G protein-gated inhibitory module of N-type (ca(v)2.2) ca2+ channels.

Voltage-dependent G protein (Gbetagamma) inhibition of N-type (CaV2.2) channels supports presynaptic inhibition and represents a central paradigm of channel modulation. Still controversial are the proposed determinants for such modulation, which reside on the principal alpha1B channel subunit. These include the interdomain I-II loop (I-II), the carboxy tail (CT), and the ...
amino terminus (NT). Here, we probed these determinants and related mechanisms, utilizing compound-state analysis with yeast two-hybrid and mammalian cell FRET assays of binding among channel segments and G proteins. Chimeric channels confirmed the unique importance of NT. Binding assays revealed selective interaction between NT and I-II elements. Coexpressing NT peptide with Gbetagamma induced constitutive channel inhibition, suggesting that the NT domain constitutes a G protein-gated inhibitory module. Such inhibition was limited to NT regions interacting with I-II, and G-protein inhibition was abolished within alpha1B channels lacking these NT regions. Thus, an NT module, acting via interactions with the I-II loop, appears fundamental to such modulation.
Mesh Terms:
Amino Acid Sequence, Animals, Calcium Channels, L-Type, Calcium Channels, N-Type, Cell Line, Electric Stimulation, GTP-Binding Protein beta Subunits, GTP-Binding Protein gamma Subunits, GTP-Binding Proteins, Humans, Ion Channel Gating, Membrane Potentials, Molecular Biology, Neural Inhibition, Patch-Clamp Techniques, Protein Binding, Protein Structure, Tertiary, Protein Subunits, Rabbits, Radioligand Assay, Rats, Recombinant Fusion Proteins, Sequence Homology, Amino Acid, Structure-Activity Relationship, Transfection, Two-Hybrid System Techniques, Yeasts
Neuron
Date: Jun. 16, 2005
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