulatory subunit RIβ is predominantly found in the brain.
Association of the two R subunits with intracellular compartments is mediated by AKAPs. The anchor proteins are a group of functionally related molecules characterized by the interaction with type I or type II of the regulatory subunits (RI and RII, respectively) of the PKA holoenzyme. The first anchor proteins have been isolated during affinity-chromatographic purification of the R subunits on cAMP-Sepharose. These associated proteins showed RII binding even after transfer onto a nitrocellulose membrane. This observation also forms the basis of the most common method (RII overlay) of detecting AKAPs. It is a modified Western blot wherein radioactively labelled RII subunits rather than a primary antibody are used as probe.
To date, little is known about the functional significance of the RI-AKAP interaction. Although RIα is mainly found in the cytosol, a number of studies show anchoring in vivo. Dynamic anchoring of the RIα subunits—as opposed to static anchoring of RII subunits—seems to be of crucial significance to the cell. Thus, association of the RI sub-units with the plasma membrane of erythrocytes and activated T lymphocytes has been described. In cAMP-mediated inhibition of T cell proliferation by type I PKA, localization of the enzyme possibly could be mediated by AKAPs. In knockout mice, which do not express any regulatory type II subunits in their skeletal muscle tissue, the RIα subunits bind to a calcium channel-associated AKAP, thereby obtaining normal, cAMP-dependent channel conductivity as a result of the proper availability of the catalytic subunits of PKA.
Furthermore, it has been shown in vivo that the catalytic subunits in the cell preferentially associate with the RII subunits, and that type I PKA holoenzyme is formed when the amount of free catalytic subunits exceeds the amount of free RII subunits.
Specificity in PKA anchoring is achieved by virtue of the targeting domain—a structural motif which, in contrast to the anchoring domain, is neither conserved in the sequence, nor in the structure of the AKAPs. Thus, AKAPs are anchored to structural elements in the cell by protein-protein interactions and to membranes by protein-lipid interactions.
The literature describes various AKAPs undergoing association with various cellular compartments, for instance with the centrosomes, mitochondria, the endoplasmic reticulum and Golgi apparatus, the plasma and nuclear membranes, and vesicles.
To date, the precise mechanisms of anchoring are known for only a few AKAPs. Thus, the myocardium-specific anchor protein mAKAP is anchored to the perinuclear membrane of the cardiomyocytes by a region including three spectrin-like repeat sequences. Two isoforms of AKAP15/18 are anchored to the plasma membrane via lipid modifications (myristoylation and palmitoylation). Three polybasic regions in the targeting domain of AKAP79 are involved in the localization of the protein on the inner postsynaptic membrane (PSD, post-synaptic density).
AKAPs were first characterized via the interaction with PKA. However, some of these proteins may also bind other enzymes involved in signal transduction.
As a result of simultaneous anchoring of enzymes catalyzing opposing reactions, such as kinases and phosphatases, these AKAPs—also referred to as scaffolding proteins—can localize entire signal complexes in the vicinity of particular substrates, thereby contributing to the specificity and regulation of the cellular response to extracellular signals. AKAP79 was the first AKAP where interaction with a plurality of enzymes could be detected. Said protein binds protein kinase A, protein kinase C and the protein phosphatase calcineurin (PP2B), each enzyme being inhibited in bound condition. Distinct signals are required for the activation of each individual enzyme, which is why various second messengers such as cAMP, calcium and phospholipids may be present together at this position. Further examples are AKAP220, which localizes PKA and protein phosphatase PP1 on the peroxisomes, and the yotiao AKAP which, in addition to PKA, also binds protein phosphatase PP1. The CG-NAP AKAP not only binds PKA and protein phosphatase PP1, but also the rho-dependent kinase PKN (NGF (nerve growth factor)-activated protein kinase) and protein phosphatase PP2A.
Other proteins may also undergo association with AKAPs. Thus, ezrin, a member of the cytoskeleton-associated ERM family ezrin, radixin and moesin, which has been identified as an AKAP, binds to a protein (EBP50/NHERF) which is involved in the regulation of the sodium-proton transport in the apical membrane of epithelial cells. AKAPs mediate the modulation of the conductivity of ion channels by localization of protein kinases and phosphatases in the vicinity of particular channel subunits probably regulated by phosphorylation and dephosphorylation.
The activity of the NMDA receptor is modulated by the yotiao AKAP which also binds protein phosphatase PP1. The phosphatase, which is active in bound condition, limits the channel conductivity of the NMDA receptor until the PKA is activated by cAMP, phosphorylating the ion channel or an associated protein so that the conductivity rapidly increases. It has also been shown that myristoylated Ht31 peptides inhibiting the interaction between PKA and AKAP suspend the cAMP-dependent inhibition of interleukin-2 transcription in Jurkat T cells, and that S-Ht31 peptides restrict sperm motility.
AKAPs are also involved in essential complex biological processes, such as insulin secretion in β-cells of the pancreas and in RINm5F cells (clonal β-cell line of rats) mediated by the hormone GLP-1 (glucagon-like peptide). The activation of PKA by GLP-1 results in phosphorylation of L-type calcium channels, favoring exocytosis of insulin from secretory granules. Ht31 peptide-mediated inhibition of PKA anchoring results in a significant reduction of insulin secretion. Said peptides neither affect cAMP formation nor the activity of the catalytic subunits of PKA. Furthermore, an increase in insulin secretion after application of GLP-1 could be detected following expression of wild-type AKAP18α in RINm5F cells compared to control cells failing to express AKAP18α.
The redistribution of the aquaporin-2 water channel from intracellular vesicles to the plasma membrane of the principal cells of the renal collecting tubule, mediated by the antidiuretic hormone arginine-vasopressin (AVP), the molecular basis of the vasopressin-mediated water reabsorption, is another example of a process requiring interaction of the PKAs with AKAP proteins (Klussmann et al., 1999). If the interaction is prevented, redistribution cannot occur. However, the interaction also plays an important role in many processes in a wide variety of cell types; for example, the interaction increases the myocardial contractility (Hulme et al., 2003).
