title: Metabotropic glutamate receptors activate phospholipase D in astrocytes through a protein kinase C-dependent and Rho-independent pathway.
abstract: Metabotropic glutamate receptors (mGluRs) are G protein-coupled receptors that mediate phospholipase D (PLD) activation in brain, but the mechanism underlying this response remains unclear. Here we used primary cultures of astrocytes as a cell model to explore the mechanism that links mGluRs to PLD. Glutamate activated both phospholipase C (PLC) and PLD with equal potency and this effect was mimicked by L-cysteinesulfinic acid, a putative neurotransmitter previously shown to activate mGluRs coupled to PLD, but not PLC, in adult brain. PLD activation by glutamate was dependent on Ca(2+) mobilization and fully blocked by both protein kinase C (PKC) inhibitors and PKC down-regulation, suggesting that PLD activation is secondary to PLC stimulation. Furthermore, brefeldin A, an inhibitor of ADP-ribosylation factor (ARF) activation, partially inhibited the activation of PLD by glutamate. By contrast, pretreatment of astrocytes with Clostridium difficile toxin B, which inactivates small G proteins of the Rho family (Rho, Rac, and Cdc42), had no effect on PLD stimulation by glutamate. Taken together, these results indicate that PLD activation by mGluRs in astrocytes is dependent on PKC and small G proteins of the ARF family, but does not require Rho proteins.
authors.affiliation: Departament de Bioquímica i Biologia Molecular, Facultat de Medicina, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain.
authors.forename: Joan-Marc
authors.initials: JM
authors.lastname: Servitja
authors.forename: Roser
authors.initials: R
authors.lastname: Masgrau
authors.forename: Raul
authors.initials: R
authors.lastname: Pardo
authors.forename: Elisabet
authors.initials: E
authors.lastname: Sarri
authors.forename: Christoph
authors.initials: C
authors.lastname: von Eichel-Streiber
authors.forename: J Silvio
authors.initials: JS
authors.lastname: Gutkind
authors.forename: Fernando
authors.initials: F
authors.lastname: Picatoste
mesh_terms: D020727:ADP-Ribosylation Factors / Q000378:metabolism; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D001426:Bacterial Proteins; D001427:Bacterial Toxins / Q000494:pharmacology; D020126:Brefeldin A / Q000494:pharmacology; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D003545:Cysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004247:DNA / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D019332:Endothelin-1 / Q000494:pharmacology; D018698:Glutamic Acid / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D008301:Maleimides / Q000494:pharmacology; D010739:Phospholipase D / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018094:Receptors, Metabotropic Glutamate / Q000187:drug effects / Q000378:metabolism*; D022502:Stress Fibers / Q000378:metabolism; D013434:Sulfenic Acids / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000031:analogs & derivatives / Q000494:pharmacology; D010738:Type C Phospholipases / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D002614:Chelating Agents; D019332:Endothelin-1; D007211:Indoles; D008301:Maleimides; D011500:Protein Synthesis Inhibitors; D018094:Receptors, Metabotropic Glutamate; D013434:Sulfenic Acids; C031815:toxB protein, Clostridium difficile; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D020126:Brefeldin A; D018698:Glutamic Acid; D004533:Egtazic Acid; C016658:phorbolol myristate acetate; D004247:DNA; D011493:Protein Kinase C; D010738:Type C Phospholipases; D010739:Phospholipase D; D020727:ADP-Ribosylation Factors; D020741:rho GTP-Binding Proteins; C100870:cysteinesulfenic acid; D003545:Cysteine; C088060:bisindolylmaleimide; D013755:Tetradecanoylphorbol Acetate