Patent Grant
8945583
The invention relates to the use of the ubiquitous vertebrate glucose transporter GLUT1 represented by SEQ ID NO: 2, or of fragments or sequences derived thereof, for the in vitro diagnosis of cancers, when used as a tumor marker, or for the screening of compounds useful for the preparation of drugs for the prevention or the treatment of pathologies linked to an infection of an individual with a PTLV, or pathologies linked to an overexpression of GLUT1 on cell surfaces, or the in vitro detection of GLUT1 on cell surfaces. The invention also relates to pharmaceutical compositions containing GLUT1, or fragments or sequences derived thereof, and their uses such as in the frame of the prevention or the treatment of pathologies linked to an infection of an individual with a PTLV.
The human T-cell leukemia virus (HTLV) is associated with leukemia and neurological syndromes. The role of viral envelopes in HTLV physiopathology is unclear and the envelope receptor, found in all vertebrate cell lines, remains unidentified.
HTLV envelope glycoproteins induce syncytium formation in vitro but their physiopathological effects are unclear. All vertebrate cell lines express functional HTLV envelope receptors, including cells resistant to HTLV envelope-mediated syncytium formation. We found that expression of the HTLV receptor-binding domain decreased lactate production due to diminished glucose consumption whereas binding-defective envelope mutants did not alter glucose metabolism. Glucose starvation increased HTLV receptor expression, reminiscent of nutrient sensing responses. Accordingly, overexpression of GLUT-1, the ubiquitous vertebrate glucose transporter, specifically increased HTLV envelope binding and GLUT-1 colocalized with HTLV envelopes. Moreover, HTLV envelope binding was highest in human erythrocytes, where GLUT-1 is abundantly expressed and is the sole glucose transporter isoform. These results demonstrate that GLUT-1 is an HTLV envelope receptor, and that this ligand/receptor interaction likely participates in the immunological and neurological disorders associated with HTLV infection.
Thus, the invention relates to the use of the ubiquitous vertebrate glucose transporter GLUT1 represented by SEQ ID NO: 2, or of fragments or sequences derived thereof, said fragments or derived sequences being able to bind to the envelope proteins of the primate T-cell leukemia viruses (PTLV), or of cells expressing GLUT1, for:
said compounds being selected for their ability to bind specifically to said GLUT1,
For illustration purpose, screened compounds mentioned above can be selected for their ability to bind specifically to said GLUT1, or fragments of GLUT1, according to the following method using a EGFP-tagged GLUT1-binding component derived from PTLV RBD (receptor binding domain) as an example of such compound able to bind to GLUT1.
A EGFP-tagged Glut1-binding component derived from PTLV RBD is applied onto live or fixed suspension or attached cells. After washes with appropriate buffer, cells are incubated for 30 min at RT, washed and analyzed or quantified as attached on an appropriate support on a fluorescent microscope or as individual cell suspension on a fluorescent analysis ell sorter (FACS). Alternatively, a non-fluorescent GLUT1-binding component derived from PTLV RBD is applied as described above and revealed with a secondary fluorochrome-tagged reagent such as a fluorochrome-tagged secondary antibody directed against the PTLV RBD or against a non fluorochrome tag attached to the said PTLV RBD component.
The invention relates more particularly to the use as defined above, of fragments of GLUT1 chosen among the followings:
These fragments of GLUT1 correspond to the predicted extracellular loops of human GLUT1 as described by Mueckler, M., and C. Makepeace. 1997. Identification of an amino acid residue that lies between the exofacial vestibule and exofacial substrate-binding site of the GLUT1 sugar permeation pathway. J Biol Chem. 272(48):30141-6.
