Aurora B but not rho/MLCK signaling is required for localization of diphosphorylated myosin II regulatory light chain to the midzone in cytokinesis.
Non-muscle myosin II is stimulated by monophosphorylation of its regulatory light chain (MRLC) at Ser19 (1P-MRLC). MRLC diphosphorylation at Thr18/Ser19 (2P-MRLC) further enhances the ATPase activity of myosin II. Phosphorylated MRLCs localize to the contractile ring and regulate cytokinesis as subunits of activated myosin II. Recently, we reported that 2P-MRLC, but not 1P-MRLC, localizes to the midzone independently of myosin II heavy chain during cytokinesis in cultured mammalian cells. However, the mechanism underlying the distinct localization of 1P- and 2P-MRLC during cytokinesis is unknown. Here, we showed that depletion of the Rho signaling proteins MKLP1, MgcRacGAP, or ECT2 inhibited the localization of 1P-MRLC to the contractile ring but not the localization of 2P-MRLC to the midzone. In contrast, depleting or inhibiting a midzone-localizing kinase, Aurora B, perturbed the localization of 2P-MRLC to the midzone but not the localization of 1P-MRLC to the contractile ring. We did not observe any change in the localization of phosphorylated MRLC in myosin light-chain kinase (MLCK)-inhibited cells. Furrow regression was observed in Aurora B- and 2P-MRLC-inhibited cells but not in 1P-MRLC-perturbed dividing cells. Furthermore, Aurora B bound to 2P-MRLC in vitro and in vivo. These results suggest that Aurora B, but not Rho/MLCK signaling, is essential for the localization of 2P-MRLC to the midzone in dividing HeLa cells.
Department of Biological Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Hiroshima, Japan.
Tomo
T
Kondo
Rieko
R
Isoda
Takayuki
T
Ookusa
Keiju
K
Kamijo
Kozue
K
Hamao
Hiroshi
H
Hosoya
D064107:Aurora Kinase B / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D048749:Cytokinesis; D005455:Fluorescent Antibody Technique; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D018613:Microscopy, Confocal; D018994:Myosin Light Chains / Q000378:metabolism*; D009219:Myosin-Light-Chain Kinase / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D015398:Signal Transduction; D054460:rho-Associated Kinases / Q000235:genetics / Q000378:metabolism*
C489850:ECT2 protein, human; D020690:GTPase-Activating Proteins; D018994:Myosin Light Chains; D011518:Proto-Oncogene Proteins; C115995:mgcRacGAP; C576921:AURKB protein, human; D064107:Aurora Kinase B; D054460:rho-Associated Kinases; D009219:Myosin-Light-Chain Kinase