title: Lipid-independent secretion of a Drosophila Wnt protein.
abstract: Wnt proteins comprise a large class of secreted signaling molecules with key roles during embryonic development and throughout adult life. Recently, much effort has been focused on understanding the factors that regulate Wnt signal production. For example, Porcupine and Wntless/Evi/Sprinter have been identified as being required in Wnt-producing cells for the processing and secretion of many Wnt proteins. Interestingly, in this study we find that WntD, a recently characterized Drosophila Wnt family member, does not require Porcupine or Wntless/Evi/Sprinter for its secretion or signaling activity. Because Porcupine is involved in post-translational lipid modification of Wnt proteins, we used a novel labeling method and mass spectrometry to ask whether WntD undergoes lipid modification and found that it does not. Although lipid modification is also hypothesized to be required for Wnt secretion, we find that WntD is secreted very efficiently. WntD secretion does, however, maintain a requirement for the secretory pathway component Rab1. Our results show that not all Wnt family members require lipid modification, Porcupine, or Wntless/Evi/Sprinter for secretion and suggest that different modes of secretion may exist for different Wnt proteins.
authors.affiliation: Howard Hughes Medical Institute and the Department of Developmental Biology, Stanford University School of Medicine, Stanford, California 94305, USA.
authors.forename: Wendy
authors.initials: W
authors.lastname: Ching
authors.forename: Howard C
authors.initials: HC
authors.lastname: Hang
authors.forename: Roel
authors.initials: R
authors.lastname: Nusse
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008055:Lipids / Q000737:chemistry*; D008565:Membrane Proteins / Q000378:metabolism*; D008954:Models, Biological; D008957:Models, Genetic; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D051153:Wnt Proteins / Q000378:metabolism*; D020761:rab1 GTP-Binding Proteins / Q000378:metabolism
chemical_list: D029721:Drosophila Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008055:Lipids; D008565:Membrane Proteins; C511046:Wls protein, Drosophila; D051153:Wnt Proteins; C504611:WntD protein, Drosophila; C103067:por protein, Drosophila; D020761:rab1 GTP-Binding Proteins