The invention also concerns the use of compounds selected for their ability to bind specifically to GLUT1 as defined above, for the preparation of drugs for the prevention or the treatment of pathologies linked to an infection of an individual with a PTLV, such as pathologies corresponding to adult T cell leukemia (ATL), HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP), as well as other HTLV-associated syndromes such as large granular lymphocyte (LGL) leukaemia (Loughran, T. P., K. G. Hadlock, R. Perzova, T. C. Gentile, Q. Yang, S. K. Foung, and B. J. Poiesz. 1998. Epitope mapping of HTLV envelope seroreactivity in LGL leukaemia. Br J. Haematol. 101(2):318-24), uveitis (Mochizuki, M., A. Ono, E. Ikeda, N. Hikita, T. Watanabe, K. Yamaguchi, K. Sagawa, and K. Ito. 1996. HTLV-I uveitis. J Acquir Immune Defic Syndr Hum Retrovirol. 13 Suppl 1:S50-6), infective dermatitis (La Grenade, L., R. A. Schwartz, and C. K. Janniger. 1996. Childhood dermatitis in the tropics: with special emphasis on infective dermatitis, a marker for infection with human T-cell leukemia virus-I. Cutis. 58(2):115-8), arthropathies (Nishioka, K., T. Sumida, and T. Hasunuma. 1996. Human T lymphotropic virus type I in arthropathy and autoimmune disorders. Arthritis Rheum. 39(8):1410-8), cutaneous T cell lymphoma (mycosis fungoides) (1. Hall, W. W., C. R. Liu, O. Schneewind, H. Takahashi, M. H. Kaplan, G. Roupe, and A. Vahlne. 1991. Deleted HTLV-I provirus in blood and cutaneous lesions of patients with mycosis fungoides. Science. 253(5017):317-20. 2. Zucker-Franklin, D., B. A. Pancake, M. Marmor, and P. M. Legler. 1997. Reexamination of human T cell lymphotropic virus (HTLV-I/II) prevalence. Proc Natl Acad Sci USA. 94(12):6403-7), polymyositis (Saito M, Higuchi I, Saito A, Izumo S, Usuku K, Bangham C R, Osame M. Molecular analysis of T cell clonotypes in muscle-infiltrating lymphocytes from patients with human T lymphotropic virus type 1 polymyositis. J Infect Dis. 2002 Nov. 1; 186(9):1231-41), and potentially other idiopathic diseases in which PTLV or PTLV sequences may be involved.
The invention relates more particularly to the use for the preparation of drugs for the prevention or the treatment of pathologies linked to an infection of an individual with a PTLV, of compounds chosen among the followings:
The invention also relates to the use of compounds selected for their ability to bind specifically to GLUT1 as defined above, for the preparation of drugs for the prevention or the treatment of pathologies linked to an overexpression of GLUT1 on cell surfaces, such as
The invention relates more particularly to the use for the preparation of drugs for the prevention or the treatment of pathologies linked to an overexpression of GLUT1 on cell surfaces, of compounds chosen among the followings:
The invention relates more particularly to the use of polypeptides corresponding to the envelope proteins of PTLV, or fragments or sequences derived thereof, said polypeptides being selected for their ability to bind specifically to the ubiquitous vertebrate glucose transporter GLUT1 represented by SEQ ID NO: 2, or of nucleotide sequences encoding said polypeptides, for the preparation of drugs for the prevention or the treatment of pathologies linked to an overexpression of GLUT1 on cell surfaces, and the in vitro diagnosis of said pathologies.
The invention concerns more particularly the use as defined above, of polypeptides able to bind to at least one of the above mentioned fragments of GLUT1 corresponding to SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31, and SEQ ID NO: 32.
The invention concerns more particularly the use as defined above, of polypeptides able to bind to at least the fragment of GLUT1 corresponding to SEQ ID NO: 32.
The invention concerns more particularly the use as defined above, of GLUT1 binding polypeptides mentioned above chosen among the followings:
The invention concerns more particularly the use mentioned above of GLUT1 binding polypeptides as defined above, characterized in that the treated or detected pathologies are the followings:
The invention relates more particularly to the use of compounds selected for their ability to bind specifically to GLUT1 as mentioned above, and more particularly GLUT1 binding polypeptides as defined above, for the in vitro detection of GLUT1 on cell surfaces in the frame of processes for the in vitro diagnosis of pathologies linked to an overexpression of GLUT1 on cell surfaces, such as pathologies defined above, said processes comprising the following steps:
The invention concerns more particularly the use of compounds as defined above for the in vitro diagnosis of cancers, characterized in that the compounds used are chosen among the compounds defined above selected for their ability to bind specifically to GLUT1.
The invention relates more particularly to the use as defined above, of GLUT1 binding polypeptides, or of nucleotide sequences encoding said polypeptides, for the preparation of drug vectors containing at their surface said polypeptides, said vectors being useful for targeting GLUT1 overexpressing cells for the prevention or the treatment of pathologies linked to an overexpression of GLUT1 on cell surfaces, said vectors containing molecules active against said pathologies, or containing genes in the frame of gene therapy of these pathologies.
