A Surveillance Function of the HSPB8-BAG3-HSP70 Chaperone Complex Ensures Stress Granule Integrity and Dynamism

Massimo Ganassi, Daniel Mateju, Ilaria Bigi, Laura Mediani, Ina Poser, Hyun O. Lee, Samuel J. Seguin, Federica F. Morelli, Jonathan Vinet, Giuseppina Leo, Orietta Pansarasa, Cristina Cereda, Angelo Poletti, Simon Alberti, Serena Carra

Research output: Contribution to journalArticle

Abstract

Stress granules (SGs) are ribonucleoprotein complexes induced by stress. They sequester mRNAs and disassemble when the stress subsides, allowing translation restoration. In amyotrophic lateral sclerosis (ALS), aberrant SGs cannot disassemble and therefore accumulate and are degraded by autophagy. However, the molecular events causing aberrant SG formation and the molecular players regulating this transition are largely unknown. We report that defective ribosomal products (DRiPs) accumulate in SGs and promote a transition into an aberrant state that renders SGs resistant to RNase. We show that only a minor fraction of aberrant SGs is targeted by autophagy, whereas the majority disassembles in a process that requires assistance by the HSPB8-BAG3-HSP70 chaperone complex. We further demonstrate that HSPB8-BAG3-HSP70 ensures the functionality of SGs and restores proteostasis by targeting DRiPs for degradation. We propose a system of chaperone-mediated SG surveillance, or granulostasis, which regulates SG composition and dynamics and thus may play an important role in ALS.

Original languageEnglish
Pages (from-to)796-810
Number of pages15
JournalMolecular Cell
Volume63
Issue number5
DOIs
Publication statusPublished - Sep 1 2016

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

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    Ganassi, M., Mateju, D., Bigi, I., Mediani, L., Poser, I., Lee, H. O., Seguin, S. J., Morelli, F. F., Vinet, J., Leo, G., Pansarasa, O., Cereda, C., Poletti, A., Alberti, S., & Carra, S. (2016). A Surveillance Function of the HSPB8-BAG3-HSP70 Chaperone Complex Ensures Stress Granule Integrity and Dynamism. Molecular Cell, 63(5), 796-810. https://doi.org/10.1016/j.molcel.2016.07.021