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FEBS J. 2006 Dec;273(24):5508-16. Epub 2006 Nov 3.

Activation of nematode G protein GOA-1 by the human muscarinic acetylcholine receptor M2 subtype. Functional coupling of G-protein-coupled receptor and G protein originated from evolutionarily distant animals.

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1
Immune Defense Unit, National Institute of Agrobiological Sciences, Ibaraki, Japan.

Abstract

Signal transduction mediated by heterotrimeric G proteins regulates a wide variety of physiological functions. We are interested in the manipulation of G-protein-mediating signal transduction using G-protein-coupled receptors, which are derived from evolutionarily distant organisms and recognize unique ligands. As a model, we tested the functionally coupling GOA-1, G alpha(i/o) ortholog in the nematode Caenorhabditis elegans, with the human muscarinic acetylcholine receptor M2 subtype (M2), which is one of the mammalian G alpha(i/o)-coupled receptors. GOA-1 and M2 were prepared as a fusion protein using a baculovirus expression system. The affinity of the fusion protein for GDP was decreased by addition of a muscarinic agonist, carbamylcholine and the guanosine 5'-[3-O-thio]triphosphate ([35S]GTPgammaS) binding was increased with an increase in the carbamylcholine concentrations in a dose-dependent manner. These effects evoked by carbamylcholine were completely abolished by a full antagonist, atropine. In addition, the affinity for carbamylcholine decreased under the presence of GTP as reported for M2-G alpha(i/o) coupling. These results indicate that the M2 activates GOA-1 as well as G alpha(i/o).

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