To analyze the effect of PKA-AKAP interaction, efficient and selective modification of the interaction, especially inhibition or decoupling, is required. At present, an Ht31 peptide is available for decoupling of the PKAs from AKAP proteins. The Ht31 peptide can be coupled to stearate so as to be present in a membrane-permeable form. However, the Ht31 peptide decouples PKA and AKAP in a way which is insufficient for many investigations or even therapeutic use. Above all, the Ht31 peptide fails to undergo selective interaction with the regulatory subunits RIIα or RIIβ of PKAs, so that the significance of the subunits for selected processes cannot be analyzed.
The object of the invention is therefore to overcome the above-mentioned drawbacks and, in particular, provide new nucleic acid sequences which encode peptides modifying, particularly decoupling, the interaction of AKAP and PKA in an efficient and specific way and, in addition, can be used as overexpressing materials in host organisms to perform model analyses with the aid of these host organisms, e.g. mice, of diseases associated with an AKAP-PKA interaction, preferably insipid diabetes, duodenal ulcer, hypertony and pancreatic diabetes.
The present invention solves the above technical problem by providing an isolated nucleic acid sequence selected from the group comprising:
Surprisingly, the nucleic acid sequences according to the invention can be used to encode peptides in accordance with Table 1 (SEQ ID Nos. 1-39) which modify, preferably inhibit, and more preferably decouple the interaction of AKAP and PKA. The nucleic acid molecules according to the invention are advantageously suited to encode peptides binding selectively to regulatory subunits of the PKAs, especially to RIIα or RIIβ. Furthermore, the peptides encoded by the nucleic acid molecules according to the invention offer a way of effecting modification, inhibition or decoupling of AKAP and PKA in dependence of the species being used. The nucleic acid molecules or the peptides derived therefrom are advantageously suited to produce transgenic organisms, e.g. mice, in which the AKAP-PKA interaction is modified in a tissue- and/or cell-specific fashion.
In a preferred embodiment of the invention the nucleic acid sequence having sufficient homology to be functionally analogous to a nucleotide sequence has at least 40% homology. In the meaning of the invention, functional analogy to the above-mentioned nucleic acid sequences or to sequences hybridizing with said nucleic acid sequences implies that the encoded homologous structures allow efficient and selective decoupling of the PKA-AKAP interaction and have high affinity in binding to RII subunits of PKA.
In another advantageous embodiment of the invention, the nucleic acid molecule has at least 60%, preferably 70%, more preferably 80%, and most preferably 90% homology to the nucleic acid molecules according to the invention.
In another preferred embodiment of the invention, the nucleic acid molecule is a genomic DNA and/or an RNA, and in a particularly preferred fashion the nucleic acid molecule is a cDNA.
The invention also relates to a vector comprising at least one nucleic acid molecule according to the invention. Further, the invention relates to a host cell comprising said vector. The invention also relates to a polypeptide encoded by at least one nucleic acid molecule according to the invention.
In a preferred embodiment of the invention the polypeptide comprises an amino acid sequence according to SEQ ID NO. 1 to SEQ ID NO. 39 or at least one polypeptide in accordance with these sequences. The invention also relates to a polypeptide which has been modified by deletion, addition, substitution, translocation, inversion and/or insertion and is functionally analogous to a polypeptide according to SEQ ID Nos. 1 to 39 and/or a polypeptide comprising a polypeptide which has sufficient homology to be functionally analogous to a polypeptide according to SEQ ID Nos. 1 to 39 or mutations thereof (deletion, addition, substitution, translocation, inversion and/or insertions).
The following peptides of the invention are particularly preferred:
The peptides of the invention are derived either (i) from AKAP18δ (SEQ ID Nos. 1 to 7) or (ii) from proteins not associated with AKAP molecules (SEQ ID Nos. 8 to 39).
The peptides according to (i):
have in common that the RIIα subunits of the PKA bind stronger than any other peptide derived from natural AKAPs. We explain this by binding via hydrogen bridges (H bridges) between peptide and RII dimer (see Fig., hydrogen bridges represented by broken lines). Correspondingly, a common feature of the peptides is the minimum number (8) of amino acids forming H bridges.
The following peptides are also derived from AKPA18δ, but involve the feature of absent binding of RII subunits of the PKAs despite high similarity of the amino acids (negative controls; if necessary, patenting can be renounced). They have in common that binding is no longer present due to structural differences (1, 2) or differences in charge (3, 4).
4 AKAP18δ-phos
The peptides according to the invention derived from proteins other than AKAPs have a well-defined size which, surprisingly, contributes to the ability of the peptides of modifying the interaction between AKAP and PKA because it has an influence on the affinity of the peptides to the RIIα subunits of the PKAs. The peptides are constituted of 25 amino acids and are therefore 25 mers.
Selecting the peptides so as to be shorter or longer (e.g. 17 mers) will change their activity. The common structural feature of peptide length, together with the functional feature of AKAP/PKA decoupling, defines the structures according to the invention. The peptides according to the invention are characterized by the general formula:
wherein x represents an arbitrary amino acid, and x more specifically represents any of the 20 biogenic amino acids (in the single-letter code, these are: A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, Y). Each amino acid disclosed in Alberts et al. (2004), Molekularbiologie der Zelle, pp. 8, 73, 79ff, 150ff, or 1717G; in Römpp (1999), Biotechnologie und Gentechnik, pp. 45ff, or in Römpp (2000), Lexikon Biochemie und Molekularbiologie, pp. 28ff, or in other standard textbooks of biology is claimed herein. These particularly preferred peptides have either a positively charged amino acid (H, K or R) in the first or second position (position is the number of the amino acid from the N terminus) or leucine in the positions 19, 18 or 14 or serine in position 4.
A functionally analogous peptide is a peptide which is capable of modifying, preferably decoupling, the PKA-AKAP interaction.
