The small GTPase Ral couples the angiotensin II type 1 receptor to the activation of phospholipase C-delta 1.
The angiotensin II type 1 receptor (AT(1)R) plays an important role in cardiovascular function and as such represents a primary target for therapeutic intervention. The AT(1)R has traditionally been considered to be coupled to the activation of phospholipase C (PLC) beta via its association with G alpha(q/11), leading to increases in intracellular inositol phosphate (IP) and release of calcium from intracellular stores. In the present study, we investigated whether the small GTPase RalA contributed to the regulation of AT(1)R endocytosis and signaling. We find that neither RalA nor RalB is required for the endocytosis of the AT(1)R, but that RalA expression is required for AT(1)R-stimulated IP formation but not 5-HT(2A) receptor-mediated IP formation. AT(1)R-activated IP formation is lost in the absence of Ral guanine nucleotide dissociation stimulator (RalGDS), and requires the beta-arrestin-dependent plasma membrane translocation of RalGDS. G alpha(q/11) small interfering RNA (siRNA) treatment also significantly attenuates both AT(1)R- and 5-HT(2A) receptor-stimulated IP formation after 30 min of agonist stimulation. PLC-delta1 has been reported to be activated by RalA, and we show that AT(1)R-stimulated IP formation is attenuated after PLC-delta 1 siRNA treatment. Taken together, our results provide evidence for a G protein-coupled recepto-activated and RalGDS/Ral-mediated mechanism for PLC-delta 1 stimulation.
Godin
Christina M
CM
J. Allyn Taylor Centre for Cell Biology, Molecular Brain Research Group, Robarts Research Institute, University of Western Ontario, 100 Perth Dr., London, Ontario, Canada.
Ferreira
Lucimar T
LT
Dale
Lianne B
LB
Gros
Robert
R
Cregan
Sean P
SP
Ferguson
Stephen S G
SS
D002460:Cell Line; D004789:Enzyme Activation / Q000502:physiology; D006801:Humans; D020559:Monomeric GTP-Binding Proteins / Q000032:analysis / Q000378:metabolism; D054803:Phospholipase C delta / Q000032:analysis / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D044140:Receptor, Angiotensin, Type 1 / Q000032:analysis / Q000378:metabolism*; D020725:ral GTP-Binding Proteins / Q000032:analysis / Q000378:metabolism*
D044140:Receptor, Angiotensin, Type 1; D054803:Phospholipase C delta; D020559:Monomeric GTP-Binding Proteins; D020725:ral GTP-Binding Proteins