Ecdysone acts through cortex glia to regulate sleep in Drosophila

Abstract

Steroid hormones are attractive candidates for transmitting long-range signals to affect behavior. These lipid-soluble molecules derived from dietary cholesterol easily penetrate the brain and act through nuclear hormone receptors (NHRs) that function as transcription factors. To determine the extent to which NHRs affect sleep: wake cycles, we knocked down each of the 18 highly conserved NHRs found in Drosophila adults and report that the ecdysone receptor (EcR) and its direct downstream NHR Eip75B (E75) act in glia to regulate the rhythm and amount of sleep. Given that ecdysone synthesis genes have little to no expression in the fly brain, ecdysone appears to act as a long-distance signal and our data suggest that it enters the brain more at night. Anti-EcR staining localizes to the cortex glia in the brain and functional screening of glial subtypes revealed that EcR functions in adult cortex glia to affect sleep. Cortex glia are implicated in lipid metabolism, which appears to be relevant for actions of ecdysone as ecdysone treatment mobilizes lipid droplets, and knockdown of glial EcR results in more lipid droplets. In addition, sleep-promoting effects of exogenous ecdysone are diminished in lsd-2 mutant flies, which are lean and deficient in lipid accumulation. We propose that ecdysone is a systemic secreted factor that modulates sleep by stimulating lipid metabolism in cortex glia.

Phylogenomics of the ecdysteroid kinase-like (EcKL) gene family in insects highlights roles in both steroid hormone metabolism and detoxification

“…Intriguingly, the subfamily C EcKL CG14314 encodes a protein that might physically interact with the ecdysteroid-phosphate phosphatase EPP/CG13604 (Murali et al 2011;Davies et al 2007), consistent with a function in ecdysteroid metabolism. Both CG5644 and CG14314 are strongly enriched for expression in the adult nervous system (Leader et al 2018) and might modulate steroidal control of sleep, behaviour and memory (Li et al 2023;Okamoto & Yamanaka 2020;Ishimoto et al 2012Ishimoto et al , 2009. CG13813 and Pinkman are D. melanogaster subfamily A genes that could also encode ecdysteroid kinases; notably, CG13813 is strongly induced by 20E in cell culture (Stoiber et al 2016;Gauhar et al 2009) and is enriched for expression in the 3 rd -instar larval ring gland (Ou et al 2016), both consistent with a function in ecdysteroid metabolism.…”

Breaking free from the clock’s tyranny restores memory to brain damaged flies

“…Thus, as a stringent test of sleep's capacity to restore function in significantly compromised brains, we intensified sleep in flies with MB ablations and analyzed Short-Term Memory (STM) using the APS, and Long-Term Memory (LTM) using courtship conditioning. To enhance sleep, we employed two independent and widely utilized approaches: Gaboxadol administration (4,(42)(43)(44)(45)(46)(47)(48)(49)(50)(51)(52)(53)(54)(55), and genetically activating sleep promoting neurons (56)(57)(58)(59)(60)(61)(62)(63)(64)(65)(66). Newly hatched Canton-S (Cs) larvae were fed Hydroxyurea (HU) to eliminate the Kenyon cells forming the α/β, α'/β' and most of the γ lobes (39).…”

Ensheathing glia promote increased lifespan and healthy brain aging

“…Intriguingly, the lifespan of Harpegnathos workers is dramatically increased (~fivefold) when they are reprogrammed into reproductive pseudo-queens ("gamergates") (Ghaninia et al, 2017). This reprogramming is accompanied Sehgal's laboratory (Li, Haynes, et al, 2022) with his permission.…”

“…Fly stocks used in this study were empty‐GAL4 (Bloomington #68384); GMR56F03‐GAL4 (Bloomington #39157); GMR10E12‐GAL4 (Bloomington #46517); GMR86E01‐GAL4 (Bloomington #45914); UAS‐GFP (Bloomington #4775); UAS‐mCD8GFP (Bloomington #5137); UAS‐p35 (Bloomington #5072); nSyb‐QF2 (Bloomington #51960); QUAS‐Aβ42 (Bloomington #83347); G‐TRACE (Bloomington #28280); UAS‐mCherry (Bloomington #35787). The UAS‐LSD2::GFP line was a generous gift from M. Welte and was obtained from A. Sehgal's laboratory (Li, Haynes, et al, 2022 ) with his permission. Iso31 was a gift from A. Sehgal (Erion et al, 2016 ).…”