The invention also relates to an organism overexpressing a nucleic acid molecule of the invention or comprising a vector of the invention and/or having a polypeptide according to the invention. For example, this can be a transgenic mouse or rat, or cattle, horse, donkey, sheep, camel, goat, pig, rabbit, guinea pig, hamster, cat, monkey or dog in which tissue- and/or cell-specific disorders of the PKA-AKAP interaction are present. In particular, such organisms, for example mice, can be used to develop pharmaceutical agents which modify, preferably decouple, the PKA-AKAP interaction.
The organisms of the invention also allow in vivo investigations of metabolic processes where PKA-AKAP interaction plays a role, or which processes require clarification as to whether AKAP-PKA interaction is involved in a particular incident.
Preferably, the organism is a transgenic mouse overexpressing the strongly binding peptide AKAP18δ-L304T or AKAP18δ-L314E specifically in the principal cells of the renal collecting tubules. Advantageously, decoupling of the PKAs from the AKAP proteins results in prevention of the vasopressin-induced redistribution of AQP2 in primarily cultured cells of the collecting tubule, so that the animals exhibit insipid diabetes, in particular. This disease is remarkable for a massive loss of water (polyuria) which e.g. human patients attempt to compensate by ingestion of large amounts of liquid (polydipsia).
For example, the transgenic organisms according to the invention allow investigations as to what extent decoupling of PKAs or of selected subunits of AKAP proteins can be regarded as a therapeutic principle and put to use. Advantageously, such investigations can be followed by analysis of optimized substances (pharmaceutical agents) having the same effect. Substances optimized in this way preferably have an aquaretic effect and can therefore be used with advantage in patients with edemas, e.g. in cases of cardiac failure or liver cirrhosis.
The invention also relates to a recognition molecule directed against said nucleic acid molecule, said vector, said host cell, and/or said polypeptide. Recognition sub-stances in the meaning of the invention are molecules capable of interacting with the above-mentioned structures such as nucleic acid molecules or sequences, vectors, host cells and/or polypeptides or fragments thereof, particularly interacting in such a way that detection of said structures is possible. In particular, said recognition substances can be specific nucleic acids binding to the above-mentioned nucleic acid molecules or polypeptides, such as antisense constructs, cDNA or mRNA molecules or fragments thereof, but also antibodies, fluorescent markers, labelled carbohydrates or lipids or chelating agents. Of course, it is also possible that the recognition substances are not proteins or nucleic acids or antibodies, but instead, antibodies directed against the same. In this event, the recognition substances can be secondary antibodies, in particular.
In a special embodiment of the invention, the recognition molecule is an antibody, an antibody fragment and/or an antisense construct, especially an RNA interference molecule.
The antibodies in the meaning of the invention bind the polypeptides in a specific manner. The antibodies may also be modified antibodies (e.g. oligomeric, reduced, oxidized and labelled antibodies). The term “antibody” used in the present specification includes intact molecules, as well as antibody fragments such as Fab, F(ab′)2 and Fv capable of binding the particular epitope determinants of the polypeptides. In these fragments, the antibody's ability of selectively binding its antigen or receptor is partially retained, the fragments being defined as follows:
The invention also relates to a pharmaceutical composition comprising said nucleic acid molecule of the invention, said vector of the invention, said host cell of the invention, said polypeptide of the invention and/or said recognition molecule of the invention, optionally together with a pharmaceutically acceptable carrier.
In a preferred embodiment of the invention the pharmaceutical composition is an aquaretic agent. Aquaretic agents in the meaning of the invention modify the interaction between PKAs and AKAP proteins; more specifically, they decouple the interaction between the two mentioned above. It will be appreciated that the recognition molecules of the invention can also be used as pharmaceutical compositions, especially those directed against the peptide according to the invention or against the coding nucleic acid.
In particular, the pharmaceutical compositions comprising the peptides of the invention, the vectors of the invention or the recognition molecules of the invention can be used in patients with edemas, particularly in cases of cardiac failure or liver cirrhosis. In the meaning of the invention, the vectors or the nucleic acid molecules of the invention can be employed as pharmaceutical composition on a nucleic acid level, whereas the peptides according to the invention, but also part of the recognition molecules of the invention, can be used on an amino acid level. Depending on whether the therapy consists in decoupling of AKAP and PKA—e.g. by means of the peptides according to the invention—or in preventing decoupling between AKAP and PKA—e.g. by means of the antibodies of the invention directed against said peptides—the peptides of the invention or the recognition molecules of the invention directed e.g. against said peptides or other structures can preferably be used as pharmaceutical composition by a person skilled in the art. In particular, the peptides of the invention can be used in decoupling of AKAP/PKA and thus in case of edemas. The recognition molecules of the invention (e.g. antibodies) are particularly useful in preventing de-coupling of AKAP/PKA, e.g. in cases of insipid diabetes.
Of course, the peptides according to the invention may also comprise conventional auxiliaries, preferably carriers, adjuvants and/or vehicles. For example, the carriers can be fillers, diluents, binders, humectants, disintegrants, dissolution retarders, absorption enhancers, wetting agents, adsorbents and/or lubricants. In this event, the peptide is specifically referred to as drug or pharmaceutical agent.
In another preferred embodiment of the invention the agent according to the invention is formulated as a gel, poudrage, powder, tablet, sustained-release tablet, premix, emulsion, brew-up formulation, drops, concentrate, granulate, syrup, pellet, bolus, capsule, aerosol, spray and/or inhalant and/or used in this form. The tablets, coated tablets, capsules, pills and granulates can be provided with conventional coatings and envelopes optionally including opacification agents, and can also be composed such that release of the active substance(s) takes place only or preferably in a particular area of the intestinal tract, optionally in a delayed fashion, to which end polymer sub-stances and waxes can be used as embedding materials.
