Research Project
6666087
DESCRIPTION (provided by applicant): The research goal is to investigate the biological roles of the Drosophila genes Palmitoyl Protein Thioesterase I and 2 (Ppt1 and Ppt2) in the developing and adult nervous system to facilitate the understanding of the pathogenesis of infantile neuronal ceroid lipofuscinosis (INCL). INCL belongs to the class of pediatric neurological disorder collectively called Batten Disease. Defects in human PPT1 lead to INCL, which is characterized by autofluorescent lipopigment inclusions, abnormal lysosomal function, extensive neuronal cell death in the developing brain, degeneration of cognitive, motor and visual functions, and premature death. Loss of PPT2 in mice also leads to similar characteristics including reduced brain size, extensive motor and neuronal degeneration, and lipopigment accumulation. PPT1 and PPT2 proteins reside in the lysosome and catalyze the removal of palmitoylated fatty acids attached to the cysteine residue of lipid-modified proteins. Although both proteins have comparable thioesterase activity in vitro, PPT2 cannot rescue the metabolic defects caused by loss of PPT1. In spite of molecular identification, studies identifying the underlying INCL pathological mechanism are limited by poor understanding of PPT1 and PPT2 normal functions. Relatively little is known about the basic biology of either lysosomal proteins, and how defective palmitoyl-protein thioesterases lead to neurotoxicity and degeneration. A fundamental understanding of Ppt1 and Ppt2 and their basic biology in a genetically tractable model system is essential. Previously we have shown that Drosophila Ppt1 exhibits Ppt1-specific enzyme activity and is likely to be the fly version of PPTI. Drosophila also contains a homologous PPT2 protein, Ppt2. We plan to (1) identify the spatial, temporal, and subcellular expression profile of Ppt1 and Ppt2 transcripts and proteins during development and adult; (2) generate Ppt2 loss-of-function mutations by P-element excision mutagenesis; and (3) analyze Ppt2 mutants and compare it to existing Ppt1 mutants at the molecular, cellular, genetic, and behavioral level. These results will allow us to generate a working model for how these proteins regulate neuronal development and maintenance, protein turnover, and intracellular trafficking. Such information may provide insight into the mechanisms of pathogenesis by identifying potential elements that are compromised in Batten Diseases.
