p21激活激酶对CPI17和1型蛋白磷酸酶的肌球蛋白结合亚基的磷酸化作用。

Phosphorylation of CPI17 and myosin binding subunit of type 1 protein phosphatase by p21-activated kinase.

作者信息

Takizawa Norio, Koga Yasuhiko, Ikebe Mitsuo

机构信息

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

出版信息

Biochem Biophys Res Commun. 2002 Oct 4;297(4):773-8. doi: 10.1016/s0006-291x(02)02302-1.

DOI:10.1016/s0006-291x(02)02302-1

PMID:12359219

Abstract

CPI17 and myosin binding subunit of type 1 protein phosphatase (MBS) are the regulators of myosin light chain phosphatase (MLCP). The function of both regulators is controlled by phosphorylation. The phosphorylation of CPI17 at Thr38 significantly enhances the inhibitory activity of CPI17 and the phosphorylation at Thr641 of MBS decreases the MLCP activity. Here, we found that p21-activated protein kinase (PAK) phosphorylates both CPI17 at Thr38 and MBS at Thr641. For CPI17, PAK specifically phosphorylated at Thr38, since the mutation of Thr38 to Ala completely abolished the phosphorylation. On the other hand, PAK phosphorylated Thr641 but not Thr799 of MBS, the site phosphorylated by Rho kinase. Because PAK phosphorylates MBS more than 1 mol/mol, it is anticipated that PAK also phosphorylates other sites in addition to Thr641. CPI17 phosphorylation induced by PAK significantly enhanced the inhibitory activity of CPI17. On the other hand, the phosphorylation of MBS by PAK also decreased the MLCP activity. These results raise the possibility that the PAK pathway plays a role in MLCP regulation.

摘要

CPI17和1型蛋白磷酸酶的肌球蛋白结合亚基（MBS）是肌球蛋白轻链磷酸酶（MLCP）的调节因子。这两种调节因子的功能均受磷酸化作用控制。CPI17在苏氨酸38处的磷酸化显著增强了CPI17的抑制活性，而MBS在苏氨酸641处的磷酸化则降低了MLCP的活性。在此，我们发现p21激活蛋白激酶（PAK）可使CPI17在苏氨酸38处以及MBS在苏氨酸641处发生磷酸化。对于CPI17，PAK特异性地在苏氨酸38处磷酸化，因为苏氨酸38突变为丙氨酸完全消除了磷酸化作用。另一方面，PAK使MBS的苏氨酸641发生磷酸化，但不使MBS的苏氨酸799（被Rho激酶磷酸化的位点）磷酸化。由于PAK使MBS磷酸化的摩尔数超过1 mol/mol，预计PAK除了使苏氨酸641磷酸化外，还会使其他位点磷酸化。PAK诱导的CPI17磷酸化显著增强了CPI17的抑制活性。另一方面，PAK对MBS的磷酸化也降低了MLCP的活性。这些结果提示PAK信号通路可能在MLCP调节中发挥作用。