Myosin heavy chain dephosphorylation during cytokinesis in dividing sea urchin embryos

Abstract

AbstractMyosin heavy chain (MHC) phosphorylation was examined throughout the period of first cleavage in developing sea urchin embryos. MHC was found to be phosphorylated in these cells and, furthermore, the relative state of myosin phosphorylation was found to decrease as cells progressed through cytokinesis. Following the completion of cytokinesis, the relative state of MHC phosphorylation returned to levels observed in precytokinesis cells. The above results were obtained with myosin immunoprecipitated from whole cell lysates. In order to specifically examine the phosphorylation, state of MHC in the cleavage furrow, a protocol was developed for the isolation of intact contractile rings from dividing sea urchin embryos. MHC was immunoprecipitated from isolated contractile rings and the relative phosphorylation state of this MHC was compared with that of MHC isolated from whole cell lysates prepared at the same time. MHC from isolated contractile rings was found to be significantly less phosphorylated than total cellular MHC, suggesting a role for MHC dephosphorylation during cytokinesis. © 1993 Wiley‐Liss, Inc.