Inhibition of mitochondrial membrane bound-glutathione transferase by mitochondrial permeability transition inhibitors including cyclosporin A.
OBJECTIVE
Effect of mitochondrial permeability transition (MPT) inhibitors on mitochondrial membrane-bound glutathione transferase (mtMGST1) activity in rat liver was investigated in vitro.


METHODS
When mitochondria were incubated with MPT inhibitors, mtMGST1 activity was decreased dose dependently and their 50% inhibition concentration (IC(50)) were 1.2 microM (cyclosporin A; CsA), 31 microM (bongkrekic acid; BKA), 1.8 mM (ADP), and 3.2 mM (ATP). The decrease of mtMGST1 activity by the MPT inhibitors was not observed in the presence of detergent Triton X-100. On the contrary, mtMGST1 inhibition by GST inhibitors such as cibacron blue (IC(50), 4.2 microM) and S-hexylglutathione (IC(50), 480 microM) was not affected in the presence of detergent. Although mtMGST1 resides in both the inner (IMM) and outer mitochondrial membranes (OMM), only mtMGST1 in the IMM was inhibited by the MPT inhibitors in the absence of detergent. GST inhibitors decreased mtMGST1 activity both in the IMM and OMM regardless of the presence or absence of detergent. Cytosolic GSTs and microsomal MGST1 were not inhibited by the MPT inhibitors.


RESULTS
These results indicate that mtMGST1 is inhibited by MPT inhibitors through membrane components, not directly by the inhibitors.


CONCLUSIONS
Since CsA binds to cyclophilin D (Cyp-D) in the mitochondrial matrix whereas BKA or ADP binds to adenine nucleotide translocator (ANT) in the IMM, it was suggested that mtMGST1 in the IMM interacts with Cyp-D/ANT and the binding of MPT inhibitors to Cyp-D or ANT causes their conformational change followed by an alteration of mtMGST1 conformation, resulting in decreasing mtMGST1 activity.
Laboratory of Molecular Genetics and Pharmacology, School of Health Sciences, Faculty of Medicine, University of the Ryukyus, 207 Uehara, Nishihara, Okinawa 903-0215, Japan.
Enkhbaatar
E
Ulziikhishig
Kang Kwang
KK
Lee
Quazi Sohel
QS
Hossain
Yumiko
Y
Higa
Naoki
N
Imaizumi
Yoko
Y
Aniya
D000244:Adenosine Diphosphate / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D001865:Bongkrekic Acid / Q000008:administration & dosage / Q000494:pharmacology; D000081406:Peptidyl-Prolyl Isomerase F; D021983:Cyclophilins / Q000378:metabolism*; D016572:Cyclosporine / Q000008:administration & dosage / Q000494:pharmacology*; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D005982:Glutathione Transferase / Q000187:drug effects* / Q000378:metabolism; D020128:Inhibitory Concentration 50; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D000226:Mitochondrial ADP, ATP Translocases / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins / Q000037:antagonists & inhibitors*; D051336:Mitochondrial Membranes / Q000378:metabolism*; D000083162:Mitochondrial Permeability Transition Pore; D011485:Protein Binding; D011487:Protein Conformation / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley
D000081406:Peptidyl-Prolyl Isomerase F; D004791:Enzyme Inhibitors; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D001865:Bongkrekic Acid; D000244:Adenosine Diphosphate; D016572:Cyclosporine; D000226:Mitochondrial ADP, ATP Translocases; C122107:microsomal glutathione S-transferase-I; D005982:Glutathione Transferase; D021983:Cyclophilins