Sustained muscle contraction induced by agonists, growth factors, and Ca(2+) mediated by distinct PKC isozymes.
The role of protein kinase C (PKC) in sustained contraction was examined in intestinal circular and longitudinal muscle cells. Initial contraction induced by agonists (CCK-8 and neuromedin C) was abolished by 1) inhibitors of Ca(2+) mobilization (neomycin and dimethyleicosadienoic acid), 2) calmidazolium, and 3) myosin light chain (MLC) kinase (MLCK) inhibitor KT-5926. In contrast, sustained contraction was not affected by these inhibitors but was abolished by 1) the PKC inhibitors chelerythrine and calphostin C, 2) PKC-epsilon antibody, and 3) a pseudosubstrate PKC-epsilon inhibitor. GDPbetaS abolished both initial and sustained contraction, whereas a Galpha(q/11) antibody inhibited only initial contraction, implying that sustained contraction was dependent on activation of a distinct G protein. Sustained contraction induced by epidermal growth factor was inhibited by calphostin C, PKC-alpha,beta,gamma antibody, and a pseudosubstrate PKC-alpha inhibitor. Ca(2+) (0.4 microM) induced an initial contraction in permeabilized muscle cells that was blocked by calmodulin and MLCK inhibitors and a sustained contraction that was blocked by calphostin C and a PKC-alpha,beta,gamma antibody. Thus initial contraction induced by Ca(2+), agonists, and growth factors is mediated by MLCK, whereas sustained contraction is mediated by specific Ca(2+)-dependent and -independent PKC isozymes. G protein-coupled receptors are linked to PKC activation via distinct G proteins.
Murthy
K S
KS
Departments of Medicine and Physiology, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298, USA.
Grider
J R
JR
Kuemmerle
J F
JF
Makhlouf
G M
GM
D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D053119:Benzophenanthridines; D001839:Bombesin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002227:Carbazoles; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D006168:Guinea Pigs; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D007211:Indoles; D007422:Intestines / Q000166:cytology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000166:cytology / Q000201:enzymology*; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors; D009281:Naphthalenes / Q000494:pharmacology; D009355:Neomycin / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D010617:Phenanthridines / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D064546:Protein Kinase C beta; D051571:Protein Kinase C-alpha; D051744:Protein Kinase C-epsilon; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012844:Sincalide / Q000494:pharmacology*
D000470:Alkaloids; D000906:Antibodies; D053119:Benzophenanthridines; D002227:Carbazoles; D004791:Enzyme Inhibitors; D005231:Fatty Acids, Unsaturated; D007093:Imidazoles; D007211:Indoles; D007527:Isoenzymes; D009281:Naphthalenes; D010446:Peptide Fragments; D010617:Phenanthridines; D010726:Phosphodiesterase Inhibitors; D011500:Protein Synthesis Inhibitors; C063769:KT 5926; C031938:calmidazolium; D004815:Epidermal Growth Factor; C040794:neuromedin C; C059778:7,7-dimethyl-5,8-eicosadienoic acid; C016299:chelerythrine; C087857:protein kinase C gamma; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D051571:Protein Kinase C-alpha; D051744:Protein Kinase C-epsilon; D009219:Myosin-Light-Chain Kinase; D009355:Neomycin; C058819:calphostin C; D012844:Sincalide; D001839:Bombesin; D002118:Calcium