title: The FGF-2-triggered protection of cardiac subsarcolemmal mitochondria from calcium overload is mitochondrial connexin 43-dependent.
abstract: OBJECTIVE
  Fibroblast growth factor 2 (FGF-2) protects the heart from ischaemia- and reperfusion-induced cell death by a mechanism linked to protein kinase C (PKC)ε-mediated connexin 43 (Cx43) phosphorylation. Cx43 localizes predominantly to gap junctions, but has also been detected at subsarcolemmal (SSM), but not interfibrillar (IFM), mitochondria, where it is considered important for cardioprotection. We have now examined the effect of FGF-2 administration to the heart on resistance to calcium-induced permeability transition (mPTP) of isolated SSM vs. IFM suspensions, in relation to mitochondrial PKCε/Cx43 levels, phosphorylation, and the presence of peptide Gap27, a Cx43 channel blocker.
  
  
  RESULTS
  FGF-2 perfusion increased resistance to calcium-induced mPTP in SSM and IFM suspensions by 2.9- and 1.7-fold, respectively, compared with their counterparts from vehicle-perfused hearts, assessed spectrophotometrically as cyclosporine A-inhibitable swelling. The salutary effect of FGF-2 was lost in SSM, but not in IFM, in the presence of Gap27. FGF-2 perfusion increased relative levels of PKCε, phospho(p) PKCε, and Tom-20 translocase in SSM and IFM, and of Cx43 in SSM. Phospho-serine (pS) 262- and pS368-Cx43 showed a 30- and 8-fold increase, respectively, in SSM from FGF-2-treated, compared with untreated, hearts. Stimulation of control SSM with phorbol 12-myristate 13-acetate (PMA), a PKC activator, increased both calcium tolerance and mitochondrial Cx43 phosphorylation at S262 and S368. The PMA-induced phosphorylation of mitochondrial Cx43 was prevented by εV1-2, a PKCε-inhibiting peptide.
  
  
  CONCLUSIONS
  SSM are more responsive than IFM to FGF-2-triggered protection from calcium-induced mPTP, by a mitochondrial Cx43 channel-mediated pathway, associated with mitochondrial Cx43 phosphorylation at PKCε target sites.
authors.affiliation: Institute of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, 351 Taché Avenue, Winnipeg, Manitoba, Canada R2H 2A6 Department of Physiology, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Wattamon
authors.initials: W
authors.lastname: Srisakuldee
authors.affiliation: Institute of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, 351 Taché Avenue, Winnipeg, Manitoba, Canada R2H 2A6.
authors.forename: Zhanna
authors.initials: Z
authors.lastname: Makazan
authors.affiliation: Institute of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, 351 Taché Avenue, Winnipeg, Manitoba, Canada R2H 2A6.
authors.forename: Barbara E
authors.initials: BE
authors.lastname: Nickel
authors.affiliation: Department of Pharmacology, Sir Charles Tupper Medical Building, Dalhousie University, Halifax, Nova Scotia, Canada.
authors.forename: Feixiong
authors.initials: F
authors.lastname: Zhang
authors.affiliation: Department of Human Anatomy and Cell Sciences, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: James A
authors.initials: JA
authors.lastname: Thliveris
authors.affiliation: Department of Pharmacology, Sir Charles Tupper Medical Building, Dalhousie University, Halifax, Nova Scotia, Canada.
authors.forename: Kishore B S
authors.initials: KB
authors.lastname: Pasumarthi
authors.affiliation: Institute of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, 351 Taché Avenue, Winnipeg, Manitoba, Canada R2H 2A6 Department of Physiology, University of Manitoba, Winnipeg, Manitoba, Canada Department of Human Anatomy and Cell Sciences, University of Manitoba, Winnipeg, Manitoba, Canada ekardami@sbrc.ca.
authors.forename: Elissavet
authors.initials: E
authors.lastname: Kardami
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D018031:Connexin 43 / Q000378:metabolism*; D017630:Connexins / Q000378:metabolism; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism*; D017629:Gap Junctions / Q000378:metabolism; D008297:Male; D026901:Membrane Transport Proteins; D046529:Microscopy, Electron, Transmission; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D033681:Mitochondrial Membrane Transport Proteins / Q000378:metabolism; D000083162:Mitochondrial Permeability Transition Pore; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins / Q000378:metabolism; D008933:Mitochondrial Swelling; D009842:Oligopeptides; D010766:Phosphorylation; D051744:Protein Kinase C-epsilon / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D012508:Sarcolemma / Q000378:metabolism / Q000648:ultrastructure; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D018031:Connexin 43; D017630:Connexins; C580592:Gja1 protein, rat; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins; D009842:Oligopeptides; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; C489998:Tomm20 protein, rat; C455880:gap 27 peptide; D016222:Fibroblast Growth Factor 2; D051744:Protein Kinase C-epsilon; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium
keywords: FGF-2 cardioprotection; Interfibrillar mitochondria; Mitochondrial connexin 43; Permeability transition; Subsarcolemmal mitochondria