Coupling To Phospholipase Research Articles

Coupling of phospholipase C and PI3K/PTEN signaling pathways in Physarum polycephalum: The action of U73122 on motile and autooscillatory activity of plasmodium

The possibility of tight coupling of phospholipase C with the signal pathway PI3K/ PTEN, a ubiquitous mechanism for the control of chemotaxis and cell shape in free-living amoebae and mammalian tissue cells, has been investigated in Physarum polycephalum plasmodium, a multinuclear amoeboid cell with the autooscillatory mode of motility. It was found that on the maintenance of contractile autooscillations and protoplasmic shuttle streaming, U73122, an inhibitor of the signal transduction to phospholipase C, induces degradation of the plasmodium frontal zone, decreases efficiency of locomotion and suppresses the chemotaxis toward glucose as well as the response of oscillator to this attractant. The identity of the effects of U73122 with those shown for wortmannin and LY294002, widely used PI3K inhibitors (Matveeva et al. 2008. Biophysics. 53, 533–538), suggests a tight coupling of the signal pathways of phospholipase C and PI3K/PTEN. U73122 increases the period of contractile oscillations and abolishes its cyclic changes attributed for the plasmodium migration. The results indicate that motile behavior of the plasmodium is under the receptor-mediated control.

Protein Kinase C Regulation of ATP-Induced Phosphoinositide Hydrolysis in Bovine Aorta Endothelial Cells

This study investigated the mechanism of protein kinase C-mediated inhibition of ATP-induced phospholipase C activation in cultured bovine aorta endothelial cells (BAEC). In BAEC labeled with 3H-inositol, phorbol myristate acetate (PMA) prevented ATP-induced inositol bisphosphate and inositol trisphosphate formation. In membranes prepared from these PMA-treated cells, Ca2+-, sodium fluoride,- GTPγS-, and ATP plus GTPγS-stimulated inositol bisphosphate, but not inositol trisphosphate, formation was inhibited. Inositol trisphosphate phosphatase activity was not altered in membranes from PMA-treated BAEC. These results suggest that 1) protein kinase C inhibits ATP-induced phospholipase C activation in BAEC through interference with the coupling of phospholipase C with a G-protein and through an effect on phospholipase C itself, and 2) different mechanisms are responsible for the inhibition by protein kinase C of the phospholipase C-mediated hydrolysis of phosphatidylinositol bisphosphate and phosphatidyl-inositol phosphate.

Phospholipase D and cell signaling

Phospholipase D, which hydrolyzes phospholipids (primarily hosphatidylcholine) to generate phosphatidic acid, has emerged as a critical component in cellular signal transduction. Research during the past year has confirmed and extended the view that phosphatidic acid and its dephosphorylated product, sn-1,2-diacylglycerol, are important intracellular second messengers and that the coupling of phospholipase D to specific receptors occurs through multiple mechanisms involving protein kinase C, protein tyrosine kinase, Ca 2+ and GTP-binding proteins.

Development of muscarinic-cholinergic stimulation of inositol phosphate production in cultured embryonic chick atrial cells. Evidence for a switch in guanine-nucleotide-binding protein coupling

We have demonstrated that muscarinic stimulation of inositol phosphate production in cultured atrial cells from chicks at 14 days in ovo is partially sensitive to inhibition by pertussis toxin. In these cells, muscarinic agonist binding is coupled to phospholipase C activity via at least two guanine-nucleotide-binding proteins (G-proteins), one sensitive to pertussis toxin and the other (Gp) insensitive to pertussis toxin [Barnett, Shamah, Lassegue, Griendling & Galper (1990) Biochem. J. 271, 437-442]. In the current study we demonstrate that during embryonic development of the chick heart, muscarinic stimulation of inositol phosphate production decreases by 50% between days 5 and 14 in ovo in cells cultured from both atrium and ventricle. In atrial cells, however, pertussis toxin-sensitive muscarinic stimulation of inositol phosphate production increased from undetectable levels at day 5 in ovo to 40% of total stimulation at day 12 in ovo. Muscarinic stimulation of inositol phosphate production in the ventricle did not become sensitive to pertussis toxin at any age studied. In permeabilized atrial cells from embryonic chicks at 5 days in ovo, guanosine 5'-[gamma-thio]triphosphate (GTP[S]) stimulated InsP1 levels by 40 +/- 10% (mean +/- S.E.M., n = 3), InsP2 levels by 117 +/- 18% and InsP3 levels by 51 +/- 8%, suggesting that at day 5 in ovo all of the muscarinic-stimulated inositol phosphate production was coupled to phospholipase C via Gp. H.p.l.c. analysis demonstrated that, in spite of these changes in coupling of phospholipase C to different G-proteins, no changes could be demonstrated in the isomers of InsP3 produced in response to carbamylcholine at both days 5 and 14 in ovo. These data demonstrate that embryonic development of the chick atrium is associated with a switch in coupling of muscarinic receptors to phospholipase C from Gp to a pertussis toxin substrate. This developmental switch in coupling of G-proteins may be related to possible developmental switches in levels of muscarinic receptor isoforms or switches in the subtype of phospholipase C.