Introduction: Phosphorylation of smooth muscle (SM) myosin regulatory light chain (RLC 20 ) is a critical switch leading to SM contraction. The canonical view held that only the short isoform kinase (MLCK1) catalyzed this reaction. It now accepted auxiliary kinases may contribute vascular tone and contractility. We have previously reported p90 ribosomal S6 (RSK2) functions as such kinase, in pa...

TNF-alpha plays a central role in the intestinal inflammation of various inflammatory disorders including Crohn's disease (CD). TNF-alpha-induced increase in intestinal epithelial tight junction (TJ) permeability has been proposed as one of the proinflammatory mechanisms contributing to the intestinal inflammation. The intracellular mechanisms involved in the TNF-alpha-induced increase in intes...

Ma, Thomas Y., Michel A. Boivin, Dongmei Ye, Ali Pedram, and Hamid M. Said. Mechanism of TNFmodulation of Caco-2 intestinal epithelial tight junction barrier: role of myosin light-chain kinase protein expression. Am J Physiol Gastrointest Liver Physiol 288: G422–G430, 2005; doi:10.1152/ajpgi.00412.2004.—TNFplays a central role in the intestinal inflammation of various inflammatory disorders inc...

A TNF-alpha-induced increase in intestinal epithelial tight junction (TJ) permeability has been proposed to be an important proinflammatory mechanism contributing to intestinal inflammation in Crohn's disease and other inflammatory conditions. Previous studies from our laboratory suggested that the TNF-alpha-induced increase in intestinal TJ permeability was mediated by an increase in myosin li...

Ma, Thomas Y., Michel A. Boivin, Dongmei Ye, Ali Pedram, and Hamid M. Said. Mechanism of TNFmodulation of Caco-2 intestinal epithelial tight junction barrier: role of myosin light-chain kinase protein expression. Am J Physiol Gastrointest Liver Physiol 288: G422–G430, 2005; doi:10.1152/ajpgi.00412.2004.—TNFplays a central role in the intestinal inflammation of various inflammatory disorders inc...

Polymorphonuclear leukocyte (PMNL) phagocytosis mediated by FcgammaRII proceeds in concert with activation of the mitogen-activated protein (MAP) kinase, extracellular signal-regulated kinase ERK2. We hypothesized that myosin light chain kinase (MLCK) could be phosphorylated and activated by ERK, thereby linking the MAP kinase pathway to the activation of cytoskeletal components required for ps...

The main regulatory mechanism of smooth muscle contraction involves Ca2+/calmodulin (CaM)-dependent phosphorylation of myosin (CDPM), by myosin light chain kinase (MLCK). It is also known that the increase in intracellular Ca2+ and phosphorylation of myosin occurs within a short time under physiological conditions, but the muscle tension may persist for a longer period of time. However, the mec...

Two myosin light chain (MLC) kinase (MLCK) proteins, smooth muscle (encoded by mylk1 gene) and skeletal (encoded by mylk2 gene) MLCK, have been shown to be expressed in mammals. Even though phosphorylation of its putative substrate, MLC2, is recognized as a key regulator of cardiac contraction, a MLCK that is preferentially expressed in cardiac muscle has not yet been identified. In this study,...

Smooth muscle myosin (SMM) light chain kinase (MLCK) phosphorylates SMM, thereby activating the ATPase activity required for muscle contraction. The abundance of active MLCK, which is tightly associated with the contractile apparatus, is low relative to that of SMM. SMM phosphorylation is rapid despite the low ratio of MLCK to SMM, raising the question of how one MLCK rapidly phosphorylates man...