Myosin light chain kinase- and PKC-dependent contraction of LES and esophageal smooth muscle.
In smooth muscle cells enzymatically isolated from circular muscle of the esophagus (ESO) and lower esophageal sphincter (LES), ACh-induced contraction and myosin light chain (MLC) phosphorylation were similar. Contraction and phosphorylation induced by purified MLC kinase (MLCK) were significantly greater in LES than ESO. ACh-induced contraction and MLC phosphorylation were inhibited by calmodulin and MLCK inhibitors in LES and by protein kinase C (PKC) inhibitors in ESO. Contraction of LES and ESO induced by the PKC agonist 1,2-dioctanoylglycerol (DG) was unaffected by MLCK inhibitors. Caldesmon and calponin concentration-dependently inhibited ACh-induced contraction of ESO and not LES. In ESO, caldesmon antagonist GS17C reversed caldesmon- but not calponin-induced ACh inhibition. GS17C caused contraction of permeabilized ESO but had much less effect on LES. GS17C-induced contraction was not affected by MLCK inhibitors, suggesting that MLCK may not regulate caldesmon-mediated contraction. DG-induced contraction of ESO and LES was inhibited by caldesmon and calponinin, suggesting that these proteins may regulate PKC-dependent contraction. We conclude that calmodulin and MLCK play a role in ACh-induced LES contraction, whereas the classical MLCK may not be the major kinase responsible for contraction and phosphorylation of MLC in ESO. ESO contraction is PKC dependent. Caldesmon and/or calponin may play a role in PKC-dependent contraction.
Sohn
U D
UD
Department of Pharmacology, College of Pharmacy, Chung Ang University, Seoul 156-756, Korea.
Cao
W
W
Tang
D C
DC
Stull
J T
JT
Haeberle
J R
JR
Wang
C L
CL
Harnett
K M
KM
Behar
J
J
Biancani
P
P
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002135:Calcium-Binding Proteins / Q000494:pharmacology; D002147:Calmodulin / Q000502:physiology; D002148:Calmodulin-Binding Proteins / Q000494:pharmacology; D002415:Cats; D002478:Cells, Cultured; D004943:Esophagogastric Junction / Q000502:physiology*; D004947:Esophagus / Q000502:physiology*; D005260:Female; D008297:Male; D008840:Microfilament Proteins; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism / Q000494:pharmacology*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000502:physiology*; D015398:Signal Transduction; D000096985:Calponins
D000109:Acetylcholine; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D008840:Microfilament Proteins; D009219:Myosin-Light-Chain Kinase; D011493:Protein Kinase C; D000096985:Calponins