Myosin Light Chain Kinase Is Necessary for Tonic Airway Smooth Muscle Contraction

Abstract

Different interacting signaling modules involving Ca2؉ / calmodulin-dependent myosin light chain kinase, Ca 2؉ -independent regulatory light chain phosphorylation, myosin phosphatase inhibition, and actin filament-based proteins are proposed as specific cellular mechanisms involved in the regulation of smooth muscle contraction. However, the relative importance of specific modules is not well defined. By using tamoxifen-activated and smooth muscle-specific knock-out of myosin light chain kinase in mice, we analyzed its role in tonic airway smooth muscle contraction. Knock-out of the kinase in both tracheal and bronchial smooth muscle significantly reduced contraction and myosin phosphorylation responses to K ؉ -depolarization and acetylcholine. Kinase-deficient mice lacked bronchial constrictions in normal and asthmatic airways, whereas the asthmatic inflammation response was not affected. These results indicate that myosin light chain kinase acts as a central participant in the contractile signaling module of tonic smooth muscle. Importantly, contractile airway smooth muscles are necessary for physiological and asthmatic airway resistance.

Myosin Phosphatase Target Subunit 1 (MYPT1) Regulates the Contraction and Relaxation of Vascular Smooth Muscle and Maintains Blood Pressure

“…Smooth muscle-specific knock-out of MLCK is lethal and results in general smooth muscle failure with markedly impaired contractile responses in ileal (32), airway, vascular (13,33), and bladder (34) (30) smooth muscle tissues. In contrast smooth muscle-specific knock-out of MYPT1 is not lethal (27) but does lead to measurable changes in contractile properties of smooth muscle tissues with in vivo consequences as with hypertension described herein.…”

Myosin Light Chain Kinase (MLCK) Regulates Cell Migration in a Myosin Regulatory Light Chain Phosphorylation-independent Mechanism

“…Western Blot Analysis-Regulatory myosin light chain phosphorylation was measured by urea/glycerol-polyacrylamide gel electrophoresis (PAGE) and immunoblotting as previously described (38,39). Cells were seeded on 60-mm Petri dishes and harvested by completely removing the medium followed by directly lysing with 1 ml of ice-cold 10% trichloroacetic acid containing 10 mM dithiothreitol in acetone.…”

The Transmembrane Protein 16A Ca2+-activated Cl− Channel in Airway Smooth Muscle Contributes to Airway Hyperresponsiveness

“…Immunostaining was the same as described previously (31). Rabbit anti-TMEM16A and mouse monoclonal smooth muscle a-actin antibody were purchased from Abcam (Cambridge, MA) and Neomarkers (Fremont, CA), respectively.…”