For example, the drugs of the present invention can be used in oral administration in any orally tolerable dosage form, including capsules, tablets and aqueous suspensions and solutions, without being restricted thereto. In case of tablets for oral application, carriers frequently used include lactose and corn starch. Typically, lubricants such as magnesium stearate are also added. For oral administration in the form of capsules, diluents that can be used include lactose and dried corn starch. In oral administration of aqueous suspensions the active substance is combined with emulsifiers and suspending agents. Also, particular sweeteners and/or flavors and/or coloring agents can be added, if desired.
The active substance(s) can also be present in micro-encapsulated form, optionally with one or more of the above-specified carrier materials.
In addition to the active substance(s), suppositories may include conventional water-soluble or water-insoluble carriers such as polyethylene glycols, fats, e.g. cocoa fat and higher esters (for example, C14 alcohols with C16 fatty acids) or mixtures of these substances.
In addition to the active substance(s), ointments, pastes, creams and gels may include conventional carriers such as animal and vegetable fats, waxes, paraffins, starch, tragacanth, cellulose derivatives, polyethylene glycols, silicones, bentonites, silica, talc and zinc oxide or mixtures of these substances.
In addition to the active substance(s), powders and sprays may include conventional carriers such as lactose, talc, silica, aluminum hydroxide, calcium silicate and polyamide powder or mixtures of these substances. In addition, sprays may include conventional propellants such as chlorofluorohydrocarbons.
In addition to the active substances CHP and gemcitabine, solutions and emulsions may include conventional carriers such as solvents, solubilizers and emulsifiers such as water, ethyl alcohol, isopropyl alcohol, ethyl carbonate, ethyl acetate, benzyl alcohol, benzyl benzoate, propylene glycol, 1,3-butylene glycol, dimethylformamide, oils, especially cotton seed oil, peanut oil, corn oil, olive oil, castor oil and sesame oil, glycerol, glycerol formal, tetrahydrofurfuryl alcohol, polyethylene glycols, and fatty esters of sorbitan, or mixtures of these substances. For parenteral application, the solutions and emulsions may also be present in a sterile and blood-isotonic form.
In addition to the active substances, suspensions may include conventional carriers such as liquid diluents, e.g. water, ethyl alcohol, propylene glycol, suspending agents, e.g. ethoxylated isostearyl alcohols, polyoxyethylenesorbitol and sorbitan esters, microcrystalline cellulose, aluminum metahydroxide, bentonite, agar, and tragacanth, or mixtures of these substances.
The drugs can be present in the form of a sterile injectable formulation, e.g. as a sterile injectable aqueous or oily suspension. Such a suspension can also be formulated by means of methods known in the art, using suitable dispersing or wetting agents (such as Tween 80) and suspending agents. The sterile injectable formulation can also be a sterile injectable solution or suspension in a non-toxic, parenterally tolerable diluent or solvent, e.g. a solution in 1,3-butanediol. Tolerable vehicles and solvents that can be used include mannitol, water, Ringer's solution, and isotonic sodium chloride solution. Furthermore, sterile, non-volatile oils are conventionally used as solvents or suspending medium. Any mild non-volatile oil, including synthetic mono- or diglycerides, can be used for this purpose. Fatty acids such as oleic acid and glyceride derivatives thereof can be used in the production of injection agents, e.g. natural pharmaceutically tolerable oils such as olive oil or castor oil, especially in their poly-oxyethylated forms. Such oil solutions or suspensions may also include a long-chain alcohol or a similar alcohol as diluent or dispersant.
The above-mentioned formulation forms may also include colorants, preservatives, as well as odor- and taste-improving additives, e.g. peppermint oil and eucalyptus oil, and sweeteners, e.g. saccharine. Preferably, the peptides according to the invention should be present in the above-mentioned pharmaceutical preparations at a concentration of about 0.01 to 99.9 wt.-%, more preferably about 0.05 to 99 wt.-% of the overall mixture.
In addition the peptides or structural homologs, e.g. peptides with D-amino acids, or functional analogs, e.g. peptide mimetics, the above-mentioned pharmaceutical preparations may include further pharmaceutical active substances. The production of the pharmaceutical preparations specified above proceeds in a usual manner according to well-known methods, e.g. by mixing the active substance(s) with the carrier material(s).
The above-mentioned preparations can be applied in humans and animals on an oral, rectal, parenteral (intravenous, intramuscular, subcutaneous), intracisternal, intravaginal, intraperitoneal route, locally (powders, ointment, drops) and used in the therapy of tumors. Injection solutions, solutions and suspensions for oral therapy, gels, brew-up formulations, emulsions, ointments or drops are possible as suitable preparations. For local therapy, ophthalmic and dermatological formulations, silver and other salts, ear drops, eye ointments, powders or solutions can be used. With animals, ingestion can be effected via feed or drinking water in suitable formulations. Moreover, the drugs or combined agents can be incorporated in other carrier materials such as plastics (plastic chains for local therapy), collagen or bone cement.
In another preferred embodiment of the invention, the peptides are incorporated in a pharmaceutical preparation at a concentration of 0.1 to 99.5, preferably 0.5 to 95, and more preferably 20 to 80 wt.-%. That is, the peptides are present in the above-specified pharmaceutical preparations, e.g. tablets, pills, granulates and others, at a concentration of preferably 0.1 to 99.5 wt.-% of the overall mixture. Those skilled in the art will be aware of the fact that the amount of active substance, i.e., the amount of an inventive compound combined with the carrier materials to produce a single dosage form, will vary depending on the patient to be treated and on the particular type of administration. Once the condition of a patient has improved, the proportion of active compound in the preparation can be modified so as to obtain a maintenance dose that will bring the disease to a halt. Depending on the symptoms, the dose or frequency of administration or both can subsequently be reduced to a level where the improved condition is retained. Once the symptoms have been alleviated to the desired level, the treatment should be terminated. However, patients may require an intermittent treatment on a long-term basis if any symptoms of the disease should recur. Accordingly, the proportion of the compounds, i.e. their concentration, in the overall mixture of the pharmaceutical preparation, as well as the composition or combination thereof, is variable and can be modified and adapted by a person of specialized knowledge in the art.
