Follistatin Like Protein 1 (FSTL1)

FSTL1 encodes a protein with similarity to follistatin, an activin-binding protein. It contains an FS module, a follistatin-like sequence containing 10 conserved cysteine residues. This gene product is thought to be an autoantigen associated with rheumatoid arthritis.FSTL1 encodes a deduced 308-amino acid protein with an N-terminal signal peptide of 20 amino acids. The number and distribution of the cysteine residues supports the existence of several intramolecular disulfide bridges.Immunohistochemical analysis demonstrated increased expression in Cd90 (THY1)-positive fibroblasts, particularly early in CIA. Monkey fibroblasts transfected with human FSTL1 spontaneously secreted more IL6, and human monocytes transfected with FSTL1 and stimulated with mitogens expressed higher IL1B, TNF, and IL6.