Protein Kinase Cδ Regulates Ethanol Intoxication and Enhancement of GABA-Stimulated Tonic Current

Abstract

Ethanol alters the distribution and abundance of PKC␦ in neural cell lines. Here we investigated whether PKC␦ also regulates behavioral responses to ethanol. PKC␦ Ϫ/Ϫ mice showed reduced intoxication when administered ethanol and reduced ataxia when administered the nonselective GABA A receptor agonists pentobarbital and pregnanolone. However, their response to flunitrazepam was not altered, suggesting that PKC␦ regulates benzodiazepine-insensitive GABA A receptors, most of which contain ␦ subunits and mediate tonic inhibitory currents in neurons. Indeed, the distribution of PKC␦ overlapped with GABA A ␦ subunits in thalamus and hippocampus, and ethanol failed to enhance tonic GABA currents in PKC␦ Ϫ/Ϫ thalamic and hippocampal neurons. Moreover, using an ATP analog-sensitive PKC␦ mutant in mouse L(tk Ϫ ) fibroblasts that express ␣4␤3␦ GABA A receptors, we found that ethanol enhancement of GABA currents was PKC␦-dependent. Thus, PKC␦ enhances ethanol intoxication partly through regulation of GABA A receptors that contain ␦ subunits and mediate tonic inhibitory currents. These findings indicate that PKC␦ contributes to a high level of behavioral response to ethanol, which is negatively associated with risk of developing an alcohol use disorder in humans.

Regulation of Extrasynaptic GABAA 4 Receptors by Ethanol-Induced Protein Kinase A, but Not Protein Kinase C Activation in Cultured Rat Cerebral Cortical Neurons

“…This finding is consistent with previous studies in our laboratory that showed no effect of PKC activation on d subunit expression in P2 membrane fractions (Werner et al, 2011). However, this result contrasts with previous studies that have found that PKC has a role in regulating extrasynaptic a4 receptor populations in the thalamus and hippocampus (Choi et al, 2008;Abramian et al, 2010;Bright and Smart, 2013). This discrepancy could be explained by a difference in regulation by brain region, cell type, or the slice preparation.…”

“…Ethanol has long been known to activate both protein kinase A (PKA) (Dohrman et al, 1996) and protein kinase C (PKC) (Messing et al, 1991), and kinases are important regulators of the behavioral effects of ethanol (Harris et al, 1995;Hodge et al, 1999;Thiele et al, 2000;Choi et al, 2008). PKCg activation by ethanol is requisite for the increase in GABA A a4 surface expression after 4 hours of ethanol exposure in cultured cerebral cortical neurons (Werner et al, 2011).…”

Dissecting the Factors Involved in the Locomotion Mode of Neuronal Migration in the Developing Cerebral Cortex

“…8). Our findings, using the dominant-negative form and RNAi, are consistent with the observation that abnormal neuronal migration was not detected in PKC␦-knockout mice (44). However, we could not exclude the possibility that PKC␦ is also involved in the locomotion mode or early phase of migration, in addition to the final phase of migration, because knockdown or dominant-negative experiments may not completely inhibit all PKC␦ activity in migrating neurons.…”

“…S1, B-G). Our findings are consistent with previous reports indicating that PKC␦-deficient mice are viable with no increase of other PKC isoforms (43) and showed no gross anatomical abnormalities and evidence of abnormal neuronal migration (44).…”

Ethanol Reduces GABAA α1 Subunit Receptor Surface Expression by a Protein Kinase Cγ-Dependent Mechanism in Cultured Cerebral Cortical Neurons

“…Ethanol has also been shown to alter the expression and translocation of various PKC isoforms (Kumar et al, 2006), but the role of these isoforms in receptor internalization is unknown. Studies with PKC and PKC␥ knockout mice have demonstrated the potential relevance of these PKC isoforms to ethanol-mediated plasticity (Hodge et al, 1999;Bowers et al, 2001;Proctor et al, 2003;Choi et al, 2008). Mutant mice lacking PKC are more sensitive to the short-term effects of ethanol, and the deletion of PKC attenuates ethanol withdrawal-associated seizures in mice (Olive et al, 2001).…”