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Am J Respir Cell Mol Biol. 1997 May;16(5):489-94.

Myosin light chain kinase in endothelium: molecular cloning and regulation.

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  • 1Department of Medicine, Indiana University School of Medicine, and Richard Roudebush Veterans Administration Center, Indianapolis, USA.


The phosphorylation of myosin light chains by myosin light chain kinase (MLCK) is a key event in agonist-mediated endothelial cell gap formation and vascular permeability. We now report the cloning and expression of a nonmuscle MLCK isoform in cultured endothelium. Screening of a human endothelial cell cDNA library identified a 7.7 kb cDNA with substantial (> 95%) homology to the coding region of the rabbit and bovine smooth muscle (SM) MLCK (amino acid #923-1913) as well as with the reported avian nonmuscle MLCK (65-70% homology). Sequence analysis also identified, however, a 5' stretch of novel sequence (amino acids #1-922) which is not contained in the open reading frame of mammalian SM MLCK, and is only 58% homologous to the avian fibroblast MLCK sequence. Immunoprecipitation with NH2-specific antisera revealed a 214 kD high molecular weight MLCK in bovine and human endothelium which exhibits MLC phosphorylation properties. Amino acid sequence analysis revealed endothelial MLCK consensus sequences for a variety of protein kinases including highly conserved potential phosphorylation sites for cAMP-dependent protein kinase A (PKA) in the CaM-binding region. Augmentation of intracellular cAMP levels markedly enhanced MLCK phosphorylation (2.5-fold increase) and reduced kinase activity in MLCK immunoprecipitates (4-fold decrease). These data suggest potentially novel mechanisms of endothelial cell contraction and barrier regulation.

[PubMed - indexed for MEDLINE]
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