title: Venom from the ectoparasitic wasp Nasonia vitripennis increases Na+ influx and activates phospholipase C and phospholipase A2 dependent signal transduction pathways in cultured insect cells.
abstract: The mode of action of venom from the ectoparasitic wasp Nasonia vitripennis in eliciting cell death was examined using an in vitro approach with BTI-TN-5B1-4 cells, and the cell responses were compared to those evoked by the extensively studied wasp toxin mastoparan. Wasp venom increased plasma membrane permeability to Na+, resulting in cellular swelling and death due to oncosis. When ouabain was used to disable Na+, K+-ATPases, the effects of venom were enhanced. Measurements of intracellular calcium using fluo-4 AM revealed a rearrangement and an increase in cytosolic [Ca+2]i within 30 min after exposure of BTI-TN-5B1-4 cells to venom. This venom-mediated increase in Ca+2 was apparently due to mobilization of intracellular stores since the changes occurred in the absence of extracellular Ca+2. Phospholipase C (PLC) inhibitors, neomycin and U-73122, blocked the venom-induced death temporarily (<3h), but by 24h, all venom-treated cells swelled and lysed. Pre-treatment of cells with caffeine or theophylline but not ryanodine attenuated the induction of oncosis by wasp venom. Anti-inflammatory peptide 1 (antiflammin 1) but not bromophenacyl bromide, agents that block phospholipase A2 (PLA2) activity, abolished the responsiveness of BTI-TN-5B1-4 cells to venom. These results suggest that venom initiates cell death by inducing Ca+2 release from intracellular stores probably via phospholipase C and IP3. A possible mode of action for venom from N. vitripennis requiring dual activation of PLC and PLA2 is discussed and compared to the pathways known to be activated by mastoparan.
authors.affiliation: Department of Biology, Loyola College in Maryland, 4501 North Charles Street, Baltimore, MD 21210, USA. drivers@loyola.edu
authors.forename: David B
authors.initials: DB
authors.lastname: Rivers
authors.forename: Mary M
authors.initials: MM
authors.lastname: Rocco
authors.forename: Anis R
authors.initials: AR
authors.lastname: Frayha
mesh_terms: D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D005260:Female; D036341:Intercellular Signaling Peptides and Proteins; D009355:Neomycin / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D010455:Peptides; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054467:Phospholipases A2; D011760:Pyrrolidinones / Q000494:pharmacology; D015398:Signal Transduction; D012964:Sodium / Q000378:metabolism*; D013806:Theophylline / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014598:Uteroglobin / Q000494:pharmacology; D014862:Wasp Venoms / Q000494:pharmacology*; D014863:Wasps
chemical_list: D004791:Enzyme Inhibitors; D004963:Estrenes; D036341:Intercellular Signaling Peptides and Proteins; D010446:Peptide Fragments; D010455:Peptides; D011760:Pyrrolidinones; D014862:Wasp Venoms; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C064645:antiflammin P1; D002110:Caffeine; C037500:mastoparan; D014598:Uteroglobin; D012964:Sodium; D013806:Theophylline; D010741:Phospholipases A; D054467:Phospholipases A2; D010738:Type C Phospholipases; D009355:Neomycin; D002118:Calcium