The role of chaperone-mediated autophagy in huntingtin degradation

PLoS One. 2012;7(10):e46834. doi: 10.1371/journal.pone.0046834. Epub 2012 Oct 11.

Abstract

Huntington Disease (HD) is caused by an abnormal expansion of polyQ tract in the protein named huntingtin (Htt). HD pathology is featured by accumulation and aggregation of mutant Htt in striatal and cortical neurons. Aberrant Htt degradation is implicated in HD pathogenesis. The aim of this study was to investigate the regulatory role of chaperone-mediated autophagy (CMA) components, heat shock protein cognate 70 (Hsc70) and lysosome-associated protein 2A (LAMP-2A) in degradation of Htt fragment 1-552aa (Htt-552). A cell model of HD was produced by overexpression of Htt-552 with adenovirus. The involvement of CMA components in degradation of Htt-552 was determined with over-expression or silencing of Hsc70 and LAMP-2A. The results confirmed previous reports that both macroautophagy and CMA were involved in degradation of Htt-552. Changing the levels of CMA-related proteins affected the accumulation of Htt-552. The lysosomal binding and luminal transport of Htt-552 was demonstrated by incubation of Htt-552 with isolated lysosomes. Expansion of the polyQ tract in Htt-552 impaired its uptake and degradation by lysosomes. Mutation of putative KFERQ motif in wild-type Htt-552 interfered with interactions between Htt-552 and Hsc70. Endogenous Hsc70 and LAMP-2A interacted with exogenously expressed Htt-552. Modulating the levels of CMA related proteins degraded endogenous full-length Htt. These studies suggest that Hsc70 and LAMP-2A through CMA play a role in the clearance of Htt and suggest a novel strategy to target the degradation of mutant Htt.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs / genetics
  • Amino Acid Sequence
  • Animals
  • Autophagy*
  • Blotting, Western
  • HSC70 Heat-Shock Proteins / genetics
  • HSC70 Heat-Shock Proteins / metabolism*
  • HeLa Cells
  • Humans
  • Huntingtin Protein
  • Lysosomal Membrane Proteins / genetics
  • Lysosomal Membrane Proteins / metabolism*
  • Lysosomal-Associated Membrane Protein 2
  • Lysosomes / metabolism
  • Microscopy, Fluorescence
  • Molecular Chaperones / genetics
  • Molecular Chaperones / metabolism
  • Mutation
  • Nerve Tissue Proteins / chemistry
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism*
  • PC12 Cells
  • Peptide Fragments / genetics
  • Peptide Fragments / metabolism
  • Protein Binding
  • Proteolysis
  • RNA Interference
  • Rats

Substances

  • HSC70 Heat-Shock Proteins
  • HTT protein, human
  • Huntingtin Protein
  • LAMP2 protein, human
  • Lysosomal-Associated Membrane Protein 2
  • Lysosomal Membrane Proteins
  • Molecular Chaperones
  • Nerve Tissue Proteins
  • Peptide Fragments

Grants and funding

This work was partially supported by the National Natural Science Foundation of China (No 30930035), and by The Priority Academic Program Development of Jiangsu Higher Education Institutes and by Jiangsu Province's Outstanding Medical Academic Leader Program (LJ201139).The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.