Integrative single-cell transcriptomic and epitranscriptomic analysis of the RBM15-m6A-IL10 regulatory axis in psoriatic keratinocytes.

BACKGROUND: Psoriasis is a chronic immune-mediated inflammatory skin disorder hallmarked by keratinocyte hyperproliferation and impaired apoptosis. N6-methyladenosine (m6A) RNA modification is emerging as a critical regulator of inflammatory gene expression. RNA-binding motif protein 15 (RBM15), a core m6A methyltransferase complex adaptor, promotes oncogenic processes across tissue types; however, its role in psoriatic keratinocyte biology and its potential regulation of interleukin-10 (IL-10)-a pivotal anti-apoptotic and immunomodulatory cytokine-remain unexplored. METHODS: Single-cell RNA sequencing data from a publicly deposited psoriasis dataset (GSE248121; 23,851 cells from two paired libraries) were analyzed using Seurat, Monocle3, CellChat, and pySCENIC. Bulk transcriptomic datasets (GSE54456, GSE30999) were used for cross-dataset validation of RBM15 and IL10 expression. In vitro, RBM15 was silenced in IL-17A/M5-stimulated HaCaT keratinocytes by siRNA. m6A modification of IL10 mRNA was mapped by methylated RNA immunoprecipitation-qPCR (MeRIP-qPCR) and validated by mRNA stability assay, luciferase reporter, and YTHDF2 RNA immunoprecipitation. Apoptosis was quantified by flow cytometry (Annexin V/PI), caspase-3/7 activity, CCK-8 viability, and Western blotting of Bcl-2 family proteins and JAK1/STAT3 pathway components. RESULTS: Integrated single-cell analysis resolved 23,851 cells into six principal cell types across psoriatic lesional (PP) and clinically normal (NS) skin. RBM15 was markedly upregulated in psoriatic keratinocytes (log2FC = 1.93 [fold change ≈3.82] ± 0.31 vs. NS; p < 0.001) and correlated inversely with IL10 along keratinocyte pseudotime trajectories (r = -0.52, p < 0.001). Cross-dataset validation confirmed concordant RBM15 upregulation and IL10 downregulation in PP lesions. Mechanistically, RBM15 installed m6A marks at two RRACH motifs in the IL10 3'UTR, promoting YTHDF2-mediated mRNA degradation (half-life reduction 53.3%; p < 0.001) and 62% suppression of IL10 protein. In vitro, RBM15 knockdown restored IL10, reduced apoptosis from 22.8% to 8.4% (p < 0.001), augmented JAK1/STAT3 phosphorylation, and elevated Bcl-2/Bcl-xL while suppressing Bax and cleaved caspase-3. IL10 neutralization fully reversed these pro-survival effects. CONCLUSION: RBM15-driven m6A modification of IL10 mRNA constitutes a previously unrecognized epitranscriptomic mechanism suppressing IL-10-mediated survival signaling in psoriatic keratinocytes. Targeting the RBM15-m6A-IL10 axis represents a mechanistically grounded and potentially tractable therapeutic direction for psoriasis, pending further in vivo and clinical validation.