title: O-linked GlcNAc modification of cardiac myofilament proteins: a novel regulator of myocardial contractile function.
abstract: In addition to O-phosphorylation, O-linked modifications of serine and threonine by beta-N-acetyl-D-glucosamine (GlcNAc) may regulate muscle contractile function. This study assessed the potential role of O-GlcNAcylation in cardiac muscle contractile activation. To identify specific sites of O-GlcNAcylation in cardiac myofilament proteins, a recently developed methodology based on GalNAz-biotin labeling followed by dithiothreitol replacement and light chromatography/tandem mass spectrometry site mapping was adopted. Thirty-two O-GlcNAcylated peptides from cardiac myofilaments were identified on cardiac myosin heavy chain, actin, myosin light chains, and troponin I. To assess the potential physiological role of the GlcNAc, force-[Ca(2+)] relationships were studied in skinned rat trabeculae. Exposure to GlcNAc significantly decreased calcium sensitivity (pCa50), whereas maximal force (F(max)) and Hill coefficient (n) were not modified. Using a pan-specific O-GlcNAc antibody, it was determined that acute exposure of myofilaments to GlcNAc induced a significant increase in actin O-GlcNAcylation. This study provides the first identification of O-GlcNAcylation sites in cardiac myofilament proteins and demonstrates their potential role in regulating myocardial contractile function.
authors.affiliation: Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Md., USA.
authors.forename: Genaro A
authors.initials: GA
authors.lastname: Ramirez-Correa
authors.forename: Wenhai
authors.initials: W
authors.lastname: Jin
authors.forename: Zihao
authors.initials: Z
authors.lastname: Wang
authors.forename: Xin
authors.initials: X
authors.lastname: Zhong
authors.forename: Wei Dong
authors.initials: WD
authors.lastname: Gao
authors.forename: Wagner B
authors.initials: WB
authors.lastname: Dias
authors.forename: Cecilia
authors.initials: C
authors.lastname: Vecoli
authors.forename: Gerald W
authors.initials: GW
authors.lastname: Hart
authors.forename: Anne M
authors.initials: AM
authors.lastname: Murphy
mesh_terms: D000117:Acetylglucosamine / Q000494:pharmacology / Q000502:physiology*; D008841:Actin Cytoskeleton / Q000187:drug effects / Q000502:physiology*; D000215:Acylation; D000818:Animals; D002236:Carbohydrate Conformation; D051379:Mice; D008810:Mice, Inbred C57BL; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology*; D009206:Myocardium; D051381:Rats
chemical_list: D000117:Acetylglucosamine