Fig. 3: S1P promotes resistance against saturated fatty acids by improving membrane homeostasis in mammalian cells.

A S1P abundance in WT MEFs ± PA 400 µM for 12 h. n = 4 biologically independent replicates for each condition. Related lipidomics in Supplementary Data 4. B, C Pseudocolor images and GP index of WT MEFs ± PA 400 µM ± S1P 10 or 1 µM ± OA 400 µM for 18 h and stained with Laurdan. Note the large number of “small” and highly packed lipid droplets induced by PA + OA (white arrows). In C, n = 15 images analyzed per condition, except for PA + OA where n = 14. D, E PA (16:0) and PalOA (16:1) abundance in the PC and PE of HEK293 cells + PA 400 µM ±S1P 10 µM for 24 h. n = 5 biologically independent replicates per condition. Related lipidomics are in Data S5. F Average GP index of the rat insulinoma INS-1E ± PA 400 µM ± S1P 10 or 1 µM ± OA 400 µM and stained with Laurdan. For each condition, from left to right, n = 19, 17, 16, 15, and 6 images analyzed. G Glucose-stimulated insulin secretion (GSIS) assay: Amount of insulin secreted (in 2 h) by INS-1E cells pre-exposed ± PA 400 µM ± S1P for 18 h. n = 4 biologically independent replicates for each condition. H Schematics of the Zn²⁺ atom inside human AdipoR2. PDB 5LX9 entry was used as model¹³. The Zn²⁺ is coordinated by three histidines. I Western-Blot of AdipoR2 and Tubulin in HEK293 cells transfected with human AdipoR2: WT sequence, H348A mutant and H202,348,350A mutations. Uncropped blots in Source Data. J Average GP index from several images of HEK293 cells transfected with human AdipoR2: WT sequence, H348A mutant and H202,348,350A mutations and challenged with PA 400 µM for 24 h. For each condition, from left to right, n = 10, 15, 10, 15 and 15 images analyzed. Data are represented as mean ± SEM. t-tests (two sided and assuming normality) were used to identify significant differences between treatments. *p < 0.05, **p < 0.01, ***p < 0.001. See also Supplementary Fig. 4 and Supplementary Data 4–6. Source data are provided as a Source Data file.