HORMONE INDUCED EFFECTS ON GLYCOLIPID METABOLISM

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The processing and assembly of glycosphingolipids, phospholipids and dolichols into mouse kidney lysosomes are studied to gain insight into a fundamental cellular process whose perturbation in genetic abnormalities affects several organs including the CNS. Mouse kidney glycolipid levels and composition are affected dramatically by testosterone induction of their synthesis and by mutations which block the exocytosis of proximal tubule cell multilamellar "lysosomal" bodies. Several pigmentation mutants with lysosomal enzyme secretion defects have been shown to have increases in kidney glycosphingolipids, dolichols and phospholipids. These abnormalities are thought to result from the formation of abnormal lysosomal organelles which then lead to a block in their exocytosis. In order to contribute to an understanding of these processes we propose to test the following hypotheses: 1) that both the saccharide and ceramide moieties influence the intracellular sorting of glycolipids: 2) that testosterone induces the biosynthesis of specific molecular species that are components of lysosomal organelles; 3) that mutations which block lysosomal exocytosis include defects that affect the formation of normal lysosomal membrane components. The lipid molecular species in different subcellular fractions from mouse kidney will be characterized and quantitated. In order to determine the subcellular sites of synthesis and sorting of "lysosomal" GSLs, the incorporation of radiolabeled precursors into specific lipid molecular species will be followed in kidney epithelial tissue culture cells. Primary and transformed kidney tissue culture cells from mouse models for Chediak-Higashi (beige) and Hermansky-Pudlak (pale ear, light ear and pallid) Syndromes will be prepared and utilized for the characterization of these mutations. Genetic homology with the human disorders will be examined by somatic cell hybridization techniques.