Borman Meredith A, MacDonald Justin A, Murányi Andrea, Hartshorne David J, Haystead Timothy A J
Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908, USA.
J Biol Chem. 2002 Jun 28;277(26):23441-6. doi: 10.1074/jbc.M201597200. Epub 2002 Apr 25.
Smooth muscle calcium sensitization reflects an inhibition of myosin light chain phosphatase (SMPP-1m) activity; however, the underlying mechanisms are not well understood. SMPP-1m activity can be modulated through phosphorylation of the myosin targeting subunit (MYPT1) by the endogenous myosin phosphatase-associated kinase, MYPT1 kinase (MacDonald, J. A., Borman, M. A., Muranyi, A., Somlyo, A. V., Hartshorne, D. J., and Haystead, T. A. (2001) Proc. Natl. Acad. Sci. U. S. A. 98, 2419-2424). Recombinant chicken gizzard MYPT1 (M130) was phosphorylated in vitro by a recombinant MYPT1 kinase, and the sites of phosphorylation were identified as Thr(654), Ser(808), and Thr(675). Introduction of recombinant MYPT1 kinase elicited a calcium-independent contraction in beta-escin-permeabilized rabbit ileal smooth muscle. Using an antibody that specifically recognizes MYPT1 phosphorylated at Thr(654) (M130 numbering), we determined that this calcium-independent contraction was correlated with an increase in MYPT1 phosphorylation. These results indicate that SMPP-1m phosphorylation by MYPT1 kinase is a mechanism of smooth muscle calcium sensitization.
平滑肌钙敏化反映了肌球蛋白轻链磷酸酶（SMPP-1m）活性的抑制；然而，其潜在机制尚未完全了解。SMPP-1m活性可通过内源性肌球蛋白磷酸酶相关激酶MYPT1激酶对肌球蛋白靶向亚基（MYPT1）的磷酸化来调节（MacDonald，J.A.，Borman，M.A.，Muranyi，A.，Somlyo，A.V.，Hartshorne，D.J.，和Haystead，T.A.（2001年）美国国家科学院院刊98，2419 - 2424）。重组鸡砂囊MYPT1（M130）在体外被重组MYPT1激酶磷酸化，磷酸化位点被确定为Thr(654)、Ser(808)和Thr(675)。在β-七叶皂苷通透的兔回肠平滑肌中，引入重组MYPT1激酶引发了不依赖钙的收缩。使用一种特异性识别在Thr(654)（M130编号）处磷酸化的MYPT1的抗体，我们确定这种不依赖钙的收缩与MYPT1磷酸化的增加相关。这些结果表明，MYPT1激酶对SMPP-1m的磷酸化是平滑肌钙敏化的一种机制。
