Background：Regulator of cell surface receptor signal transduction. Plays a central role in retinal vascularization by regulating norrin(NDP) signal transduction. Acts in concert with norrin(NDP) to promote FZD4 multimerization and subsequent activation of FZD4, leading to promote accumulation of beta-catenin(CTNNB1) and stimulate LEF/TCF-mediated transcriptional programs. Suprisingly, it only activate the norrin(NDP)-dependent activation of FZD4, while it does not activate the Wnt-dependent activation of FZD4, suggesting the existence of a Wnt-independent signaling that also promote accumulation the beta-catenin(CTNNB1)(By similarity). Acts as a regulator of membrane proteinases such as ADAM10 and MMP14/MT1-MMP. Activates ADAM10-dependent cleavage activity of amyloid precursor protein(APP). Activates MMP14/MT1-MMP-dependent cleavage activity.
