A Role for the Chaperone Complex BAG3-HSPB8 in Actin Dynamics, Spindle Orientation and Proper Chromosome Segregation during Mitosis.
The co-chaperone BAG3, in complex with the heat shock protein HSPB8, plays a role in protein quality control during mechanical strain. It is part of a multichaperone complex that senses damaged cytoskeletal proteins and orchestrates their seclusion and/or degradation by selective autophagy. Here we describe a novel role for the BAG3-HSPB8 complex in mitosis, a process involving profound changes in cell tension homeostasis. BAG3 is hyperphosphorylated at mitotic entry and localizes to centrosomal regions. BAG3 regulates, in an HSPB8-dependent manner, the timely congression of chromosomes to the metaphase plate by influencing the three-dimensional positioning of the mitotic spindle. Depletion of BAG3 caused defects in cell rounding at metaphase and dramatic blebbing of the cortex associated with abnormal spindle rotations. Similar defects were observed upon silencing of the autophagic receptor p62/SQSTM1 that contributes to BAG3-mediated selective autophagy pathway. Mitotic cells depleted of BAG3, HSPB8 or p62/SQSTM1 exhibited disorganized actin-rich retraction fibres, which are proposed to guide spindle orientation. Proper spindle positioning was rescued in BAG3-depleted cells upon addition of the lectin concanavalin A, which restores cortex rigidity. Together, our findings suggest the existence of a so-far unrecognized quality control mechanism involving BAG3, HSPB8 and p62/SQSTM1 for accurate remodelling of actin-based mitotic structures that guide spindle orientation.
Centre de Recherche sur le Cancer de l'Université Laval and Département de Biologie Moléculaire, Biochimie Médicale et Pathologie, Université Laval, Quebec, Canada; Oncology, Centre de Recherche du CHU de Québec-Université Laval, Quebec, Canada.
Margit
M
Fuchs
Centre de Recherche sur le Cancer de l'Université Laval and Département de Biologie Moléculaire, Biochimie Médicale et Pathologie, Université Laval, Quebec, Canada; Oncology, Centre de Recherche du CHU de Québec-Université Laval, Quebec, Canada.
Carole
C
Luthold
Centre de Recherche sur le Cancer de l'Université Laval and Département de Biologie Moléculaire, Biochimie Médicale et Pathologie, Université Laval, Quebec, Canada; Oncology, Centre de Recherche du CHU de Québec-Université Laval, Quebec, Canada.
Solenn M
SM
Guilbert
Centre de Recherche sur le Cancer de l'Université Laval and Département de Biologie Moléculaire, Biochimie Médicale et Pathologie, Université Laval, Quebec, Canada; Oncology, Centre de Recherche du CHU de Québec-Université Laval, Quebec, Canada.
Alice Anaïs
AA
Varlet
Centre de Recherche sur le Cancer de l'Université Laval and Département de Biologie Moléculaire, Biochimie Médicale et Pathologie, Université Laval, Quebec, Canada; Oncology, Centre de Recherche du CHU de Québec-Université Laval, Quebec, Canada.
Herman
H
Lambert
Centre de Recherche sur le Cancer de l'Université Laval and Département de Biologie Moléculaire, Biochimie Médicale et Pathologie, Université Laval, Quebec, Canada; Oncology, Centre de Recherche du CHU de Québec-Université Laval, Quebec, Canada.
Alexandra
A
Jetté
Reproduction, Perinatal Health and Child Health, Centre de Recherche du CHU de Québec-Université Laval, Quebec, Canada; Centre de Recherche sur le Cancer de l'Université Laval and Département de Pédiatrie, Université Laval, Quebec, Canada.
Sabine
S
Elowe
Centre de Recherche sur le Cancer de l'Université Laval and Département de Biologie Moléculaire, Biochimie Médicale et Pathologie, Université Laval, Quebec, Canada; Oncology, Centre de Recherche du CHU de Québec-Université Laval, Quebec, Canada.
Jacques
J
Landry
Centre de Recherche sur le Cancer de l'Université Laval and Département de Biologie Moléculaire, Biochimie Médicale et Pathologie, Université Laval, Quebec, Canada; Oncology, Centre de Recherche du CHU de Québec-Université Laval, Quebec, Canada.
Josée N
JN
Lavoie
D008841:Actin Cytoskeleton / Q000235:genetics*; D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics* / Q000378:metabolism; D051017:Apoptosis Regulatory Proteins / Q000235:genetics* / Q000378:metabolism; D001343:Autophagy / Q000235:genetics; D020090:Chromosome Segregation / Q000235:genetics; D003208:Concanavalin A / Q000008:administration & dosage; D006367:HeLa Cells; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D018869:Heat-Shock Response / Q000235:genetics; D006801:Humans; D061986:MCF-7 Cells; D008938:Mitosis / Q000235:genetics; D018832:Molecular Chaperones; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D059748:Proteolysis; D034741:RNA, Small Interfering; D000071456:Sequestosome-1 Protein; D008941:Spindle Apparatus / Q000235:genetics*
D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; C414431:BAG3 protein, human; C413214:HSPB8 protein, human; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D034741:RNA, Small Interfering; C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein; D003208:Concanavalin A; D017346:Protein Serine-Threonine Kinases