Fig. 3

Overview of S1P metabolism. The de novo pathway begins with small molecules such as serine and palmitoyl-CoA and subsequently by the activity of SPT, KDHR, CerS, and dihydro-ceramide desaturase forming ceramide which can be utilized for S1P formation. The acidic environment of endosomes and lysosomes degradation of complex sphingolipids, including sphingomyelin, forms sphingosine, then are phosphorylated by SphK1 and SphK2. Furthermore, plasma membrane sphingomyelin by the action of sphingomyelinase to ceramide. SPT: Serine palmitoyl transferase; KDHR: 3-ketodihydrosphingosine reductase; CerS: ceramides synthases; SphK1/2: Sphingosine kinase 1/2; SGPP1/2: S1P phosphatase. The chemical structures used in the present illustration were drawn using ChemDraw Professional 21.0 software, and the figure was drawn by using Biorender https://www.biorender.com/