Native group-III metabotropic glutamate receptors are coupled to the mitogen-activated protein kinase/phosphatidylinositol-3-kinase pathways.
We used cultured cerebellar granule cells to examine whether native group-III metabotropic glutamate (mGlu) receptors are coupled to the mitogen-activated protein kinase (MAPK) and phosphatidylinositol-3-kinase (PI-3-K) pathways. Cultured granule cells responded to the group-III mGlu receptor agonist, L-2-amino-4-phosphonobutanoate (l-AP4), with an increased phosphorylation and activity of MAPKs (ERK-1 and -2) and an increased phosphorylation of the PI-3-K target, protein kinase B (PKB/AKT). These effects were attenuated by the group-III antagonists, alpha-methyl-serine-O -phosphate (MSOP) and (R,S )-alpha-cyclopropyl-4-phosphonophenylglycine (CPPG), or by pretreatment of the cultures with pertussis toxin. l-AP4 also induced the nuclear translocation of beta-catenin, a downstream effector of the PI-3-K pathway. To assess the functional relevance of these mechanisms we examined the ability of l-AP4 to protect granule cells against apoptosis by trophic deprivation, induced by lowering extracellular K(+) from 25 to 10 mm. Neuroprotection by l-AP4 was attenuated by MSOP and abrogated by the compounds PD98059 and UO126, which inhibit the MAPK pathway, or by the compound LY294002, which inhibits the PI-3-K pathway. Taken together, these results show for the first time that native group-III mGlu receptors are coupled to MAPK and PI-3-K, and that activation of both pathways is necessary for neuroprotection mediated by this particular class of receptors.
Iacovelli
L
L
Department of Human Physiology and Pharmacology, University of Rome La Sapienza, Rome, Italy.
Bruno
V
V
Salvatore
L
L
Melchiorri
D
D
Gradini
R
R
Caricasole
A
A
Barletta
E
E
De Blasi
A
A
Nicoletti
F
F
D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000613:Aminobutyrates / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000201:enzymology; D018696:Neuroprotective Agents / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D015534:Trans-Activators; D051176:beta Catenin
D000613:Aminobutyrates; D003598:Cytoskeletal Proteins; D004791:Enzyme Inhibitors; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D020928:Mitogen-Activated Protein Kinases; D018696:Neuroprotective Agents; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011188:Potassium; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D018094:Receptors, Metabotropic Glutamate; D015534:Trans-Activators; D051176:beta Catenin; C495268:Ctnnb1 protein, rat; C494920:Akt1 protein, rat; C012729:2-amino-4-phosphonobutyric acid