Relationship between specific binding of ~(125)I-ω-conotoxin GVIA and GTP binding protein: effects of the GTP analogues, mastoparan and AlF_4~-

摘要

We investigated whether the specific binding or labeling of 125I-ω-CgTX on crude membranes from chick whole brain was affected when endogenous GTP binding protein (G protein) was activated by GTP analogues, mastoparan (MP) and aluminum fluoride (AlF4?; AlCl3+NaF). Both GTPγS and Gpp(NH)p attenuated the inhibitory effect of selective N-type Ca channel inhibitors such as aminoglycoside antibiotics (AGs) or dynorphine (1-13)(Dyn) on specific 125I-ω-CgTX binding in a dose-dependent manner. On the other hand, the inhibitory effects of the divalent metal cations Cd2+, Co2+, Mg2+ and Mn2+ on such binding were not attenuated by GTPγS. MP and AlF4? also attenuated the inhibitory effect of Neo on this binding similar to GTPγS. The attenuating effect of MP was enhanced by the presence of Mg2+ in a dose-dependent manner. However, GTP analogues, MP and AlF4?, did not affect binding or labeling without AGs or Dyn. GTPγS, MP and AlF4? also attenuated the specific labeling of a 215-kDa band in crude membranes with 125I-ω-CgTX using the cross-linker DSS (non-reduced condition) in the presence of Neo. These results indicate that there are direct or indirect relationships between N-type Ca channels and G proteins via binding sites for AGs or MP.