Plasma membrane caveolae are specialized domains that have a central role in modulating intracellular cholesterol homeostasis. Alterations in the expression of caveolin-1, a cholesterol-binding proteins of caveolae, and accumulation of unesterified cholesterol within a caveolin-1 containing subcellular compartment, has been shown to occur within tissues and/or cultured cells derived from mice and humans with Niemann Pick type C (NPC). Our preliminary studies indicate that the NPC gene product (NPC1) is found in the detergent insoluble cellular fraction the same cellular fraction enriched in caveolae, implicating a direct relationship between NPC1 and caveolar function. Based on these observations, we believe that NPC is a unique and important model in which to define further the relationship between caveolae and intracellular cholesterol trafficking. The goals of this research project are to: 1) Determine if NPC1 is localized to caveolae. 2) Determine if cholesterol is enriched within caveolae isolated from NPC fibroblasts. 3) Determine the contribution of LDL-derived cholesterol and endogenously synthesized cholesterol to caveolae in NPC. 4) Determine if cholesterol efflux from caveolae from LDL-derived cholesterol and endogenously synthesized cholesterol to HDL is disrupted in NPC. 5) Determine the effects of disrupting caveolin-1 expression in heterozygous NPC cells on the trafficking of LDL-derived cholesterol and endogenously synthesized cholesterol to caveolae. These experiments will directly address the role of caveolae in cholesterol homeostasis as well as define the intracellular trafficking pathways utilized to regulate the removal of excess cholesterol mediated by HDL, an important process responsible for the preventing of atherosclerosis.
