Protein kinase D increases maximal Ca2+-activated tension of cardiomyocyte contraction by phosphorylation of cMyBP-C-Ser315.
Cardiac myosin-binding protein C (cMyBP-C) is involved in the regulation of cardiac myofilament contraction. Recent evidence showed that protein kinase D (PKD) is one of the kinases that phosphorylate cMyBP-C. However, the mechanism by which PKD-induced cMyBP-C phosphorylation affects cardiac contractile responses is not known. Using immunoprecipitation, we showed that, in contracting cardiomyocytes, PKD binds to cMyBP-C and phosphorylates it at Ser(315). The effect of PKD-mediated phosphorylation of cMyBP-C on cardiac myofilament function was investigated in permeabilized ventricular myocytes, isolated from wild-type (WT) and from cMyBP-C knockout (KO) mice, incubated in the presence of full-length active PKD. In WT myocytes, PKD increased both myofilament Ca(2+) sensitivity (pCa(50)) and maximal Ca(2+)-activated tension of contraction (T(max)). In cMyBP-C KO skinned myocytes, PKD increased pCa(50) but did not alter T(max). This suggests that cMyBP-C is not involved in PKD-mediated sensitization of myofilaments to Ca(2+) but is essential for PKD-induced increase in T(max). Furthermore, the phosphorylation of both PKD-Ser(916) and cMyBP-C-Ser(315) was contraction frequency-dependent, suggesting that PKD-mediated cMyBP-C phosphorylation is operational primarily during periods of increased contractile activity. Thus, during high contraction frequency, PKD facilitates contraction of cardiomyocytes by increasing Ca(2+) sensitivity and by an increased T(max) through phosphorylation of cMyBP-C.
Department of Molecular Genetics, Cardiovascular Research Institute Maastricht, Maastricht University, the Netherlands. ellen.dirkx@maastrichtUniv.nl
Ellen
E
Dirkx
Olivier
O
Cazorla
Robert W
RW
Schwenk
Ilka
I
Lorenzen-Schmidt
Sakthivel
S
Sadayappan
Johan
J
Van Lint
Lucie
L
Carrier
Guillaume J J M
GJ
van Eys
Jan F C
JF
Glatz
Joost J F P
JJ
Luiken
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004558:Electric Stimulation; D056966:Excitation Contraction Coupling / Q000187:drug effects; D047468:Immunoprecipitation; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009200:Myocardial Contraction / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology*; D009210:Myofibrils / Q000201:enzymology; D010766:Phosphorylation; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D011917:Rats, Inbred Lew; D012694:Serine; D000099163:Myosin Binding Protein C
D000319:Adrenergic beta-Antagonists; D002352:Carrier Proteins; D011493:Protein Kinase C; D012694:Serine; D000099163:Myosin Binding Protein C; C089212:protein kinase D