The invention relates more particularly to the use as defined above, of GLUT1 binding polypeptides, or of nucleotide sequences encoding said polypeptides, for the preparation of drug vectors containing at their surface GLUT1 binding polypeptides, said vectors being useful for targeting GLUT1 overexpressing tumor cells, or cells involved in the inflammatory mechanism, or activated cells of the immune system, or cells of the central nervous system, for the prevention or the treatment of related pathologies as defined above.
The invention concerns more particularly the use of GLUT1 binding polypeptides, or of nucleotide sequences encoding said polypeptides, for the preparation of drug vectors as defined above, wherein the molecules active against the pathologies are antitumor molecules, or molecules against inflammatory conditions, immune or auto-immune diseases, or disorders of the central nervous system.
The invention also relates to the use of nucleotide sequences encoding polypeptides compounds selected for their ability to bind specifically to GLUT1 as defined above, such as nucleotide sequences encoding the polypeptides defined above, or fragments thereof, for the preparation, by substitution of one or several nucleotides of said nucleotide sequences, of mutant nucleotide sequences encoding corresponding mutant polypeptides unable to bind to GLUT1.
The invention also concerns the use of mutant polypeptides unable to bind to GLUT1 as defined above:
The invention relates more particularly to the use as defined above, of mutant polypeptides corresponding to the polypeptides defined above, wherein:
are substituted by another aminoacid, natural or not, such as mutant polypeptides corresponding to the polypeptides mentioned above wherein said D and/or A residues are substituted by A.
The invention also relates to the use of mutant nucleotide sequences encoding corresponding mutant polypeptides unable to bind to GLUT1 as defined above, for the preparation of transgenic mammal cells expressing said mutant polypeptides, said cells having a negative transdominant effect with regard to PTLV, thus preventing infection and dissemination of this latter in the organism.
The invention also concerns pharmaceutical compositions containing GLUT1 represented by SEQ ID NO: 2, or fragments or sequences derived thereof, said fragments or derived sequences being able to bind to the envelope proteins of the primate T-cell leukemia viruses (PTLV), in association with a pharmaceutically acceptable carrier.
The invention relates more particularly to pharmaceutical compositions containing mutant polypeptides corresponding to the polypeptides defined above, wherein:
are substituted by another aminoacid, natural or not, such as mutant polypeptides corresponding to the polypeptides mentioned above wherein said D and/or A residues are substituted by A,
in association with a pharmaceutically acceptable carrier.
The invention also concerns transgenic mammal cells expressing mutant polypeptides unable to bind to GLUT1 as defined above, said cells having a negative transdominant effect with regard to PTLV, thus preventing infection and dissemination of this latter in the organism.
The invention relates more particularly to pharmaceutical compositions containing transgenic mammal cells as defined above, in association with a pharmaceutically acceptable carrier.
The invention also concerns therapeutic vectors useful for targeting GLUT1 overexpressing cells in pathologies linked to an overexpression of GLUT1 on cell surfaces, such as defined above, said vectors containing at their surface GLUT1 binding polypeptides chosen among those defined above, and containing molecules active against said pathologies, as defined above, or containing genes in the frame of gene therapy.
The invention relates more particularly to pharmaceutical compositions containing therapeutic vectors as described above, in association with a pharmaceutically acceptable carrier.
The invention also relates to a method for the screening of compounds useful for:
said method comprising:
The invention relates more particularly to a method for the screening of compounds useful for the prevention or the treatment of pathologies linked to an overexpression of GLUT1 on cell surfaces, and the in vitro diagnosis of said pathologies, comprising the steps described above:
The invention also concerns a method for the in vitro diagnosis pathologies linked to an overexpression of GLUT1 on cell surfaces, characterized in that it comprises:
The invention relates more particularly to a method as defined above for the in vitro diagnosis of pathologies mentioned above.
The invention also concerns a kit for the in vitro diagnosis of pathologies linked to an overexpression of GLUT1 on cell surfaces as described above, comprising compounds, and more particularly polypeptides, selected for their ability to bind specifically to GLUT1 as defined above, said compounds or polypeptides being optionally labeled, and, if necessary reagents for the detection of the binding of said compounds or polypeptides to GLUT1 initially present on cell surfaces in the biological sample.
