Department of Pathology, Baylor College of Medicine, One Baylor Plaza, S217, Houston, TX 77030, USA.
Mol Cell Biol. 2010 May;30(9):2280-92. doi: 10.1128/MCB.01392-09. Epub 2010 Feb 22.
In somatic cells, abscission, the physical separation of daughter cells at the completion of cytokinesis, requires CEP55, ALIX, and TSG101. In contrast, cytokinesis is arrested prior to abscission in differentiating male germ cells that are interconnected by TEX14-positive intercellular bridges. We have previously shown that targeted deletion of TEX14 disrupts intercellular bridges in all germ cells and causes male sterility. Although these findings demonstrate that intercellular bridges are essential for spermatogenesis, it remains to be shown how TEX14 and other proteins come together to prevent abscission and form stable intercellular bridges. Using a biochemical enrichment of male germ cell intercellular bridges, we identified additional bridge proteins, including CEP55. Although CEP55 is highly expressed in testes at the RNA level, there is no report of the presence of CEP55 in germ cells. We show here that CEP55 becomes a stable component of the intercellular bridge and that an evolutionarily conserved GPPX3Y motif of TEX14 binds strongly to CEP55 to block similar GPPX3Y motifs of ALIX and TSG101 from interacting and localizing to the midbody. Thus, TEX14 prevents the completion of cytokinesis by altering the destiny of CEP55 from a nidus for abscission to an integral component of the intercellular bridge.
在体细胞中，胞质分裂完成时子细胞的物理分离需要 CEP55、ALIX 和 TSG101。相比之下，在通过 TEX14 阳性细胞间桥相互连接的分化雄性生殖细胞中，胞质分裂在胞质分裂前被阻断。我们之前已经表明，靶向删除 TEX14 会破坏所有生殖细胞中的细胞间桥，并导致雄性不育。尽管这些发现表明细胞间桥对于精子发生至关重要，但仍需要表明 TEX14 和其他蛋白质如何聚集在一起以防止胞质分裂并形成稳定的细胞间桥。使用雄性生殖细胞细胞间桥的生化富集，我们鉴定了其他桥接蛋白，包括 CEP55。尽管 CEP55 在 RNA 水平上在睾丸中高度表达，但没有报道 CEP55 存在于生殖细胞中。我们在这里表明 CEP55 成为细胞间桥的稳定组成部分，并且 TEX14 的进化保守 GPPX3Y 基序与 CEP55 结合牢固，以阻止 ALIX 和 TSG101 的类似 GPPX3Y 基序相互作用并定位到中体。因此，TEX14 通过改变 CEP55 的命运，将其从胞质分裂的核点转变为细胞间桥的一个组成部分，从而阻止胞质分裂的完成。
