Enrichment and Detection of Wnt Proteins from Cell Culture Media.

Wnt proteins are secreted, lipid-modified growth factors with a wide range of activities across all metazoan species. Their production, secretion, and signaling range are under tight cellular control such that detection of Wnt proteins in biological samples is often extremely difficult. In this chapter, we describe a protocol to detect secreted Wnt proteins in the culture medium of cell lines that ectopically or endogenously express Wnt genes. This protocol uses an affinity resin, called Blue Sepharose, that binds and thereby enriches Wnt proteins, followed by immunoblotting for the Wnt protein of interest. This method for detecting Wnt proteins will aid in the isolation of biologically active Wnt proteins, provide an assay to study the molecular basis of Wnt secretion, and potentially offer a means to detect trace amounts of Wnt proteins associated with pathological states.