Abstract-Abnormal vascular smooth muscle cell (VSMC) contraction plays an important role in vascular diseases. The RhoA/ROCK signaling pathway is now well recognized to mediate vascular smooth muscle contraction in response to vasoconstrictors by inhibiting myosin phosphatase (MLCP) activity and increasing myosin light chain phosphorylation. Two ROCK isoforms, ROCK1 and ROCK2, are expressed in many tissues, yet the isoform-specific roles of ROCK1 and ROCK2 in vascular smooth muscle and the mechanism of ROCK-mediated regulation of MLCP are not well understood. In this study, ROCK2, but not ROCK1, bound directly to the myosin binding subunit of MLCP, yet both ROCK isoforms regulated MLCP and myosin light chain phosphorylation. Despite that both ROCK1 and ROCK2 regulated MLCP, the ROCK isoforms had distinct and opposing effects on VSMC morphology and ROCK2, but not ROCK1, had a predominant role in VSMC contractility. These data support that although the ROCK isoforms both regulate MLCP and myosin light chain phosphorylation through different mechanisms, they have distinct roles in VSMC function. (Circ Res. 2009;104:531-540.)Key Words: ROCK Ⅲ myosin phosphatase Ⅲ myosin light chain Ⅲ myosin binding subunit I ncreased vascular tone plays an important role in the pathophysiology of vascular diseases including hypertension, atherosclerosis, and myocardial infarction. 1-3 Vascular tone is regulated by the contraction of vascular smooth muscle cells (VSMC) in the blood vessel wall. Vascular smooth muscle contraction is tightly coupled to the phosphorylation of the regulatory myosin light chain, 4 which is regulated by the opposing activities of myosin light chain (MLC) kinase (MLCK) and myosin light chain phosphatase (MLCP) (reviewed elsewhere 5 ). MLCP dephosphorylates MLC, leading to vascular smooth muscle relaxation (reviewed elsewhere 6,7 ). MLCP activity is highly regulated by both vasoconstrictor and vasodilator signaling pathways. Nitrovasodilators stimulate cGMP-dependent protein kinase 1␣, which activates MLCP to cause MLC dephosphorylation and smooth muscle relaxation. 8 -10 Vasoconstrictors, conversely, inhibit MLCP, leading to MLC phosphorylation and smooth muscle contraction (reviewed elsewhere 6 ). Vasoconstrictor-mediated MLCP inhibition occurs by either phosphorylation of the MLCP inhibitory protein CPI-17 11 or by phosphorylation of the myosin binding subunit (MBS) of MLCP at inhibitory sites T696 and T850. [12][13][14] The RhoA/ROCK pathway is the most extensively studied mechanism of MLCP inhibition. Vasoconstrictor G proteincoupled receptor agonists lead to activation of RhoA guanine nucleotide exchange factors and GTP loading of the monomeric GTPase RhoA. 15 GTP-bound RhoA then binds and activates its downstream effector ROCK, 16 -18 which in turn phosphorylates MBS 19 at the 2 phosphorylation sites, 12,13 leading to inhibition of MLCP activity. 14 Phosphorylation at T850 also has been shown to cause dissociation of MBS from myosin. 20 More recently, T850 has been implicated as the major ROCK phosp...

By using an engaged interprofessional team, we optimized use of our on-site outpatient pharmacy and increased the percentage of pediatric patients leaving the hospital with new discharge medications in hand to >80%. This, accompanied by increased rates of bedside medication delivery and pharmacist teaching, was associated with improvements in caregiver discharge-medication related experience and understanding.

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