This study identifies a novel biochemical mechanism for the regulation of smooth muscle contractility, wherein Rho kinase phosphorylates MYPT1 at Thr850 to dissociate PP1M from myosin.
Rho kinase is known to control smooth muscle contractility by phosphorylating the 110 kDa myosin-targetting subunit (MYPT1) of the myosin-associated form of protein phosphatase 1 (PP1M). Phosphorylation of MYPT1 at Thr695 has previously been reported to inhibit the catalytic activity of PP1. Here, we show that the phosphorylation of Thr850 by Rho kinase dissociates PP1M from myosin, providing a second mechanism by which myosin phosphatase activity is inhibited.
Velasco et al. (2002) studied this question.