Phosphoproteomic Analysis of the Amygdala Response to Adolescent Glucocorticoid Exposure Reveals G-Protein Coupled Receptor Kinase 2 as a Target for Reducing Motivation for Alcohol

Abstract

Early life stress is associated with risk for developing alcohol use disorders (AUDs) in adulthood. Though the neurobiological mechanisms underlying this vulnerability are not well understood, evidence suggests that aberrant glucocorticoid and noradrenergic system functioning play a role. The present study investigated the long-term consequences of chronic exposure to elevated glucocorticoids during adolescence on the risk of increased alcohol-motivated behavior, and on amygdalar function in adulthood. A discovery-based analysis of the amygdalar phosphoproteome using mass spectrometry was employed, to identify changes in function. Adolescent corticosterone (CORT) exposure increased alcohol, but not sucrose, self-administration, and enhanced stress-induced reinstatement with yohimbine in adulthood. Phosphoproteomic analysis indicated that the amygdala phosphoproteome was significantly altered by adolescent CORT exposure, generating a list of potential novel mechanisms involved in the risk of alcohol drinking. In particular, increased phosphorylation at serines 296–299 on the α2A adrenergic receptor (α2AAR), mediated by the G-protein coupled receptor kinase 2 (GRK2), was evident after adolescent CORT exposure. We found that intra-amygdala infusion of a peptidergic GRK2 inhibitor reduced alcohol seeking, as measured by progressive ratio and stress reinstatement tests, and induced by the α2AAR antagonist yohimbine. These results suggest that GRK2 represents a novel target for treating stress-induced motivation for alcohol which may counteract alterations in brain function induced by adolescent stress exposure.

Sex- and age-dependent effects of chronic corticosterone exposure on depressive-like, anxiety-like, and fear-related behavior: Role of amygdala glutamate receptors in the rat

“…This model elicits depressivelike effects in the sucrose preference test and FST and maladaptive processing of fear-related memory Monsey et al, 2014), but has no effects on anxiety-like behavior (e.g., the elevated plus maze), when tested in adult males. Chronic CORT exposure in adolescence produces increases in impulsive choice in male rats (Torregrossa et al, 2012), enhances cue-related alcohol craving in female rats (Bertholomey et al, 2016) and enhances 10.3389/fnbeh.2022.950000 alcohol-, but not sucrose-motivated behavior in male rats (Bertholomey et al, 2018) when tested in adulthood, indicating that elevated CORT levels during this critical developmental period can lead to long-lasting changes in pathological behavior. Importantly, the chronic CORT model has been used to determine the persistent effects of a brief, fixed duration of elevated glucocorticoid levels, as testing occurs long after the CORT has washed out (>10 days), and circulating CORT levels have returned to baseline.…”

Editorial for Special Issue: Neuroproteomics

“…Just as protein phosphorylation plays a key role in the molecular mechanisms underlying drug addiction, the articles by Bertholomey et al [31] and Miller et al [32] indicate that this PTM also plays an important role in alcohol use disorders (AUDS) and nicotine addiction, respectively. Bertholomey et al [31] describe how early life stress is associated with an increased risk of developing AUDs. Although the neurobiological mechanisms underlying this effect are not well understood, abnormal glucocorticoid and noradrenergic system functioning may play a role.…”

“…Although the neurobiological mechanisms underlying this effect are not well understood, abnormal glucocorticoid and noradrenergic system functioning may play a role. Bertholomey et al [31] studied the impact of chronic exposure during adolescence to elevated levels of the glucocorticoid stress hormone corticosterone (CORT) on amygdalar function and on the risk of developing AUDS. Adolescent CORT exposure increased alcohol, but not sucrose self-administration, and enhanced stress-induced reinstatement with yohimbine in adulthood.…”

“…LFQ phosphoproteomic analyses revealed that adolescent CORT exposure resulted in 16 changes in protein phosphorylation in the amygdala, which provided a list of potential novel mechanisms involved in increasing the risk of alcohol drinking. Of particular interest, Bertholomey et al [31] found that adolescent CORT exposure resulted in increased phosphorylation of the α 2A adrenergic receptor (α 2A AR) mediated by G protein-coupled receptor kinase 2 (GRK2). Bertholomey et al [31] also found that intra-amygdala infusion of a peptidergic GRK2 inhibitor reduced alcohol seeking, suggesting that GRK2 may provide a novel target for treating stress-induced AUDS.…”