title: MEK inhibitors block BDNF-dependent and -independent expression of GABA(A) receptor subunit mRNAs in cultured mouse cerebellar granule neurons.
abstract: Brain-derived neurotrophic factor (BDNF) can regulate the maturation of developing cerebellar granule neurons. Within 1-2 days of culture, BDNF induces the expression of granule neuron terminal differentiation markers, particularly GABA(A) receptor alpha6 subunit (GABA(A)alpha6) mRNA. Other trophic factors including insulin-like growth factor, the neurotrophin NT-3, pituitary adenylate cyclase-activating polypeptide (PACAP), and fetal bovine serum failed to induce this early expression. The expression of other GABA(A) receptor subunits, including alpha1 and gamma2, was also enhanced by exposure of developing granule neurons to BDNF. This BDNF-dependent expression of GABA(A) receptor subunit mRNAs could be effectively blocked by treatment with the mitogen-activated protein kinase kinase (MEK) inhibitors, PD98059 or U0126. In the absence of BDNF, GABA(A)alpha6 expression occurs but not until 3-4 days of culture. This BDNF-independent expression of GABA(A)alpha6 was also inhibited by PD98059. Further studies showed that the BDNF-dependent expression GABA(A)alpha6 could also be reduced by LY294002, an inhibitor of the phosphatidylinositol 3-kinase, or depolarizing concentrations of KCl. These results thus suggest that both BDNF-dependent and -independent expressions of GABA(A) receptor subunits require the activation of MEK and the mitogen-activated protein kinase (MAPK) pathway. However, it is also likely that other signaling pathways modulate this maturation process.
authors.affiliation: Department of Pharmacology, University of Maryland School of Medicine, Baltimore, MD 21201, USA. bbulleit@promega.com
authors.forename: R F
authors.initials: RF
authors.lastname: Bulleit
authors.forename: T
authors.initials: T
authors.lastname: Hsieh
mesh_terms: D000818:Animals; D001798:Blood Proteins / Q000494:pharmacology; D019208:Brain-Derived Neurotrophic Factor / Q000378:metabolism* / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002454:Cell Differentiation / Q000502:physiology; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000502:physiology*; D002867:Chromones / Q000494:pharmacology; D003587:Cytomegalovirus / Q000235:genetics; D003594:Cytoplasmic Granules; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000502:physiology; D017930:Genes, Reporter; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D048369:MAP Kinase Kinase 1; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors*; D009025:Morpholines / Q000494:pharmacology; D009474:Neurons / Q000166:cytology / Q000201:enzymology*; D009479:Neuropeptides / Q000494:pharmacology; D020933:Neurotrophin 3 / Q000494:pharmacology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D011401:Promoter Regions, Genetic / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D012333:RNA, Messenger / Q000096:biosynthesis*; D011963:Receptors, GABA-A / Q000235:genetics*; D014701:Veratridine / Q000494:pharmacology
chemical_list: C495402:Adcyap1 protein, mouse; D001798:Blood Proteins; D019208:Brain-Derived Neurotrophic Factor; D002121:Calcium Channel Blockers; D002867:Chromones; D004791:Enzyme Inhibitors; D005419:Flavonoids; D009025:Morpholines; D009479:Neuropeptides; D020933:Neurotrophin 3; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D012333:RNA, Messenger; D011963:Receptors, GABA-A; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D007334:Insulin-Like Growth Factor I; D014701:Veratridine; D017346:Protein Serine-Threonine Kinases; D048369:MAP Kinase Kinase 1; C482127:Map2k1 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one