Dephosphorylation of the two regulatory components of myosin phosphatase, MBS and CPI17

FEBS Letters

Niiro, Naohisa¹  Ikebe, Mitsuo¹  Takizawa, Norio¹ 

[1]Department of Physiology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA

关键词: Smooth muscle;    Myosin phosphatase;    CPI17;    Rho-kinase;    Protein kinase C;    Phospholipid;    MLC;    myosin light chain;    MLCK;    myosin light chain kinase;    PP1;    type 1 protein phosphatase;    MLCP;    myosin light chain phosphatase;    MBS;    myosin binding subunit of PP1;    PP1c;    catalytic subunit of PP1;    PP2A;    type 2A protein phosphatase;    PP2Ac;    catalytic subunit of PP2A;    PP2B;    type 2B protein phosphatase;    PP2C;    type 2C protein phosphatase;    PKC;    protein kinase C;    2-ME;    2-mercaptoethanol;    PS;    phosphatidylserine;    PI;    phosphatidylinositol;    AA;    arachidonic acid;    DAG;    diacylglycerol;    LPA;    lysophosphatidic acid;   

DOI  :  10.1016/S0014-5793(02)02451-1

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Dephosphorylation of the two key regulatory factors of myosin light chain phosphatase (MLCP), CPI17 and MBS (myosin binding subunit) of MLCP was studied. While Thr38 phosphorylated CPI17 is quite susceptible to protein phosphatases, phosphorylated MBS was highly resistant to dephosphorylation. Type 2A, 2B and 2C protein phosphatases (PP2A, PP2B and PP2C), but not type 1 (PP1), dephosphorylated CPI17. The majority of the CPI17 phosphatase activity in smooth muscle was attributed to PP2A and PP2C. Phospholipids inhibited dephosphorylation of MBS and arachidonic acid (AA) inhibited PP2A activity against both MBS and CPI17, raising the possibility that AA favors the preservation of active MLCP. Consistently, while the phosphorylation of CPI17 was promptly decreased when the agonist was removed, the phosphorylation of MBS was unchanged in intact smooth muscle fiber. The results suggest that MBS phosphorylation mediated regulation of MLCP is not suitable for regulating rapid change in myosin phosphorylation. On the other hand, phosphorylated CPI17 is readily dephosphorylated thus likely to play a role in regulating fast phosphorylation–dephosphorylation cycle in cells.

【 授权许可】

Unknown