An increase or a decrease in myosin II phosphorylation inhibits macrophage motility.

Abstract

Abstract. Myosin II purified from mammalian nonmuscle cells is phosphorylated on the 20-kD light chain subunit (MLC2o) by the Cat+/calmodulin-dependent enzyme myosin light chain kinase (MLCK) . The importance of MLC2o phosphorylation in regulating cell motility was investigated by introducing either antibodies to MLCK (MK-Ab) or a Cat+/calmodulin-independent, constitutively active form of MLCK (MK -) into macrophages . The effects of these proteins on cell motility were then determined using a quantitative chemotaxis assay. Chemotaxis is significantly diminished in macrophages containing MKAb compared to macrophages containing control antibodies . Moreover, there is an C ELLULAR locomotion by mammalian cells is essential for embryogenesis, cell-mediated killing (4), and the formation of metastatic colonies by cancer cells. Cell motility is a complex process that requires the coordinated regulation and the interaction of numerous reactions. ATP hydrolysis by actin and myosin II and myosin II polymerization/depolymerization are thought to be among the reactions involved in mediating translational motility (2, 23) . In mammalian nonmuscle cells, both ATP hydrolysis (3,30,31) and filament formation (1Q 27) by myosin II are regulated by phosphorylation of the 20-kD light chain of myosin (MLC2o)' by myosin light chain kinase (MLCK) (2) . Therefore, MLCK and MLC20 phosphorylation are thought to play critical roles in regulating cell motility.However, the role of filamentous myosin (myosin II) in cell motility is unclear. Experiments on the slime mold Dictyostelium discoideum have questioned the importance of filamentous myosin in cell motility (14,22) . Dictyostelium contains two myosins designated myosin I and myosin II (24) . Myosin I is a single-headed myosin with a short heavy chain that does not form filaments (24) . Myosin I associates with lipids (1) and has been localized in the leading edges of lamellipodia of migrating Dictyostelium ameba (17 inverse relationship between the number of cells that migrate and the amount of MKAb introduced into cells . Interestingly, there is also an inverse relationship between the number of cells that migrate and the amount of MK-introduced into cells. Other experiments demonstrated that MKAb decreased intracellular MLC 20 phosphorylation while MK-increased MLC2o phosphorylation . MK-also increased the amount of myosin associated with the cytoskeleton . These data demonstrate that the regulation of MLCK is an important aspect of cell motility and suggest that MLC2o phosphorylation must be maintained within narrow limits during translational motility by mammalian cells.II is similar to mammalian muscle and nonmuscle myosins in that it has two globular heads, a coiled-coiled tail, and an ability to form filaments . In contrast to mammalian nonmuscle and smooth muscle myosin II, ATP hydrolysis and filament formation by Dictyostelium myosin II are regulated by both heavy chain and light chain phosphorylation (24) . Interestingly, Diciyostelium in which myosin II heavy chain expres...

Saccharomyces boulardiiInterferes with EnterohemorrhagicEscherichia coli-Induced Signaling Pathways in T84 Cells

“…Phosphorylation of the 20-kDa MLC on the serine or threonine residue is an important determinant of contractile tension in both smooth muscle and nonmuscle cells (9,30,32). In this study, we demonstrated that EHEC infection induces time-dependent phosphorylation of MLC.…”

Synaptic transmission and plasticity are modulated by nonmuscle myosin II at the neuromuscular junction ofDrosophila

“…In our previous work on vesicle mobility, we (Seabrooke et al 2010) likewise found similar phenotypic effects when NMMII was up-or downregulated. Additionally, a study of macrophage motility reported that inhibition or enhancement of Myosin II phosphorylation both had the same effect on cell migration (Wilson et al 1991). Furthermore, phosphorylation of the regulatory light chain of NMMII is crucial for cytokinesis (Matsumura 2005), but overexpression of myosin II in fission yeast inhibits cytokinesis (May et al 1997).…”

Myosin Light Chain Kinase Regulates Capacitative Ca 2+ Entry in Human Monocytes/Macrophages

“…17,18 In monocytes/ macrophages, MLCK is implicated in several activities important in atherosclerosis. Thus, MLCK is important for macrophage motility 19 and regulates neutrophil migration across the endothelium. 20 MLCK activation was recently proven to be critical in cytoskeletal changes resulting in pseudopod formation during phagocytosis.…”