BAG3 and BAG6 differentially affect the dynamics of stress granules by targeting distinct subsets of defective polypepti
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ORIGINAL PAPER
BAG3 and BAG6 differentially affect the dynamics of stress granules by targeting distinct subsets of defective polypeptides released from ribosomes Laura Mediani 1 & Veronica Galli 1 & Arianna Dorotea Carrà 1 & Ilaria Bigi 1 & Jonathan Vinet 1 & Massimo Ganassi 1 & Francesco Antoniani 1 & Tatiana Tiago 1 & Marco Cimino 1 & Daniel Mateju 2 & Cristina Cereda 3 & Orietta Pansarasa 3 & Simon Alberti 2,4 & Jessica Mandrioli 5 & Serena Carra 1 Received: 26 May 2020 / Revised: 10 July 2020 / Accepted: 15 July 2020 # Cell Stress Society International 2020
Abstract Stress granules (SGs) are dynamic ribonucleoprotein granules induced by environmental stresses. They play an important role in the stress response by integrating mRNA stability, translation, and signaling pathways. Recent work has connected SG dysfunction to neurodegenerative diseases. In these diseases, SG dynamics are impaired because of mutations in SG proteins or protein quality control factors. Impaired SG dynamics and delayed SG dissolution have also been observed for SGs that accumulate misfolding-prone defective ribosomal products (DRiPs). DRiP accumulation inside SGs is controlled by a surveillance system referred to as granulostasis and encompasses the molecular chaperones VCP and the HSPB8-BAG3-HSP70 complex. BAG3 is a member of the BAG family of proteins, which includes five additional members. One of these proteins, BAG6, is functionally related to BAG3 and able to assist degradation of DRiPs. However, whether BAG6 is involved in granulostasis is unknown. We report that BAG6 is not recruited into SGs induced by different types of stress, nor does it affect SG dynamics. BAG6 also does not replace BAG3’s function in SG granulostasis. We show that BAG3 and BAG6 target different subsets of DRiPs, and BAG3 binding to DRiPs is mediated by HSPB8 and HSP70. Our data support the idea that SGs are sensitive to BAG3-HSP70-bound DRiPs but not to BAG6-bound DRiPs. Additionally, only BAG3 is strongly upregulated in the stress recovery phase, when SGs dissolve. These data exclude a role for BAG6 in granulostasis and point to a more specialized function in the clearance of a specific subset of DRiPs. Keywords BAG proteins . Co-chaperones . Newly synthesized proteins . Protein clearance . Stress granule dynamics
Introduction * Serena Carra [email protected] 1
Centre for Neuroscience and Nanotechnology, Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy
2
Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
3
Genomic and post-Genomic Center, IRCCS Mondino Foundation, Via Mondino 2, 27100 Pavia, Italy
4
Biotechnology Center (BIOTEC), Center for Molecular and Cellular Bioengineering (CMCB), Technische Universität Dresden, Tatzberg 47/49, 01307 Dresden, Germany
5
Department of Neuroscience, St. Agostino Estense Hospital, Azienda Ospedaliero Universitaria di Modena, Modena, Italy
Stress granules (SGs) are ribonucleoprotein (RNP) granules that contai
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