G Protein-Gated Inhibitory Module of N-Type (Ca V2.2) Ca 2+ Channels

• Published in: Neuron (Cambridge, Mass.) Vol. 46; no. 6; pp. 891 - 904
• Main Authors: Agler, Heather L., Evans, Jenafer, Tay, Lai Hock, Anderson, Molly J., Colecraft, Henry M., Yue, David T.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 2005
• ISSN: 0896-6273; 1097-4199
• DOI: 10.1016/j.neuron.2005.05.011

Voltage-dependent G protein (Gβγ) inhibition of N-type (Ca V2.2) 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 α 1B 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 Gβγ 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 α 1B channels lacking these NT regions. Thus, an NT module, acting via interactions with the I-II loop, appears fundamental to such modulation.