eLife (Nov 2017)

CHIP as a membrane-shuttling proteostasis sensor

  • Yannick Kopp,
  • Wei-Han Lang,
  • Tobias B Schuster,
  • Adrián Martínez-Limón,
  • Harald F Hofbauer,
  • Robert Ernst,
  • Giulia Calloni,
  • R Martin Vabulas

DOI
https://doi.org/10.7554/eLife.29388
Journal volume & issue
Vol. 6

Abstract

Read online

Cells respond to protein misfolding and aggregation in the cytosol by adjusting gene transcription and a number of post-transcriptional processes. In parallel to functional reactions, cellular structure changes as well; however, the mechanisms underlying the early adaptation of cellular compartments to cytosolic protein misfolding are less clear. Here we show that the mammalian ubiquitin ligase C-terminal Hsp70-interacting protein (CHIP), if freed from chaperones during acute stress, can dock on cellular membranes thus performing a proteostasis sensor function. We reconstituted this process in vitro and found that mainly phosphatidic acid and phosphatidylinositol-4-phosphate enhance association of chaperone-free CHIP with liposomes. HSP70 and membranes compete for mutually exclusive binding to the tetratricopeptide repeat domain of CHIP. At new cellular locations, access to compartment-specific substrates would enable CHIP to participate in the reorganization of the respective organelles, as exemplified by the fragmentation of the Golgi apparatus (effector function).

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