title: Functionally conservative substitutions at cardiac troponin I S43/45.
abstract: A phospho-null Ala substitution at protein kinase C (PKC)-targeted cardiac troponin I (cTnI) S43/45 reduces myocyte and cardiac contractile function. The goal of the current study was to test whether cTnIS43/45N is an alternative, functionally conservative substitution in cardiac myocytes. Partial and more extensive endogenous cTnI replacement was similar at 2 and 4 days after gene transfer, respectively, for epitope-tagged cTnI and cTnIS43/45N. This replacement did not significantly change thin filament stoichiometry. In functional studies, there were no significant changes in the amplitude and/or rates of contractile shortening and re-lengthening after this partial (2 days) and extensive (4 days) replacement with cTnIS43/45N. The cTnIS43/45N substitution also was not associated with adaptive changes in the myocyte Ca(2+) transient or in phosphorylation of the protein kinase A and C-targeted cTnIS23/24 site. These results provide evidence that cTnIS43/45N is a functionally conservative substitution, and may be appropriate for use as a phospho-null in rodent models designed for studies on PKC modulation of cardiac performance.
authors: Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, MI 48109, USA.
authors: Sarah E
authors: SE
authors: Lang
authors: Department of Cardiac Surgery, University of Michigan, Ann Arbor, MI 48109, USA; Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA.
authors: Tamara K
authors: TK
authors: Stevenson
authors: Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
authors: Dongyang
authors: D
authors: Xu
authors: Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA.
authors: Ryan
authors: R
authors: O'Connell
authors: Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, MI 48109, USA; Department of Cardiac Surgery, University of Michigan, Ann Arbor, MI 48109, USA; Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA. Electronic address: wfall@med.umich.edu.
authors: Margaret V
authors: MV
authors: Westfall
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D000939:Epitopes / Q000737:chemistry; D018014:Gene Transfer Techniques; D016297:Mutagenesis, Site-Directed; D009200:Myocardial Contraction; D009206:Myocardium / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012518:Sarcomeres / Q000378:metabolism; D015398:Signal Transduction; D019210:Troponin I / Q000235:genetics / Q000378:metabolism*
chemical_list: D000939:Epitopes; D019210:Troponin I; D011493:Protein Kinase C; D002118:Calcium
keywords: Heart; Myofilament; Phosphorylation; Troponin