Parthenolide enhances ADORA2A receptor internalization through direct sesquiterpene lactone-mediated cysteine modification

Parthenolide directly targets ADORA2A receptors through its reactive sesquiterpene lactone moiety, which forms covalent Michael adducts with specific cysteine residues in the receptor’s extracellular domains or transmembrane regions. This covalent modification induces conformational changes that promote rapid receptor internalization and degradation, effectively reducing surface ADORA2A availability independent of extracellular adenosine concentrations. The alkylating properties of parthenolide’s α-methylene-γ-lactone group enable selective targeting of nucleophilic cysteine thiols within the ADORA2A structure, particularly those involved in disulfide bond formation critical for proper receptor folding and membrane stability. This direct pharmacological intervention bypasses the complex inflammatory cascade involving NF-κB, ectonucleotidases, and cytokine networks, instead achieving ADORA2A pathway suppression through post-translational receptor modification. The resulting decrease in functional surface ADORA2A receptors in neuronal and glial populations within mood-regulating circuits leads to reduced adenosine sensitivity and altered neurotransmitter balance. This mechanism predicts that parthenolide’s effects should be irreversible within the timeframe of receptor turnover, persist in the presence of high extracellular adenosine levels, and show selectivity based on cysteine accessibility rather than cell-type-specific inflammatory status. Experimental validation would involve demonstrating parthenolide-induced ADORA2A internalization in primary neuronal cultures, identifying specific cysteine modification sites through mass spectrometry, and showing that cysteine-to-serine mutations in these positions confer resistance to parthenolide-mediated receptor downregulation.