Probing the Role of Myosin Regulatory Light Chain Phosphorylation in Cytokinesis

Fishkind et al., J. Cell Biol. 114:967-975 (1991)

At least part of the cell division forces are generated by myosin II, which is in turn regulated by the phosphorylation of regulatory light chain at Ser-19 and/or Thr-18. To investigate the functional role of this regulatory mechanism, a constitutively active fragment of myosin light chain kinase was microinjected into dividing NRK cells..

Constitutive Phosphorylation of Myosin Regulatory Light Chain Induces Membrane Blebbing but Has No Effect on Cytokinesis

Constitutively active fragments of myosin light chain kinase cause blebbing of the membrane in regions outside the equator, which may reflect disorganized cortical contractions. However cells divide normally, suggesting that there is an alternative regulatory mechanism that dominates over myosin light chain phosphorylation, and that myosin regulatory light chain phosphorylation is not the primary switch that defines the timing and location of cytokinesis. Recording time, 9 min (upper), and 8 min (lower).