title: Wnt proteins are lipid-modified and can act as stem cell growth factors.
abstract: Wnt signalling is involved in numerous events in animal development, including the proliferation of stem cells and the specification of the neural crest. Wnt proteins are potentially important reagents in expanding specific cell types, but in contrast to other developmental signalling molecules such as hedgehog proteins and the bone morphogenetic proteins, Wnt proteins have never been isolated in an active form. Although Wnt proteins are secreted from cells, secretion is usually inefficient and previous attempts to characterize Wnt proteins have been hampered by their high degree of insolubility. Here we have isolated active Wnt molecules, including the product of the mouse Wnt3a gene. By mass spectrometry, we found the proteins to be palmitoylated on a conserved cysteine. Enzymatic removal of the palmitate or site-directed and natural mutations of the modified cysteine result in loss of activity, and indicate that the lipid is important for signalling. The purified Wnt3a protein induces self-renewal of haematopoietic stem cells, signifying its potential use in tissue engineering.
authors.affiliation: Howard Hughes Medical Institute and Department of Developmental Biology, Stanford University School of Medicine, Stanford, California 94305, USA.
authors.forename: Karl
authors.initials: K
authors.lastname: Willert
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Brown
authors.forename: Esther
authors.initials: E
authors.lastname: Danenberg
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Duncan
authors.forename: Irving L
authors.initials: IL
authors.lastname: Weissman
authors.forename: Tannishtha
authors.initials: T
authors.lastname: Reya
authors.forename: John R
authors.initials: JR
authors.lastname: Yates
authors.forename: Roel
authors.initials: R
authors.lastname: Nusse
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D017124:Conserved Sequence; D003545:Cysteine / Q000235:genetics; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004331:Drosophila melanogaster; D006133:Growth Substances / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000187:drug effects; D007739:L Cells; D050356:Lipid Metabolism; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010169:Palmitic Acids / Q000378:metabolism*; D011506:Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D012995:Solubility; D015534:Trans-Activators / Q000378:metabolism; D051153:Wnt Proteins; D060508:Wnt3 Protein; D060509:Wnt3A Protein; D029867:Xenopus Proteins; D014982:Xenopus laevis; D029961:Zebrafish Proteins; D051176:beta Catenin
chemical_list: C495266:CTNNB1 protein, Xenopus; C495267:CTNNB1 protein, mouse; D003598:Cytoskeletal Proteins; D006133:Growth Substances; D010169:Palmitic Acids; D011506:Proteins; D015534:Trans-Activators; C555506:WNT3A protein, Xenopus; D051153:Wnt Proteins; D060508:Wnt3 Protein; D060509:Wnt3A Protein; C555511:Wnt3a protein, mouse; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; D051176:beta Catenin; C094521:wnt8a protein, zebrafish; D003545:Cysteine