The invention is further illustrated with the detailed description hereafter of the determination of GLUT1 as a specific receptor for PTLV RBD.
The human T-cell leukemia virus (HTLV) type 1 and 2 are present in all areas of the world as endemic or sporadic infectious agents [Slattery, 1999]. The etiological role of HTLV-1 in adult T cell leukemia (ATL) and tropical spastic paraparesis/HTLV-associated myelopathy (TSP/HAM) has been well established [Poiesz, 1980; Yoshida, 1982; Gessain, 1985; Osame, 1986]. The apparently restricted tropism of HTLV to T lymphocytes in infected patients[Cavrois, 1996; Hanon, 2000] contrasts with the ability of the viral-encoded envelope glycoprotein (Env) to bind to and direct entry into all vertebrate cell types tested in vitro[Sutton, 1996; Trejo, 2000; Kim, 2003]. Retroviral infections depend on early interactions between Env and cellular receptors. Identification of cellular receptors and coreceptors for other retroviral envelopes have helped to elucidate certain aspects of retrovirus physiopathology as well as their transmission and spreading within organisms and populations[Berger, 1999; Clapham, 2001; Weiss, 2002]. However, no clear association between HTLV Env and HTLV-associated diseases has been established and the identity of the receptor(s) for HTLV-1 and HTLV-2 Env has remained elusive.
Numerous cell surface components have been shown to play a role in HTLV Env-mediated syncytia formation [Niyogi, 2001; Daenke, 1999; Hildreth, 1997]. Nevertheless, HTLV Env-dependent cell membrane fusion and syncytia formation appear to be distinct from receptor binding per se [Denesvre, 1996; Daenke, 2000; Kim, 2000; Kim, 2003]. The search for HTLV Env receptor has been hindered in part by its ubiquitous presence [Sutton, 1996; Trejo, 2000; Jassal, 2001; Kim, 2003]. Additionally, the induction of rampant syncytium formation in cell culture upon expression of HTLV Env [Hoshino, 1983; Nagy, 1983] has prevented efficient and persistent Env expression. Based on our observation that the HTLV Env amino terminal domain shares striking structural and functional homology with that of murine leukemia viruses (MLV), we defined HTLV Env receptor-binding domain (RBD) and derived HTLV Env-based tools that overcome the problem of syncytia formation [Kim, 2000; Kim, 2003]. We were thus able to follow specific interactions between the Env RBD and a primary HTLV receptor. Using these tools, we have previously shown that the HTLV receptor is expressed on the surface on T lymphocytes, the major HTLV reservoir in vivo, only following T cell receptor activation[Manel, 2003].
Here we describe striking metabolic alterations in cell cultures following expression of HTLV envelopes as well as HTLV receptor binding domains. These alterations are characterized by a defect in the acidification of the cell culture medium associated with a decreased lactate production and a decline in glucose consumption and uptake. These observations as well as the knowledge that Env receptors for the related MLV and most of the gammaretrovirus belong to the family of multiple-membrane spanning transporters[Overbaugh, 2001] prompted us to test ubiquitous lactate and glucose transport-associated molecules as receptors for HTLV Env. We show that the ubiquitous GLUT-1 glucose transporter, present in all vertebrates, is an essential and specific component of the receptor for HTLV. Moreover, interaction of GLUT-1 with the entire HTLV-1 and HTLV-2 envelopes as well as the truncated HTLV-1 and HTLV-2 RBDs alters glucose metabolism.
