Document Detail

Crucial Role for Ca2+/Calmodulin-Dependent Protein Kinase-II in Regulating Diastolic Stress of Normal and Failing Hearts via Titin Phosphorylation.
MedLine Citation:
PMID:  23283722     Owner:  NLM     Status:  Publisher    
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, Ca2(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 CaMKIIδ/γ double-knockout (DKO) mouse, transgenic CaMKIIδC-overexpressing (TG) 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 SILAC mouse heart mixed with wildtype (WT) or DKO heart. Fpassive 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 ~100% in TG versus WT hearts. Conserved CaMKII-dependent phosphosites were identified within titin's PEVK-domain by quantitative mass spectrometry and confirmed in recombinant human PEVK-fragments. CaMKII also phosphorylated the cardiac titin N2B-unique sequence (N2Bus). Phosphorylation at specific PEVK/N2Bus sites was decreased in DKO and amplified in TG versus WT hearts. Fpassive was elevated in DKO and reduced in TG compared to WT cardiomyocytes. CaMKII-administration lowered Fpassive 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/N2Bus sites than non-failing 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.
Nazha Hamdani; Judith Krysiak; Michael M Kreusser; Stefan Neef; Cristobal G Dos Remedios; Lars S Maier; Markus Krüger; Johannes Backs; Wolfgang A Linke
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-1-2
Journal Detail:
Title:  Circulation research     Volume:  -     ISSN:  1524-4571     ISO Abbreviation:  Circ. Res.     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-1-3     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0047103     Medline TA:  Circ Res     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
1Cardiovascular Physiology, Ruhr University Bochum, Ruhr University Bochum, MA 3/56, Bochum, D-44780, GERMANY.
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