We investigated which subtypes of G-protein β subunits participate in voltage-dependent modulation of N-type calcium channels. Calcium currents were recorded from cultured rat superior cervical ganglion neurons injected intranuclearly with DNA encoding five different G-protein β subunits. Gβ1 and Gβ2 strongly mimicked the fast voltage-dependent inhibition of calcium channels produced by many G-protein-coupled receptors. The Gβ5 subunit produced much weaker effects than Gβ1 and Gβ2, whereas Gβ3 and Gβ4 were nearly inactive in these electrophysiological studies. The specificity implied by these results was confirmed and extended using the yeast two- hybrid system to test for protein-protein interactions. Here, Gβ1 or Gβ2 coupled to the GAL4-activation domain interacted strongly with a channel sequence corresponding to the intracellular loop connecting domains I and II of a α1 subunit of the class B calcium channel fused to the GAL4 DNA- binding domain. In this assay, the Gβ5 subunit interacted weakly, and Gβ3 and Gβ4 failed to interact. Together, these results suggest that Gβ1 and/or Gβ2 subunits account for most of the voltage-dependent inhibition of N-type calcium channels and that the linker between domains I and II of the calcium channel α1 subunit is a principal receptor for this inhibition.
|Number of pages||8|
|Journal||Journal of Neuroscience|
|State||Published - Nov 15 1998|
- Calcium channel
- Ion channel modulation
- Sympathetic neurons
- Yeast 2-hybrid