HTLV Envelopes Alter Lactate Metabolism
Cell proliferation in standard culture media is accompanied by acidification of the milieu that translates into a color change from red to yellow tones in the presence of the phenol-red pH indicator. Upon transfection of either highly syncytial HTLV-1 and HTLV-2 envelopes, or a non-syncytial chimeric envelope that harbors the HTLV-1 RBD in a MLV Env backbone (H183FEnv), culture medium did not readily acidify, and harbored red tones for several days post-transfection (
Decrease of pH in cell culture is primarily due to extracellular accumulation of lactate [Warburg, 1956]. Lactate is the major byproduct of anaerobic glycolysis in vitro and its excretion is mediated by an H+/lactate symporter [Halestrap, 1999]. We monitored lactate content in culture supernatants following transfection of various retroviral envelopes and RBD. Lactate accumulation was consistently 3-fold lower in H183FEnv- and HTLV RBD-transfected cells than in control- or MLV Env-transfected cells (
Receptor Binding and Lactate Metabolism
To examine whether a direct relationship exists between binding of the HTLV envelope receptor and diminished extracellular acidification and lactate accumulation, we attempted to generate HTLV-1 RBD (H1RBD) mutants with impaired receptor binding capacities. To this end, mutations resulting in single alanine substitutions were introduced at two different positions in H1RBD, D106 and Y114 which are highly conserved among primate T-lymphotropic viruses. Although both D106A and Y114A RBD mutants were expressed and secreted as efficiently as the wild-type H1RBD (
Extracellular lactate accumulates in cell cultures following its transport across cellular membranes by the MCT1 monocarboxylate transporter[Garcia, 1994]. Because HTLV and MLV share a common organization of the extracellular envelope [Kim, 2000] and the receptors for MLV Env are multispanning metabolite transporters [Overbaugh, 2001], we assessed whether the HTLV RBD bound to MCT1. Moreover, similar to our previous data concerning expression of the HTLV receptor on T cells [Manel, 2003], expression of MCT1 chaperone CD147 [Kirk, 2000] increases during T cell activation [Kasinrerk, 1992]. However, separate and combined overexpression of MCT1 and CD 147 did not result in increased H1RBD binding, arguing against a role for these molecules as receptors for HTLV Env.
HTLV Receptor and Glucose Metabolism
In addition to a decrease in extracellular lactate accumulation, expression of the HTLV RBD also led to decreased intracellular lactate content, indicative of metabolic alterations upstream of lactate transport. In cell cultures, lactate accumulation results from the degradation of glucose during anaerobic glycolysis. Therefore, we assessed whether the decreased accumulation of lactate observed upon expression of HTLV RBD was linked to glucose metabolism. We measured glucose consumption as normalized to cellular protein content. Glucose consumption of cells expressing an HTLV RBD within the context of the H183FEnv entire envelope or the H1RED was significantly decreased as compared to control cells (
HTLV Envelopes Bind Glucose Transporter-1
A simple model whereby the HTLV envelope inhibits glucose consumption via direct binding to a glucose transporter can explain the metabolic effects described above. Upon evaluation of the different glucose transporter candidates, GLUT-1 appears to be the only one encompassing all the known properties of the HTLV receptor. Indeed, GLUT-1 expression is increased upon glucose deprivation and is transports glucose in all vertebrate cells [Mueckler, 1985], while fructose is transported by GLUT-5. Furthermore, GLUT-1 is not expressed on resting primary T cells and its expression is induced upon T cell activation [Rathmell, 2000; Chakrabarti, 1994] with kinetics that are strikingly similar to what we have reported for the HTLV receptor [Manel, 2003]. Since human but not murine erythrocytes have been described to be the cells exhibiting the highest concentration of GLUT-1[ Mueckler, 1994], we evaluated HTLV receptor availability on freshly isolated red blood cells. Binding of H1RBD on human erythrocytes was strikingly efficient, reaching levels higher than those observed on any other tested cell type, whereas ARBD binding to erythrocytes was minimal (
In order to directly test the ability of HTLV envelopes to bind GLUT-1, we derived a tagged GLUT-1 expression vector and overexpressed this protein in HeLa cells. Both H1RBD and H2RBD binding was dramatically increased upon GLUT-1 overexpression (
