Ischemic dysfunction in transgenic mice expressing troponin I lacking protein kinase C phosphorylation sites.
To determine the in vivo functional significance of troponin I (TnI) protein kinase C (PKC) phosphorylation sites, we created a transgenic mouse expressing mutant TnI, in which PKC phosphorylation sites at serines-43 and -45 were replaced by alanine. When we used high-perfusate calcium as a PKC activator, developed pressures in transgenic (TG) perfused hearts were similar to wild-type (WT) hearts (P = not significant, NS), though there was a 35% and 32% decrease in peak-systolic intracellular calcium (P < 0.01) and diastolic calcium (P < 0.005), respectively. The calcium transient duration was prolonged in the TG mice also (12-27%, ANOVA, P < 0.01). During global ischemia, TG hearts developed ischemic contracture to a greater extent than WT hearts (41 +/- 18 vs. 69 +/- 10 mmHg, perfusate calcium 3.5 mM, P < 0.01). In conclusion, expression of mutant TnI lacking PKC phosphorylation sites results in a marked alteration in the calcium-pressure relationship, and thus susceptibility to ischemic contracture. The reduced intracellular calcium and prolonged calcium transients suggests that a potent feedback mechanism exists between the myofilament and the processes controlling calcium homeostasis.
MacGowan
G A
GA
Pittsburgh Nuclear Magnetic Resonance Center for Biomedical Research, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA. macgowanga@msx.upmc.edu
Du
C
C
Cowan
D B
DB
Stamm
C
C
McGowan
F X
FX
Solaro
R J
RJ
Koretsky
A P
AP
Del Nido
P J
PJ
D000409:Alanine / Q000235:genetics; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002118:Calcium / Q000378:metabolism; D005246:Feedback / Q000502:physiology; D005260:Female; D006706:Homeostasis / Q000502:physiology; D066298:In Vitro Techniques; D051379:Mice; D008822:Mice, Transgenic; D016296:Mutagenesis / Q000502:physiology; D017202:Myocardial Ischemia / Q000378:metabolism*; D015428:Myocardial Reperfusion Injury / Q000378:metabolism; D009206:Myocardium / Q000201:enzymology / Q000473:pathology; D009929:Organ Size; D010101:Oxygen Consumption / Q000502:physiology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012694:Serine / Q000235:genetics; D019210:Troponin I / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D017725:Ventricular Pressure / Q000502:physiology
D019210:Troponin I; D012694:Serine; D011493:Protein Kinase C; D000409:Alanine; D002118:Calcium