Augmented protein kinase C-alpha-induced myofilament protein phosphorylation contributes to myofilament dysfunction in experimental congestive heart failure.
It is becoming clear that upregulated protein kinase C (PKC) signaling plays a role in reduced ventricular myofilament contractility observed in congestive heart failure. However, data are scant regarding which PKC isozymes are involved. There is evidence that PKC-alpha may be of particular importance. Here, we examined PKC-alpha quantity, activity, and signaling to myofilaments in chronically remodeled myocytes obtained from rats in either early heart failure or end-stage congestive heart failure. Immunoblotting revealed that PKC-alpha expression and activation was unaltered in early heart failure but increased in end-stage congestive heart failure. Left ventricular myocytes were isolated by mechanical homogenization, Triton-skinned, and attached to micropipettes that projected from a force transducer and motor. Myofilament function was characterized by an active force-[Ca(2+)] relation to obtain Ca(2+)-saturated maximal force (F(max)) and myofilament Ca(2+) sensitivity (indexed by EC(50)) before and after incubation with PKC-alpha, protein phosphatase type 1 (PP1), or PP2a. PKC-alpha treatment induced a 30% decline in F(max) and 55% increase in the EC(50) in control cells but had no impact on myofilament function in failing cells. PP1-mediated dephosphorylation increased F(max) (15%) and decreased EC(50) ( approximately 20%) in failing myofilaments but had no effect in control cells. PP2a-dependent dephosphorylation had no effect on myofilament function in either group. Lastly, PP1 dephosphorylation restored myofilament function in control cells hyperphosphorylated with PKC-alpha. Collectively, our results suggest that in end-stage congestive heart failure, the myofilament proteins exist in a hyperphosphorylated state attributable, in part, to increased activity and signaling of PKC-alpha.
Belin
Rashad J
RJ
Department of Physiology and Biophysics, Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, IL 60612, USA.
Sumandea
Marius P
MP
Allen
Edward J
EJ
Schoenfelt
Kelly
K
Wang
Helen
H
Solaro
R John
RJ
de Tombe
Pieter P
PP
D008841:Actin Cytoskeleton / Q000201:enzymology* / Q000473:pathology; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D004195:Disease Models, Animal; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006333:Heart Failure / Q000201:enzymology* / Q000473:pathology; D006352:Heart Ventricles / Q000201:enzymology / Q000473:pathology; D009119:Muscle Contraction / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000201:enzymology* / Q000473:pathology; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D051571:Protein Kinase C-alpha / Q000378:metabolism* / Q000494:pharmacology; D054648:Protein Phosphatase 2; D051381:Rats; D017207:Rats, Sprague-Dawley; D020127:Recovery of Function / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects
D051571:Protein Kinase C-alpha; D010749:Phosphoprotein Phosphatases; C514014:Ppp2ca protein, rat; D054648:Protein Phosphatase 2; D002118:Calcium