– Interleukin-17 receptor D (IL-17 RD), also known as SEF (similar expression to FGFs), is a type I transmembrane protein that is found in both the cytoplasm and plasma membrane. IL-17RD functions as a feedback inhibitor of fibroblast growth factor mediated Ras-MAPK signaling and ERK activation. It may inhibit FGF-induced FGFR1 tyrosine phosphorylation, regulate the nuclear ERK signaling pathway by spatially blocking nuclear translocation of activated ERK By similarity, and mediate JNK activation and may be involved in apoptosis. IL-17RD interacts with the IL-17R downstream molecule TRAF6. It has been proposed that the IL-17RD intracellular domain interacts with IL-17R and TRAF6 to deliver the downstream signal.