Epsilon-isoenzyme of protein kinase C induces a Ca(2+)-independent contraction in vascular smooth muscle.
We provide here the first direct evidence for in situ functional specificity of protein kinase C (PKC)-epsilon as a regulator of smooth muscle contractility. PKC is known to cause a Ca(2+)-independent contraction of ferret aortic smooth muscle, and the expression of two Ca(2+)-independent PKC isoenzymes, epsilon and zeta, has been demonstrated in this tissue. To test directly the hypothesis that one of these isoenzymes regulates contractility, constitutively active forms of PKC-epsilon and PKC-zeta were applied to saponin-permeabilized single ferret aortic smooth muscle cells. PKC-zeta caused no significant force response, but PKC-epsilon induced contraction of a magnitude (105 +/- 8 micrograms) similar to that produced by phenylephrine (110 +/- 10 micrograms), a relatively selective alpha 1-adrenergic agonist that triggers a PKC-dependent contraction. The PKC-epsilon-induced contraction was reversed by the PKC pseudosubstrate inhibitory peptide, PKC19-31. The myosin light chain kinase inhibitor 1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine (ML-9) did not affect the force response of PKC-epsilon-activated cells, suggesting that PKC-epsilon may induce this contraction solely via thin filament disinhibition. In support of this conclusion, calponin and caldesmon were shown to be good in vitro substrates of PKC-epsilon but not of PKC-zeta.
Horowitz
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A
Program in Smooth Muscle Research, Charles A. Dana Research Institute, Harvard-Thorndike Laboratory, Beth Israel Hospital, Boston, Massachusetts, USA.
Clément-Chomienne
O
O
Walsh
M P
MP
Morgan
K G
KG
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002148:Calmodulin-Binding Proteins / Q000378:metabolism; D005289:Ferrets; D007527:Isoenzymes / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D008840:Microfilament Proteins / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009219:Myosin-Light-Chain Kinase / Q000502:physiology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D051744:Protein Kinase C-epsilon; D000096985:Calponins; D000099221:Protein Kinase C zeta
D002118:Calcium; D002135:Calcium-Binding Proteins; D002148:Calmodulin-Binding Proteins; D007527:Isoenzymes; D008840:Microfilament Proteins; D009219:Myosin-Light-Chain Kinase; D011493:Protein Kinase C; D051744:Protein Kinase C-epsilon; D000096985:Calponins; D000099221:Protein Kinase C zeta