Journal article
Platelet-activating factor stimulates multiple signaling pathways in cultured rat mesangial cells
Journal of cellular physiology, Vol.153(2), pp.244-255
11/1992
DOI: 10.1002/jcp.1041530204
PMID: 1331121
Abstract
We have previously reported that platelet-activating factor (PAF) elevates cytosolic free calcium concentration ([Ca2+]i) in fura-2-loaded glomerular mesangial cells. To confirm that this increase in [Ca2+]i is a result of receptor-mediated activation of phospholipase C, we investigated hydrolysis of phosphatidylinositol-4,5-bisphosphate (PtdIns-4,5-P2) in PAF-treated mesangial cells. PAF (10(-7) M) stimulated a rapid and transient formation of inositol trisphosphate. In concomitant experiments, PAF stimulated a biphasic accumulation of 3H-arachidonate-labeled 1,2-diacylglycerol (DAG). The secondary elevation in DAG was coincident with a rise in 3H-phosphorylcholine (PC) and 3H-phosphorylethanolamine (PE) suggesting that PAF stimulates delayed phospholipase activities which hydrolyze alternate phospholipids besides the polyphosphoinositides. This PAF-stimulated elevation in 3H-water soluble phosphorylbases was seen at 5 min but not at 15 sec suggesting that the initial rise in DAG as well as the initial elevation in [Ca2+]i are due primarily to PtdIns-4,5-P2 hydrolysis. PAF also stimulated PGE2 as well as 3H-arachidonic acid and 3H-lyso phosphatidylcholine (PtdCho) formation. We suggest that arachidonate released specifically from PtdCho via phospholipase A2 is a source of this PAF-elevated PGE2. It has been postulated that anti-inflammatory prostaglandins may antagonize the contractile and proinflammatory effects of PAF via activation of adenylate cyclase. Surprisingly, exogenous PAF reduced basal and receptor-mediated cAMP concentration indicating that PAF-stimulated transmembrane signaling pathways may oppose receptor-mediated activation of adenylyl cyclase. We have taken advantage of the different sensitivities of phospholipases A2 and C(s) to PMA, EGTA, and pertussis toxin to dissociate phospholipase A2 and C activities. Acute PMA-treatment enhanced PAF-stimulated PGE2 formation, reduced PAF-induced elevations in [Ca2+]i and had no effect upon PAF-stimulated 3H-PE. We have also demonstrated that phospholipase A2, but not PtdIns-specific phospholipase C, was sensitive to external calcium concentration. The role of a GTP-binding protein to couple PAF-receptors to the PtdIns-specific phospholipase C was confirmed as GTP gamma S synergistically elevated PAF-stimulated inositol phosphate formation. We also demonstrated that pertussis toxin ADP-ribosylates a single protein of an apparent 42 kD mass and that PAF pretreatment reduced subsequent ADP-ribosylation in a time-dependent manner. However, pertussis toxin had no effect upon phospholipase C-generated water soluble phosphorylbases or inositol phosphates. In contrast, PAF-stimulated phospholipase A2 and PAF-inhibited adenylyl cyclase activities were sensitive to pertussis toxin.
Details
- Title: Subtitle
- Platelet-activating factor stimulates multiple signaling pathways in cultured rat mesangial cells
- Creators
- Mark Kester - Department of Medicine, Case Western Reserve University, School of Medicine, Cleveland, OhioChristie P ThomasJin WangMichael J Dunn
- Resource Type
- Journal article
- Publication Details
- Journal of cellular physiology, Vol.153(2), pp.244-255
- Publisher
- United States
- DOI
- 10.1002/jcp.1041530204
- PMID
- 1331121
- ISSN
- 0021-9541
- eISSN
- 1097-4652
- Grant note
- HL22563 / NHLBI NIH HHS DK41684 / NIDDK NIH HHS AR40225 / NIAMS NIH HHS
- Language
- English
- Date published
- 11/1992
- Academic Unit
- Stead Family Department of Pediatrics; Obstetrics and Gynecology; Nephrology; Internal Medicine
- Record Identifier
- 9983986256402771
Metrics
22 Record Views