Myosin heavy chain dephosphorylation during cytokinesis in dividing sea urchin embryos

Abstract

Myosin 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.Q 1993 Wiley-Lis, Inc.

Molecular analysis of racE function inDictyostelium

“…Previous studies have shown that cells experience an increase in internal pressure as they enter cytokinesis (Burton and Taylor, 1997;Erickson and Trinkaus, 1976;Laster and Mackenzie, 1996). This is probably induced by the increased activity of myosin II during cytokinesis (Chen et al, 1994;Egelhoff et al, 1993;Larochelle and Epel, 1993;Pollenz et al, 1992;Satterwhite et al, 1992). Thus, cells must have enough tensile strength in their cortices to withstand the changes in internal pressure generated during cell division.…”

In vivo phosphorylation of regulatory light chain of myosin II in sea urchin eggs and its role in controlling myosin localization and function during cytokinesis

“…It is possible that like in Dictyostelium [Egelhoff et al, 1993;Sabry et al, 1997], fission yeast [Motegi et al, 2004], and some mammalian cells [Rosenberg and Ravid, 2006], localization of myosin may be regulated through phosphorylation of myosin heavy chain on its tail in the sea urchin eggs. It has been reported that a phosphorylation level of myosin heavy chain is spatiotemporally regulated in the sea urchin eggs [Larochelle and Epel, 1993]. However, the relationship between the heavy chain phosphorylation and myosin localization remains to be investigated in the sea urchin egg.…”

Differential localization in cells of myosin II heavy chain kinases during cytokinesis and polarized migration

“…Although it is clear throughout the animal kingdom and in protozoa that the mass of myosin II in the division furrow decreases steadily with furrow ingression, no mechanism has been identified in any other system that can explain this regulated disassembly. Dynamic changes in MHC phosphorylation levels within the contractile ring have been reported in dividing sea urchin embryos [35], suggesting that MHC phosphorylation as a mechanism regulating furrow myosin II disassembly may occur in other systems besides D. discoideum . We suggest that MHCK-C participates in this regulated myosin II filament disassembly in D. discoideum , and that this function may be regulated at both the cellular and biochemical level.…”