Myosin Assembly Regulation by 14-3-3

Abstract

The regulation of non-muscle myosin II is key to a number of processes, including cell migration, tissue morphogenesis, and cytokinesis. We have been using the social amoeba Dictyostelium discoideum as a model organism to study how myosin II is regulated in cytokinesis. One major pathway that we have discovered is the racE–14-3-3 pathway, which maintains the uniformity of myosin II at the cortex and increases myosin II turnover, as shown by FRAP analysis and in vitro studies. We have demonstrated that 14-3-3 associates directly with the myosin II assembly domain to inhibit bipolar thick filament (BTF) assembly. This effect is observed in wild-type as well as in constitutively assembled or unassembled mutant forms of myosin II, and the exact 14-3-3 binding site is being mapped by mutational analysis. Furthermore, a bioinformatics analysis has predicted a similar 14-3-3 binding site in the mammalian non-muscle myosin IIA and IIB assembly domains. We are investigating if the 14-3-3–myosin II interactions that we have observed in Dictyostelium are also present in the mammalian system. We are thus pursuing a possible conserved mechanism for phosphorylation-independent regulation of myosin assembly by 14-3-3 proteins.