Ligand for members of the frizzled family of seven transmembrane receptors (Probable). Functions in the canonical Wnt signaling pathway that results in activation of transcription factors of the TCF/LEF family (PubMed:20093360, PubMed:21244856, PubMed:24841207, PubMed:26902720). Required for normal embryonic mesoderm development and formation of caudal somites. Required for normal morphogenesis of the developing neural tube (By similarity). Mediates self-renewal of the stem cells at the bottom on intestinal crypts (in vitro) (PubMed:26902720). Forms a soluble 1:1 complex with AFM; this prevents oligomerization and is required for prolonged biological activity (PubMed:26902720). The complex with AFM may represent the physiological form in body fluids (PubMed:26902720). Homooligomer; disulfide-linked, leading to inactivation (By similarity). Interacts with PORCN (PubMed:20826466). Interacts with APCDD1 and WLS (PubMed:16678095, PubMed:20393562). Component of the Wnt-Fzd-LRP5-LRP6 signaling complex that contains a WNT protein, a FZD protein and LRP5 or LRP6. Interacts directly in the complex with LRP6 (PubMed:20093360). Interacts with glypican GPC3 (PubMed:16227623). Interacts with PKD1 (via extracellular domain) (PubMed:27214281). Moderately expressed in placenta and at low levels in adult lung, spleen, and prostate. Palmitoleoylation by PORCN is required for efficient binding to frizzled receptors. Palmitoleoylation is required for proper trafficking to cell surface, vacuolar acidification is critical to release palmitoleoylated WNT3A from WLS in secretory vesicles (PubMed:20826466, PubMed:21244856, PubMed:24292069). Depalmitoleoylated by NOTUM, leading to inhibit Wnt signaling pathway, possibly by promoting disulfide bond formation and oligomerization (PubMed:25731175). Proteolytic processing by TIKI1 and TIKI2 promotes oxidation and formation of large disulfide-bond oligomers, leading to inactivation of WNT3A. Disulfide bonds have critical and distinct roles in secretion and activity. Loss of each conserved cysteine in WNT3A results in high molecular weight oxidized Wnt oligomers, which are formed through inter-Wnt disulfide bonding. Belongs to the Wnt family. A palmitoylation site was proposed at Cys-77, but it was later shown that this cysteine is engaged in a disulfide bond (PubMed:24292069).