title: Lysosome membrane lipid microdomains: novel regulators of chaperone-mediated autophagy.
abstract: Chaperone-mediated autophagy (CMA) is a selective mechanism for the degradation of soluble cytosolic proteins in lysosomes. The limiting step of this type of autophagy is the binding of substrates to the lysosome-associated membrane protein type 2A (LAMP-2A). In this work, we identify a dynamic subcompartmentalization of LAMP-2A in the lysosomal membrane, which underlies the molecular basis for the regulation of LAMP-2A function in CMA. A percentage of LAMP-2A localizes in discrete lysosomal membrane regions during resting conditions, but it exits these regions during CMA activation. Disruption of these regions by cholesterol-depleting agents or expression of a mutant LAMP-2A excluded from these regions enhances CMA activity, whereas loading of lysosomes with cholesterol significantly reduces CMA. Organization of LAMP-2A into multimeric complexes, required for translocation of substrates into lysosomes via CMA, only occurs outside the lipid-enriched membrane microdomains, whereas the LAMP-2A located within these regions is susceptible to proteolytic cleavage and degradation. Our results support that changes in the dynamic distribution of LAMP-2A into and out of discrete microdomains of the lysosomal membrane contribute to regulate CMA.
authors.affiliation: Department of Anatomy and Structural Biology, Marion Bessin Liver Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
authors.forename: Susmita
authors.initials: S
authors.lastname: Kaushik
authors.forename: Ashish C
authors.initials: AC
authors.lastname: Massey
authors.forename: Ana Maria
authors.initials: AM
authors.lastname: Cuervo
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001343:Autophagy / Q000502:physiology*; D002784:Cholesterol / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism* / Q000648:ultrastructure; D052119:Lysosomal-Associated Membrane Protein 2 / Q000235:genetics / Q000378:metabolism*; D008247:Lysosomes / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D021962:Membrane Microdomains / Q000378:metabolism* / Q000648:ultrastructure; D051379:Mice; D016253:Microscopy, Immunoelectron; D018832:Molecular Chaperones / Q000502:physiology*; D008969:Molecular Sequence Data; D009154:Mutation; D041681:NIH 3T3 Cells; D021381:Protein Transport; D051381:Rats; D017208:Rats, Wistar
chemical_list: D052119:Lysosomal-Associated Membrane Protein 2; D018832:Molecular Chaperones; D002784:Cholesterol