Nishihama Ryuichi, Schreiter Jennifer H, Onishi Masayuki, Vallen Elizabeth A, Hanna Julia, Moravcevic Katarina, Lippincott Margaret F, Han Haesun, Lemmon Mark A, Pringle John R, Bi Erfei
Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA.
J Cell Biol. 2009 Jun 15;185(6):995-1012. doi: 10.1083/jcb.200903125.
Cytokinesis requires coordination of actomyosin ring (AMR) contraction with rearrangements of the plasma membrane and extracellular matrix. In Saccharomyces cerevisiae, new membrane, the chitin synthase Chs2 (which forms the primary septum [PS]), and the protein Inn1 are all delivered to the division site upon mitotic exit even when the AMR is absent. Inn1 is essential for PS formation but not for Chs2 localization. The Inn1 C-terminal region is necessary for localization, and distinct PXXP motifs in this region mediate functionally important interactions with SH3 domains in the cytokinesis proteins Hof1 (an F-BAR protein) and Cyk3 (whose overexpression can restore PS formation in inn1Delta cells). The Inn1 N terminus resembles C2 domains but does not appear to bind phospholipids; nonetheless, when overexpressed or fused to Hof1, it can provide Inn1 function even in the absence of the AMR. Thus, Inn1 and Cyk3 appear to cooperate in activating Chs2 for PS formation, which allows coordination of AMR contraction with ingression of the cleavage furrow.
胞质分裂需要肌动球蛋白环（AMR）收缩与质膜和细胞外基质重排的协调。在酿酒酵母中，即使没有AMR，新膜、几丁质合酶Chs2（形成初级隔膜[PS]）和蛋白Inn1在有丝分裂退出时都会被输送到分裂位点。Inn1对PS形成至关重要，但对Chs2定位并非必需。Inn1的C末端区域对于定位是必需的，并且该区域中不同的PXXP基序介导了与胞质分裂蛋白Hof1（一种F-BAR蛋白）和Cyk3（其过表达可恢复inn1Delta细胞中的PS形成）中SH3结构域的功能重要相互作用。Inn1的N末端类似于C2结构域，但似乎不结合磷脂；尽管如此，当过表达或与Hof1融合时，即使在没有AMR的情况下它也能提供Inn1功能。因此，Inn1和Cyk3似乎在激活Chs2以形成PS方面相互协作，这使得AMR收缩与分裂沟的内陷得以协调。
