Increased expression of protein kinase A inhibitor α (PKI-α) and decreased PKA-regulated genes in chronic intermittent alcohol exposure

Abstract

Intermittent models of alcohol exposure that mimic human patterns of alcohol consumption produce profound physiological and biochemical changes and induce rapid increases in alcohol self-administration. We used high-density oligonucleotide microarrays to investigate gene expression changes during chronic intermittent alcohol exposure in three brain regions that receive mesocorticolimbic dopaminergic projections and that are believed to be involved in alcohol's reinforcing actions: the medial prefrontal cortex, the nucleus accumbens and the amygdala. An independent replication of the experiment was used for RT-PCR validation of the microarray results. The protein kinase A inhibitor alpha (PKI-alpha, Pkia), a member of the endogenous PKI family implicated in reducing nuclear PKA activity, was found to be increased in all three regions tested. Conversely, we observed a downregulation of the expression of several PKA-regulated transcripts in one or more of the brain regions studied, including the activity and neurotransmitter-regulated early gene (Ania) - 1, -3, -7, -8, the transcription factors Egr1 and NGFI-B (Nr4a1) and the neuropeptide NPY. Reduced expression of PKA-regulated genes in mesocorticolimbic projection areas may have motivational significance in the rapid increase in alcohol self-administration induced by intermittent alcohol exposure.

PKA catalytic subunit compartmentation regulates contractile and hypertrophic responses to β-adrenergic signaling

“…This inference is corroborated by a history of observations that PKI can specifically inhibit nuclear PKA activity by competitively inhibiting free PKA catalytic subunit and by inducing active export of PKA catalytic subunit from the nucleus [26]. In particular PKIα overexpression has been shown to decrease the expression of PKA-regulated genes in neurons [30] and recent studies over-expressing PKIα’s inhibitory domain demonstrate protection from ISO-stimulated cardiac hypertrophy in transgenic mice [50], though the over-expressed PKI in those experiments did not localize specifically to the nucleus. While these results suggest PKI may limit nuclear PKA activity in a mechanism analogous to PDE-regulation of cAMP, we cannot exclude the possibility that nuclear PKA activity is regulated by other proteins.…”

“…2A, 2B), then differences between nuclear and cytosolic AKAR phosphorylation are likely explained by either greater nuclear phosphatase activity or decreased nuclear PKA availability. In addition to limited PKA catalytic subunit nuclear import, nuclear PKA availability may also be modulated by competitive inhibition and export of PKA catalytic subunit by PKI [26, 30]. To better understand if the differential ISO sensitivity of nuclear and cytosolic AKAR were quantitatively explained by nuclear phosphatase activity or by nuclear PKA availability, we simulated perturbations to these mechanisms in our model and then experimentally validated corollaries to each hypothesis.…”

Adolescent and adult rat cortical protein kinase A display divergent responses to acute ethanol exposure

“…Differences in PKA activity may also be associated with age-related differences in phosphodiesterases. Alternatively, age-related differences in PKA inhibitor (PKI-α) may also be a factor and should be explored, particularly as PKI-α has been suggested to play a role in PKA-mediated gene regulation following chronic intermittent ethanol exposure (Repunte-Canonigo, Lutjens, van der Stap, & Sanna, 2007). Therefore, it is critical that future studies examine these possibilities in relation to age-dependent differences in PKA activity following ethanol exposure.…”

Gene Expression Under the Influence: Transcriptional Profiling of Ethanol in the Brain

“…The effect of two series of four cycles of intermittent ethanol vapor inhalation one week apart, a paradigm known to induce physical dependence [66] and ethanol self-administration escalation [67], was analyzed in the prefrontal cortex, hippocampus and nucleus accumbens of C57Bl/6J mice [30]. Transcriptional disruption was strikingly stronger in the prefrontal cortex than in other brain regions at the end of chronic ethanol exposure, as previously found in rats exposed to two weeks of chronic intermittent ethanol inhalation [31]. Functional clustering of the 284 genes regulated in the prefrontal cortex highlighted the Ras/MAPK and notch signaling pathways, as well as ubiquitination.…”

“…Genes governing circadian rhythms were over-represented among the few genes that were affected in the nucleus accumbens under both conditions. Interestingly, while the nucleus accumbens of C57Bl/6J mice was more responsive than prefrontal cortex to an acute ethanol challenge [54], an opposite pattern was found following chronic intermittent exposure to ethanol both in Wistar rats [31] and in C57Bl/6J mice [30], suggesting that tolerance to transcriptional disruption develops in the nucleus accumbens over the course of ethanol exposure, while the prefrontal cortex gets recruited later on in the process of ethanol dependence.…”