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The role of chaperone-mediated autophagy in huntingtin degradation

Lin Qi1, Xing-Ding Zhang, Jun-Chao Wu

  • 1Department of Pharmacology and Laboratory of Aging and Nervous Diseases, Soochow University School of Pharmaceutical Science, Suzhou, China.

Plos One
|October 17, 2012
PubMed

Insights

Chaperone-mediated autophagy (CMA) components, heat shock protein cognate 70 (Hsc70) and lysosome-associated protein 2A (LAMP-2A), regulate huntingtin (Htt) degradation. Modulating CMA proteins offers a strategy for clearing mutant Htt in Huntington Disease.

Area of Science:

  • Neuroscience
  • Cell Biology
  • Molecular Biology

Background:

  • Huntington Disease (HD) is a neurodegenerative disorder caused by expanded polyQ repeats in the huntingtin (Htt) protein.
  • Accumulation and aggregation of mutant Htt in neurons are hallmarks of HD pathology.
  • Dysfunctional protein degradation pathways, including autophagy, are implicated in HD pathogenesis.

Purpose of the Study:

  • To investigate the role of chaperone-mediated autophagy (CMA) components, Hsc70 and LAMP-2A, in the degradation of the Htt fragment 1-552aa (Htt-552).
  • To explore whether modulating CMA components can influence Htt degradation and potentially serve as a therapeutic strategy for HD.

Main Methods:

  • Established a cell model of HD by overexpressing Htt-552 using adenovirus.
  • Manipulated the expression levels of Hsc70 and LAMP-2A (overexpression or silencing) to assess their impact on Htt-552 degradation.
  • Utilized isolated lysosomes to study the direct interaction and transport of Htt-552.
  • Investigated the interaction between Htt-552 and Hsc70 by mutating a putative KFERQ motif.
  • Examined the interaction of endogenous Hsc70 and LAMP-2A with exogenously expressed Htt-552.
  • Assessed the effect of modulating CMA proteins on endogenous full-length Htt degradation.

Main Results:

  • Confirmed that both macroautophagy and CMA are involved in Htt-552 degradation.
  • Demonstrated that altering the levels of CMA proteins (Hsc70, LAMP-2A) affects Htt-552 accumulation.
  • Showed that expanded polyQ tracts in Htt-552 impair its lysosomal uptake and degradation.
  • Identified that mutation of the KFERQ motif in Htt-552 disrupts its interaction with Hsc70.
  • Confirmed interactions between endogenous Hsc70/LAMP-2A and exogenously expressed Htt-552.
  • Found that modulating CMA proteins leads to the degradation of endogenous full-length Htt.

Conclusions:

  • Hsc70 and LAMP-2A, via CMA, play a significant role in the clearance of huntingtin protein.
  • These findings suggest a novel therapeutic strategy targeting CMA for the degradation of mutant Htt in Huntington Disease.

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