title: PKCβII modulation of myocyte contractile performance.
abstract: Significant up-regulation of the protein kinase Cβ(II) (PKCβ(II)) develops during heart failure and yet divergent functional outcomes are reported in animal models. The goal here is to investigate PKCβ(II) modulation of contractile function and gain insights into downstream targets in adult cardiac myocytes. Increased PKCβ(II) protein expression and phosphorylation developed after gene transfer into adult myocytes while expression remained undetectable in controls. The PKCβ(II) was distributed in a peri-nuclear pattern and this expression resulted in diminished rates and amplitude of shortening and re-lengthening compared to controls and myocytes expressing dominant negative PKCβ(II) (PKCβDN). Similar decreases were observed in the Ca(2+) transient and the Ca(2+) decay rate slowed in response to caffeine in PKCβ(II)-expressing myocytes. Parallel phosphorylation studies indicated PKCβ(II) targets phosphatase activity to reduce phospholamban (PLB) phosphorylation at residue Thr17 (pThr17-PLB). The PKCβ inhibitor, LY379196 (LY) restored pThr17-PLB to control levels. In contrast, myofilament protein phosphorylation was enhanced by PKCβ(II) expression, and individually, LY and the phosphatase inhibitor, calyculin A each failed to block this response. Further work showed PKCβ(II) increased Ca(2+)-activated, calmodulin-dependent kinase IIδ (CaMKIIδ) expression and enhanced both CaMKIIδ and protein kinase D (PKD) phosphorylation. Phosphorylation of both signaling targets also was resistant to acute inhibition by LY. These later results provide evidence PKCβ(II) modulates contractile function via intermediate downstream pathway(s) in cardiac myocytes.
authors.affiliation: Dept. of Surgery, Cardiac Surgery Section, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Hyosook
authors.initials: H
authors.lastname: Hwang
authors.forename: Dustin A
authors.initials: DA
authors.lastname: Robinson
authors.forename: Tamara K
authors.initials: TK
authors.lastname: Stevenson
authors.forename: Helen C
authors.initials: HC
authors.lastname: Wu
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Kampert
authors.forename: Francis D
authors.initials: FD
authors.lastname: Pagani
authors.forename: D Brad
authors.initials: DB
authors.lastname: Dyke
authors.forename: Jody L
authors.initials: JL
authors.lastname: Martin
authors.forename: Sakthival
authors.initials: S
authors.lastname: Sadayappan
authors.forename: Sharlene M
authors.initials: SM
authors.lastname: Day
authors.forename: Margaret V
authors.initials: MV
authors.lastname: Westfall
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D005455:Fluorescent Antibody Technique; D008297:Male; D009200:Myocardial Contraction / Q000235:genetics / Q000502:physiology*; D032383:Myocytes, Cardiac / Q000378:metabolism*; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D064546:Protein Kinase C beta; D011817:Rabbits; D051381:Rats; D015398:Signal Transduction
chemical_list: D011493:Protein Kinase C; D064546:Protein Kinase C beta; D002118:Calcium