title: The mitochondrial phosphate carrier interacts with cyclophilin D and may play a key role in the permeability transition.
abstract: The mitochondrial permeability transition pore (MPTP) plays a key role in cell death, yet its molecular identity remains uncertain. Although knock-out studies have confirmed critical roles for both cyclophilin-D (CyP-D) and the adenine nucleotide translocase (ANT), given a strong enough stimulus MPTP opening can occur in the absence of either. Here we provide evidence that the mitochondrial phosphate carrier (PiC) may also be a critical component of the MPTP. Phenylarsine oxide (PAO) was found to activate MPTP opening in the presence of carboxyatractyloside (CAT) that prevents ANT binding to immobilized PAO. Only four proteins from solubilized CAT-treated beef heart inner mitochondrial membranes bound to immobilized PAO, one of which was the PiC. GST-CyP-D pull-down and co-immunoprecipitation studies revealed CsA-sensitive binding of PiC to CyP-D; this increased following diamide treatment. Co-immunoprecipitation of the ANT with the PiC was also observed but was insensitive to CsA treatment. N-ethylmaleimide and ubiquinone analogues (UQ(0) and Ro 68-3400) inhibited phosphate transport into rat liver mitochondria with the same concentration dependence as their inhibition of MPTP opening. UQ(0) and Ro 68-3400 also induced the "m" conformation of the ANT, as does NEM, and reduced the binding of both the PiC and ANT to the PAO column. We propose a model for the MPTP in which a calcium-triggered conformational change of the PiC, facilitated by CyP-D, induces pore opening. An interaction of the PiC with the ANT may enable agents that bind to either transporter to modulate pore opening.
authors.affiliation: Department of Biochemistry and The Bristol Heart Institute, University of Bristol, School of Medical Sciences, University Walk, Bristol BS8 1TD, United Kingdom.
authors.forename: Anna W C
authors.initials: AW
authors.lastname: Leung
authors.forename: Pinadda
authors.initials: P
authors.lastname: Varanyuwatana
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Halestrap
mesh_terms: D000818:Animals; D001152:Arsenicals / Q000494:pharmacology; D016227:Benzoquinones / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology*; D000081406:Peptidyl-Prolyl Isomerase F; D021983:Cyclophilins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016572:Cyclosporine / Q000494:pharmacology; D003986:Dibenzocycloheptenes / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005033:Ethylmaleimide / Q000494:pharmacology; D017136:Ion Transport / Q000187:drug effects; D008929:Mitochondria, Heart / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000378:metabolism*; D000226:Mitochondrial ADP, ATP Translocases / Q000037:antagonists & inhibitors / Q000378:metabolism; D051336:Mitochondrial Membranes / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D028061:Phosphate Transport Proteins / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D011487:Protein Conformation / Q000187:drug effects; D051381:Rats; D013141:Spiro Compounds / Q000494:pharmacology
chemical_list: D001152:Arsenicals; D016227:Benzoquinones; D000081406:Peptidyl-Prolyl Isomerase F; D003986:Dibenzocycloheptenes; D004791:Enzyme Inhibitors; D024101:Mitochondrial Proteins; D028061:Phosphate Transport Proteins; C480229:Ro 68-3400; D013141:Spiro Compounds; C029341:oxophenylarsine; C109863:ubiquinone-O; D016572:Cyclosporine; D000226:Mitochondrial ADP, ATP Translocases; D021983:Cyclophilins; D005033:Ethylmaleimide