A Role for the Chaperone Complex BAG3-HSPB8 in Actin Dynamics, Spindle Orientation and Proper Chromosome Segregation during Mitosis.
A Role for the Chaperone Complex BAG3-HSPB8 in Actin Dynamics, Spindle Orientation and Proper Chromosome Segregation during Mitosis.
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DOI：
10.1371/journal.pgen.1005582
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发表时间：
2015-10
期刊：
影响因子：
4.5
通讯作者：
Lavoie JN
中科院分区：
文献类型：
--
作者：
Fuchs M;Luthold C;Guilbert SM;Varlet AA;Lambert H;Jetté A;Elowe S;Landry J;Lavoie JN
与热休克蛋白HSPB 8复合的共伴侣BAG 3在机械应变期间的蛋白质质量控制中起作用。它是多分子伴侣复合物的一部分，该复合物感知受损的细胞骨架蛋白并通过选择性自噬协调它们的隔离和/或降解。在这里，我们描述了一个新的作用，BAG 3-HSPB 8复合物在有丝分裂，一个过程中涉及细胞张力稳态的深刻变化。BAG 3在有丝分裂进入时高度磷酸化，并定位于中心体区域。BAG 3以HSPB 8依赖的方式通过影响有丝分裂纺锤体的三维定位来调节染色体向中期板的及时聚集。BAG 3的耗尽导致细胞在中期变圆的缺陷和与异常纺锤体旋转相关的皮质的戏剧性起泡。在自噬受体p62/SQSTM 1沉默后观察到类似的缺陷，所述自噬受体p62/SQSTM 1有助于BAG 3介导的选择性自噬途径。有丝分裂细胞耗尽BAG 3，HSPB 8或p62/SQSTM 1表现出紊乱的肌动蛋白丰富的收缩纤维，这是建议指导纺锤体的方向。适当的纺锤体定位被救出BAG 3耗尽细胞后，加入凝集素伴刀豆球蛋白A，恢复皮质硬度。总之，我们的研究结果表明，存在一个迄今尚未认识到的质量控制机制，涉及BAG 3，HSPB 8和p62/SQSTM 1的肌动蛋白为基础的有丝分裂结构，指导纺锤体方向的准确重塑。小分子热休克蛋白（sHSP/HSPB）是一类不依赖ATP的分子伴侣。它们中的一些在应激期间保护蛋白质组免于聚集，另一些通过不明确的机制调节正常的生物过程。HSPB蛋白和细胞骨架元件之间的相互作用越来越多地与它们在人类退行性疾病和癌症中的作用有关。例如，含有HSPB 8及其共伴侣BAG 3的多伴侣复合物将通过促进F-肌动蛋白结构内受损组分的自噬清除来维持肌细胞完整性。选择性自噬是一种靶向的蛋白质降解机制，用于消除受损的细胞器和蛋白质。它还可以调节在细胞骨架的强烈重塑过程中从其功能相关位点去除信号蛋白，因为它发生在有丝分裂期间。在这里，我们报告了一个新的作用，HSPB 8和BAG 3在哺乳动物细胞有丝分裂过程中，涉及自噬受体p62/SQSTM 1。我们发现，减少任何蛋白质内的HSPB 8-BAG 3-p62/SQSTM信号轴同样损害有丝分裂的进展和染色体分离的有丝分裂纺锤体的方向和有丝分裂特异性肌动蛋白结构的组装。我们的研究结果建立了一个独特的作用，热休克蛋白B 8在一个新的功能，BAG 3在有丝分裂细胞分裂和基因组的稳定性，通过影响肌动蛋白细胞骨架的重塑。
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. Small heat shock proteins (sHSP/HSPB) form a diverse family of ATP-independent chaperones. Some of them protect the proteome against aggregation during stress and others regulate normal biological processes through ill-defined mechanisms. Interactions between HSPB proteins and elements of the cytoskeleton are increasingly linked to their implication in human degenerative diseases and cancer. For instance, a multichaperone complex containing HSPB8 and its co-chaperone BAG3 would maintain muscle cell integrity by promoting the autophagic clearance of damaged components within F-actin structures. Selective autophagy is a targeted protein degradation mechanism for elimination of damaged organelles and proteins. It may also regulate removal of signaling proteins from their functionally relevant sites during intense remodeling of the cytoskeleton, as it occurs during mitosis. Here, we report a novel role for HSPB8 and BAG3 during mitosis in mammalian cells that involves the autophagic receptor p62/SQSTM1. We show that a reduction of any protein within the HSPB8-BAG3-p62/SQSTM signaling axis similarly impairs mitotic progression and chromosome segregation by affecting orientation of the mitotic spindle and assembly of mitotic-specific actin structures. Our findings establish a unique role for HSPB8 in a novel function of BAG3 in mitotic cell division and genome stability, through effect on remodeling of the actin cytoskeleton.