Differential Activation of Phospholipase D by VPAC and PAC₁ Receptors

Abstract

A BSTRACT : To investigate the phospholipase D (PLD) responses of the VIP/PACAP receptors, VPAC 1 and VPAC 2 , and the PACAP-specific PAC 1 receptors (short and "hop" intracellular loop 3 (i3) splice variants), stable CHO cell lines expressing similar levels of each wildtype receptor were generated (except for the VPAC 1 receptor clone which showed considerably lower expression and lesser responses in signalling assays). All clones caused activation of PLD in response to agonists, as monitored by [ 3 H]phosphatidylbutanol production. The PLD responses of the PAC 1 "hop", but not the "null" receptor, were sensitive to the ARF inhibitor, brefeldin A (BFA) (as were VPAC 1 and VPAC 2 responses). Chimeric constructs of VPAC 2 receptors containing i3 of either PAC 1 hop or PAC 1 null receptors were transiently expressed in COS 7 cells and PLD responses were measured. Only the PLD response of the hop construct was sensitive to BFA. This suggests that i3 motifs in certain Group II GPCRs may play a key role in determining their linkage to ARF-dependent PLD activation.

Molecular mechanisms involved in vasoactive intestinal peptide receptor activation and regulation: current knowledge, similarities to and differences from the A family of G-protein-coupled receptors

“…Both VPAC1 and VPAC2 are able to activate PLD (phospholipase D). PLD responses induced by VPAC2 are not affected by PLC inhibitors, PTx or PKA inhibitors, but are sensitive to brefeldin A, which is an inhibitor of ARF (ADP-ribosylation factor) known to act as a direct activator of PLD [23]. In pancreatic β-cells, VIP-induced-sustained stimulation of insulin secretion is mediated by PI3K (phosphatidylinositol 3-kinase) activation by VPAC2 [24].…”

Stimulatory and suppressive signal transduction regulates vasoactive intestinal peptide receptor-1 (VPAC-1) in primary mouse CD4 T cells

“…VPAC receptors are widely expressed in mammalian tissues, including the immune compartment (Dorsam et al 2000, Johnson et al, 1996. Two GPS superfamily peptides bind two different VIP receptors (K d = 1-3 nM), termed vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP), and couple through G s , G i/o , and G q (O'Dorisio et al, 1981, Dorsam et al, 2001, Xia et al, 1996, Delporte et al, 1995, McCulloch et al, 2000, reviewed by Delgado et al, 2004). In T cells, VIP and PACAP are involved in various cellular functions including, proliferation (Ottaway andGreenberg 1984, Wang et al, 2000), trafficking (Ottaway 1984), cytokine expression (Tang et al, 1996, Voice et al, 2001, apoptosis (Delgado et al, 2002) and adhesion (Johnston et al, 1994, Xia et al, 1996; reviewed by Delgado et al, 2004).…”

The Involvement of PACAP/VIP System in the Synaptic Transmission in the Hippocampus

“…The PAC1 receptor also strongly stimulates Gαq and the phospholipase C (PLC)/protein kinae C (PKC) signaling pathway, whereas VPAC1 and VPAC2 receptors activate this signaling pathway relatively weakly ). In addition, PAC1/VPAC receptor activation can increase the concentration of intracellular calcium ([Ca 2+ ] i ) (Dickson et al 2006), as well as modulate the activity of phospholipase D (McCulloch et al 2000) in some cell types.…”