Novel activation of non-selective cationic channels by dinitrosyl iron-thiosulfate in PC12 cells

Low molecular mass dinitrosyl iron complexes (DNICs) are nitrosating agents and it is known that the dinitrosyl iron moiety can be transferred to proteins. The aim of the present study was to determine if the formation of protein-bound dinitrosyl iron can modulate ionic channel activity. In PC12 cells, dinitrosyl iron-thiosulfate (50 microM) caused irreversible activation of a depolarizing inward current (IDNIC). IDNIC was partially inhibited by the metal chelator diethyldithiocarbamate (DETC, 1 mM), but not by the reducing/denitrosylating agent dithiothreitol (DTT, 5 mM). The activation of IDNIC was not reproduced by application of nitric oxide (NO., 100 microM), S-nitrocysteine (200 microM) or ferrous iron-thiosulfate (50 microM), and was not prevented by the irreversible guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo-[4, 3-a]quinoxalin-1-one (ODQ, 1 microM). Similarly, intracellular perfusion of dinitrosyl iron-thiosulfate (100 microM) did not result in activation of IDNIC. Ion replacement experiments show that the DETC-sensitive component of IDNIC is a non-selective cationic current. In accordance, IDNIC was blocked by antagonists of receptor-operated calcium entry, gadolinium (25 microM) and SK&F 96365 (25 microM). Single-channel measurements from outside-out patches reveal that the DETC-sensitive component of IDNIC is an inward current carried by a cationic channel having a conductance of 50 pS. The present observations suggest that the formation of ion channel-bound dinitrosyl iron represents another mechanism of regulation of ion channel activity by NO.-related species, which may be particularly important in pathophysiological processes where NO. is overproduced.