Stimulation of rabbit aortic smooth muscle cells with PGF2alpha increased diphosphorylated MLC20 content and spread its distribution along fibrillary structures colocalized with actin.
Diphosphorylation and monophosphorylation of MLC20 in smooth muscle cells appear to be regulated by different mechanisms, with diphosphorylation being more sensitive to protein kinase inhibitors.
Using the specific antibodies pLC1 and pLC2 for mono- and diphosphorylated 20-kDa myosin light chain (MLC20) at Ser19 and at both Thr18 and Ser19, respectively, we visualized the dynamics of the MLC20 phosphorylation in rabbit aortic smooth muscle cells (cell line SM-3) stimulated with PGF2alpha. In the resting state, the diphosphorylated form was located in the peripheral region of the cell, such as the leading edge or the adhesion plaque, and the monophosphorylated form was located not only in the peripheral region but also on a discontinuous fibrillary structure along the long axis of the cell. After stimulation with 30 microM PGF2alpha, although localization of the monophosphorylated form changed little, the content of the diphosphorylated form increased and the distribution spread along the fibrillary structure to an extent the same as or similar to that of the monophosphorylated form, which colocalized with actin filament bundles. The diphosphorylation of MLC20 was more sensitive to protein kinase inhibitors, HA-1077, HA-1100, staurosporine, wortmannin, and ML-9, than was the monophosphorylation. In light of these observations, we propose that MLC20 diphosphorylation and monophosphorylation are regulated by different mechanisms.
Sakurada et al. (Mon,) reported a other. PGF2alpha vs. Resting state was evaluated on Dynamics and localization of MLC20 phosphorylation. Stimulation of rabbit aortic smooth muscle cells with PGF2alpha increased diphosphorylated MLC20 content and spread its distribution along fibrillary structures colocalized with actin.