PI(3,4,5)P₃potentiates phospholipase C-β activity

Abstract

Phospholipase C-β (PLC-β) isozymes are key effectors in G protein-coupled signaling pathways. Previously, we had shown that PLC-β1 and PLC-β3 bound immobilized PIP 3 . In this study, PIP 3 was found to potentiate Ca 2+ -stimulated PLC-β activities using an in vitro reconstitution assay. LY294002, a specific PI 3-kinase inhibitor, significantly inhibited 10 minutes agonist-stimulated total IP accumulation. Both LY294002 and wortmannin inhibited 90 seconds agonist-stimulated IP 3 accumulation in intact cells. Moreover, transfected p110CAAX, a constitutively activated PI 3-kinase catalytic subunit, increased 90 seconds oxytocin-stimulated IP 3 accumulation. Receptorligand binding assays indicated that LY294002 did not affect G protein-coupled receptors directly, suggesting a physiological role for PIP 3 in directly potentiating PLC-β activity. When co-expressed with p110CAAX, fluorescence-tagged PLC-β3 was increasingly localized to the plasma membrane. Additional observations suggest that the PH domain of PLC-β is not important for p110CAAX-induced membrane association.

PI3 kinase inhibitor PI828 uncouples aminergic GPCRs and Ca2+mobilization irrespectively of its primary target

“…Notable among PH domain-containing proteins are the kinases PDK1 and Akt (Jean and Kiger, 2014; Vanhaesebroeck et al, 2010), which are involved in regulation of multiple intracellular targets in a PIP 3 -dependent manner. In particular, the PI3K/Akt pathway can modulate Ca 2+ release by controlling activity of IP 3 receptors and PLC (Frégeau et al, 2011; Szado et al, 2008; Zhang et al, 2009). The involvement of the PI3K/Akt axis in the regulation of Ca 2+ release was particularly demonstrated in MDCK cells (Santoso et al, 2011), COS-7 cells (Marchi et al, 2012), and RINm5F cells (Frégeau et al, 2011).…”