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BioMed Research International
Volume 2013 (2013), Article ID 358643, 9 pages
http://dx.doi.org/10.1155/2013/358643
Research Article

Regulation of PKC Autophosphorylation by Calponin in Contractile Vascular Smooth Muscle Tissue

1Department of Health Sciences, Boston University, 635 Commonwealth Avenue, Boston, MA 02215, USA
2Department of Pharmacology, College of Medicine, Dankook University, 119 Dandaero, Chungnam, Cheonan-si 330-714, Republic of Korea

Received 20 August 2013; Revised 10 October 2013; Accepted 24 October 2013

Academic Editor: Goutam Ghosh Choudhury

Copyright © 2013 Hak Rim Kim et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Protein kinase C (PKC) is a key enzyme involved in agonist-induced smooth muscle contraction. In some cases, regulatory phosphorylation of PKC is required for full activation of the enzyme. However, this issue has largely been ignored with respect to PKC-dependent regulation of contractile vascular smooth muscle (VSM) contractility. The first event in PKC regulation is a transphosphorylation by PDK at a conserved threonine in the activation loop of PKC, followed by the subsequent autophosphorylation at the turn motif and hydrophobic motif sites. In the present study, we determined whether phosphorylation of PKC is a regulated process in VSM and also investigated a potential role of calponin in the regulation of PKC. We found that calponin increases the level of in vitro PKC phosphorylation at the PDK and hydrophobic sites, but not the turn motif site. In vascular tissues, phosphorylation of the PKC hydrophobic site, but not turn motif site, as well as phosphorylation of PDK at S241 increased in response to phenylephrine. Calponin knockdown inhibits autophosphorylation of cellular PKC in response to phenylephrine, confirming results with recombinant PKC. Thus these results show that autophosphorylation of PKC is regulated in dVSM and calponin is necessary for autophosphorylation of PKC in VSM.