S1PR3
Overview
S1PR3 is a sphingosine-1-phosphate receptor implicated in migration of T-bet⁺CD11c⁺ B cells toward the splenic marginal zone. It is included here mainly as a cautionary case: it is essential for S1P-directed chemotaxis in vitro and completely dispensable in vivo, in the same paper.
⚠ Thin page — single source, murine. All claims trace to Song2022 - Tfh Outside Germinal Centers Drive T-bet CD11c B Cells.
Related S1P receptors appear elsewhere in the wiki without pages: S1PR2 (S1pr2) confines B cells to the germinal centre and is the basis of the fate-mapping system Song2022 uses; S1PR1 is downregulated in tissue-resident memory B cells alongside CD69 upregulation (see Tissue-Resident Memory B Cell).
Key Points from Literature
- S1pr3 transcript increased between days 8 and 15 post-infection, i.e. as the infection resolved and the cells relocated to the marginal zone — alongside Cnr2 (cannabinoid receptor 2), which has also been implicated in marginal zone migration (see Song2022 - Tfh Outside Germinal Centers Drive T-bet CD11c B Cells, murine RNA-seq; 1,433 genes differentially expressed between these timepoints)
- In transwell migration toward S1P: FTY720 (which targets S1PR1 and S1PR3) limited chemotaxis, and TY52156, a selective S1PR3 inhibitor, abolished it completely (see Song2022 - Tfh Outside Germinal Centers Drive T-bet CD11c B Cells, murine ex vivo)
- ★ But in vivo it is dispensable: mixed bone marrow chimeras of CD45.1-marked wild-type with CD45.2 S1pr3⁻/⁻ or S1pr3⁺/⁻ cells showed no advantage of S1pr3-sufficient over S1pr3-deficient cells in populating the marginal-zone compartment at day 15 (see Song2022 - Tfh Outside Germinal Centers Drive T-bet CD11c B Cells)
- The authors attribute the discrepancy to compensation by CNR2 and CXCR3, both of which were highly expressed — and state explicitly that this was not further investigated (named as a study limitation)
- CXCR3 was expressed more highly on T-bet⁺CD11c⁺ B cells than on naive follicular or GC counterparts, and its ligands are produced at the marginal zone (see Song2022 - Tfh Outside Germinal Centers Drive T-bet CD11c B Cells). See CXCR3.
Contradictions & Debates
★ In vitro necessity versus in vivo redundancy. A selective inhibitor completely abolishes S1P-directed migration, yet genetic deletion produces no competitive disadvantage in vivo. Both results are from the same paper and the authors flag the conflict themselves. The proposed explanation — redundancy with CNR2 and CXCR3 — is untested.
The methodological lesson is the transferable part: a chemotaxis assay that isolates one ligand–receptor pair can report a requirement that the intact animal does not have. This is worth remembering when reading any single-receptor migration claim in this wiki, including the CXCR5/CXCR3 rewiring account on Follicular Exclusion.
Related Pages
CXCR3, CXCR5, LFA-1, VLA-4, Follicular Exclusion, Tissue-Resident Memory B Cell, Germinal Center, DN2 B Cell