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 GABAA 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 GABAAγ2, gephyrin and β-tubulin. Serine de-phosphorylation of GABAAγ2 reduced association of GABARAP with GABAAγ2. Climbing fiber activity did not influence the expression of GABAAγ2. Rather, it decreased its serine phosphorylation. Climbing fiber discharge decreased both expression of GABARAP and serine phosphorylation of GABAAγ2. Consequently, climbing fiber activity may reduce the surface expression of GABAA receptors in Purkinje cells rendering Purkinje cells less susceptible to interneuronal GABAergic inhibition.
- GABA receptor
- Serine phosphorylation
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience