Cdc4p, a Contractile Ring Protein Essential for Cytokinesis inSchizosaccharomyces pombe, Interacts with a Phosphatidylinositol 4-Kinase

Abstract

The proposed function of Cdc4p, an essential contractile ring protein in Schizosaccharomyces pombe, is that of a myosin essential light chain. However, five conditionally lethal cdc4 alleles exhibit complementation in diploids. Such interallelic complementation is not readily explained if the sole function of Cdc4p is that of a myosin essential light chain. Complementation of cdc4 alleles could occur only if different mutant forms can assemble into an active oligomeric complex or if Cdc4p has more than one essential function. To search for other proteins that may interact with Cdc4p, we performed a two-hybrid screen and identified two such candidates: one similar to Saccharomyces cerevisiae Vps27p and the other a putative phosphatidylinositol (PI) 4-kinase. Binding of Cdc4p to the latter and to myosin heavy chain (Myo2p) was confirmed by immunosorbent assays. Deletion studies demonstrated interaction between the Cdc4p C-terminal domain and the PI 4-kinase C-terminal domain. Furthermore, interaction was abolished by the Cdc4p C-terminal domain point mutation, Gly 107 to Ser. This allele also causes failure of cytokinesis. Ectopic expression of the PI 4-kinase C-terminal domain caused cytokinesis defects that were most extreme in cells carrying the G107S allele. We suggest that Cdc4p plays multiple roles in cytokinesis and that interaction with a PI 4-kinase may be important for contractile ring assembly and/or function.

Cooperation Between the Septins and the Actomyosin Ring and Role of a Cell-Integrity Pathway During Cell Division in Fission Yeast

“…Another hypothesis is that cdc4-s16 also compromises the function of some other Cdc4-binding partner that is part of a pathway that normally complements the pathway involving the septins. In this regard, it should be noted that there is good evidence that both S. pombe Cdc4 and its S. cerevisiae counterpart, Mlc1, interact with partners other than the type II myosin heavy chains and that these other partners are also important for cytokinesis (Stevens and Davis 1998;Boyne et al 2000;Shannon and Li 2000;Desautels et al 2001;D'Souza et al 2001;Motegi et al 2001;Win et al 2001;Lord and Pollard 2004;Luo et al 2004;Mulvihill et al 2006;Park et al 2009). The other partners include type V myosin heavy chains (S. pombe Myo51 and perhaps Myo52; S. cerevisiae Myo2), which are thought to be involved in the delivery of new plasma-membrane and cell-wall materials to the division site or (for Myo51) in some unknown function within the AMR; IQGAPs (S. pombe Rng2 and S. cerevisiae Iqg1), which may also be involved in plasma-membrane and cell-wall formation in addition to their roles in AMR function; and a phosphatidylinositol 4-kinase (S. pombe Pik1).…”

Breaking up is hard to do – membrane traffic in cytokinesis

“…For instance, the ganglioside GM1 and cholesterol were shown to accumulate at the cleavage furrow of dividing Xenopus laevis embryos, where they might regulate Src and PLCγ-dependent signalling (Ng et al, 2005). Recent evidence has also shown that PtdIns(4,5)P 2 accumulates at the cleavage furrow in mammalian and Schizosaccharomyces pombe cells (Desautels et al, 2001;Emoto et al, 2005;Field et al, 2005), whereas phosphatidylinositol (3,4,5)-trisphosphate [PtdIns(3,4,5)P 3 ] is enriched at the poles of the dividing cells (Janetpopoulos et al, 2005) (Fig. 1B).…”

“…The furrow then ingresses, leaving a thin intercellular connection between the cells, and a midbody-ring structure is assembled. (B) During furrowing, the composition of the plasma membrane (PM) of the furrow changes -levels of cholesterol, GM1 and PtdIns(4,5)P 2 increase (Desautels et al, 2001;Emoto et al, 2005;Field et al, 2005), PE redistributes into the outer leaflet (Emoto and Umeda, 2000). Increased levels of PtdIns(4,5)P 2 might be controlled by Rab35 (see text).…”

Synthesis and function of membrane phosphoinositides in budding yeast, Saccharomyces cerevisiae

“…These results demonstrate the evolutionary conservation of the Frq1-Pik1 interaction. Curiously, in Schizosaccharomyces pombe, another small EF-hand-type Ca 2+ -binding protein, Cdc4 (the fission yeast counterpart of S. cerevisiae Mlc1), the ortholog of mammalian myosin light chain (which associates with type V myosins), reportedly interacts physically with the COOH-terminal region of SpPik1 [220]. Because of its role in regulating actin-associated Type V myosin, SpCdc4 was implicated in actin-dependent processes, like cytokinesis [218,219].…”