Cortical actin turnover during cytokinesis requires myosin II.
The involvement of myosin II in cytokinesis has been demonstrated with microinjection, genetic, and pharmacological approaches; however, the exact role of myosin II in cell division remains poorly understood. To address this question, we treated dividing normal rat kidney (NRK) cells with blebbistatin, a potent inhibitor of the nonmuscle myosin II ATPase. Blebbistatin caused a strong inhibition of cytokinesis but no detectable effect on the equatorial localization of actin or myosin. However, whereas these filaments dissociated from the equator in control cells during late cytokinesis, they persisted in blebbistatin-treated cells over an extended period of time. The accumulation of equatorial actin was caused by the inhibition of actin filament turnover, as suggested by a 2-fold increase in recovery half-time after fluorescence photobleaching. Local release of blebbistatin at the equator caused localized accumulation of equatorial actin and inhibition of cytokinesis, consistent with the function of myosin II along the furrow. However, treatment of the polar region also caused a high frequency of abnormal cytokinesis, suggesting that myosin II may play a second, global role. Our observations indicate that myosin II ATPase is not required for the assembly of equatorial cortex during cytokinesis but is essential for its subsequent turnover and remodeling.
Guha
Minakshi
M
Department of Physiology, University of Massachussetts Medical School, Worcester, 01605, USA.
Zhou
Mian
M
Wang
Yu-Li
YL
D000199:Actins / Q000378:metabolism*; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002478:Cells, Cultured; D048749:Cytokinesis / Q000187:drug effects / Q000502:physiology*; D036681:Fluorescence Recovery After Photobleaching; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology*; D024462:Myosin Type II / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D015800:Protozoan Proteins; D011806:Quinolinium Compounds; D051381:Rats
D000199:Actins; C481052:Alexa fluor 546; D006576:Heterocyclic Compounds, 4 or More Rings; D015800:Protozoan Proteins; D011806:Quinolinium Compounds; C472645:blebbistatin; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C033142:myosin-heavy-chain kinase; D024462:Myosin Type II