Partial replacement of cardiac troponin I with a non-phosphorylatable mutant at serines 43/45 attenuates the contractile dysfunction associated with PKCepsilon phosphorylation.
We have previously reported a transgenic mouse that over-expresses constitutively active PKCepsilon in the myocardium and exhibits a steady progression to heart failure. Associated with the decline in function was an increased phosphorylation of sarcomeric proteins including cardiac troponin I (cTnI). To determine whether PKCepsilon phosphorylation of cTnI is sufficient to induce cardiac maladaptation, we have generated a double transgenic mouse (DbTG) that expresses constitutively active PKCepsilon and cTnI harboring non-phosphorylatable mutations in the putative PKC phosphorylation sites (S43A, S45A). We compared the hemodynamic and biochemical properties of the hearts from the DbTG mice to the non-transgenic and single transgenic lines at both 3 and 12 months of age. While no significant differences in LV function were noted in 3-month groups, the depression of function in the PKCepsilon mice was attenuated in the double transgenic mice at 12 months. The improvement in cardiac function was correlated with decreased beta-myosin heavy chain and ANF mRNA expression in the 12m DbTG mice. The extent of cTnI phosphorylation was determined using a novel one-dimensional, non-equilibrium isoelectric focusing technique. At 3 months the migration of cTnI phospho-species was different in the PKCepsilon mice and to a lesser degree in the DbTG compared to all other groups. At 12 months additional phospho-species were observed in both the PKCepsilon and DbTG samples, along with an overall shift in the distribution of phospho-species in all groups due to age. These results suggest that phosphorylation of cTnI by PKCepsilon is associated with contractile dysfunction and partial replacement of serines 43/45 improves cardiac performance. Therefore, we conclude that phosphorylation of cTnI at Ser 43 and 45 may contribute to the progression of failure.
Scruggs
Sarah B
SB
Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois, USA.
Walker
Lori A
LA
Lyu
Theodore
T
Geenen
David L
DL
Solaro
R John
RJ
Buttrick
Peter M
PM
Goldspink
Paul H
PH
D000375:Aging / Q000235:genetics / Q000378:metabolism; D019943:Amino Acid Substitution; D000818:Animals; D002460:Cell Line; D006333:Heart Failure / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D009200:Myocardial Contraction / Q000235:genetics; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D051744:Protein Kinase C-epsilon / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000235:genetics; D019210:Troponin I / Q000235:genetics / Q000378:metabolism*; D016277:Ventricular Function, Left / Q000235:genetics
D019210:Troponin I; D051744:Protein Kinase C-epsilon