title: AAV-mediated knock-down of HRC exacerbates transverse aorta constriction-induced heart failure.
abstract: BACKGROUND
  Histidine-rich calcium binding protein (HRC) is located in the lumen of sarcoplasmic reticulum (SR) that binds to both triadin (TRN) and SERCA affecting Ca(2+) cycling in the SR. Chronic overexpression of HRC that may disrupt intracellular Ca(2+) homeostasis is implicated in pathogenesis of cardiac hypertrophy. Ablation of HRC showed relatively normal phenotypes under basal condition, but exhibited a significantly increased susceptibility to isoproterenol-induced cardiac hypertrophy. In the present study, we characterized the functions of HRC related to Ca(2+) cycling and pathogenesis of cardiac hypertrophy using the in vitro siRNA- and the in vivo adeno-associated virus (AAV)-mediated HRC knock-down (KD) systems, respectively.
  
  
  RESULTS
  AAV-mediated HRC-KD system was used with or without C57BL/6 mouse model of transverse aortic constriction-induced failing heart (TAC-FH) to examine whether HRC-KD could enhance cardiac function in failing heart (FH). Initially we expected that HRC-KD could elicit cardiac functional recovery in failing heart (FH), since predesigned siRNA-mediated HRC-KD enhanced Ca(2+) cycling and increased activities of RyR2 and SERCA2 without change in SR Ca(2+) load in neonatal rat ventricular cells (NRVCs) and HL-1 cells. However, AAV9-mediated HRC-KD in TAC-FH was associated with decreased fractional shortening and increased cardiac fibrosis compared with control. We found that phospho-RyR2, phospho-CaMKII, phospho-p38 MAPK, and phospho-PLB were significantly upregulated by HRC-KD in TAC-FH. A significantly increased level of cleaved caspase-3, a cardiac cell death marker was also found, consistent with the result of TUNEL assay.
  
  
  CONCLUSIONS
  Increased Ca(2+) leak and cytosolic Ca(2+) concentration due to a partial KD of HRC could enhance activity of CaMKII and phosphorylation of p38 MAPK, causing the mitochondrial death pathway observed in TAC-FH. Our results present evidence that down-regulation of HRC could deteriorate cardiac function in TAC-FH through perturbed SR-mediated Ca(2+) cycling.
authors.affiliation: College of Life Sciences and Systems Biology Research Center, Gwangju Institute of Science and Technology (GIST), Buk-gu, Gwangju, Republic of Korea.
authors.forename: Chang Sik
authors.initials: CS
authors.lastname: Park
authors.forename: Hyeseon
authors.initials: H
authors.lastname: Cha
authors.forename: Eun Jeong
authors.initials: EJ
authors.lastname: Kwon
authors.forename: Dongtak
authors.initials: D
authors.lastname: Jeong
authors.forename: Roger J
authors.initials: RJ
authors.lastname: Hajjar
authors.forename: Evangelia G
authors.initials: EG
authors.lastname: Kranias
authors.forename: Chunghee
authors.initials: C
authors.lastname: Cho
authors.forename: Woo Jin
authors.initials: WJ
authors.lastname: Park
authors.forename: Do Han
authors.initials: DH
authors.lastname: Kim
mesh_terms: D000818:Animals; D001011:Aorta / Q000473:pathology*; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006332:Cardiomegaly / Q000473:pathology; D002352:Carrier Proteins / Q000378:metabolism*; D003250:Constriction; D003600:Cytosol / Q000378:metabolism; D000229:Dependovirus / Q000378:metabolism*; D004195:Disease Models, Animal; D004452:Echocardiography / Q000379:methods; D005786:Gene Expression Regulation; D006321:Heart / Q000502:physiology; D006333:Heart Failure / Q000235:genetics* / Q000503:physiopathology; D006639:Histidine / Q000737:chemistry*; D006706:Homeostasis; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009124:Muscle Proteins / Q000378:metabolism*; D010641:Phenotype; D010766:Phosphorylation; D034741:RNA, Small Interfering / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism*
chemical_list: D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D009124:Muscle Proteins; D034741:RNA, Small Interfering; C070048:triadin; D006639:Histidine; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D007545:Isoproterenol; D002118:Calcium