Lysosome‐Associated Membrane Protein 1 Rescues Cholesterol Accumulation in NPC1 Mutant Cell by Enhancing Lysosome‐ER Contacts

Abstract

Niemann‐Pick type C (NPC) disease is a neurodegenerative disorder caused by mutations in NPC1 or NPC2 gene, encoding a lysosomal membrane and luminal protein, respectively. NPC disease is linked to the disruption of intracellular cholesterol trafficking and is characterized by excessive accumulation of free cholesterol in lysosomes. The functions of NPC1 and NPC2 proteins are involved in the exit of lysosomal cholesterol by poorly understood mechanisms. Understanding the molecular mechanisms involved in lysosomal cholesterol export is critical for NPC therapy.We hypothesized that the lysosome‐associated membrane protein 1 (LAMP‐1) can mediate lysosomal cholesterol export in the absence of NPC1 function. By filipin staining, we demonstrated that 2‐hydroxypropyl‐β‐cyclodextrin (HPβCD) or HPγCD treatment rescues lysosomal cholesterol accumulation in NPC1 mutant cells derived from NPC patient. By proteomic analysis, immunoblotting, and confocal microscopy, we showed that HPβCD or HPγCD treatment in NPC1 mutant cells increases the expression of the LAMP‐1 protein and redistributes lysosomes toward the cell periphery. Overexpression and knockdown of LAMP‐1 in HeLa cells suggested that LAMP‐1 plays an important role in lysosomal cholesterol export. By confocal microscopy, we further demonstrated that LAMP‐1 is involved in establishing membrane contacts between lysosomes and the endoplasmic reticulum (ER). By analyzing the cholesterol content and proteome profile of isolated lysosomes, we provide new insights on the effect of HPβCD and HPγCD in modulating lysosomal functions and in reducing lysosomal cholesterol accumulation in NPC1 mutant cells.In conclusion, our studies suggest that LAMP‐1 can restore cellular cholesterol homeostasis by modulating lysosome positioning, potentially enhancing lysosome‐to‐ER cholesterol transport for cholesterol esterification and metabolism. Further studies on LAMP‐1 functions and lysosome dynamics are warranted to better understand NPC disease mechanisms and to design effective therapies for NPC.Support or Funding InformationThis study was supported by the Startup Fund, Pilot Grant, and Seed Grant to B.S. from Meharry Medical College.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.