The regulation of myosin II in Dictyostelium.
Dictyostelium conventional myosin (myosin II) is an abundant protein that plays a role in various cellular processes such as cytokinesis, cell protrusion and development. This review will focus on the signal transduction pathways that regulate myosin II during cell movement. Myosin II appears to have two modes of action in Dictyostelium: local stabilization of the cytoskeleton by myosin filament association to the actin meshwork (structural mode) and force generation by contraction of actin filaments (motor mode). Some processes, such as cell movement under restrictive environment, require only the structural mode of myosin. However, cytokinesis in suspension and uropod retraction depend on motor activity as well. Myosin II can self-assemble into bipolar filaments. The formation of these filaments is negatively regulated by heavy chain phosphorylation through the action of a set of novel alpha kinases and is relatively well understood. However, only recently it has become clear that the formation of bipolar filaments and their translocation to the cortex are separate events. Translocation depends on filamentous actin, and is regulated by a cGMP pathway and possibly also by the cAMP phosphodiesterase RegA and the p21-activated kinase PAKa. Myosin motor activity is regulated by phosphorylation of the regulatory light chain through myosin light chain kinase A. Unlike conventional light chain kinases, this enzyme is not regulated by calcium but is activated by cGMP-induced phosphorylation via an upstream kinase and subsequent autophosphorylation.
Bosgraaf
Leonard
L
Department of Biology, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands.
van Haastert
Peter J M
PJ
D015105:3',5'-Cyclic-AMP Phosphodiesterases; D008841:Actin Cytoskeleton / Q000378:metabolism; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002465:Cell Movement / Q000502:physiology*; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D019852:Diacylglycerol Kinase / Q000378:metabolism; D004023:Dictyostelium / Q000166:cytology / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000378:metabolism; D024462:Myosin Type II / Q000737:chemistry / Q000378:metabolism*; D015800:Protozoan Proteins / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
D015800:Protozoan Proteins; D019852:Diacylglycerol Kinase; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D015105:3',5'-Cyclic-AMP Phosphodiesterases; C112742:regA protein, Dictyostelium; D024462:Myosin Type II; D018995:Myosin Heavy Chains; D006152:Cyclic GMP