Myosin phosphatase target subunit 1 (MBS) is a subunit of myosin phosphatase, which regulates actin-myosin interactions via Rho, a small GTPase. RhoA, in its GTP-bound form, interacts with MBS to control myosin light chain (MLC) phosphorylation, affecting smooth muscle contraction and nonmuscle cell function. Rho-kinase, activated by GTP-RhoA, phosphorylates MBS, inhibiting myosin phosphatase. Overexpression or activation of RhoA increases MBS and MLC phosphorylation. MBS plays a critical role in modulating actin-myosin interactions and is regulated by RhoA signaling. Several isoforms of this gene arise from alternative splicing.