Acts as a carrier protein that releases fibroblast-binding factors (FGFs) from the extracellular matrix (EM) storage and thus enhances the mitogenic activity of FGFs. Enhances FGF2 signaling during tissue repair, angiogenesis and in tumor growth (By similarity). Found in a complex with FGFBP1, FGF1 and FGF2. Interacts with FGF1, FGF7, FGF10, FGF22 and HSPG2 (By similarity). Interacts with FGF2. Extracellular and plasma membrane-associated. Expressed in intestine, ovary, lung, placenta and normal and wounded skin. Expressed in digestive system, skin, hair follicles, the dental germ, respiratory tract, various glandular tissues, kidney, liver and certain areas of the central nervous system between 8 and 16 dpc (at protein level). Expressed. in embryo between 9 to 18 dpc. Expressed at 14 dpc in the epithelial cells and 18 dpc in basal epithelial cells of intestinal crypts. Expressed in mesenchymal and epidermal structures of the body wall at 9 dpc. Expressed in basal cells of the subepidermal layer of the skin at 12 dpc. Expressed in hair follicles at 14 dpc. Expression is significantly up-regulated in skin papillomas and carcinomas. Belongs to the fibroblast growth factor-binding protein family.