The C-terminus of Gi family G-proteins as a determinant of 5-HT(1A) receptor coupling.
Using a universal signaling assay employing G-protein chimeras comprising the C-terminal five amino acids of Gi1/2, Gi3, Go, and Gz fused to Gq, the calcium mobilizing G-protein, we explored the role of the C-terminus of Gi family G-proteins as a determinant for 5-HT(1A) receptor functional coupling. Co-expression of the 5-HT(1A) receptor with each of the Gq/Gi family chimeras resulted in a concentration-dependent increase in calcium upon addition of 5-HT, although the coupling efficiency differed dramatically. Gq/Gi3 resulted in the most efficient coupling based on both potency and relative maximum response to 5-HT. Gq/Go also produced efficient coupling in terms of relative 5-HT efficacy (76% of the Gq/Gi3 maximum response), although 5-HT exhibited 4-fold lower agonist potency, and Gq/Gz and Gq/Gi1/2 conferred poor functional coupling. Agonist potencies and relative efficacies determined for a number of 5-HT(1A) receptor agonists using Gq/Gi3 coupling were significantly weaker than those described previously for coupling through the native G-protein. These results indicate the C-terminus of Gi3 as an important determinant for coupling to the 5-HT(1A) receptor, while the reduced functional agonist activities suggest additional motifs participate in receptor/G-protein coupling.
Kowal
Dianne
D
Wyeth Research, Neuroscience Discovery Research, CN-8000, Princeton, NJ 08543-8000, USA.
Zhang
Jean
J
Nawoschik
Stanley
S
Ochalski
Rafal
R
Vlattas
Angela
A
Shan
Qin
Q
Schechter
Lee
L
Dunlop
John
J
D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism*; D006801:Humans; D011985:Receptors, Serotonin / Q000378:metabolism*; D044263:Receptors, Serotonin, 5-HT1; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured
D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D011993:Recombinant Fusion Proteins; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D002118:Calcium