Lack of Kinase Regulation of Canonical Transient Receptor Potential 3 (TRPC3) Channel-dependent Currents in Cerebellar Purkinje Cells

Charmaine Nelson,Maike D Glitsch

doi:10.1074/jbc.m111.246553

Abstract

Canonical transient receptor potential (TRPC) channels are widely expressed in the brain and play several roles in development and normal neuronal function. In the cerebellum, Purkinje cell TRPC3 channels underlie the slow excitatory postsynaptic potential observed after parallel fiber stimulation. In these cells TRPC3 channel opening requires stimulation of metabotropic glutamate receptor 1, activation of which can also lead to the induction of long term depression (LTD), which underlies cerebellar motor learning. LTD induction requires protein kinase C (PKC) and protein kinase G (PKG) activation, and although PKC phosphorylation targets are well established, virtually nothing is known about PKG targets in LTD. Because TRPC3 channels are inhibited after phosphorylation by PKC and PKG in expression systems, we examined whether native TRPC3 channels in Purkinje cells are a target for PKG or PKC, thereby contributing to cerebellar LTD. We find that in Purkinje cells, activation of TRPC3-dependent currents is not inhibited by conventional PKC or PKG to any significant extent and that inhibition of these kinases does not significantly impact on TRPC3-mediated currents either. Based on these and previous findings, we propose that TRPC3-dependent currents may differ significantly in their regulation from those overexpressed in expression systems.

Highlights

TRPC3 channels are inhibited by protein kinase C (PKC) and protein kinase G (PKG), which induce cerebellar long term depression (LTD)
Because TRPC3 channels are inhibited after phosphorylation by PKC and PKG in expression systems, we examined whether native TRPC3 channels in Purkinje cells are a target for PKG or PKC, thereby contributing to cerebellar LTD
We found that the DHPG-dependent current had a near-linear current-voltage profile that is typical for TRPC3 currents reported in the literature (26 –28) (Fig. 1A)

Summary

Introduction

TRPC3 channels are inhibited by PKC and PKG, which induce cerebellar LTD. We investigate if PKC- and PKG-mediated modulation of cerebellar TRPC3 channels contributes to cerebellar LTD. Purkinje cell TRPC3 channels underlie the slow excitatory postsynaptic potential observed after parallel fiber stimulation In these cells TRPC3 channel opening requires stimulation of metabotropic glutamate receptor 1, activation of which can lead to the induction of long term depression (LTD), which underlies cerebellar motor learning. We find that in Purkinje cells, activation of TRPC3-dependent currents is not inhibited by conventional PKC or PKG to any significant extent and that inhibition of these kinases does not significantly impact on TRPC3-mediated currents either. Based on these and previous findings, we propose that TRPC3-dependent currents may differ significantly in their regulation from those overexpressed in expression systems

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Conclusion