Myosin light-chain phosphatase (MLCP)

Myosin light-chain phosphatase (MLCP) is a heterotrimeric enzyme that plays a critical role in regulating the contractile state of smooth muscle and various non-muscle cellular processes. It is composed of a catalytic subunit (Protein phosphatase 1 catalytic subunit beta), a large regulatory subunit (Myosin phosphatase target subunit 1 or 2), and a smaller accessory subunit. The primary biological function of MLCP is the dephosphorylation of the 20 kDa regulatory light chain of myosin II, which promotes muscle relaxation and inhibits actomyosin-based motility. MLCP activity is a focal point for several signaling pathways; for instance, it is inhibited by the RhoA/ROCK pathway to induce calcium sensitization and sustained contraction, while it is activated by the NO/cGMP/PKG pathway to facilitate relaxation. Dysregulation of this enzyme is linked to numerous diseases, including hypertension, asthma, and cancer, where it influences cell migration and invasion. Although direct clinical inhibitors are currently lacking due to the ubiquitous nature of its catalytic subunit, MLCP remains a major therapeutic target through indirect modulation by ROCK inhibitors and nitric oxide donors.

Other names

Myosin phosphataseMPMLC phosphataseProtein phosphatase 1 regulatory subunit 12APPP1R12AMYPT1PP1-MYPT1 complexMyosin-binding subunitMBS

Dephosphorylation of the regulatory light chain of myosin II (MLC20) at Ser-19, leading to muscle relaxation and inhibition of actomyosin-based motility.