M-RIP Targets Myosin Phosphatase to Stress Fibers to Regulate Myosin Light Chain Phosphorylation in Vascular Smooth Muscle Cells

Surks, Howard K.; Riddick, Nadeene; Ohtani, Ken-Ichi

doi:10.1074/jbc.m506863200

Cited by 58 publications

(84 citation statements)

References 52 publications

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“…3B) or by mRNA analysis (MRIP; 85-95% decrease of mRNA levels in three separate experiments). As expected from previous studies (Koga and Ikebe, 2005;Surks et al, 2005;Xia et al, 2005), siMRIP or siMYPT1 transfections alone increased the number of actin fibers (data not shown; see also Fig. 6A-D).…”

Section: Nuak2 Targeted To Actin Stress Fibers By Mripsupporting

confidence: 76%

“…Although treatment with the ROCK inhibitor Y27632 leads to rapid disassembly of actin stress fibers in normal cells, in MRIPdownregulated cells Y27632-mediated fiber loss is significantly impaired (Surks et al, 2005), which was suggested to reflect the inability of MYPT1 and MLCP to target to fibers. To investigate disassembly of actin stress fibers upon ROCK inhibition in NUAK2-expressing cells they were treated with 10 M Y27632 for 30 minutes and analyzed for actin fibers.…”

Section: Nuak2 Expression Renders Central Actin Stress Fibers Resistamentioning

confidence: 99%

“…Several observations suggest that this interaction participates in the recruitment of MLCP to dephosphorylate MLC on actomyosin fibers: (1) MRIP directly associates with actin filaments through an N-terminal domain containing a pleckstrin homology (PH) domain and an acidic stretch (Mulder et al, 2003) and with MYPT through its C-terminal coil-coiled regions (Mulder et al, 2004;Surks et al, 2003) (shown schematically in Fig. 1A), (2) enhanced MRIP expression in cells leads to disruption of actin stress fibers (Mulder et al, 2003), (3) MRIP downregulation increases actin stress bundles and MLC phosphorylation, and shifts MYPT1 from a particulate to a soluble fraction (Koga and Ikebe, 2005;Surks et al, 2005), and (4) actin stress fibers in cells where MRIP (Surks et al, 2005) or MYPT (Xia et al, 2005) is downregulated are not disassembled following inhibition of ROCK by Y27632, implying that MLCP requires the association of MYPT and MRIP for efficient dephosphorylation of MLC. In the present study, we find that MLCP activation, which is crucial for actin stress fiber dynamics, is counteracted by a previously unrecognized association between MRIP and the inducible kinase NUAK2 (also known as SNARK).…”

Section: Introductionmentioning

confidence: 99%

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An association between NUAK2 and MRIP reveals a novel mechanism for regulation of actin stress fibers

Vallenius

Vaahtomeri

Kovac

et al. 2011

Journal of Cell Science

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SummaryActin stress fiber assembly and contractility in nonmuscle motile cells requires phosphorylation of myosin regulatory light chain (MLC). Dephosphorylation and disassembly are mediated by MLC phosphatase, which is targeted to actin fibers by the association of its regulatory subunit MYPT1 with myosin phosphatase Rho-interacting protein (MRIP). In the present study, we identify the kinase NUAK2 as a second protein targeted by MRIP to actin fibers. Association of NUAK2 with MRIP increases MLC phosphorylation and promotes formation of stress fibers. This activity does not require the kinase activity of NUAK2 but is dependent on both MRIP and MYPT1, indicating that the NUAK2-MRIP association inhibits fiber disassembly and MYPT1-mediated MLC dephosphorylation. NUAK2 levels are strongly induced by stimuli increasing actomyosin fiber formation, and NUAK2 is required for fiber maintenance in exponentially growing cells, implicating NUAK2 in a positive-feedback loop regulating actin stress fibers independently of the MLC kinase Rho-associated protein kinase (ROCK). The identified MRIP-NUAK2 association reveals a novel mechanism for the maintenance of actin stress fibers through counteracting MYPT1 and, together with recent results, implicates the NUAK proteins as important regulators of the MLC phosphatase acting in both a kinase-dependent and kinase-independent manner.

