8-Nitro-cGMP Attenuates the Interaction between SNARE Complex and Complexin through S-Guanylation of SNAP-25

8-Nitroguanosine 3',5'-cyclic monophosphate (8-nitro-cGMP) is the second messenger in nitric oxide/reactive oxygen species redox signaling. This molecule covalently binds to protein thiol groups, called S-guanylation, and exerts various biological functions. Recently, we have identified synaptosomal-associated protein 25 (SNAP-25) as a target of S-guanylation, and demonstrated that S-guanylation of SNAP25 enhanced SNARE complex formation. In this study, we have examined the effects of S-guanylation of SNAP-25 on the interaction between the SNARE complex and complexin (cplx), which binds to the SNARE complex with a high affinity. Pull-down assays and coimmunoprecipitation experiments have revealed that S-guanylation of Cys90 in SNAP-25 attenuates the interaction between the SNARE complex and cplx. In addition, blue native-PAGE followed by Western blot analysis revealed that the amount of cplx detected at a high molecular weight decreased upon 8-nitro-cGMP treatment in SH-SY5Y cells. These results demonstrated for the first time that S-guanylation of SNAP-25 attenuates the interaction between the SNARE complex and cplx.