title: Regulation of PKC autophosphorylation by calponin in contractile vascular smooth muscle tissue.
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 PKCα 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.
authors.affiliation: Department of Health Sciences, Boston University, 635 Commonwealth Avenue, Boston, MA 02215, USA ; Department of Pharmacology, College of Medicine, Dankook University, 119 Dandaero, Chungnam, Cheonan-si 330-714, Republic of Korea.
authors.forename: Hak Rim
authors.initials: HR
authors.lastname: Kim
authors.affiliation: Department of Health Sciences, Boston University, 635 Commonwealth Avenue, Boston, MA 02215, USA.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Gallant
authors.affiliation: Department of Health Sciences, Boston University, 635 Commonwealth Avenue, Boston, MA 02215, USA.
authors.forename: Kathleen G
authors.initials: KG
authors.lastname: Morgan
mesh_terms: D020816:Amino Acid Motifs; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002148:Calmodulin-Binding Proteins / Q000378:metabolism; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology; D008840:Microfilament Proteins / Q000378:metabolism*; D009119:Muscle Contraction / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000378:metabolism* / Q000502:physiology*; D010766:Phosphorylation / Q000502:physiology; D011493:Protein Kinase C / Q000378:metabolism*; D000096985:Calponins; D000099291:Adducins
chemical_list: D002135:Calcium-Binding Proteins; D002148:Calmodulin-Binding Proteins; D008840:Microfilament Proteins; D011493:Protein Kinase C; D000096985:Calponins; D000099291:Adducins