PPP1R14A (Protein phosphatase 1 regulatory subunit 14A) is a phosphorylation-dependent inhibitory protein for smooth muscle myosin phosphate. Myosin phosphatase can reverse MYL (myosin light chain) phosphorylation to induce a state of relaxation. However, during agonist-induced contraction at constant Ca2+ concurrent inhibition of myosin phosphatase leads to increases in MYL phosphorylation and tension.