WNT FAMILY PROTEINS ARE SECRETED AND ASSOCIATED WITH THE CELL-SURFACE

Members of the Wnt gene family are proposed to function in both normal development and differentiation as well as in mammary tumorigenesis. To understand the function of Wnt proteins in these two processes, we present here a biochemical characterization of seven Wnt family member s. For these studies, AtT-20 cells, a neuroendocrine cell line previou sly shown to efficiently process and secrete Wnf-1, was transfected wi th expression vectors encoding Wnt family members. All of the newly ch aracterized Wnt proteins are glycosylated, secreted proteins that are tightly associated with the cell surface or extracellular matrix. We h ave also identified native Wnt proteins in retinoic acid-treated P19 e mbryonal carcinoma cells, and they exhibit the same biochemical charac teristics as the recombinant proteins. These data suggest that Wnt fam ily members function in cell to cell signaling in a fashion similar to Wnt-1.