Integrated ecdysone and <i>O-</i> linked <i>N</i> -acetylglucosamine signaling coordinates intestinal stem cell proliferation in <i>Drosophila</i> midgut

Steroid hormones and nutrient-sensitive signaling pathways play critical roles in the regulation of stem cell activity, maintenance of tissue homeostasis, and the coordination of metabolic functions. In Drosophila, the steroid hormone ecdysone and the nutrient-responsive posttranslational modification O-linked N-acetylglucosaminylation (O-GlcNAcylation) are emerging as key regulators of intestinal stem cell (ISC) behavior. This study aimed to investigate how the interplay between ecdysone signaling and O-GlcNAcylation controls ISC proliferation and gut homeostasis, particularly in the context of aging. We showed that ecdysone receptor (EcR) expression increases during aging and upon increased O-GlcNAcylation and that both genetic overexpression of EcR and exogenous 20-hydroxyecdysone treatment promote ISC proliferation and increase O-GlcNAc levels. Conversely, the knockdown of EcR or O-GlcNAc transferase suppressed ISC proliferation and reduced DNA damage accumulation. Our results show that EcR signaling induces DNA damage response and cooperates with O-GlcNAcylation to regulate ISC activity, suggesting a positive feedback loop involving hormones and nutrients. These results highlight the interaction between EcR and O-GlcNAc as a metabolic gatekeeper that balances regenerative activity and genomic integrity in the aging gut. These findings provide a potential mechanistic link for therapeutic strategies for age-related and metabolic diseases involving abnormal stem cell proliferation.