title: Altered calsequestrin glycan processing is common to diverse models of canine heart failure.
abstract: Calsequestrin-2 (CSQ2) is a resident glycoprotein of junctional sarcoplasmic reticulum that functions in the regulation of SR Ca(2+) release. CSQ2 is biosynthesized in rough ER around cardiomyocyte nuclei and then traffics transversely across SR subcompartments. During biosynthesis, CSQ2 undergoes N-linked glycosylation and phosphorylation by protein kinase CK2. In mammalian heart, CSQ2 molecules subsequently undergo extensive mannose trimming by ER mannosidase(s), a posttranslational process that often regulates protein breakdown. We analyzed the intact purified CSQ2 from mongrel canine heart tissue by electrospray mass spectrometry. The average molecular mass of CSQ2 in normal mongrel dogs was 46,306 ± 41 Da, corresponding to glycan trimming of 3-5 mannoses, depending upon the phosphate content. We tested whether CSQ2 glycan structures would be altered in heart tissue from mongrel dogs induced into heart failure (HF) by two very different experimental treatments, rapid ventricular pacing or repeated coronary microembolizations. Similarly dramatic changes in mannose trimming were found in both types of induced HF, despite the different cardiomyopathies producing the failure. Unique to all samples analyzed from HF dog hearts, 20-40 % of all CSQ2 contained glycans that had minimal mannose trimming (Man9,8). Analyses of tissue samples showed decreases in CSQ2 protein levels per unit levels of mRNA for tachypaced heart tissue, also indicative of altered turnover. Quantitative immunofluorescence microscopy of frozen tissue sections suggested that no changes in CSQ2 levels occurred across the width of the cell. We conclude that altered processing of CSQ2 may be an adaptive response to the myocardium under stresses that are capable of inducing heart failure.
authors: Division of Cardiology/Electrophysiology, Department of Internal Medicine, Wayne State University, Detroit, MI 48201, USA.
authors: Sony
authors: S
authors: Jacob
authors: Naama H
authors: NH
authors: Sleiman
authors: Stephanie
authors: S
authors: Kern
authors: Larry R
authors: LR
authors: Jones
authors: Javier A
authors: JA
authors: Sala-Mercado
authors: Timothy P
authors: TP
authors: McFarland
authors: Hani H
authors: HH
authors: Sabbah
authors: Steven E
authors: SE
authors: Cala
mesh_terms: D000818:Animals; D009320:Atrial Natriuretic Factor / Q000378:metabolism; D002155:Calsequestrin / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D003208:Concanavalin A / Q000737:chemistry; D004195:Disease Models, Animal; D004285:Dogs; D018870:Endoplasmic Reticulum, Rough / Q000378:metabolism; D015870:Gene Expression; D006031:Glycosylation; D057809:HEK293 Cells; D006333:Heart Failure / Q000378:metabolism*; D006352:Heart Ventricles / Q000378:metabolism; D006801:Humans; D008351:Mannans / Q000378:metabolism; D008970:Molecular Weight; D020097:Natriuretic Peptide, Brain / Q000378:metabolism; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D002155:Calsequestrin; D008351:Mannans; D012333:RNA, Messenger; D003208:Concanavalin A; D020097:Natriuretic Peptide, Brain; D009320:Atrial Natriuretic Factor