title: Interplay between the effects of a Protein Kinase C phosphomimic (T204E) and a dilated cardiomyopathy mutation (K211Δ or R206W) in rat cardiac troponin T blunts the magnitude of muscle length-mediated crossbridge recruitment against the β-myosin heavy chain background.
abstract: Failing hearts of dilated cardiomyopathy (DCM)-patients reveal systolic dysfunction and upregulation of several Protein Kinase C (PKC) isoforms. Recently, we demonstrated that the functional effects of T204E, a PKC phosphomimic of cardiac troponin T (TnT), were differently modulated by α- and β-myosin heavy chain (MHC) isoforms. Therefore, we hypothesized that the interplay between the effects of T204E and a DCM-linked mutation (K211Δ or R206W) in TnT would modulate contractile parameters linked-to systolic function in an MHC-dependent manner. To test our hypothesis, five TnT variants (wildtype, K211Δ, K211Δ + T204E, R206W, and R206W + T204E) were generated and individually reconstituted into demembranated cardiac muscle fibers from normal (α-MHC) and propylthiouracil-treated (β-MHC) rats. Steady-state and mechano-dynamic measurements were performed on reconstituted fibers. Myofilament Ca(2+) sensitivity (pCa50) was decreased by both K211Δ and R206W to a greater extent in α-MHC fibers (~0.15 pCa units) than in β-MHC fibers (~0.06 pCa units). However, T204E exacerbated the attenuating influence of both mutants on pCa50 only in β-MHC fibers. Moreover, the magnitude of muscle length (ML)-mediated crossbridge (XB) recruitment was decreased by K211Δ + T204E (~47 %), R206W (~34 %), and R206W + T204E (~36 %) only in β-MHC fibers. In relevance to human hearts, which predominantly express β-MHC, our data suggest that the interplay between the effects of DCM mutations, PKC phosphomimic in TnT, and β-MHC lead to systolic dysfunction by attenuating pCa50 and the magnitude of ML-mediated XB recruitment.
authors.affiliation: Department of Integrative Physiology and Neuroscience, Washington State University, 205 Veterinary Biomedical Research Building, Pullman, WA, 99164-7620, USA.
authors.forename: John Jeshurun
authors.initials: JJ
authors.lastname: Michael
authors.affiliation: Department of Integrative Physiology and Neuroscience, Washington State University, 205 Veterinary Biomedical Research Building, Pullman, WA, 99164-7620, USA.
authors.forename: Sampath K
authors.initials: SK
authors.lastname: Gollapudi
authors.affiliation: Department of Integrative Physiology and Neuroscience, Washington State University, 205 Veterinary Biomedical Research Building, Pullman, WA, 99164-7620, USA. murali@vetmed.wsu.edu.
authors.forename: Murali
authors.initials: M
authors.lastname: Chandra
mesh_terms: D000818:Animals; D002311:Cardiomyopathy, Dilated / Q000378:metabolism*; D006801:Humans; D009154:Mutation; D032383:Myocytes, Cardiac / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D020107:Troponin T / Q000378:metabolism*
chemical_list: D020107:Troponin T; D011493:Protein Kinase C; D018995:Myosin Heavy Chains
keywords: Dilated cardiomyopathy; Muscle length-mediated crossbridge recruitment dynamics; Myosin heavy chain; Protein Kinase C; Troponin T