Metabotropic GABAB receptors are known to modulate the activity of voltage-dependent calcium channels. Previously, we have shown that GABAB receptors couple to a non-Gi/o G-protein to enhance calcium influx through L-type calcium channels by activating protein kinase C in neonatal rat hippocampal neurons. In this study, the components of this signaling pathway were investigated further. Gαq was knocked down using morpholino oligonucleotides prior to examining GABAB-mediated enhancement of calcium influx. When Gαq G-proteins were eliminated using morpholino-mediated knockdown, the enhancing effects of the GABABreceptor agonist baclofen (10 μM) on calcium current or entry were eliminated. These data suggest that GABAB receptors couple to Gαq to regulate calcium influx. Confocal imaging analysis illustrating colocalization of GABAB receptors with Gαq supports this hypothesis. Furthermore, baclofen treatment caused translocation of PKCα (protein kinase C α) but not PKCβ or PKCε, suggesting that it is the α isoform of PKC that mediates calcium current enhancement. Inhibition of calcium/calmodulin-dependent kinase II did not affect the baclofen-mediated enhancement of calcium levels. In summary, activation of GABAB receptors during development leads to increased calcium in a subset of neurons through Gαq signaling and PKCα activation without the involvement of calcium/calmodulin-dependent kinase II.
Title : GABAB receptors couple to Gαq to mediate increases in voltage-dependent calcium current during development
Author : Andrew Karls andMichelle Mynlieff et al
Date : 28 AUG 2015
Post : Article first published online
Keywords:
Abstract
Metabotropic GABAB receptors are known to modulate the activity of voltage-dependent calcium channels. Previously, we have shown that GABAB receptors couple to a non-Gi/o G-protein to enhance calcium influx through L-type calcium channels by activating protein kinase C in neonatal rat hippocampal neurons. In this study, the components of this signaling pathway were investigated further. Gαq was knocked down using morpholino oligonucleotides prior to examining GABAB-mediated enhancement of calcium influx. When Gαq G-proteins were eliminated using morpholino-mediated knockdown, the enhancing effects of the GABABreceptor agonist baclofen (10 μM) on calcium current or entry were eliminated. These data suggest that GABAB receptors couple to Gαq to regulate calcium influx. Confocal imaging analysis illustrating colocalization of GABAB receptors with Gαq supports this hypothesis. Furthermore, baclofen treatment caused translocation of PKCα (protein kinase C α) but not PKCβ or PKCε, suggesting that it is the α isoform of PKC that mediates calcium current enhancement. Inhibition of calcium/calmodulin-dependent kinase II did not affect the baclofen-mediated enhancement of calcium levels. In summary, activation of GABAB receptors during development leads to increased calcium in a subset of neurons through Gαq signaling and PKCα activation without the involvement of calcium/calmodulin-dependent kinase II.
Activation of GABAB receptors in the neonatal rat hippocampus enhances voltage-dependent calcium currents independently of Gi/o. In this study, knockdown of Gαq with morpholino oligonucleotides abolished enhancement of calcium influx and protein kinase Cα was activated by GABAB receptors. Therefore, we hypothesize that GABAB receptors couple to Gq to activate PKCα leading to enhancement of L-type calcium current.