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1Boston Biomedical Research Institute, Watertown 02472; 2Department of Physiology, Tufts University Graduate School of Biomedical Sciences, Boston 02111; and 3Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115
Submitted 22 May 2003 ; accepted in final form 4 September 2003
Caveolin is a principal component of caveolar membranes. In the present study, we utilized a decoy peptide approach to define the degree of involvement of caveolin in PKC-dependent regulation of contractility of differentiated vascular smooth muscle. The primary isoform of caveolin in ferret aorta vascular smooth muscle is caveolin-1. Chemical loading of contractile vascular smooth muscle tissue with a synthetic caveolin-1 scaffolding domain peptide inhibited PKC-dependent increases in contractility induced by a phorbol ester or an
agonist. Peptide loading also resulted in a significant inhibition of phorbol ester-induced adducin Ser662 phosphorylation, an intracellular monitor of PKC kinase activity, ERK1/2 activation, and Ser789 phosphorylation of the actin binding protein caldesmon.
-Agonist-induced ERK11/2 activation was also inhibited by the caveolin-1 peptide. Scrambled peptide-loaded tissues or sham-loaded tissues were unaffected with respect to both contractility and signaling. Depolarization-induced activation of contraction was not affected by caveolin peptide loading. Similar results with respect to contractility and ERK1/2 activation during exposure to the phorbol ester or the
-agonist were obtained with the cholesterol-depleting agent methyl-
-cyclodextrin. These results are consistent with a role for caveolin-1 in the coordination of signaling leading to the regulation of contractility of smooth muscle.
signal transduction; extracellular signal-regulated kinase 1/2; caldesmon; decoy peptide
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