In This Issue In This Issue Monitoring MLCK yosin light chain kinase (MLCK) is a busy protein— it phosphorylates myosin's regulatory light chain (and thus activates myosin) during nonmuscle cell contraction, cytokinesis, stress fiber formation, and motility. In general, MLCK is known to be present at the cellular sites implicated in these events, but the results of Chew et al. (page 543) are so...

We have shown previously that only the long myosin light chain kinase (MLCK), which is the predominant MLCK isoform expressed in nonmuscle cells, localizes to the cleavage furrow. To further examine the in vivo localization of the long MLCK in HeLa cells and the mechanisms responsible for kinase targeting during the cell cycle, we examined the distribution of the endogenous kinase and construct...

During locomotion, adult rodent lumbar motoneurons fire in high-frequency (80-100 Hz) 1-2 s bursts every several seconds, releasing between 10,000 and 20,000 vesicles per burst. The estimated total vesicle pool size indicates that all vesicles would be used within 30 s; thus, a mechanism for rapid endocytosis and vesicle recycling is necessary to maintain effective transmission and motor behavi...

Strenuous exercise results in damage to skeletal muscle that is manifested in delayed muscle pain, prolonged strength loss, and increases in muscle proteins in the blood, especially creatine kinase (CK) and myoglobin (Mb). Some individuals experience profound changes in these variables in response to standard laboratory exercise or recreational activities. We proposed that variations in genes c...

To understand the roles of Rho-kinase and myosin light chain kinase (MLCK) for the contraction and organization of stress fibers, we treated cultured human foreskin fibroblasts with several MLCK, Rho-kinase, or calmodulin inhibitors and analyzed F-actin organization in the cells. Some cells were transfected with green fluorescent protein (GFP)-labeled actin, and the effects of inhibitors were a...

The cellular mechanisms that control arterial diameter in vivo, particularly in hypertension, are uncertain. Here, we report a method that permits arterial intracellular Ca(2+) concentration ([Ca(2+)](i)), myosin light-chain kinase (MLCK) activation, and artery external diameter to be recorded simultaneously with arterial blood pressure (BP) in living mice under 1.5% isofluorane anesthesia. The...

We have partially purified myosin light chain kinase (MLCK) and myosin light chain phosphatase (MLCP) from Dictyostelium discoideum. MLCK was purified 4,700-fold with a yield of approximately 1 mg from 350 g of cells. The enzyme is very acidic as suggested by its tight binding to DEAE. Dictyostelium MLCK has an apparent native molecular mass on HPLC G3000SW of approximately 30,000 D. Mg2+ is re...

Vascular hyporeactivity is an important factor in irreversible shock, and post-shock mesenteric lymph (PSML) blockade improves vascular reactivity after hemorrhagic shock. This study explored the possible involvement of myosin light chain kinase (MLCK) in PSML-mediated vascular hyporeactivity and calcium desensitization. Rats were divided into sham (n=12), shock (n=18), and shock+drainage (n=18...

Considerable evidence suggests that protein kinase C activation participates in the regulation of vascular smooth muscle tone. The objective of the current study was to examine the relations between inhibition of protein kinase C (PKC) and myosin light-chain kinase (MLCK) and vasorelaxation and blood pressure regulation in spontaneously hypertensive rats (SHR). Putative PKC inhibitors from two ...

BACKGROUND Previous studies suggest that Dupuytren's disease is caused by fibroblast and myofibroblast contractility. Cell contractility in smooth muscle cells is caused by calcium-dependent and calcium-independent signaling mechanisms. In the calcium-dependent pathway, calcium/calmodulin activates myosin light chain kinase (MLCK). In this study, the effects of calcium/calmodulin inhibition wit...