| First Author | Hamdani N | Year | 2013 |
| Journal | Circ Res | Volume | 112 |
| Issue | 4 | Pages | 664-74 |
| PubMed ID | 23283722 | Mgi Jnum | J:200470 |
| Mgi Id | MGI:5508699 | Doi | 10.1161/CIRCRESAHA.111.300105 |
| Citation | Hamdani N, et al. (2013) Crucial role for Ca2(+)/calmodulin-dependent protein kinase-II in regulating diastolic stress of normal and failing hearts via titin phosphorylation. Circ Res 112(4):664-74 |
| abstractText | RATIONALE: Myocardial diastolic stiffness and cardiomyocyte passive force (F(passive)) depend in part on titin isoform composition and phosphorylation. Ca(2+)/calmodulin-dependent protein kinase-II (CaMKII) phosphorylates ion channels, Ca(2+)-handling proteins, and chromatin-modifying enzymes in the heart, but has not been known to target titin. OBJECTIVE: To elucidate whether CaMKII phosphorylates titin and modulates F(passive) in normal and failing myocardium. METHODS AND RESULTS: Titin phosphorylation was assessed in CaMKIIdelta/gamma double-knockout (DKO) mouse, transgenic CaMKIIdeltaC-overexpressing mouse, and human hearts, by Pro-Q-Diamond/Sypro-Ruby staining, autoradiography, and immunoblotting using phosphoserine-specific titin-antibodies. CaMKII-dependent site-specific titin phosphorylation was quantified in vivo by mass spectrometry using stable isotope labeling by amino acids in cell culture mouse heart mixed with wild-type (WT) or DKO heart. F(passive) of single permeabilized cardiomyocytes was recorded before and after CaMKII-administration. All-titin phosphorylation was reduced by >50% in DKO but increased by up to approximately 100% in transgenic versus WT hearts. Conserved CaMKII-dependent phosphosites were identified within the PEVK-domain of titin by quantitative mass spectrometry and confirmed in recombinant human PEVK-fragments. CaMKII also phosphorylated the cardiac titin N2B-unique sequence. Phosphorylation at specific PEVK/titin N2B-unique sequence sites was decreased in DKO and amplified in transgenic versus WT hearts. F(passive) was elevated in DKO and reduced in transgenic compared with WT cardiomyocytes. CaMKII-administration lowered F(passive) of WT and DKO cardiomyocytes, an effect blunted by titin antibody pretreatment. Human end-stage failing hearts revealed higher CaMKII expression/activity and phosphorylation at PEVK/titin N2B-unique sequence sites than nonfailing donor hearts. CONCLUSIONS: CaMKII phosphorylates the titin springs at conserved serines/threonines, thereby lowering F(passive). Deranged CaMKII-dependent titin phosphorylation occurs in heart failure and contributes to altered diastolic stress. |
