{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,31]],"date-time":"2026-07-31T17:42:22Z","timestamp":1785519742189,"version":"3.56.0"},"reference-count":76,"publisher":"Wiley","issue":"14","license":[{"start":{"date-parts":[[2014,6,3]],"date-time":"2014-06-03T00:00:00Z","timestamp":1401753600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"funder":[{"DOI":"10.13039\/100000002","name":"National Institutes of Health Grants","doi-asserted-by":"crossref","award":["R01 HL112778"],"award-info":[{"award-number":["R01 HL112778"]}],"id":[{"id":"10.13039\/100000002","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/100000002","name":"National Institutes of Health Grants","doi-asserted-by":"crossref","award":["P01 HL110869"],"award-info":[{"award-number":["P01 HL110869"]}],"id":[{"id":"10.13039\/100000002","id-type":"DOI","asserted-by":"crossref"}]},{"name":"Moss Heart Fund"},{"name":"Fouad A. and Val Imm Bashour Distinguished Chair in Physiology, National Basic Research Program of China","award":["2009CB942602"],"award-info":[{"award-number":["2009CB942602"]}]},{"name":"National Natural Science Funding of China","award":["31272311"],"award-info":[{"award-number":["31272311"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["The Journal of Physiology"],"published-print":{"date-parts":[[2014,7,15]]},"abstract":"<jats:sec><jats:title>Key points<\/jats:title><jats:p><jats:list list-type=\"bullet\">\n<jats:list-item><jats:p>Smooth muscle myosin regulatory light chain (RLC) phosphorylation depends on the relative activities of myosin light chain kinase (MLCK), activated by Ca<jats:sup>2+<\/jats:sup>\u2013calmodulin, and myosin light chain phosphatase (MLCP).<\/jats:p><\/jats:list-item>\n<jats:list-item><jats:p>MYPT1 is a scaffolding protein subunit of MLCP that binds the catalytic subunit PP1c\u03b4 and myosin, affects the conformation of PP1c\u03b4 for effective inhibition by phosphorylated CPI\u201017, and is phosphorylated at two sites that inhibit PP1c\u03b4 activity.<\/jats:p><\/jats:list-item>\n<jats:list-item><jats:p>A conditional knockout of MYPT1 in smooth muscles of adult mice resulted in modest changes in bladder smooth muscle contractile and relaxation responses to KCl or carbachol even though the amount of PP1c\u03b4 protein was reduced.<\/jats:p><\/jats:list-item>\n<jats:list-item><jats:p>A new a procedure to quantify phosphorylation of MYPT1 showed substantial phosphorylation in wild\u2010type tissues under resting conditions, predicting attenuation of MLCP activity. Reduced PP1c\u03b4 activity in MYPT1\u2010deficient tissues may be similar to the attenuated MLCP activity in wild\u2010type tissues resulting from constitutively phosphorylated MYPT1.<\/jats:p><\/jats:list-item>\n<jats:list-item><jats:p>In contrast to results obtained with the conditional knockout of MLCK in smooth muscle, MYPT1 is not necessary for smooth muscle function because its loss may not change the effective MLCP activity.<\/jats:p><\/jats:list-item>\n<\/jats:list><\/jats:p><\/jats:sec><jats:sec><jats:title>Abstract<\/jats:title><jats:p>Smooth muscle contraction initiated by myosin regulatory light chain (RLC) phosphorylation is dependent on the relative activities of Ca<jats:sup>2+<\/jats:sup>\u2013calmodulin\u2010dependent myosin light chain kinase (MLCK) and myosin light chain phosphatase (MLCP). We have investigated the physiological role of the MLCP regulatory subunit MYPT1 in bladder smooth muscle containing a smooth muscle\u2010specific deletion of MYPT1 in adult mice. Deep\u2010sequencing analyses of mRNA and immunoblotting revealed that MYPT1 depletion reduced the amount of PP1c\u03b4 with no compensatory changes in expression of other MYPT1 family members. Phosphatase activity towards phosphorylated smooth muscle heavy meromyosin was proportional to the amount of PP1c\u03b4 in total homogenates from wild\u2010type or MYPT1\u2010deficient tissues. Isolated MYPT1\u2010deficient tissues from MYPT1<jats:sup>SM\u2212\/\u2212<\/jats:sup> mice contracted with moderate differences in response to KCl and carbachol treatments, and relaxed rapidly with comparable rates after carbachol removal and only 1.5\u2010fold slower after KCl removal. Measurements of phosphorylated proteins in the RLC signalling and actin polymerization modules during contractions revealed moderate changes. Using a novel procedure to quantify total phosphorylation of MYPT1 at Thr696 and Thr853, we found substantial phosphorylation in wild\u2010type tissues under resting conditions, predicting attenuation of MLCP activity. Reduced PP1c\u03b4 activity in MYPT1\u2010deficient tissues may be similar to the attenuated MLCP activity in wild\u2010type tissues resulting from constitutively phosphorylated MYPT1. Constitutive phosphorylation of MYPT1 Thr696 and Thr853 may thus represent a physiological mechanism acting in concert with agonist\u2010induced MYPT1 phosphorylation to inhibit MLCP activity. In summary, MYPT1 deficiency may not cause significant derangement of smooth muscle contractility because the effective MLCP activity is not changed.<\/jats:p><\/jats:sec>","DOI":"10.1113\/jphysiol.2014.273011","type":"journal-article","created":{"date-parts":[[2014,5,16]],"date-time":"2014-05-16T10:07:07Z","timestamp":1400234827000},"page":"3031-3051","source":"Crossref","is-referenced-by-count":24,"title":["Constitutive phosphorylation of myosin phosphatase targeting subunit\u20101 in smooth muscle"],"prefix":"10.1113","volume":"592","author":[{"given":"Ming\u2010Ho","family":"Tsai","sequence":"first","affiliation":[{"name":"Department of Physiology University of Texas Southwestern Medical Center  Dallas TX 75390 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Audrey N.","family":"Chang","sequence":"additional","affiliation":[{"name":"Department of Physiology University of Texas Southwestern Medical Center  Dallas TX 75390 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jian","family":"Huang","sequence":"additional","affiliation":[{"name":"Department of Physiology University of Texas Southwestern Medical Center  Dallas TX 75390 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Weiqi","family":"He","sequence":"additional","affiliation":[{"name":"Model Animal Research Center and MOE Key Laboratory of Model Animal for Disease Study Nanjing University  Nanjing China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"H. 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