G protein-induced trafficking of voltage-dependent calcium channels.

Calcium channels are well known targets for inhibition by G protein-coupled receptors, and multiple forms of inhibition have been described. Here we report a novel mechanism for G protein-mediated modulation of neuronal voltage-dependent calcium channels that involves the destabilization and subsequent removal of calcium channels from the plasma membrane. Imaging experiments in living sensory neurons show that, within seconds of receptor activation, calcium channels are cleared from the membrane and sequestered in clathrin-coated vesicles.

RGS12 interacts with the SNARE-binding region of the Cav2.2 calcium channel.

Activation of GABAB receptors in chick dorsal root ganglion (DRG) neurons inhibits the Cav2.2 calcium channel in both a voltage-dependent and voltage-independent manner. The voltage-independent inhibition requires activation of a tyrosine kinase that phosphorylates the alpha1 subunit of the channel and thereby recruits RGS12, a member of the "regulator of G protein signaling" (RGS) proteins.

Mapping of RGS12-Cav2.2 channel interaction.

The alpha1 (pore-forming) subunit of the Cav2.2 (N-type) channel is tyrosine phosphorylated by Src kinase upon activation of GABAB receptors. The tyrosine-phosphorylated form of the alpha1 subunit of the Cav2.

N-type Ca2+ channels as scaffold proteins in the assembly of signaling molecules for GABAB receptor effects.

An emerging concept in signal transduction is the organization of neuronal receptors and channels into microdomains in which signaling proteins are brought together to regulate functional responses. With the multiplicity of potential protein-protein interactions arises the need for the regulation and timing of these interactions. We have identified N-type Ca(2+) channel-signaling molecule complexes formed at different times upon activation of gamma-aminobutyric acid, type B, receptors.