Interaction of GLUT-1 with its ligand cytochalasin B inhibits glucose transport [Kasahara, 1977]. Since we showed that binding of HTLV envelopes to GLUT-1 inhibits glucose consumption and uptake, we tested whether cytochalasin B would abrogate HTLV RBD binding. Indeed, cytochalasin B treatment of Jurkat T cells dramatically inhibited binding of H1RBD, whereas binding of ARBD was not affected (
Viral receptor permits entry and thus infection. No cellular system currently exists that lacks GLUT-1 expression. Thus, we developed a system in which HTLV infection is specifically inhibited at the level of envelope-receptor interaction. In this system, overexpression of HTLV-2 RBD interferes with infecting incoming HTLV particles and specifically decreases HTLV titers by at least 2 logs, while no effect is detected on control AMLV titers. To determine if GLUT-1 is an entry receptor for HTLV, we overexpressed GLUT-1, GLUT-3 or Pit2 in addition to the interfering H2RBD. While Pit2 and GLUT-3 had no effect on HTLV titers, GLUT-1 completely alleviated the interference to infection induced by H2RBD (
Discussion
Here we show that HTLV-1 and -2 envelopes interact with GLUT-1 through their receptor binding domains. This interaction strongly inhibits glucose consumption and glucose uptake, leading to decreased lactate production and a block in extracellular milieu acidification. Mutations that specifically altered receptor binding of both HTLV-1 and 2 envelopes released the block in glucose consumption, indicative of a direct correlation between receptor binding determinants in the HTLV envelopes and glucose transport. Glucose starvation was rapidly followed by increased binding of HTLV envelopes, highlighting a nutrient-sensing negative feedback loop between glucose availability and cell surface HTLV receptor expression. Further evidence converged to identify GLUT-1 as the receptor, including increased binding of HTLV RBD upon overexpression of GLUT-1 but not GLUT-3, immunoprecipitation of GLUT-1 by H1RBD but not the receptor-binding mutant H1RBD Y114A, uppermost binding of HTLV RBD on human erythrocytes, where GLUT-1 is the major glucose transporter isoform, and no binding of HTLV RBD on human primary hepatocytes and murine erythrocytes, where GLUT-1 is minimally expressed. Finally, GLUT-1 could specifically alleviate interference to infection induced by HTLV RBD. GLUT-1 fits all other known properties of the HTLV receptor. Indeed, as previously demonstrated for the HTLV receptor [Manel, 2003], GLUT-1, but not the GLUT 2-4 isoforms, is not expressed on resting T lymphocytes [Chakrabarti, 1994; Korgun, 2002] and is induced upon immunological [Frauwirth, 2002; Yu, 2003] or pharmacological [Chakrabarti, 1994] activation. Moreover, GLUT-1 orthologues are highly conserved among vertebrates, but are highly divergent between vertebrates and insects [Escher, 1999].
GLUT-1 is thus a new member of the multimembrane spanning metabolite transporters that serve as receptors for retroviral envelopes. Interestingly, until now, all envelopes that recognize these receptors have been encoded by retroviruses that have a so-called simple genetic organization, such as MLV, feline leukemia viruses, porcine endogenous retrovirus and the gibbon ape leukemia virus [Overbaugh, 2001], whereas HTLV belongs to the so-called complex retroviruses which code for several additional regulatory proteins. However, we have shown that in contrast to the wide phylogenetic divergence of their genomic RNA, the envelopes of HTLV and MLV share a similar modular organization with some highly conserved amino acid motifs in their respective receptor binding domains [Kim, 2000].
Cell-to-cell contact appears to be required for HTLV transmission, and the cytoskeleton appears to play a major role in this process [Igakura, 2003]. Indeed, we observed that the HTLV receptor, despite pancellular expression, is specifically concentrated to mobile membrane regions and cell-to-cell contact areas. It should therefore be expected that the HTLV envelope receptor is associated to the cytoskeleton. Importantly, a cytoplasmic-binding partner of GLUT-1, GLUT1CBP, which encodes a PDZ domain, has been reported to link GLUT-1 to the cytoskeleton [Bunn, 1999]. It will therefore be interesting to evaluate the respective roles of the HTLV envelope, its cytoskeleton-associated cellular partners, such as GLUT-1, GLUT1CBP and their immediate interacting cell components.
Because expression of the HTLV receptor is induced upon glucose starvation, transmission of HTLV may be more efficient in cells that are locally starved for glucose, such as lymphocytes in lymph nodes [Yu, 2003]. Furthermore, the ability of circulating erythrocytes to dock HTLV, as shown here, might provide a means to distribute HTLV to such tissues.
