Lysosome membrane lipid microdomains: novel regulators of chaperone-mediated autophagy

EMBO J. 2006 Sep 6;25(17):3921-33. doi: 10.1038/sj.emboj.7601283. Epub 2006 Aug 17.

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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Autophagy / physiology*
  • Cholesterol / metabolism
  • Intracellular Membranes / metabolism*
  • Intracellular Membranes / ultrastructure
  • Lysosomal-Associated Membrane Protein 2 / genetics
  • Lysosomal-Associated Membrane Protein 2 / metabolism*
  • Lysosomes / metabolism*
  • Lysosomes / ultrastructure
  • Male
  • Membrane Microdomains / metabolism*
  • Membrane Microdomains / ultrastructure
  • Mice
  • Microscopy, Immunoelectron
  • Molecular Chaperones / physiology*
  • Molecular Sequence Data
  • Mutation
  • NIH 3T3 Cells
  • Protein Transport
  • Rats
  • Rats, Wistar

Substances

  • Lysosomal-Associated Membrane Protein 2
  • Molecular Chaperones
  • Cholesterol