METTL14 protects sheep small intestinal epithelial cells against Escherichia coli F17 infection by influencing the PI3K–Akt signaling pathway

Escherichia coli F17 is emerging as one of the main causes of bacterial diarrhea in sheep. After lambs are infected, the bacteria colonize the small intestinal epithelial cells (IECs) through adhesion of F17 fimbriae. This colonization triggers the release of enterotoxins, disrupting the intestinal mucosa and resulting in symptoms such as diarrhea. These pathological effects contribute to considerable global economic losses and continuously impact the economic development of the sheep farming industry. Meanwhile, m⁶A methylation, the most prevalent form of messenger RNA (mRNA) modification, participates in fundamental pathophysiological and metabolic processes of RNAs. Methyltransferase-like 14 (METTL14), a key component of the m⁶A methyltransferase complex, has been identified as playing an important role in cell migration and invasion. In addition, METTL14 has been demonstrated to contribute to the antimicrobial mechanisms of cells. However, its potential role in IECs in E. coli F17-infected sheep remains unclear. In this study, we demonstrate that METTL14 regulates the susceptibility of sheep small intestinal epithelial cells to E. coli F17. Specifically, we observed that METTL14 expression was significantly increased in sheep IECs following E. coli F17 infection. Using bacterial adhesion assays (bacterial counting, Gram staining, and fimbrial gene expression analysis), together with vimentin protein detection, western blotting, and scratch tests, we demonstrate that METTL14 overexpression or knockdown affects the susceptibility of sheep IECs to E. coli F17. Furthermore, RNA-seq analysis after METTL14 knockdown, combined with pathway inhibition experiments, revealed that the PI3K-Akt signaling pathway is involved in the anti-adhesion response. Blocking this pathway confirmed that METTL14 modulates the susceptibility of IECs to E. coli F17 via PI3K-Akt signaling. These findings provide new insights into the pathogenic mechanism of E. coli F17 and establish an experimental basis for enhancing sheep resistance to E. coli-related diseases.