title: The peripheral-type benzodiazepine receptor is involved in control of Ca2+-induced permeability transition pore opening in rat brain mitochondria.
abstract: The peripheral-type benzodiazepine receptor (PBR) is an 18 kDa mitochondrial membrane protein with still elusive function in cell death. Here, we studied whether PBR is involved in Ca2+-induced permeability transition pore (PTP) opening in isolated rat brain mitochondria (RBM). PTP opening is important in mitochondrial events leading to programmed cell death. Immunoblots revealed a single 18 kDa anti-PBR antibody-immunoreactive band in purified RBM. Adenine nucleotide transporter, a key PTP component, was found in the PBR-immunoprecipitate. In isolated intact RBM, addition of a specific anti-PBR antibody [H. Li, Z. Yao, B. Degenhardt, G. Teper, V. Papadopoulos, Cholesterol binding at the cholesterol recognition/interaction amino acid consensus (CRAC) of the peripheral-type benzodiazepine receptor and inhibition of steroidogenesis by an HIV TAT-CRAC peptide, Proc. Natl. Acad. Sci. U.S.A. 98 (2001) 1267-1272] delayed Ca2+-induced dissipation of membrane potential (psi(m)) and diminished cyclosporine A-sensitive Ca2+ efflux, which are both indicative for the suppression of PTP opening. Moreover, anti-PBR antibody caused partial retention of Ca2+ in the mitochondrial matrix in spite of psi(m) dissipation, and reduced activation of respiratory rate at Ca2+-induced PTP opening. A release of pro-apoptotic factors, AIF and cytochrome c, from RBM was shown at threshold Ca2+ load. Anti-PBR antibody blocked the release of AIF but did not affect the cytochrome c release. Addition of ATP was able to initiate PTP closing, associated with psi(m) restoration and Ca2+ re-accumulation. At the same time mitochondrial protein phosphorylation (incorporation of 32P from [gamma-32P]ATP) occurred and anti-PBR antibody was able to inhibit phosphorylation of these proteins. The endogenous PBR ligand, protoporphyrin IX, facilitated PTP opening and phosphorylation of the mitochondrial proteins, thus, inducing effects opposite to anti-PBR antibody. This study provides evidence for PBR involvement in PTP opening, controlling the Ca2+-induced Ca2+ efflux, and AIF release from mitochondria, important stages of initiation of programmed cell death.
authors.affiliation: Institut für Neurobiochemie, Otto-von-Guericke-Universität Magdeburg, Medizinische Fakultät, Leipziger Strasse 44, 39120 Magdeburg, Germany.
authors.forename: Tamara
authors.initials: T
authors.lastname: Azarashvili
authors.forename: Dmitry
authors.initials: D
authors.lastname: Grachev
authors.forename: Olga
authors.initials: O
authors.lastname: Krestinina
authors.forename: Youri
authors.initials: Y
authors.lastname: Evtodienko
authors.forename: Igor
authors.initials: I
authors.lastname: Yurkov
authors.forename: Vassilios
authors.initials: V
authors.lastname: Papadopoulos
authors.forename: Georg
authors.initials: G
authors.lastname: Reiser
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D051033:Apoptosis Inducing Factor / Q000378:metabolism; D001570:Benzodiazepinones / Q000494:pharmacology; D001921:Brain / Q000378:metabolism*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002352:Carrier Proteins / Q000187:drug effects / Q000276:immunology / Q000302:isolation & purification / Q000502:physiology*; D016572:Cyclosporine / Q000494:pharmacology; D045304:Cytochromes c / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D000226:Mitochondrial ADP, ATP Translocases / Q000302:isolation & purification; D033681:Mitochondrial Membrane Transport Proteins / Q000187:drug effects / Q000502:physiology*; D000083162:Mitochondrial Permeability Transition Pore; D010766:Phosphorylation; D011524:Protoporphyrins / Q000494:pharmacology; D051381:Rats; D011963:Receptors, GABA-A / Q000187:drug effects / Q000276:immunology / Q000302:isolation & purification / Q000502:physiology*
chemical_list: D000906:Antibodies; D051033:Apoptosis Inducing Factor; D001570:Benzodiazepinones; D002352:Carrier Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D011524:Protoporphyrins; D011963:Receptors, GABA-A; C069997:Tspo protein, rat; C028513:4'-chlorodiazepam; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D000001:Calcimycin; D016572:Cyclosporine; D000255:Adenosine Triphosphate; D045304:Cytochromes c; D000226:Mitochondrial ADP, ATP Translocases; C028025:protoporphyrin IX; D002118:Calcium