MODIFICATION OF HIPPOCAMPAL SYNAPTIC PROTEINS BY NITRIC OXIDE-STIMULATED ADP-RIBOSYLATION

Nitric oxide has been shown to be an important neuronal signaling mole cule that participates in both behavioral and synaptic plasticity. To better understand the potential mechanisms by which NO regulates synap tic function, the ability of NO to stimulate the modification of synap tic proteins by ADP ribosylation was examined. Two NO donors, sodium n itroprusside and 3-morpholinosydnonimine, stimulated the ADP ribosylat ion of proteins at apparent molecular masses of 42, 48, 51, 54, and 74 kD in hippocampal synaptosomes. This stimulation was likely owing to the production of NO by the donors; ADP ribosylation was not stimulate d by non-NO decomposition products of sodium nitroprusside, and quench ing of superoxide anion did not inhibit Sin-1-induced ADP ribosylation . Experiments using NAD(+) that was radiolabeled on the nicotinamide m oiety demonstrated that the modification of proteins of molecular mass es of 30, 33, and 38 kD are not true ADP ribosylation, whereas labelin g of the 42-, 48-, 51-, 54-, and 74-kD proteins Likely represent ADP r ibosylation. Some of the substrates were brain specific (54 and 74 kD) , whereas others (42 and 51 kD) were present in multiple nonbrain tiss ues.