ANGIOTENSIN-II AT2 RECEPTORS DO NOT INTERACT WITH GUANINE-NUCLEOTIDE BINDING-PROTEINS

We have studied the effect of GTP-gamma-S on the affinity and binding kinetics of angiotensin II in plasma membrane particulate prepared from tissues expressing either only AT1 (human renal artery smooth muscle cells), only AT2 (human myometrium and bovine cerebellar cortex) or both angiotensin II receptor subtypes (rat adrenal glomerulosa). We also examined the ability of angiotensin II to stimulate GTP-gamma-[S-35] incorporation in these membrane preparations. In contrast to its effects on angiotensin II binding to the AT1 receptor, GTP-gamma-S does not affect binding parameters to the AT2 receptor. Moreover, in tissues expressing solely AT2 receptors, angiotensin II was unable to induce GTP-gamma-[S-35] incorporation. These findings indicate that AT2 receptors do not interact with G-proteins and that angiotensin II must therefore mediate some of its effects through G-protein-independent mechanisms.