The Small GTPase Ral Couples the Angiotensin II Type 1 Receptor to the Activation of Phospholipase C-δ1

Abstract

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) ␤ via its association with G␣ 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 ␤-arrestin-dependent plasma membrane translocation of RalGDS. G␣ 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-␦1 has been reported to be activated by RalA, and we show that AT 1 R-stimulated IP formation is attenuated after PLC-␦1 siRNA treatment. Taken together, our results provide evidence for a G protein-coupled recepto-activated and RalGDS/Ral-mediated mechanism for PLC-␦1 stimulation.

Functional PDF Signaling in the Drosophila Circadian Neural Circuit Is Gated by Ral A-Dependent Modulation

“…We speculate there is a daily generation of distinctive PDF receptors (distinguished by their location, post-translational modification and/or by other signaling components) and that RalA is needed to promote their timely fusion with the plasma membrane. However, other RalA-based mechanisms are also possible (Nakashima et al , 1999; Jullien-Flores et al , 2000; Matsuzaki et al , 2002; Godin et al , 2010). Regardless of the precise interactions between the GPCR and RalA, finding a close apposition of RalA with PDFR in hEK cells (Suppl.…”

Alopecia in a Viable Phospholipase C Delta 1 and Phospholipase C Delta 3 Double Mutant

“…Phospholipase C delta isozymes are associated with signal transduction processes involved in cell cycle regulation and cell proliferation [2], [7], [30], [31], [35], [89]–[92], and are altered in various tumours and tumour cell lines [93]–[97]. PLCD1 protein can also translocate to the nucleus and exert direct effects in the nuclear compartment [6], [7], [33], [34], [98].…”

“…The PH domain targets PLCD proteins to PIP 2 in the plasma membrane and induces activating conformational alterations of the catalytic domain, which is essential for PLCD function [13], [20]–[29]. The activity of PLCD1 is also regulated by the interaction with other proteins such as calmodulin and small GTPases [30]–[32], and through site specific phosphorylation by protein kinase C alpha (PKC alpha) [29]. Some PLCD proteins can translocate to the nucleus and PIP 2 derivatives play important roles in nuclear function [3], [5]–[7], [33], [34].…”

The Phospholipase C Isozymes and Their Regulation

“…Additional studies indicate that GPCR indirectly activate PLC-δ through signaling pathways selective for other PLC isoforms. For example, inositol phosphate production downstream of the angiotensin II type 1 receptor requires activation of PLC-β isoforms via Gα q/11 and is potentiated by interaction between RalA and PLC-δ1 (Godin et al 2010; Sidhu et al 2005). Thus, PLC-δ1 may serve as an amplifier of signaling initiated or mediated by other PLC isoforms (Guo et al 2010).…”