Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA.
Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA.
Sci Adv. 2023 Jul 14;9(28):eadg3913. doi: 10.1126/sciadv.adg3913.
Cytokinetic abscission, the last step of cell division, is regulated by the ESCRT machinery. In response to mitotic errors, ESCRT proteins, namely, ALIX, CHMP4B, and CHMP4C, accumulate in the cytosolic compartments termed "abscission checkpoint bodies" (ACBs) to delay abscission and prevent tumorigenesis. ALIX contributes to the biogenesis and stability of ACBs via an unknown mechanism. We show that ALIX phase separates into nondynamic condensates in vitro and in vivo, mediated by the amyloidogenic portion of its proline-rich domain. ALIX condensates confined CHMP4 paralogs in vitro. These condensates dissolved and reformed upon reversible tyrosine phosphorylation of ALIX, mediated by Src kinase and PTP1B, and sequestration of CHMP4C altered their Src-mediated dissolution. NMR analysis revealed how ALIX triggers the activation of CHMP4 proteins, which is required for successful abscission. These results implicate ALIX's phase separation in the modulation of ACBs. This study also highlights how posttranslational modifications can control protein phase separation.
胞质分裂的最后一步是由 ESCRT 机器调控的。为了应对有丝分裂错误，ESCRT 蛋白（即 ALIX、CHMP4B 和 CHMP4C）在称为“胞质分裂检查点体”（ACBs）的细胞质隔室中积累，以延迟胞质分裂并防止肿瘤发生。ALIX 通过未知机制有助于 ACBs 的发生和稳定性。我们表明，ALIX 在体外和体内通过其富含脯氨酸结构域的淀粉样蛋白部分相分离成非动态凝聚物。ALIX 凝聚物在体外限制了 CHMP4 同系物的形成。这些凝聚物在 Src 激酶和 PTP1B 介导的 ALIX 可逆酪氨酸磷酸化以及 CHMP4C 的隔离下溶解和重新形成，并且 CHMP4C 的隔离改变了它们的 Src 介导的溶解。NMR 分析揭示了 ALIX 如何触发 CHMP4 蛋白的激活，这对于成功的胞质分裂是必需的。这些结果表明 ALIX 的相分离在调节 ACBs 中起作用。本研究还强调了翻译后修饰如何控制蛋白质相分离。
