title: Climbing fiber-evoked Purkinje cell discharge reduces expression of GABA(A) receptor-associated protein and decreases its interaction with GABA(A) receptors.
abstract: Sustained neuronal activity induces synaptic remodeling, in part, by altering gene expression. We have used a major climbing fiber pathway onto cerebellar Purkinje cells to investigate the effects of sustained climbing fiber-evoked glutamatergic synaptic transmission on transcription, expression and phosphorylation of proteins related to the regulation of inhibitory GABA(A) receptor function. Binocular horizontal optokinetic stimulation was used to modulate climbing fiber signals to Purkinje cells in the flocculus and nodulus of rabbits and mice. Purkinje cells in the flocculus and nodulus ipsilateral to the eye stimulated in the Posterior→Anterior direction received increased climbing fiber activity. Purkinje cells in flocculus and nodulus ipsilateral to the eye stimulated in the Anterior→Posterior direction received decreased climbing fiber activity. We identified changes in levels of gene transcripts in floccular and nodular Purkinje cells with the technique of differential display RT-PCR. Increased climbing fiber input reduced transcript levels and expression of GABA receptor-associated protein (GABARAP). Using a protein 'pull down' technique, we showed that GABARAP interacts with serine phosphorylated GABA(A)γ2, gephyrin and β-tubulin. Serine de-phosphorylation of GABA(A)γ2 reduced association of GABARAP with GABA(A)γ2. Climbing fiber activity did not influence the expression of GABA(A)γ2. Rather, it decreased its serine phosphorylation. Climbing fiber discharge decreased both expression of GABARAP and serine phosphorylation of GABA(A)γ2. Consequently, climbing fiber activity may reduce the surface expression of GABA(A) receptors in Purkinje cells rendering Purkinje cells less susceptible to interneuronal GABAergic inhibition.
authors.affiliation: Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, Oregon 97239, USA. Qianz@ohsu.edu
authors.forename: Zuyuan
authors.initials: Z
authors.lastname: Qian
authors.forename: Vadim
authors.initials: V
authors.lastname: Yakhnitsa
authors.forename: Neal H
authors.initials: NH
authors.lastname: Barmack
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins / Q000378:metabolism; D002531:Cerebellum / Q000166:cytology; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D047468:Immunoprecipitation / Q000379:methods; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008869:Microtubule-Associated Proteins; D017120:Nystagmus, Optokinetic / Q000502:physiology; D010766:Phosphorylation / Q000187:drug effects; D010775:Photic Stimulation / Q000379:methods; D054645:Protein Phosphatase 1 / Q000378:metabolism; D054648:Protein Phosphatase 2 / Q000378:metabolism; D011689:Purkinje Cells / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D011817:Rabbits; D011963:Receptors, GABA-A / Q000378:metabolism*; D012694:Serine / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014404:Tubulin / Q000378:metabolism
chemical_list: D000906:Antibodies; D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; C480861:GABARAP protein, mouse; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D012333:RNA, Messenger; D011963:Receptors, GABA-A; D014404:Tubulin; C073441:gephyrin; D012694:Serine; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; D013755:Tetradecanoylphorbol Acetate