The fission yeast Chs2 protein interacts with the type-II myosin Myo3p and is required for the integrity of the actomyosin ring

Abstract

In Schizosaccharomyces pombe cytokinesis requires the function of a contractile actomyosin ring. Fission yeast Chs2p is a transmembrane protein structurally similar to chitin synthases that lacks such enzymatic activity. Chs2p localisation and assembly into a ring that contracts during division requires the general system for polarised secretion, some components of the actomyosin ring, and an active septation initiation network. Chs2p interacts physically with the type-II myosin Myo3p revealing a physical link between the plasma membrane and the ring. In chs2Δ mutants, actomyosin ring integrity is compromised during the last stages of contraction and it remains longer in the midzone. In synchronous cultures, chs2Δ cells exhibit a delay in septation with respect to the control strain. All these results show that Chs2p participates in the correct functioning of the medial ring.

The Fission Yeast SEL1 Domain Protein Cfh3p

“…Thus, it is not surprising that Cfh3p is 26 and 28% identical to ScChs4p and CaChs4p, respectively, and that these identity values only increase to 29 and 30%, respectively, when the comparison is restricted to the SEL1 domains. Our results show that Cfh3p plays a role in the regulation of glucan synthesis, in agreement with the idea that in S. pombe Chs-like proteins have maintained a general function not related to chitin synthesis, as reported for Chs2p and Cfr1p (42,46,47). In this case, the function would be to ensure the stabilization of enzymes involved in cell wall synthesis at the plasma membrane.…”

“…The following results are inconsistent with this conclusion. (i) In our previous work (46,47) and in this work we observed that Chs2p localized at internal vesicles in both the WT and the cfh3⌬ strain (supplemental Fig. S4), depending on the culture conditions.…”

“…Matsuo et al (38) suggested that Cfh3p/Chr4p would be a regulator of Chs2p, a chitin synthase-like protein that lacks such activity and is required for the stability of the contractile actomyosin ring during its contraction (46,47), because they found that in a chr4⌬ mutant Chs2p could be observed at the ring and in some cytoplasmic dots. The following results are inconsistent with this conclusion.…”

F-BAR domain protein Rga7 collaborates with Cdc15 and Imp2 to ensure proper cytokinesis in fission yeast

“…Several membrane-associated proteins have been shown to ensure CAR integrity, including the F-BAR-containing proteins Cdc15 and Imp2 that bind to the CAR or the equatorial membrane (Celton-Morizur et al, 2004;Martín-García and Valdivieso, 2006;Roberts-Galbraith et al, 2009). We have found that Rga7 cooperates with Cdc15 and Imp2 in maintaining CAR stability, especially during contraction, as judged by the presence of uncompleted septa without CARs, when the function of Rga7 and Cdc15 or Imp2 is simultaneously affected.…”

Inn1 and Cyk3 regulate chitin synthase during cytokinesis in budding yeasts

“…The role of Chs2-Inn1-Cyk3 in mycelial fungi remains to be explored in the future, but the fission yeast proteins Chs2, Fic1 (the orthologue of Inn1: Fic15'Fifteen interacting C2-domain' as it interacts with the Cdc15 orthologue of ScHof1) and Cyk3 are known to be present at the cleavage site (Martín-García et al, 2003;Roberts-Galbraith et al, 2009;Pollard et al, 2012), though they only have a minor role in cytokinesis (Mishra et al, 2004;Martín-García and Valdivieso, 2006;Roberts-Galbraith et al, 2009;Pollard et al, 2012).…”