Unzipping the Role of Myosin Light Chain Phosphatase in Smooth Muscle Cell Relaxation

Qi Quan Huang, Steven A. Fisher, Frank V. Brozovich

Research output: Contribution to journalArticle

67 Citations (Scopus)

Abstract

Recently, it has been hypothesized that myosin light chain (MLC) phosphatase is activated by cGMP-dependent protein kinase (PKG) via a leucine zipper-leucine zipper (LZ-LZ) interaction through the C-terminal LZ in the myosin-binding subunit (MBS) of MLC phosphatase and the N-terminal LZ of PKG (Surks, H. K., Mochizuki, N., Kasai, Y., Georgescu, S. P., Tang, K. M., Ito, M., Lincoln, T. M., and Mendelsohn, M. E. (1999) Science 286, 1583-1587). Alternative splicing of a 3′-exon produces a LZ+ or LZ - MBS, and the sensitivity to cGMP-mediated smooth muscle relaxation correlates with the relative expression of LZ+/LZ- MBS isoforms (Khatri, J. J., Joyce, K. M., Brozovich, F. V., and Fisher, S. A. (2001) J. Biol. Chem. 276, 37250-37257). In the present study, we determined the effect of LZ+/LZ- MBS isoforms on cGMP-induced MLC20 dephosphorylation. Four avian smooth muscle MBS-recombinant adenoviruses were prepared and transfected into cultured embryonic chicken gizzard smooth muscle cells. The expressed exogenous MBS isoforms were shown to replace the endogenous isoform in the MLC phosphatase holoenzyme. The interaction of type I PKG (PKGI) with the MBS did not depend on the presence of cGMP or the MBS LZ. However, direct activation of PKGI by 8-bromo-cGMP produced a dose-dependent decrease in MLC20 phosphorylation (p < 0.05) only in smooth muscle cells expressing a LZ+ MBS. These results suggest that the activation of MLC phosphatase by PKGI requires a LZ + MBS, but the binding of PKGI to the MBS is not mediated by a LZ-LZ interaction. Thus, the relative expression of LZ+/LZ- MBS isoforms could explain differences in tissue sensitivity to NO-mediated vasodilatation.

Original languageEnglish (US)
Pages (from-to)597-603
Number of pages7
JournalJournal of Biological Chemistry
Volume279
Issue number1
DOIs
StatePublished - Jan 2 2004
Externally publishedYes

Fingerprint

Myosin-Light-Chain Phosphatase
Muscle Relaxation
Myosins
Smooth Muscle Myocytes
Muscle
Cells
Leucine Zippers
Protein Isoforms
Chemical activation
Smooth Muscle Myosins
Avian Gizzard
Cyclic GMP-Dependent Protein Kinases
Holoenzymes
Phosphorylation
Alternative Splicing
Adenoviridae
Vasodilation
Smooth Muscle
Chickens
Exons

ASJC Scopus subject areas

  • Biochemistry

Cite this

Unzipping the Role of Myosin Light Chain Phosphatase in Smooth Muscle Cell Relaxation. / Huang, Qi Quan; Fisher, Steven A.; Brozovich, Frank V.

In: Journal of Biological Chemistry, Vol. 279, No. 1, 02.01.2004, p. 597-603.

Research output: Contribution to journalArticle

Huang, Qi Quan ; Fisher, Steven A. ; Brozovich, Frank V. / Unzipping the Role of Myosin Light Chain Phosphatase in Smooth Muscle Cell Relaxation. In: Journal of Biological Chemistry. 2004 ; Vol. 279, No. 1. pp. 597-603.
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