title: Phosphorylation of myosin II regulatory light chain controls its accumulation, not that of actin, at the contractile ring in HeLa cells.
abstract: During cytokinesis in eukaryotic cells, an actomyosin-based contractile ring (CR) is assembled along the equator of the cell. Myosin II ATPase activity is stimulated by the phosphorylation of the myosin II regulatory light chain (MRLC) in vitro, and phosphorylated MRLC localizes at the CR in various types of cells. Previous studies have determined that phosphorylated MRLC plays an important role in CR furrowing. However, the role of phosphorylated MRLC in CR assembly remains unknown. Here, we have used confocal microscopy to observe dividing HeLa cells expressing fluorescent protein-tagged MRLC mutants and actin during CR assembly near the cortex. Di-phosphomimic MRLC accumulated at the cell equator earlier than non-phosphorylatable MRLC and actin. Interestingly, perturbation of myosin II activity by non-phosphorylatable MRLC expression or treatment with blebbistatin, a myosin II inhibitor, did not alter the time of actin accumulation at the cell equator. Furthermore, inhibition of actin polymerization by treatment with latrunculin A had no effect on MRLC accumulation at the cell equator. Taken together, these data suggest that phosphorylated MRLC temporally controls its own accumulation, but not that of actin, in cultured mammalian cells.
authors.affiliation: Department of Biological Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Japan.
authors.forename: Tomo
authors.initials: T
authors.lastname: Kondo
authors.forename: Shiho
authors.initials: S
authors.lastname: Itakura
authors.forename: Kozue
authors.initials: K
authors.lastname: Hamao
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hosoya
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D048749:Cytokinesis / Q000502:physiology; D006367:HeLa Cells; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology; D006801:Humans; D018994:Myosin Light Chains / Q000378:metabolism*; D024462:Myosin Type II / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010766:Phosphorylation; D053778:Thiazolidines / Q000494:pharmacology
chemical_list: D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D006576:Heterocyclic Compounds, 4 or More Rings; C466107:MRLC2 protein, human; D018994:Myosin Light Chains; D053778:Thiazolidines; C472645:blebbistatin; D024462:Myosin Type II; C037067:latrunculin A