The identification of GLUT-1 as a receptor for HTLV envelopes provides additional clues as to the ubiquitous in vitro expression of the receptor on cell lines and the paradoxical restriction of HTLV tropism to T lymphocytes in vivo. Rapid and dramatic metabolic alterations associated with the blockade of glucose consumption are likely to take place upon expression of the HTLV envelope in vivo, early after infection. Therefore, we propose that in vivo, HTLV infection initially spreads with a large tropism, however early after infection the vast majority of cells that are highly dependent on GLUT-1 activity are rapidly eliminated. In contrast, resting T lymphocytes that have an extremely low metabolic rate and as such are much less dependent on glucose uptake, can tolerate this effect and are therefore maintained in vivo. Furthermore, local imbalances in the access to glucose following HTLV infection may lead to specific physiological alterations [Akaoka, 2001]. In this regard, it will be of interest to study the potential relationship between HTLV-associated neuropathologies and the specific dependence of neurons on GLUT-1 mediated glucose consumption [Siegel, 1998].
Methods.
Cell culture. 293T human embryonic kidney and HeLa cervical carcinoma cells were grown in Dulbecco's modified Eagle medium (DMEM) with high glucose (4.5 g/l) and Jurkat T-cells were grown in RPMI supplemented with 10% fetal bovine serum (FBS) at 37° C. in a 5% CO2-95% air atmosphere. For glucose starvation experiments, cells were grown in either glucose-free DMEM (Life Technologies) or glucose-free RPMI—(Dutscher) with 10% dialyzed FBS (Life Technologies) and glucose (1 g/l) was supplemented when indicated.
Expression vectors. Full length envelope expression vectors for HTLV-1 (pCEL/2[Denesvre, 1995]) and Friend ecotropic MLV (pCEL/F [Denesvre, 1995]), have been previously described. For the HTLV-2 envelope, a fragment from pHTE2 [Rosenberg, 1998] encompassing the tax, rex and env genes and the 3′ LTR was inserted in the pCSI [Battini, 1999] vector (pCSIX.H2). Full length envelope expression vectors for amphotropic MLV (pCSI.A), or devoid of its R peptide (pCSI.AΔR), and H183FEnv that contains the N-terminal 183 amino acids of the HTLV-1 receptor-binding domain in the F-MLV envelope background, as well as truncated envelope expression vectors, derived from pCSI and encoding either of the first 215 residues of HTLV-1 SU (H1RBD), the first 178 residues of HTLV2-SU (H2RBD) or the first 397 residues of the amphotropic murine leukemia virus (MLV) SU (ARBD), fused to a C-terminal rabbit IgG Fc tag (rFc) or to EGFP (H2RBD-GFP). All point mutations introduced in HTLV-1 and -2 RBD constructs were generated using the quickchange site-directed mutagenesis method and mutations were verified by sequencing. Human Glut-1 and Glut-3 cDNA were amplified by PCR from the pLib HeLa cDNA library (Clontech), and inserted into pCHIX, a modified version of the pCSI vector that contains a cassette comprising a factor Xa cleavage site, two copies of the hemagglutinin (HA) tag, and a histidine tag. The resulting construct (pCHIX.hGLUT1) encodes a GLUT-1 protein with a HA-His tag at the C-terminal end. GLUT-1 and GLUT-3 were also inserted in a modified pCSI vector containing a DsRed2 C-terminal tag. Similarly, human CD147 was amplified from 293T total RNA by RT-PCR and inserted into the pCHIX backbone in frame with the HA-His tag (pCHIX.hCD147).
Envelope expression and metabolic measurements. 293T cells were transfected with the various envelope expression vectors using a modified version of the calcium phosphate method. After an overnight transfection, cells were washed in phosphate-buffered saline (PBS) and fresh medium was added. Media were harvested at the indicated time points, filtered through a 0.45-μm pore-size filter, and lactate and glucose were measured with enzymatic diagnostic kits (Sigma). Values were normalized to cellular protein content using the Bradford assay (Sigma) after solubilization of cells in lysis buffer (50 mM Tris-HCl pH 8.0, 150 mM NaCl, 0.1% sodium dodecyl sulfate, 1.0% Nonidet P-40, 0.5% deoxycholate) and clarification by centrifugation.
