title: Interaction of Wnt-1 proteins with the binding protein BiP.
abstract: The mouse Wnt-1 gene, a target for insertional activation in mouse mammary tumor virus-induced mammary tumors, encodes poorly secreted, cysteine-rich glycoproteins required for proper central nervous system development. We have been analyzing the biosynthesis of Wnt-1 proteins in several cell lines that express Wnt-1 cDNA from heterologous promoters. A protein of 78 kDa was found to be associated with the intracellular forms of Wnt-1 proteins in mammalian and avian cells by using multiple antisera against Wnt-1 proteins. We have identified p78 as the binding protein BiP with anti-BiP antisera and by its release from Wnt-1 immunoprecipitates upon incubation with MgCl2 and ATP. Experiments with a Wnt-1 mutant that lacks the sequence encoding the signal peptide indicates that Wnt-1 proteins must enter the secretory pathway in order to interact with BiP. We demonstrate that Wnt-1 proteins are associated with BiP in cells in which active Wnt-1 proteins are produced, such as a cultured mammary epithelial cell line and Wnt-1 transgenic mouse mammary tumor cells. The association of Wnt-1 proteins with BiP may be a factor in determining the efficiency of secretion of Wnt-1 gene products.
authors.affiliation: Department of Microbiology, University of California, San Francisco 94143-0502.
authors.forename: J
authors.initials: J
authors.lastname: Kitajewski
authors.forename: J O
authors.initials: JO
authors.lastname: Mason
authors.forename: H E
authors.initials: HE
authors.lastname: Varmus
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D002461:Cell Line, Transformed; D005656:Fungal Proteins / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000378:metabolism*; D011233:Precipitin Tests; D021382:Protein Sorting Signals / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051153:Wnt Proteins; D051155:Wnt1 Protein; D029961:Zebrafish Proteins
chemical_list: D005656:Fungal Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C060153:KAR2 protein, yeast; D021382:Protein Sorting Signals; D011518:Proto-Oncogene Proteins; D051153:Wnt Proteins; D051155:Wnt1 Protein; D029961:Zebrafish Proteins; D000255:Adenosine Triphosphate