Myosin light chain kinase inhibitors ML-7 and ML-9 inhibit mouse lung carcinoma cell attachment to the fibronectin substratum.

We studied the effects of various protein kinase inhibitors on the attachment of mouse lung carcinoma 3LL cells to the fibronectin (FN) substratum. Calmodulin antagonists (W-7 and W-13) and myosin light chain kinase inhibitors (ML-7 and ML-9) exhibited the inhibitory effect for the attachment, while inhibitors of protein kinases A and C were ineffective. Since Arg-Gly-Asp-containing hexapeptide blocked the attachment, cell surface FN receptor appeared to be involved in this mechanism. These results support the hypothesis that the cell attachment requires the rearrangement of the cytoskeleton in association with the phosphorylation of myosin light chain which would lead to the clustering of the cell surface FN receptors.