Those skilled in the art will be aware of the fact that the compounds of the invention can be contacted with an organism, preferably a human or an animal, on various routes. Furthermore, a person skilled in the art will also be familiar with the fact that the pharmaceutical agents in particular can be applied at varying dosages. Application should be effected in such a way that a disease is combated as effectively as possible or the onset of such a disease is prevented by a prophylactic administration. Concentration and type of application can be determined by a person skilled in the art using routine tests. Preferred applications of the compounds of the invention are oral application in the form of powders, tablets, fluid mixture, drops, capsules or the like, rectal application in the form of suppositories, solutions and the like, parenteral application in the form of injections, infusions and solutions, and local application in the form of ointments, pads, dressings, lavages and the like. Contacting with the compounds according to the invention is preferably effected in a prophylactic or therapeutic fashion.
For example, the suitability of the selected form of application, of the dose, application regimen, selection of adjuvant and the like can be determined by taking serum aliquots from the patient, i.e., human or animal, and testing for the presence of indicators of disease in the course of the treatment procedure. Alternatively or concomitantly, the condition of the kidneys, but also, the amount of T cells or other cells of the immune system can be determined in a conventional manner so as to obtain a general survey on the immunologic constitution of the patient and, in particular, the constitution of organs important to the metabolism. Additionally, the clinical condition of the patient can be observed for the desired effect. Where insufficient therapeutic effectiveness is achieved, the patient can be subjected to further treatment using the agents of the invention, optionally modified with other well-known medicaments expected to bring about an improvement of the overall constitution. Obviously, it is also possible to modify the carriers or vehicles of the pharmaceutical agent or to vary the route of administration.
In addition to oral ingestion, e.g. intramuscular or subcutaneous injections or injections into the blood vessels can be envisaged as another preferred route of therapeutic administration of the compounds according to the invention. At the same time, supply via catheters or surgical tubes can also be used, e.g. via catheters directly leading to particular organs such as the kidneys.
In a preferred embodiment the compounds according to the invention can be employed in a total amount of 0.05 to 500 mg/kg body weight per 24 hours, preferably 5 to 100 mg/kg body weight. Advantageously, this is a therapeutic quantity which is used to prevent or improve the symptoms of a disorder or of a responsive, pathologically physiological condition.
Obviously, the dose will depend on the age, health and weight of the recipient, degree of the disease, type of required simultaneous treatment, frequency of the treatment and type of the desired effects and side-effects. The daily dose of 0.05 to 500 mg/kg body weight can be applied as a single dose or multiple doses in order to furnish the desired results. In particular, pharmaceutical agents are typically used in about 1 to 10 administrations per day, or alternatively or additionally as a continuous infusion. Such administrations can be applied as a chronic or acute therapy. It will be appreciated that the amounts of active substance that are combined with the carrier materials to produce a single dosage form may vary depending on the host to be treated and on the particular type of administration. In a preferred fashion, the daily dose is distributed over 2 to 5 applications, with 1 to 2 tablets including an active substance content of 0.05 to 500 mg/kg body weight being administered in each application. Of course, it is also possible to select a higher content of active substance, e.g. up to a concentration of 5000 mg/kg. The tablets can also be sustained-release tablets, in which case the number of applications per day is reduced to 1 to 3. The active substance content of sustained-release tablets can be from 3 to 3000 mg. If the active substance—as set forth above—is administered by injection, the host is preferably contacted 1 to 10 times per day with the compounds of the invention or by using continuous infusion, in which case quantities of from 1 to 4000 mg per day are preferred. The preferred total amounts per day were found advantageous both in human and veterinary medicine. It may become necessary to deviate from the above-mentioned dosages, and this depends on the nature and body weight of the host to be treated, the type and severity of the disease, the type of formulation and application of the drug, and on the time period or interval during which the administration takes place. Thus, it may be preferred in some cases to contact the organism with less than the amounts mentioned above, while in other cases the amount of active substance specified above has to be surpassed. A person of specialized knowledge in the art can determine the optimum dosage required in each case and the type of application of the active substances.
In another particularly preferred embodiment of the invention the pharmaceutical agent is used in a single administration of from 1 to 100, especially from 2 to 50 mg/kg body weight. In the same way as the total amount per day, the amount of a single dose per application can be varied by a person of specialized knowledge in the art. Similarly, the compounds used according to the invention can be employed in veterinary medicine with the above-mentioned single concentrations and formulations together with the feed or feed formulations or drinking water. A single dose preferably includes that amount of active substance which is administered in one application and which normally corresponds to one whole, one half daily dose or one third or one quarter of a daily dose. Accordingly, the dosage units may preferably include 1, 2, 3 or 4 or more single doses or 0.5, 0.3 or 0.25 single doses. In a preferred fashion, the daily dose of the compounds according to the invention is distributed over 2 to 10 applications, preferably 2 to 7, and more preferably 3 to 5 applications. Of course, continuous infusion of the agents according to the invention is also possible.
In a particularly preferred embodiment of the invention, 1 to 2 tablets are administered in each oral application of the compounds of the invention. The tablets according to the invention can be provided with coatings and envelopes well-known to those skilled in the art or can be composed in a way so as to release the active substance(s) only in preferred, particular regions of the host.
It is preferred in another embodiment of the invention that the compounds according to the invention are optionally associated with each other or, coupled to a carrier, enclosed in liposomes, and, in the meaning of the invention, such enclosure in liposomes does not necessarily imply that the compounds of the invention are present inside the liposomes. Enclosure in the meaning of the invention may also imply that the compounds of the invention are associated with the membrane of the liposomes, e.g. in such a way that the compounds are anchored on the exterior membrane. Such a representation of the inventive compounds in or on liposomes is advantageous in those cases where a person skilled in the art selects the liposomes such that the latter have an immune-stimulating effect. Various ways of modifying the immune-stimulating effect of liposomes are known to those skilled in the art from DE 198 51 282. The lipids can be ordinary lipids, such as esters and amides, or complex lipids, e.g. glycolipids such as cerebrosides or gangliosides, sphingolipids or phospholipids.
