Dear Editor,Processing-bodies (P-bodies) are cytoplasmic membraneless organelles that regulate mRNA translation through phase separation. Despite extensive molecular characterization, the physiological signals controlling their assembly remain poorly understood. Sodium arsenite, a widely used P-body chemical regulator, causes rapid cell death, limiting insights into regulatory mechanisms.Through an unbiased screen of 1520 FDA-approved drugs, we identified glucocorticoids as potent inducers of P-body formation, establishing an unrecognized connection between steroid hormone signaling and cytoplasmic RNA granule dynamics (supplementary figures deposited in Zenodo; https://zenodo.org/records/17368807). Glucocorticoids such as dexamethasone and prednisolone, widely prescribed, increased P-body numbers at clinically relevant concentrations (0.1–1 μM) within 48 h across multiple cell lines (A549, HeLa, and Mel501) (Fig. 1a left). To assess glucocorticoid receptor (GR) involvement and system dynamics, we used complementary approaches: GR antagonism (RU486) completely blocked P-body formation and FKBP5 upregulation, while glucocorticoid withdrawal rapidly reversed the phenotype within 24 h (Fig. 1a, right). This GR-dependent reversible response defines a tightly regulated pathway.Fig. 1Full size imageNovel post-transcriptional dimension of glucocorticoid action through mRNA translation and P-body remodeling. a Glucocorticoid receptor (GR) activation increases P-body numbers in different epithelial cell lines. (Left) Quantification of P-body numbers per cell in A549 cells treated for 48 h with Dexa (0.1 or 1 µM), Pred (0.1 or 1 µM), RU486 (1 µM; a glucocorticoid inhibitor, 1 h pre-treatment), or sodium arsenite (Ars; 0.5 mM for 30 min). (Right) Quantification of P-body numbers per cell in A549 cells treated with 0.1 µM Dexa for 48 h, followed by 24 h in reference medium (Withdrawal), with corresponding immunofluorescence images showing DDX6 (green), glucocorticoid receptor (GR, red), and nuclei (DAPI, blue). b The GRα isoform is required for glucocorticoid-induced P-body accumulation. (Top) Quantification of P-body numbers per cell in A549 control (CTL) or GR knockout (KO GR) cells treated with 0.1 µM Dexa for 48 h. (Bottom) Quantification of P-body numbers per cell in A549 GFP and A549 KO GR cells rescued with GFP-GRα, treated for 48 h with Dexa ranging from 10−4 to 1 µM. c GR activation promotes a P-body-associated AU-rich bias in mRNA translation fate. (Top) Correlation of differential mRNA (RNA-seq) and protein (mass spectrometry) fold changes after 48 h of 1 µM Dexa treatment. Highlighted gene sets include NR3C1-induced genes (red), P-body-targeted genes (purple), and genes showing increased (green) or decreased (blue) protein output relative to mRNA changes. (Bottom) GC content of CDS (coding sequence) for each gene category and the frequency of optimal codon (Fop) within CDS regions for the same gene categories. d LSM14B expression inversely correlates with GR-dependent P-body accumulation. (Top) Quantification of P-body numbers in A549 cells transfected with siCTL or two siRNAs against LSM14B, and in GFP and LSM14B-GFP A549 cells treated with 0.1 µM Dexa for 48 h. (Bottom) LSM14B-positive P-body numbers per cell in A549 cells treated with 0.1 µM Dexa for 48 h and followed by Dexa withdrawal for 24 h (Withdrawal). Scale bars: 10 µm. P-bodies were quantified in at least 100 cells per condition from at least three independent biological experiments. After Shapiro-Wilk normality testing, data were analyzed using Kruskal-Wallis tests with Dunn’s post hoc comparisons. Significance: * p