Signalling at a distance: transport of Wingless in the embryonic epidermis of Drosophila.
Secreted signalling molecules affect the behavior of cells at a distance. Here we discuss how the Wnt family member Wingless reaches distant cells within the embryonic epidermis of Drosophila. We consider three possible mechanisms: free diffusion, restricted diffusion and active transport. We argue that free diffusion is unlikely to occur. However, a variant of restricted diffusion may account for Wingless transport. It may be that Wingless is carried from one side of a cell to the other by a drifting transmembrane protein such as a specific receptor or a glycosaminoglycan. Transfer from cell-to-cell would involve release from the donor cell and recapture in an adjacent cell. Alternatively, Wingless might be transported by a mechanism akin to transcytosis. This would involve the packaging of Wingless in specialized vesicles at one end of a cell, active transport across the cell, and vesicle fusion and Wingless release on the other side. We describe the evidence in favor and against these two alternatives.
Pfeiffer
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The Ridgeway, The National Institute for Medical Research (N.I.M.R.), Mill Hill, London, NW7 1AA, UK.
Vincent
J P
JP
D000818:Animals; D001693:Biological Transport, Active / Q000502:physiology; D002352:Carrier Proteins / Q000502:physiology; D002450:Cell Communication / Q000502:physiology*; D004058:Diffusion; D004330:Drosophila / Q000196:embryology*; D029721:Drosophila Proteins; D004817:Epidermis / Q000196:embryology / Q000378:metabolism*; D006025:Glycosaminoglycans / Q000378:metabolism; D015388:Organelles / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000378:metabolism* / Q000502:physiology; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D051155:Wnt1 Protein
D002352:Carrier Proteins; D029721:Drosophila Proteins; D006025:Glycosaminoglycans; D011518:Proto-Oncogene Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D051155:Wnt1 Protein; C074622:wg protein, Drosophila