For example, it is possible to replace single amino acids or groups of amino acids without adversely affecting the activity of the peptides with respect to accomplishing the object of the present invention. For replacement of such amino acids, reference is made to appropriate standard textbooks of biochemistry and genetics.
Various ways of preparing peptides have been disclosed in the prior art. Peptides designed starting from the peptides of the invention using such methods are included in the teaching according to the invention. For example, one way of generating functionally analogous peptides has been described in PNAS USA 1998, Oct. 13, 9521, 12179-84; WO 99/6293 and/or WO 02/38592, and the above teachings are hereby incorporated in the disclosure of the invention. That is, all peptides, peptide fragments or structures comprising peptides generated using the methods mentioned above—starting from the peptides of the invention—are peptides in the meaning of the invention, provided they accomplish the object of the invention. Furthermore, the peptides according to the invention are lead structures for the development of peptide mimetics.
As is well-known to those skilled in the art, some amino acids have analogous physicochemical properties so that these amino acids advantageously can be replaced by each other. For example, these include the group of amino acids (a) glycine, alanine, valine, leucine and/or isoleucine; or the amino acids (b) serine and threonine, the amino acids (c) asparagine and glutamine, the amino acids (d) aspartic acid and glutamic acid; the amino acids (e) lysine and arginine, as well as the group of aromatic amino acids (f) phenylalanine, tyrosine and/or tryptophan. Amino acids within one and the same group (a-f) can be replaced with one another. Furthermore, the amino acids can be replaced by modified amino acids or specific enantiomers. Further modifications are possible in accordance with the teaching of WO 99/62933 or WO 02/38592 which hereby are incorporated in the disclosure of the teaching of the invention.
In another preferred embodiment the peptide comprises a linker and/or a spacer selected from the group comprising α-aminocarboxylic acids as well as homo- and heterooligomers thereof, α,ω-aminocarboxylic acids and branched homo- or heterooligomers thereof, other amino acids, as well as linear and branched homo- or heterooligomers (peptides); amino-oligoalkoxyalkylamines; maleinimidocarboxylic acid derivatives; oligomers of alkylamines; 4-alkylphenyl derivatives; 4-oligoalkoxyphenyl or 4-oligoalkoxyphenoxy derivatives; 4-oligoalkylmercaptophenyl or 4-oligoalkylmercaptophenoxy derivatives; 4-oligoalkylaminophenyl or 4-oligoalkylaminophenoxy derivatives; (oligoalkylbenzyl)phenyl or 4-(oligoalkylbenzyl)phenoxy derivatives, as well as 4-(oligoalkoxybenzyl)phenyl or 4-(oligoalkoxybenzyl)phenoxy derivatives; trityl derivatives; benzyloxyaryl or benzyloxyalkyl derivatives; xanthen-3-yloxyalkyl derivatives; (4-alkylphenyl)- or ω-(4-alkylphenoxy)alkanoic acid derivatives; oligoalkylphenoxyalkyl or oligoalkoxyphenoxyalkyl derivatives; carbamate derivatives; amines; trialkylsilyl or dialkylalkoxysilyl derivatives; alkyl or aryl derivatives and/or combinations thereof; other possible structures have been described in EP 1 214 350 which hereby is incorporated in the disclosure of the invention.
In a preferred fashion, synthetic peptides or fragments thereof can be multimerized by chemical crosslinkers or coupled to a carrier molecule such as BSA, dextran, KLH or others. Chemical crosslinkers used to this end are listed in “Bioconjugate Techniques”, Greg T. Hermanson, Academic Press, 1996, which hereby is incorporated in the disclosure of the teaching according to the invention. Preferred crosslinkers are homobifunctional crosslinkers, preferably NHS esters such as DSP, DTSSP, DSS, BS, DST, sulfo-DST, BSOCOES, sulfo-BSOCOES, EGS, sulfo-EGS, DSG or DSC, homobifunctional imidoesters such as DMA, DMP, DMS or DTBP, homobifunctional sulfhydryl-reactive crosslinkers such as DPDPB, BMH or BMOE, difluorobenzene derivatives such as DFDNB or DFDNPS, homobifunctional photoreactive crosslinkers such as BASED, homobifunctional aldehydes such as formaldehyde or glutaraldehyde, bisepoxides such as 1,4-butanediol diglycidyl ethers, homobifunctional hydrazides such as adipic dihydrazides or carbohydrazides, bisdiazonium derivatives such as bis-diazotized o-tolidine, benzidine or bisalkylhaloid.
Also preferred are heterobifunctional crosslinkers, especially amine-reactive and sulfhydryl-reactive crosslinkers such as SPDP, LC-SPDP, sulfo-LC-SPDP, SMPT, sulfo-LC-SMPT, SMCC, sulfo-SMCC, MBS, sulfo-MBS, SIAB, sulfo-SIAB, SMPB, sulfo-SMBP, GMBS, sulfo-GMBS, SIAX, SIAXX, SIAC, SIACX or NPIA, carbonyl-reactive and sulfhydryl-reactive crosslinkers such as MPBH, M2C2H or PDPH, amine-reactive and photoreactive crosslinkers such as NHS-ASA, sulfo-NHS-ASA, sulfo-NHS-LC-ASA, SASD, HSAB, sulfo-HSAB, SANPAH, sulfo-SANPAH, ANB-NOS, SAND, SADP, sulfo-SADP, sulfo-SAPB, SAED, sulfo-SAMCA, p-nitrophenyldiazopyruvate or PNP-DTP, sulfhydryl- and photoreactive crosslinkers such as ASIB, APDP, benzophenone-4-iodoacetamide or benzophenone-4-maleinimide, carbonyl-reactive and photoreactive crosslinkers such as ABH, carboxylate-reactive and photoreactive crosslinkers such as ASBA, arginine-reactive crosslinkers such as APG, trifunctional crosslinkers such as 4-azido-2-nitrophenylbiocytin 4-nitrophenyl ester, sulfo-SEBD, TSAT and/or TMEA.
