Direct binding of G-protein βλ complex to voltage-dependent calcium channels

Abstract

Voltage-dependent Ca2+ channels play a central role in controlling neurotransmitter release at the synapse. They can be inhibited by certain G-protein-coupled receptors, acting by a pathway intrinsic to the membrane. Here we show that this inhibition results from a direct interaction between the G-protein betagamma complex and the pore-forming alpha1 subunits of several types of these channels. The interaction is mediated by the cytoplasmic linker connecting the first and second transmembrane repeats. Within this linker, binding occurs both in the alpha1 interaction domain (AID), which also mediates the interaction between the alpha1 and beta subunits of the channel, and in a second downstream sequence. Further analysis of the binding site showed that several amino-terminal residues in the AID are critical for Gbetagamma binding, defining a site distinct from the carboxy-terminal residues shown to be essential for binding the beta-subunit of the Ca2+ channel. Mutation of an arginine residue within the N-terminal motif abolished betagamma binding and rendered the channel refractory to G-protein modulation when expressed in Xenopus oocytes, showing that the interaction is indeed responsible for G-protein-dependent modulation of Ca2+ channel activity.

The cytoplasmic coiled-coil mediates cooperative gating temperature sensitivity in the voltage-gated H+ channel Hv1

“…Findings derived from the study of Hv channels, a minimal voltage-gated channel, may offer principles common to other larger and more complex ion channels; force transmission between the cytoplasmic domain and the gate within the transmembrane region may also occur in other ion channels in which gating modulators interact with a region adjacent to the transmembrane gate [39][40][41][42][43] .…”

N-Type Calcium Channels in the Developing Rat Hippocampus: Subunit, Complex, and Regional Expression

“…Of greater interest is whether the degree of ␣ 1B -␤ 3 complexation changes in development. Changes in heteromer composition in development are well documented (Sheng et al, 1994;Murray et al, 1995) and would be especially significant for V DCC s because the ␣ 1B -␤ subunit interaction is known to be promiscuous Liu et al, 1996a;Scott et al, 1996) and can be displaced by interaction with G-proteins (De Waard et al, 1997;Zamponi et al, 1997). Moreover, multiple ␤ subunits can exist in individual cell types (Liu et al, 1996b), and different ␤ subunits confer discrete kinetic characteristics to V DCC s (De Waard and Campbell, 1995).…”

Control of gating mode by a single amino acid residue in transmembrane segment IS3 of the N-type Ca 2+ channel

“…This interaction could be direct or mediated indirectly through one of the known G protein interaction sites on the Ca v 2.2 channel. The presence of G protein interaction sites (14)(15)(16)(17), sites of protein kinase C modulation (17), and a site of Ca v ␤ subunit binding (51) in L I-II points to the S4 segments in domains I and II as the most likely targets. Identification of a molecular interaction between G protein ␤␥ subunits and the intracellular end of an S4 segment would provide direct biochemical evidence for the voltage sensor-trapping mechanism of G protein action proposed here on the basis of functional studies.…”

“…N-type channels are inhibited by activation of G protein-coupled receptors (9), which regulate neurotransmitter release by means of a negative feedback loop (10,11). G protein inhibition is mediated by G␤␥ subunits (12,13), which bind to multiple target sites in the intracellular loop connecting domains I and II (L I-II ) (14)(15)(16)(17), the C terminus (18,19), and the N terminus (20)(21)(22)(23). Binding of G proteins is thought to cause a shift of gating mode from an easily activated ''willing'' (W) state to a ''reluctant'' (R) state (24).…”