Receptors with a heptahelical structure initiate signal transduction by interacting with specific Gα proteins. The aim of this study was to analyze the ability of type 1 (AT1) and type 2 (AT2) angiotensin receptors to recognize the receptor coupling regions of Gα proteins using our previously described technique (Ikezu, T., Okamoto, T., Komatsuzaki, K., Matsui, T., Martyn, J.A.J., Nishimoto, I., 1996. Negative transactivation of cAMP response element by familial Alzheimer's mutants of APP. EMBO J. 15, 2468-2475; Komatsuzaki, K., Murayama, Y., Giambarella, U., Ogata, E., Seino, S., Nishimoto, I., 1996. A novel system that reports the G-proteins linked to a given receptor: a study of the type 3 somatostatin receptor. FEBS Lett. 406, 165-170). Chimeric Gαs protein constructs, whose receptor binding regions contained sequences from the four major families of Gα proteins (Gαq, Gαi, Gα12, Gαs), were cotransfected with AT1 or AT2 receptors in COS cells, then stimulated with angiotensin II (Ang II). Changes in cellular cAMP were assayed on cell lysates by enzyme immunoassay. In the case of the Gαq family, cotransfection of AT1 with Gα11/Gαs, Gα14/Gαs, Gα16/Gαs, elicited significant increases in cAMP after agonist stimulation. Confirmatory results were found using an independent [35S]GTPγS binding assay. Further examination using chimeric G proteins for Gα12 proteins and Gαi family proteins provided evidence that the AT1 receptor can recognize sequences from Gα12, Gαi1/i2, Gαz, Gαo, while both receptors interacted with Gαi3. These results provide a Gα protein recognition database for both AT1 and AT2 receptors, which may be important for understanding the full spectrum of cellular responses mediated by the hormone Ang II.
ASJC Scopus subject areas