Cell surface proteoglycan that bears heparan sulfate (By similarity). Negatively regulates the hedgehog signaling pathway when attached via the GPI-anchor to the cell surface by competing with the hedgehog receptor PTC1 for binding to hedgehog proteins (By similarity). Binding to the hedgehog protein SHH triggers internalization of the complex by endocytosis and its subsequent lysosomal degradation (By similarity). Positively regulates the canonical Wnt signaling pathway by binding to the Wnt receptor Frizzled and stimulating the binding of the Frizzled receptor to Wnt ligands (By similarity). Positively regulates the non-canonical Wnt signaling pathway (By similarity). Binds to CD81 which decreases the availability of free CD81 for binding to the transcriptional repressor HHEX, resulting in nuclear translocation of HHEX and transcriptional repression (By similarity). Inhibits the dipeptidyl peptidase activity of DPP4 (By similarity). Plays a role in limb patterning and skeletal development by controlling the cellular response to BMP4 (By similarity). Modulates the effects of growth factors BMP2, BMP7 and FGF7 on renal branching morphogenesis (By similarity). Required for coronary vascular development (By similarity). Plays a role in regulating cell movements during gastrulation (By similarity). Heterodimer; disulfide-linked (By similarity). Cleavage by a furin-like convertase results in production of alpha and beta chains which form a disulfide-linked heterodimer (By similarity). Interacts with DPP4 (By similarity). Interacts with FGF2 (PubMed:9065409). Interacts with WNT5A (By similarity). Also interacts with WNT3A and WNT7B (By similarity). Interacts with hedgehog protein SHH; the heparan sulfate chains are not required for the interaction (By similarity). Also interacts with hedgehog protein IHH (By similarity). Interacts with CD81 (By similarity). Interacts with Wnt receptors FZD4, FZD7 and FZD8; the heparan sulfate chains are required for the interaction (By similarity). In the intestine, expression decreases gradually from 20 dpc and finally becomes undetectable after weaning around 24 days after birth. O-glycosylated; contains heparan sulfate. Cleaved intracellularly by a furin-like convertase to generate 2 subunits, alpha and beta, which remain associated through disulfide bonds and are associated with the cell surface via the GPI-anchor. This processing is essential for its role in inhibition of hedgehog signaling. A second proteolytic event may result in cleavage of the protein on the cell surface, separating it from the GPI-anchor and leading to its shedding from the cell surface. Belongs to the glypican family.