Coordinated regulation of cell differentiation by sphingosine-1-phosphate receptors in renal epithelial cells.

Sphingolipids regulate essential cellular processes, with sphingosine-1-phosphate (S1P) emerging as a critical modulator of proliferation, migration, and differentiation. While intracellular S1P governs sphingolipid metabolism during renal epithelial differentiation, its role as a ligand for S1P receptors (S1PRs) remains poorly understood. Here, we investigated the roles of S1PR1, S1PR2, and S1PR3 during the differentiation of Madin-Darby canine kidney (MDCK) cells. We found that S1PR2 and S1PR3 are critical for apical membrane formation, while S1PR2 additionally regulates adherens junction (AJ) maturation and actin cytoskeleton reorganization, essential for a differentiated epithelial morphology. Functional assays, including pharmacological inhibition and genetic silencing, showed that inhibition of S1PR2 impaired AJ formation and disrupted epithelial differentiation. Notably, S1PR2 restoration re-established AJ formation and epithelial organization, which underscores its critical role in maintaining cell-cell adhesion. Interestingly, S1PR2 exhibited distinct localization patterns throughout the differentiation process, transitioning from predominantly intracellular structures in proliferating cells to a more discrete peripheral/plasma membrane distribution along cell-cell boundaries in differentiated cells. These findings provide new insights into the spatial regulation of S1P signaling during renal epithelial differentiation and highlighted the emerging role of S1PR signaling in epithelial cell organization. This work broadens our understanding of S1PR2 mechanisms and suggests differential roles across stages of epithelial differentiation, thus offering potential therapeutic strategies for conditions involving renal epithelial dysfunction.