Department of Biochemistry and Molecular Biology, Alberta Children's Hospital Research Institute, University of Calgary, Calgary, AL T2N 4N1, Canada.
Genetics. 2022 May 5;221(1). doi: 10.1093/genetics/iyac043.
Microtubule severing plays important role in cell structure and cell division. The microtubule severing protein katanin, composed of the MEI-1/MEI-2 subunits in Caenorhabditis elegans, is required for oocyte meiotic spindle formation; however, it must be inactivated for mitosis to proceed as continued katanin expression is lethal. Katanin activity is regulated by 2 ubiquitin-based protein degradation pathways. Another ubiquitin ligase, HECD-1, the homolog of human HECTD1/HECT domain E3 ubiquitin protein ligase 1, regulates katanin activity without affecting katanin levels. In other organisms, HECD-1 is a component of the striatin-interacting kinase phosphatase complex, which affects cell proliferation and a variety of signaling pathways. Here we conducted a systematic screen of how mutations in striatin-interacting kinase phosphatase components affect katanin function in C. elegans. Striatin-interacting kinase phosphatase core components (FARL-11, CASH-1, LET-92, and GCK-1) were katanin inhibitors in mitosis and activators in meiosis, much like HECD-1. By contrast, variable components (SLMP-1, OTUB-2) functioned as activators of katanin activity in mitosis, indicating they may function to alter striatin-interacting kinase phosphatase core function. The core component CCM-3 acted as an inhibitor at both divisions, while other components (MOB-4, C49H3.6) showed weak interactions with katanin mutants. Additional experiments indicate that katanin may be involved with the centralspindlin complex and a tubulin chaperone. HECD-1 shows ubiquitous expression in the cytoplasm throughout meiosis and early development. The differing functions of the different subunits could contribute to the diverse functions of the striatin-interacting kinase phosphatase complex in C. elegans and other organisms.
微管切割在细胞结构和细胞分裂中起着重要作用。微管切割蛋白katanin，由秀丽隐杆线虫中的 MEI-1/MEI-2 亚基组成，是卵母细胞减数分裂纺锤体形成所必需的；然而，为了让有丝分裂继续进行，它必须失活，因为持续的katanin 表达是致命的。katanin 的活性受 2 种基于泛素的蛋白质降解途径调节。另一种泛素连接酶 HECD-1，是人类 HECTD1/HECT 结构域 E3 泛素蛋白连接酶 1 的同源物，调节katanin 的活性而不影响其水平。在其他生物体中，HECD-1 是 striatin 相互作用激酶磷酸酶复合物的一个组成部分，该复合物影响细胞增殖和多种信号通路。在这里，我们进行了一项系统筛选，研究 striatin 相互作用激酶磷酸酶成分的突变如何影响线虫中的 katanin 功能。striatin 相互作用激酶磷酸酶核心成分（FARL-11、CASH-1、LET-92 和 GCK-1）在有丝分裂中是 katanin 的抑制剂，在减数分裂中是激活剂，与 HECD-1 非常相似。相比之下，可变成分（SLMP-1、OTUB-2）在有丝分裂中是 katanin 活性的激活剂，表明它们可能改变 striatin 相互作用激酶磷酸酶核心功能。核心成分 CCM-3 在两个分裂中都作为抑制剂起作用，而其他成分（MOB-4、C49H3.6）与 katanin 突变体的相互作用较弱。进一步的实验表明，katanin 可能与中心体纺锤体复合物和微管伴侣有关。HECD-1 在整个减数分裂和早期发育过程中在细胞质中广泛表达。不同亚基的不同功能可能有助于 striatin 相互作用激酶磷酸酶复合物在秀丽隐杆线虫和其他生物体中的多样化功能。
