Azarashvili T, Krestinina O, Galvita A, Grachev D, Baburina Y, Stricker R, Evtodienko Y, Reiser G. Ca 2ϩ -dependent permeability transition regulation in rat brain mitochondria by 2Ј,3Ј-cyclic nucleotides and 2Ј,3Ј-cyclic nucleotide 3Ј-phosphodiesterase. Am J Physiol Cell Physiol 296: C1428 -C1439, 2009. First published April 8, 2009 doi:10.1152/ajpcell.00006.2009.-Recent evidence indicates that 2Ј,3Ј-cyclic nucleotide 3Ј-phosphodiesterase (CNP), a marker enzyme of myelin and oligodendrocytes, is also present in neural and nonneural mitochondria. However, its role in mitochondria is still completely unclear. We found CNP in rat brain mitochondria and studied the effects of CNP substrates, 2Ј,3Ј-cyclic nucleotides, on functional parameters of rat brain mitochondria. 2Ј,3Ј-cAMP and 2Ј,3Ј-cNADP stimulated Ca 2ϩ overload-induced Ca 2ϩ release from mitochondrial matrix. This Ca 2ϩ release under threshold Ca 2ϩ load correlated with membrane potential dissipation and mitochondrial swelling. The effects of 2Ј,3Ј-cyclic nucleotides were suppressed by cyclosporin A, a potent inhibitor of permeability transition (PT). PT development is a key stage in initiation of apoptotic mitochondriainduced cell death. 2Ј,3Ј-cAMP effects were observed on the functions of rat brain mitochondria only when PT was developed. This demonstrates involvement of 2Ј,3Ј-cAMP in PT regulation in rat brain mitochondria. We also discovered that, under PT development, the specific enzymatic activity of CNP was reduced. Thus we hypothesize that suppression of CNP activity under threshold Ca 2ϩ load leads to elevation of 2Ј,3Ј-cAMP levels that, in turn, promote PT development in rat brain mitochondria. Similar effects of 2Ј,3Ј-cyclic nucleotides were observed in rat liver mitochondria. Involvement of CNP in PT regulation was confirmed in experiments using mitochondria from CNP-knockdown oligodendrocytes (OLN93 cells). CNP reduction in these mitochondria correlated with lowering the threshold for Ca 2ϩ overload-induced Ca 2ϩ release. Thus our results reveal a new function for CNP and 2Ј,3Ј-cAMP in mitochondria, being a regulator/promotor of mitochondrial PT. oligodendrocyte mitochondria; 2Ј,3Ј-cyclic nucleotide 3Ј-phosphodiesterase; permeability transition; calcium transport THE ENZYME 2Ј,3Ј-CYCLIC NUCLEOTIDE 3Ј-phosphodiesterase (CNP, EC 3.1.4.37) accounts for ϳ2-5% of the total protein in the central nervous system myelin and 0.5-1% of peripheral nervous system myelin (36). CNP catalyzes the hydrolysis of 2Ј,3Ј-cyclic nucleotides to form the corresponding 2Ј-monophosphates (3). CNP was shown to be an integral protein of myelin of oligodendrocytes in the central nervous system and of peripheral myelin in Schwann cells (36,39). The majority of studies investigating the role of CNP were focused exclusively on the expression of CNP in oligodendrocytes and Schwann cells and the involvement of CNP in myelinogenesis. However, there is increasing evidence showing that this enzyme is present in a variety of other cell types. CNP-like enzyme activity was found ...

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