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Section: Nuak2 Targeted To Actin Stress Fibers By Mripsupporting

confidence: 76%

Section: Nuak2 Expression Renders Central Actin Stress Fibers Resistamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An association between NUAK2 and MRIP reveals a novel mechanism for regulation of actin stress fibers

Vallenius

Vaahtomeri

Kovac

et al. 2011

Journal of Cell Science

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“…In this respect it is interesting that phosphorylation of T855 reduces binding of myosin [8]. Another view is that the cell localization of myosin II could involve another protein, such as M-RIP (aka p116RIP) [9].…”

Section: Properties Of Mypt1mentioning

confidence: 99%

Myosin phosphatase target subunit: Many roles in cell function

Matsumura

Hartshorne

2008

Biochemical and Biophysical Research Communications

167

195

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Phosphorylation of myosin II is important in many aspects of cell function and involves a myosin kinase, e.g. myosin light chain kinase, and a myosin phosphatase (MP). MP is regulated by the myosin phosphatase target subunit (MYPT1). The domain structure, properties, and genetic analyses of MYPT1 and its isoforms are outlined. MYPT1 binds the catalytic subunit of type 1 phosphatase, δ isoform, and also acts as an interactive platform for many other proteins. A key reaction for MP is with phosphorylated myosin II and the first process shown to be regulated by MP was contractile activity of smooth muscle. In cell division and cell migration myosin II phosphorylation also plays a critical role and these are discussed. However, based on the wide range of partners for MYPT1 it is likely that MP is implicated with substrates other than myosin II. Open questions are whether the diverse functions of MP reflect different cellular locations and/or specific roles for the MYPT1 isoforms.

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“…For RhoA activation, GTP-bound RhoA was measured by using GST-Rhotekin-RBD binding assays as described (32). For determination of RhoA-S188-PO 4, WT and LZM VSMC lysates were resolved by SDS/PAGE and immunoblotted with anti-RhoA-S188-PO 4 antibodies in standard fashion, as described in SI Text.…”

Section: Rt-pcrmentioning

confidence: 99%

High blood pressure arising from a defect in vascular function

Michael

Surks

Wang

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

127

146

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Hypertension, a major cardiovascular risk factor and cause of mortality worldwide, is thought to arise from primary renal abnormalities. However, the etiology of most cases of hypertension remains unexplained. Vascular tone, an important determinant of blood pressure, is regulated by nitric oxide, which causes vascular relaxation by increasing intracellular cGMP and activating cGMPdependent protein kinase I (PKGI). Here we show that mice with a selective mutation in the N-terminal protein interaction domain of PKGI␣ display inherited vascular smooth muscle cell abnormalities of contraction, abnormal relaxation of large and resistance blood vessels, and increased systemic blood pressure. Renal function studies and responses to changes in dietary sodium in the PKGI␣ mutant mice are normal. These data reveal that PKGI␣ is required for normal VSMC physiology and support the idea that high blood pressure can arise from a primary abnormality of vascular smooth muscle cell contractile regulation, suggesting a new approach to the diagnosis and therapy of hypertension and cardiovascular diseases.cyclic nucleotides ͉ hypertension ͉ nitric oxide ͉ vascular biology ͉ vascular smooth muscle E levated blood pressure is a major risk factor for cardiovascular diseases and is responsible for widespread morbidity and mortality (1). Blood pressure is regulated by a variety of complex neurohumoral and mechanical signals that together determine systemic vascular tone and resistance (2, 3). The prevailing model for elevated blood pressure states that renal abnormalities of sodium handling cause volume expansion, increased systemic vascular resistance, and hypertension, and a large number of physiologic and genetic studies support this model and the central role of the renal renin-angiotensinaldosterone system in blood pressure regulation (4-8). Changes in vascular morphology and tone can increase vascular resistance and blood pressure (5), but the hypothesis that primary abnormalities of vascular smooth muscle tone can cause hypertension has not been sufficiently tested (6).Vascular smooth muscle contraction is initiated by both calcium-dependent and -independent mechanisms. Increases in intracellular calcium from receptor-or ion channel-activated pathways (2) lead to activation of myosin light chain kinase, which phosphorylates myosin light chains, activating myosin ATPase and increasing vascular smooth muscle cell (VSMC) contraction and vascular tone. The central calcium-independent pathway regulating VSMC tension is mediated by the GTPase RhoA and Rho kinase, which promote VSMC differentiation, stress fiber formation, and contraction, also increasing vascular tone (2, 7). Conversely, VSMC relaxation is mediated by activation of myosin light chain phosphatase (MLCP), which dephosphorylates myosin light chains to cause relaxation. The relative proportion of phosphorylated and dephosphorylated myosin light chains thus determines the state of VSMC tone (reviewed in ref.2). Nitric oxide, the most important endogenous vasodilator, cause...

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M-RIP Targets Myosin Phosphatase to Stress Fibers to Regulate Myosin Light Chain Phosphorylation in Vascular Smooth Muscle Cells

Cited by 58 publications

References 52 publications

An association between NUAK2 and MRIP reveals a novel mechanism for regulation of actin stress fibers

An association between NUAK2 and MRIP reveals a novel mechanism for regulation of actin stress fibers

Myosin phosphatase target subunit: Many roles in cell function

High blood pressure arising from a defect in vascular function

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