In another preferred embodiment of the invention the peptides of the invention and structures produced in a recombinant fashion are linked by peptide bridges having a length of from 0 to 50 amino acids. Also included are recombinant proteins consisting of two N-terminal and one C-terminal sequence, or hexamers consisting of three N-terminal sequences and three C-terminal sequences, or multimers of the above-mentioned recombinant structures, wherein a peptide bridge of 0 to 50 amino acids can be pre-sent between each of the N- and C-terminal sequences. For purification, solubilization, or changes in conformation, the peptides can be provided with specific fusion components either on the N or C terminus, such as CBP (calmodulin binding protein), His-tag and/or others. Similar constructs can also be encoded by DNA used in therapy.
The invention also relates to a kit comprising a nucleic acid molecule of the invention, a vector of the invention, a host cell of the invention, a polypeptide of the invention, a recognition molecule of the invention and/or a pharmaceutical composition, optionally together with information—e.g. an instruction leaflet or an internet address referring to homepages including further information, etc.—concerning handling or combining the contents of the kit. For example, the information concerning handling the contents of the kit may comprise a therapeutic regimen for edemas, cardiac failure, liver cirrhosis, hyperinsulinism, hypertony, duodenal ulcer. Also, the information may comprise explanations referring to the use of the materials and products of the invention in diagnosing diseases associated with AKAP-PKA interaction or decoupling thereof. The kit according to the invention may also be used in basic research. In basic research, the kit can preferably be used to detect whether a metabolic phenomenon is associated with interaction or absent interaction of AKAP and PKA. More specifically, the kit according to the invention allows to determine which subunits of AKAP and/or PKA are responsible for interaction of the above two molecules or failure of such interaction to take place.
The products of the invention, such as peptides, vectors, nucleic acid molecules, may comprise other advantageous nucleic acids, amino acids, carbohydrates or lipids. For example, it may be preferred to modify the peptides with a fatty residue, such as stearate, in such a way that the peptides have good membrane permeability. These peptides can be used to perform experiments on cell cultures. Such peptides can be used as tools to effect particularly efficient decoupling of PKA from AKAP proteins in cells, cell cultures, tissue cultures, organ cultures or organisms. More specifically, the peptides in the meaning of the invention can be used in cell cultures to answer the question whether a particular process depends on anchoring of the PKA on AKAP proteins. Owing to the advantageous high affinity for human RIIα subunits of PKA, the peptides according to the invention are suitable especially for investigations in human systems. By comparison with peptides binding PKA with different affinity it will also be possible to make quantitative statements defining to what extent PKA-AKAP interaction is necessary to ensure the progress of a physiological process. In particular, the kits according to the invention can be used to study the progress of such a physiological process. Advantageously, the peptides according to the invention bind the RII subunits of PKA more strongly than the typical PKA binding domains of AKAP18δ.
Advantageously, the peptides of the invention have RIIα or RIIβ specificity so that the kit can be used e.g. to obtain highly detailed insight into the interaction. More specifically, decoupling of one or another regulatory subunit of PKA from AKAP proteins may furnish information as to which PKA, type IIα or type IIβ, is involved in the respective process to be investigated. In particular, the peptide A18δRIIβRnl selectively binds RIIβ subunits of PKA.
The invention also relates to a method for the modification, especially inhibition, and preferably decoupling, of an AKAP-PKA interaction or an interaction of AKAP or PKA subunits, comprising the steps of:
In a preferred fashion the interaction is analyzed or modified on a regulatory R subunit and more preferably on an RIIα and/or RIIβ subunit.
The invention also relates to the use of a nucleic acid molecule of the invention, a host cell of the invention, an organism of the invention, a polypeptide of the invention, a recognition molecule of the invention, a pharmaceutical composition of the invention and/or a kit of the invention for the modification, especially inhibition, of an AKAP-PKA interaction. The invention also relates to the use of fragments or partial regions of the peptides or nucleic acids according to the invention. Furthermore, extension of the peptides or nucleic acids of the invention by additional amino acids or nucleotides can be envisaged. Of course, it is also possible to modify the peptides with lipid or carbohydrate structures.
In a preferred embodiment of the invention, especially of the use according to the invention, the cell—e.g. as a cell culture—or the organism is used as a model for tissue—and/or cell-specific AKAP-PKA interaction, particularly as a model for insipid diabetes. Other preferred models are cell cultures or tissues comprising the nucleic acid molecules or peptides of the invention.
In another preferred embodiment of the invention the vasopressin-induced redistribution of AQP2 is modified, particularly prevented, as a result of the AKAP-PKA modification.
In another particularly preferred embodiment the polypeptide and/or the pharmaceutical composition are used as agents causing loss of water, particularly as aquaretic agents.
In another preferred embodiment of the invention, especially of the use according to the invention, the interaction of the RIIα or RIIβ subunit of PKA with AKAP is modified, particularly inhibited.
In another preferred use, the subunits are of human or murine origin.
Without intending to be limiting, the invention will be explained in more detail with reference to the following examples.
All chemicals and solvents were purchased from Fluka (Steinheim) or Sigma Aldrich (Munich) and used without further purification steps. Fmoc-protected amino acid penta-fluorophenyl esters were purchased from Novabiochem Merck Biosciences GmbH (Darmstadt).
Peptide libraries were synthesized by means of automatic SPOT synthesis on Whatman 50 cellulose membranes according to standard protocols using Fmoc chemistry and AutoSpot Robot ATE 222 (Intavis Bioanalytical Instruments AG, Cologne). The protective groups of the amino acid side chains were removed using a mixture of trifluoroacetic acid (TFA) in dichloromethane (DCM) (Frank, 1992; Kramer and Schneider-Mergener, 1998). For control, spots (about 50 nmol of peptide per spot) were cut from the cellulose membrane, removed from the membrane by treatment with 0.05 M NaOH, and analyzed using HPLC and MALDI-TOF mass spectrometry.
