Plant inner membrane anion channel (PIMAC) function in plant mitochondria.
To date, the existence of the plant inner membrane anion channel (PIMAC) has been shown only in potato mitochondria, but its physiological role remains unclear. In this study, by means of swelling experiments in K(+) and ammonium salts, we characterize a PIMAC-like anion-conducting pathway in mitochondria from durum wheat (DWM), a monocotyledonous species phylogenetically far from potato. DWM were investigated since they possess a very active potassium channel (PmitoK(ATP)), so implying a very active matching anion uniport pathway and, possibly, a coordinated function. As in potato mitochondria, the electrophoretic uptake of chloride and succinate was inhibited by matrix [H(+)], propranolol, and tributyltin, and was insensitive to Mg(2+), N,N'-dicyclohexylcarbodiimide (DCCD) and mercurials, thus showing PIMAC's existence in DWM. PIMAC actively transports dicarboxylates, oxodicarboxylates, tricarboxylates and Pi. Interestingly, a novel mechanism of swelling in ammonium salts of isolated plant mitochondria is reported, based on electrophoretic anion uptake via PIMAC and ammonium uniport via PmitoK(ATP). PIMAC is inhibited by physiological compounds, such as ATP and free fatty acids, by high electrical membrane potential (Delta Psi), but not by acyl-CoAs or reactive oxygen species. PIMAC was found to cooperate with dicarboxylate carrier by allowing succinate uptake that triggers succinate/malate exchange in isolated DWM. Similar results were obtained using mitochondria from the dicotyledonous species topinambur, so suggesting generalization of results. We propose that PIMAC is normally inactive in vivo due to ATP and Delta Psi inhibition, but activation may occur in mitochondria de-energized by PmitoK(ATP) (or other dissipative systems) to replace or integrate the operation of classical anion carriers.
Dipartimento di Scienze Agro-ambientali, Chimica e Difesa Vegetale, Facoltà di Agraria, Università degli Studi di Foggia, Via Napoli, 25, 71100 Foggia, Italy.
Maura Nicoletta
MN
Laus
Mario
M
Soccio
Daniela
D
Trono
Luigi
L
Cattivelli
Donato
D
Pastore
D000255:Adenosine Triphosphate / Q000494:pharmacology; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D005227:Fatty Acids / Q000494:pharmacology; D006368:Helianthus / Q000187:drug effects / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007473:Ion Channels / Q000378:metabolism*; D019787:Linoleic Acid / Q000494:pharmacology; D008293:Malates / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008634:Mersalyl / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000187:drug effects / Q000378:metabolism*; D008933:Mitochondrial Swelling / Q000187:drug effects; D009243:NAD / Q000494:pharmacology; D009995:Osmosis / Q000187:drug effects; D011433:Propranolol / Q000494:pharmacology; D012996:Solutions; D019802:Succinic Acid / Q000378:metabolism; D013481:Superoxides / Q000494:pharmacology; D014908:Triticum / Q000187:drug effects / Q000378:metabolism*
D005227:Fatty Acids; D007473:Ion Channels; D008293:Malates; D012996:Solutions; D009243:NAD; D013481:Superoxides; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D008634:Mersalyl; C030298:malic acid; D000255:Adenosine Triphosphate; D019787:Linoleic Acid; D011433:Propranolol; D019802:Succinic Acid; D006861:Hydrogen Peroxide