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Role of serine-threonine phosphoprotein phosphatases in smooth muscle contractility

Lookup NU author(s): Dr Tim Butler, Emeritus Professor Nick Europe-Finner


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The degree of phosphorylation of Myosin Light Chain 20 (MLC20) is a major determinant of force generation in smooth muscle. Myosin phosphatases (MP) all contain Protein Phosphatase 1 as catalytic subunits and are the major enzymes that dephosphorylate MLC20. MYPT1, the main regulatory subunit of MP in all smooth muscles, is a key convergence point of both contractile and relaxatory pathways. Combinations of regulatory mechanisms including isoform splicing, multiple phosphorylation sites and scaffolding proteins modulate MYPT1 activity with tissue- and agonist- specificities to affect contraction and relaxation. Other PP1 phosphatases that do not target myosin, as well as PP2A and PP2B dephosphorylate a range of proteins that affect smooth muscle contraction. This review discusses the role of phosphatases in smooth muscle contractility with a focus on MYPT1 in uterine smooth muscle. The myometrium shares characteristics of vascular and other visceral smooth muscles, yet during normal pregnancy undergoes hypertrophy, hyperplasia, quiescence and labor as normal physiology processes. The myometrium presents an accessible model for the study of normal and pathological smooth muscle function and a better understanding of myometrial physiology may allow the development of novel therapeutics for the many disorders of myometrial physiology from preterm labor to dysmenorrhea.

Publication metadata

Author(s): Butler T, Paul J, Europe-Finner GN, Smith R, Cheng-Chan E

Publication type: Review

Publication status: Published

Journal: American Journal of Physiology-Cell Physiology

Year: 2013

Volume: 304

Issue: 6

Pages: C485-C504

Print publication date: 16/01/2013

ISSN (print): 0363-6143


DOI: 10.1152/ajpcell.00161.2012