Assay of hexose uptake. 2-deoxy-D[1-−3H]glucose, D[U-14C]fructose and 3-O-[14C]methyl-D-glucose were obtained from Amersham. Hexose uptake assay were adapted from Harrison et al (REF HARRISON 1991). After transfection, approximatively 250,000 were seeded/well in 24-well plates. The next day, cells were washed two times in PBS, incubated in serum-free DMEM, washed one time in serum-free glucose-free DMEM, and incubated for 20′ in 500 μl serum-free glucose-free DMEM modulo inhibitors (20 μM cytochalasin B, 300 μM phloretin; SIGMA). Uptake was initiated by adding labeled hexoses to a final concentration of 0.1 mM (2 μCi/ml for 2-2-deoxy-D[1-3H]glucose and 0.2 μCi/ml for D[U-14C]fructose and 3-O-[14C]methyl-D-glucose) and cells were incubated for 5′ additional minutes. Cells were then resuspended in 500 μl cold serum-free glucose-free DMEM, wash one time in serum-free glucose-free DMEM, and solubilized in 400 μl of 0.1% SDS. 3 μl was used for Bradford normalization, while the rest was used for detection of either 3H or 14C by liquid scintillation in a Beckman counter.
Western blots. Culture media (10 μl) from 293T cells expressing wild type or mutant HTLV-1 RBDs, and/or GLUT-1 or GLUT-3 expression vecotor. were subjected to electrophoresis on SDS-15% acrylamide gels, transferred onto nitrocellulose (Protran; Schleicher & Schuell), blocked in PBS containing 5% powdered milk and 0.5% Tween 20, probed with either a 1:5000 dilution of horseradish peroxidase-conjugated anti-rabbit immunoglobulin or 1:2000 dilution of anti-HA 12CA5 (Roche) monoclonal antibody followed by a 1:5000 dilution of horseradish peroxidase-conjugated anti-mouse immunoglobulin, and visualized using an enhanced chemiluminescence kit (Amersham).
Binding assays. Binding assays were carried out as previously described [Manel, 2003]. Briefly, 5×105 cells (293T, HeLa, Jurkat or freshly isolated human erythrocytes) were incubated with 500 μl of H1RBD, H2RBD or ARBD supernatants for 30 min at 37° C., washed with PBA (1% BSA, 0.1% sodium azide in PBS), and incubated with a sheep anti-rabbit IgG antibody conjugated to fluorescein isothiocyanate (Sigma). When indicated, cytochalasin B (20 μM; Sigma) was added to cells for 1 hour prior to binding analyses. Binding was analyzed on a FACSCalibur (Becton Dickinson) and data analysis was performed using CellQuest (Becton Dickinson) and WinMDI (Scripps) softwares.
Infections. 293T cells were transfected in 6-wells plate, and one day after transfection, medium was replaced by high glucose DMEM supplemented with fructose (5 g/l) and non-essential amino acids. The next day, infection was initiated by adding supernatants containing MLV particles pseuodtyped with either HTLV-2 or A-MLV envelopes. The following day, fresh medium was added, and 24 hours later cells were fixed and stained for alkaline phosphatase activity and dark focus of infection were counted. Viral particles were obtained by transfecting 293T cells with pLAPSN, pGagPoule and either pCSIX.H2 or pCSI.A, and harvesting the 0.45 μm-filtered supernatants 24 hours latter.
Figure Legends
15. Daenke, S., McCracken, S. A. & Booth, S. Human T-cell leukaemia/lymphoma virus type 1 syncytium formation is regulated in a cell-specific manner by ICAM-1, ICAM-3 and VCAM-1 and can be inhibited by antibodies to integrin beta2 or beta7. J Gen Virol 80, 1429-36. (1999).
| Number | Date | Country | Kind |
|---|---|---|---|
| 03291067 | May 2003 | EP | regional |
This application is a division of application Ser. No. 10/555,289 filed on Nov. 2, 2005; which is the 35 U.S.C. 371 national stage of International application PCT/EP04/04624 filed on Apr. 30, 2004; which claimed priority to Europe application 03291067.1 filed May 2, 2003. The entire contents of each of the above-identified applications are hereby incorporated by reference.
| Number | Name | Date | Kind |
|---|---|---|---|
| 20100056448 | Battini et al. | Mar 2010 | A1 |
| Number | Date | Country |
|---|---|---|
| WO 9213946 | Aug 1992 | WO |
| WO 9641193 | Dec 1996 | WO |
| WO 9803197 | Jan 1998 | WO |
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| Number | Date | Country | |
|---|---|---|---|
| 20100056448 A1 | Mar 2010 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10555289 | US | |
| Child | 12547924 | US |