The ATP concentration was adjusted to 10 μM by addition of non-radioactive ATP (addition of 5 μl of a 1 mM solution). The batch was incubated on ice for another 50 min.
The reaction was quenched by adding dextran blue and removing free nucleotides. The free ATP was removed on a Sephadex G50 column.
Separation of Labelled RII Subunit of PKA from Free Nucleotides on Sephadex G50 Columns
Non-incorporated nucleotides were separated from the RII subunits by fractionation on Sephadex G 50 columns.
Until used, the column was sealed with parafilm at the top thereof.
A peptide library derived from the wild-type amino acid sequence of the PKA binding domain of AKAP18δ (PEDAELVRLSKRLVENAVLKAVQQY; Henn et al., 2004) was synthesized on a membrane. To this end, each amino acid of the wild-type sequence was substituted with the 20 possible amino acids.
Alto et al. (2003) have developed a peptide, AKAPIS, which inhibits the interaction between the murine RIIα subunit of PKA with an affinity increased by 5 times (KD=0.45 nM) compared to the Ht31 peptide (KD=2.2 nM).
In our RII overlay experiments the peptides AKAPIS and Ht31 barely bind the human RIIα and the RIIβ subunit of PKA from rats; in contrast, the peptides AKAP18δ-wt, AKAP18δ-L304T and AKAP18δ-L314E identified by us bind strongly. This result suggests species-related differences between the murine and human RIIα subunits, resulting in different binding affinities for the same peptides.
To find peptides binding either RIIα or RIIβ subunits of PKA, thus specifically inhibiting the interaction of AKAP proteins with the type IIα or type IIβ PKA, peptides that might block the AKAP binding pocket were derived by means of three-dimensional structural models of the PKA subunits from the wild-type PKA binding domain of AKAP18δ. The peptides (1-19) were synthesized in parallel on two membranes and subsequently tested in RII overlay experiments for their binding ability to RIIα or RIIβ subunits of PKA (
Starting from the sequence of peptide 7, two peptide libraries were synthesized on membranes and subjected to RII overlay experiments using RIIα and RIIβ subunits, respectively, as probes.
In addition to the peptides described in
Identification of peptides inhibiting the interaction of AKAP proteins with PKA. A library of peptides derived from the PKA binding domain of AKAP18δ was synthesized on a membrane. The membrane was incubated with radiolabelled regulatory RIIα and RIIβ subunits of PKA (RII overlay experiment). Each black dot represents a peptide having bound the RII subunits thereto (detected using a phosphoimager). The amino acid sequences of the peptides can be read with the help of the abbreviations as specified (single-letter code).
Vertical: Sequence of the wild-type PKA binding domain of AKAP18δ.
Horizontal: the 20 amino acids used in the substitution of the wild-type sequence.
Identification of AKAP18δ-derived peptides inhibiting the interaction of AKAP proteins with the regulatory RIIα and RIIβ subunits of PKA. A: Peptides derived from the PKA binding domain of AKAP18δ were synthesized on two membranes. The membranes were incubated with radiolabelled regulatory RIIα (upper row) or RIIβ subunits (row below) of the PKA (RII overlay experiment). Each black dot represents a peptide having bound the RII subunits thereto (detected using a phosphoimager). For quantification, the signals were evaluated by means of densitometry and correlated with the signal obtained for AKAP18δ-wt. B: The amino acid sequences of the peptides (single-letter code) specified in A.
AKAP18δ-derived peptides binding the RIIα and RIIβ subunits of PKA with varying strength. A: The peptides 1-19 derived from the PKA binding domain of AKAP18δ were synthesized on two membranes. The membranes were incubated with radio-labelled regulatory RIIα (upper row) or RIIβ subunits (row below) of the PKA (RII overlay experiment). Each black dot represents a peptide having bound the RII subunits thereto (detected using a phosphoimager). For quantification, the signals were evaluated by means of densitometry and correlated with the signal obtained for AKAP18δ-wt. Owing to the great difference in binding to both RII subunits, peptide No. 7 is highlighted in red printing. B: The amino acid sequences of the peptides (single-letter code) specified with 1-19 in A.
Different AKAP18δ-derived peptides bind the RIIα and RIIβ subunits of PKA with different strength. Two libraries of peptides derived from peptide 7 of
Identification of peptides inhibiting the AKAP-PKA interactions. Candidate peptides were synthesized on a membrane and incubated with radiolabelled regulatory RII□ subunits of PKA (RII overlay experiment). All black dots represent peptides having bound regulatory PKA subunits (detected using a phosphoimager).
Influence of hydrogen bridges on binding between peptides and RIIα subunits of PKA. (A, B): Comparative schematic representation of the interaction between RIIα and the peptides AKAP18δ-wt or AKAP18δ-L314E and between RIIα, Ht31 or AKAPIS. RIIα is represented as a rectangle and by selected amino acids, the peptides are represented with the help of their amino acid sequence. Amino acids as participants of a hydrogen bridge are linked by a broken line. Amino acids of peptides located in positions for hydrophobic molecular contacts are highlighted in green (position of amino acids of AKAP18δ-wt given in comparison to the protein). (C, D): To investigate the influence of the amino acids on the binding strength, alanine-substituted peptides were synthesized on membranes, checked for RIIα binding by means of RII overlay and quantified using densitometry. Starting from AKAP18δ-L314E, the peptides were substituted in all possible combinations with amino acids capable of forming hydrogen bridges (see A). The quantification for all peptides, sorted by affinity, is illustrated in C. The quantification for all single substitutions (as specified), as well as representative “spots” from an RII overlay (top) are illustrated in D.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2004 031 579.5 | Jun 2004 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/DE2005/001181 | 6/29/2005 | WO | 00 | 12/8/2008 |
