title: Ischemic dysfunction in transgenic mice expressing troponin I lacking protein kinase C phosphorylation sites.
abstract: 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.
authors.affiliation: Pittsburgh Nuclear Magnetic Resonance Center for Biomedical Research, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA. macgowanga@msx.upmc.edu
authors.forename: G A
authors.initials: GA
authors.lastname: MacGowan
authors.forename: C
authors.initials: C
authors.lastname: Du
authors.forename: D B
authors.initials: DB
authors.lastname: Cowan
authors.forename: C
authors.initials: C
authors.lastname: Stamm
authors.forename: F X
authors.initials: FX
authors.lastname: McGowan
authors.forename: R J
authors.initials: RJ
authors.lastname: Solaro
authors.forename: A P
authors.initials: AP
authors.lastname: Koretsky
authors.forename: P J
authors.initials: PJ
authors.lastname: Del Nido
mesh_terms: 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
chemical_list: D019210:Troponin I; D012694:Serine; D011493:Protein Kinase C; D000409:Alanine; D002118:Calcium