Simon Eléanor, Bonche Raphaël, Maarouf Yassine, Nawrot-Esposito Marie-Paule, Romero Nuria Magdalena
Université Côte d'Azur, INRAE, CNRS, Sophia Agrobiotech Institute (ISA), Sophia Antipolis, France.
Université Côte d'Azur, INRAE, CNRS, INSERM, Sophia Agrobiotech Institute (ISA), Sophia Antipolis, France.
Nat Commun. 2025 Jul 1;16(1):5501. doi: 10.1038/s41467-025-60579-7.
Steroid hormones, crucial for development and physiology, were traditionally believed to diffuse passively through membranes. However, recent evidence shows insect steroid ecdysone being secreted via regulated exocytosis, but the mechanisms ensuring successful hormone release into circulation remain unclear. Our study identifies specialized membrane protrusions, signaling filopodia, in the Drosophila prothoracic gland as essential for vesicle-mediated steroid release. Confocal imaging reveals that these actin- and tubulin-rich structures form a membrane-intertwined basal domain critical for secretion. Disrupting filopodia by interfering with basement membrane interactions-Perlecan or β-integrin-or filopodia-specific protein expression-α-actinin-significantly reduces ecdysone signaling by impairing its release, despite proper production in the gland. Additionally, filopodia dynamics, such as length and density, align with secretion timing and hormone circulating levels, suggesting their role in synchronizing release with physiological needs. The systematic presence of membrane protrusions in steroid-secreting glands across species prompts a comprehensive re-evaluation of steroid release mechanisms.
类固醇激素对发育和生理过程至关重要，传统观点认为它们可被动扩散穿过细胞膜。然而，最近有证据表明昆虫类固醇蜕皮激素是通过调节性胞吐作用分泌的，但确保激素成功释放到循环系统中的机制仍不清楚。我们的研究确定了果蝇前胸腺中一种特殊的膜突出结构——信号丝状伪足，它对囊泡介导的类固醇释放至关重要。共聚焦成像显示，这些富含肌动蛋白和微管蛋白的结构形成了一个对分泌至关重要的膜交织基底结构域。通过干扰基底膜相互作用（如基底膜蛋白聚糖或β-整合素）或丝状伪足特异性蛋白表达（如α-辅肌动蛋白）来破坏丝状伪足，尽管腺体中激素产生正常，但会通过损害其释放而显著降低蜕皮激素信号。此外，丝状伪足的动态变化，如长度和密度，与分泌时间和激素循环水平一致，表明它们在使释放与生理需求同步方面发挥作用。跨物种类固醇分泌腺中膜突出结构的系统性存在促使人们对类固醇释放机制进行全面重新评估。
