Regulation of myosin light chain phosphorylation by RhoB in neuronal cells

The phosphorylation of rnyosin light chain (MLC) is a key regulatory point in the control of cellular morphology. Evidence suggests that RhoA-a member of the Rho GTPase family-regulates MLC phosphorylation via Rho kinase (ROK). Neurotics display subtle alterations in their cytoarchitecture during the synaptic plasticity following high-frequency stimulation. We have recently demonstrated that RhoB, and not RhoA, is activated in neurones by high-frequency stimulation. However, the downstream consequences of RhoB activation in cells are unclear. In this study, we tested the hypothesis that RhoB might stimulate neuronal MLC phosphorylation. Transfection of PC12 cells with constitutively active RhoB increased MLC phosphorylation. Conversely, dominant-negative RhoB vectors reduced MLC phosphorylation. The effect of RhoB was attenuated by pretreatment with a selective ROK inhibitor. This confirms that Rho GTPases are important regulators of MLC phosphorylation, but suggests that, in neuronal cells, the control is exerted via RhoB rather than RhoA. (C) 2004 Elsevier Inc. All rights reserved.