| Summary: | 碩士 === 國立中興大學 === 生物化學研究所 === 89 === Focal adhesion kinase (FAK), a cytoplasmic protein tyrosine kinase, plays an important role in the control of integrin-mediated cell behavior. It has been shown that fibroblasts derived from FAK-null mouse embryos (MEF FAK-/- cells) exhibit a rounded morphology and defects in cell migration. In this study, we have found that the expression level of myosin light chain kinase (MLCK) in MEF FAK-/- cells was 3-fold higher than in MEF FAK+/+ cells, which was in accordance with an increased phosphorylation of myosin regulatory light chain (RLC) at Ser-19 in MEF FAK-/- cells. Immunofluorescence studies revealed that MLCK, RLC, and phosphorylated RLC in MEF FAK-/- cells were all around the cell periphery. Disruption of cortical actin rings in MEF FAK-/- cells by cytochalasin D prevented the peripheral accumulation of MLCK, suggesting that the formation of cortical actin rings by FAK deficiency may be necessary for peripheral MLCK accumulation. Expression of v-Src in MEF FAK-/- cells reversed their rounded morphology to fibroblast-like spreading phenotype, prevents cortical MLCK accumulation, and accompanies with increasing cell migration. These results suggest that the MLCK localization but not its activity may be the key to regulate cell migration.
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