Follistatin-like protein 1 modulates IL-17 signaling via IL-17RC regulation in stromal cells.

Follistatin-like protein 1 (FSTL-1) possesses several newly identified roles in mammalian biology, including interleukin (IL)-17-driven inflammation, though the mechanism underlying FSTL-1 influence on IL-17-mediated cytokine production is unknown. Using parallel in vitro bone marrow stromal cell models of FSTL-1 suppression, we employed unbiased microarray analysis to identify FSTL-1-regulated genes and pathways that could influence IL-17-dependent production of IL-6 and granulocyte colony-stimulating factor. We discovered that FSTL-1 modulates Il17rc gene expression. Specifically, FSTL-1 was necessary for Il17rc gene transcription, IL-17RC surface protein expression and IL-17-dependent cytokine production. This work identifies a mechanism by which FSTL-1 influences IL-17-driven inflammatory signaling in vitro and reveals a novel function for FSTL-1, as a modulator of gene expression. Thus enhanced understanding of the interplay between FSTL-1 and IL-17-mediated inflammation may provide insight into potential therapeutic targets of IL-17-mediated diseases and warrants ongoing study of in vivo models and clinical scenarios of FSTL-1-influenced diseases.