title: Identification and Characterization of a G Protein-binding Cluster in α7 Nicotinic Acetylcholine Receptors.
abstract: α7 nicotinic acetylcholine receptors (nAChRs) play an important role in synaptic transmission and inflammation. In response to ligands, this receptor channel opens to conduct cations into the cell but desensitizes rapidly. In recent studies we show that α7 nAChRs bind signaling proteins such as heterotrimeric GTP-binding proteins (G proteins). Here, we demonstrate that direct coupling of α7 nAChRs to G proteins enables a downstream calcium signaling response that can persist beyond the expected time course of channel activation. This process depends on a G protein-binding cluster (GPBC) in the M3-M4 loop of the receptor. A mutation of the GPBC in the α7 nAChR (α7345-348A) abolishes interaction with Gαq as well as Gβγ while having no effect on receptor synthesis, cell-surface trafficking, or α-bungarotoxin binding. Expression of α7345-348A, however, did significantly attenuate the α7 nAChR-induced Gαq calcium signaling response as evidenced by a decrease in PLC-β activation and IP3R-mediated calcium store release in the presence of the α7 selective agonist choline. Taken together, the data provides new evidence for the existence of a GPBC in nAChRs serving to promote intracellular signaling.
authors.affiliation: From the Department of Molecular Neuroscience, Krasnow Institute for Advanced Study and Department of Computer Science, George Mason University, Fairfax, Virginia 22030 and the INOVA Neuroscience Program, Annandale, Virginia 22003.
authors.forename: Justin R
authors.initials: JR
authors.lastname: King
authors.affiliation: From the Department of Molecular Neuroscience, Krasnow Institute for Advanced Study and Department of Computer Science, George Mason University, Fairfax, Virginia 22030 and the INOVA Neuroscience Program, Annandale, Virginia 22003.
authors.forename: Jacob C
authors.initials: JC
authors.lastname: Nordman
authors.affiliation: From the Department of Molecular Neuroscience, Krasnow Institute for Advanced Study and Department of Computer Science, George Mason University, Fairfax, Virginia 22030 and the INOVA Neuroscience Program, Annandale, Virginia 22003.
authors.forename: Samuel P
authors.initials: SP
authors.lastname: Bridges
authors.affiliation: From the Department of Molecular Neuroscience, Krasnow Institute for Advanced Study and Department of Computer Science, George Mason University, Fairfax, Virginia 22030 and the INOVA Neuroscience Program, Annandale, Virginia 22003.
authors.forename: Ming-Kuan
authors.initials: MK
authors.lastname: Lin
authors.affiliation: From the Department of Molecular Neuroscience, Krasnow Institute for Advanced Study and Department of Computer Science, George Mason University, Fairfax, Virginia 22030 and the INOVA Neuroscience Program, Annandale, Virginia 22003 nkabbani@gmu.edu.
authors.forename: Nadine
authors.initials: N
authors.lastname: Kabbani
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D016716:PC12 Cells; D051381:Rats; D017386:Sequence Homology, Amino Acid; D064569:alpha7 Nicotinic Acetylcholine Receptor / Q000737:chemistry / Q000378:metabolism*
chemical_list: D064569:alpha7 Nicotinic Acetylcholine Receptor; D019204:GTP-Binding Proteins
keywords: Cys loop receptor; G protein; binding motif; calcium intracellular release; choline; inositol 1,4,5-trisphosphate (IP3); nicotinic acetylcholine receptors (nAChR); phospholipase C