α(1,3)‐Fucosylation alters STAT3‐dependent IL‐17 production in vivo

Mice deficient in α(1,3)‐fucosyltransferase (FucT)‐IV and ‐VII (DKO) lack selectin ligand activity, have severe deficiencies in leukocyte trafficking, and have a marked increase in circulating IL‐ 17a compared to wild‐type (WT) mice. We sought to determine how the loss of FucT‐IV/‐VII activity alters the intracellular signaling cascade responsible for IL‐17a induction. Mononuclear leukocytes were isolated from the spleen of WT and DKO mice. Messenger RNA was isolated and converted to cDNA. qPCR was performed using Sybr green‐based detection and standardized to B‐actin. DKO mice have elevated transcript levels of RORγT and IL‐17a (18‐fold and 30‐fold, respectively) compared to WT, and reduced levels of STAT3 and SOCS3 transcript (5‐fold and 6‐fold, respectively). Protein for western blots was isolated from the whole spleen of 12 week old male mice, separated on a 10% polyacrylamide gel, transferred to a 0.22 μm nitrocellulose membrane and probed with antibodies to SOCS3, RORγT, STAT3, or γ‐Tubulin. DKO mice have drastically reduced levels of STAT3 and SOCS3 protein and increased levels of RORγT protein compared to WT mice. These data show that loss of FucT‐IV and ‐ VII activity alters the STAT3 signaling cascade thought to be solely responsible for IL‐17a induction. They suggest that loss of FucT‐IV and ‐VII activity may allow an alternate signaling pathway to drive IL‐17a production independent of STAT3.