title: Cardiac-specific overexpression of sarcolipin inhibits sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA2a) activity and impairs cardiac function in mice.
abstract: Sarcolipin (SLN) inhibits the cardiac sarco(endo)plasmic reticulum Ca(2+) ATPase (SERCA2a) by direct binding and is superinhibitory if it binds through phospholamban (PLN). To determine whether overexpression of SLN in the heart might impair cardiac function, transgenic (TG) mice were generated with cardiac-specific overexpression of NF-SLN (SLN tagged at its N terminus with the FLAG epitope). The level of NF-SLN expression (the NF-SLN/PLN expression ratio) was equivalent to that which induces profound superinhibition when coexpressed with PLN and SERCA2a in HEK-293 cells. In TG hearts, the apparent affinity of SERCA2a for Ca(2+) was decreased compared with non-TG littermate control hearts. Invasive hemodynamic and echocardiographic analyses revealed impaired cardiac contractility and ventricular hypertrophy in TG mice. Basal PLN phosphorylation was reduced. In isolated papillary muscle subjected to isometric tension, peak amplitudes of Ca(2+) transients and peak tensions were reduced, whereas decay times of Ca(2+) transients and relaxation times of tension were increased in TG mice. Isoproterenol largely restored contractility in papillary muscle and stimulated PLN phosphorylation to wild-type levels in intact hearts. No compensatory changes in expression of SERCA2a, PLN, ryanodine receptor, and calsequestrin were observed in TG hearts. Coimmunoprecipitation indicated that overexpressed NF-SLN was bound to both SERCA2a and PLN, forming a ternary complex. These data suggest that NF-SLN overexpression inhibits SERCA2a through stabilization of SERCA2a-PLN interaction in the absence of PLN phosphorylation and through the inhibition of PLN phosphorylation. Inhibition of SERCA2a impairs contractility and calcium cycling, but responsiveness to beta-adrenergic agonists may prevent progression to heart failure.
authors.affiliation: Department of Internal Medicine and Therapeutics, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Michio
authors.initials: M
authors.lastname: Asahi
authors.forename: Kinya
authors.initials: K
authors.lastname: Otsu
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Nakayama
authors.forename: Shungo
authors.initials: S
authors.lastname: Hikoso
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Takeda
authors.forename: Anthony O
authors.initials: AO
authors.lastname: Gramolini
authors.forename: Maria G
authors.initials: MG
authors.lastname: Trivieri
authors.forename: Gavin Y
authors.initials: GY
authors.lastname: Oudit
authors.forename: Takashi
authors.initials: T
authors.lastname: Morita
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Kusakari
authors.forename: Shuta
authors.initials: S
authors.lastname: Hirano
authors.forename: Kenichi
authors.initials: K
authors.lastname: Hongo
authors.forename: Shinichi
authors.initials: S
authors.lastname: Hirotani
authors.forename: Osamu
authors.initials: O
authors.lastname: Yamaguchi
authors.forename: Alan
authors.initials: A
authors.lastname: Peterson
authors.forename: Peter H
authors.initials: PH
authors.lastname: Backx
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kurihara
authors.forename: Masatsugu
authors.initials: M
authors.lastname: Hori
authors.forename: David H
authors.initials: DH
authors.lastname: MacLennan
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology; D000252:Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004452:Echocardiography; D004721:Endoplasmic Reticulum / Q000201:enzymology; D006321:Heart / Q000502:physiology*; D006439:Hemodynamics / Q000235:genetics; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D009200:Myocardial Contraction; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism*; D011510:Proteolipids / Q000235:genetics / Q000378:metabolism*; D011817:Rabbits; D011994:Recombinant Proteins / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000201:enzymology; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D014162:Transfection
chemical_list: D009124:Muscle Proteins; D011510:Proteolipids; D011994:Recombinant Proteins; C077258:sarcolipin; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D002118:Calcium