Wingless/Wnt signal transduction requires distinct initiation and amplification steps that both depend on Arrow/LRP.
Members of the Wg/Wnt family provide key intercellular signals during embryonic development and in the maintenance of homeostatic processes, but critical aspects of their signal transduction pathways remain controversial. We have found that canonical Wg signaling in Drosophila involves distinct initiation and amplification steps, both of which require Arrow/LRP. Expressing a chimeric Frizzled2-Arrow protein in flies that lack endogenous Wg or Arrow showed that this construct functions as an activated Wg receptor but is deficient in signal amplification. In contrast, a chimeric Arrow protein containing the dimerization domain of Torso acted as a potent amplifier of Wg signaling but could not initiate Wg signaling on its own. The two chimeric proteins synergized, so that their co-expression largely reconstituted the signaling levels achieved by expressing Wg itself. The amplification function of Arrow/LRP appears to be particularly important for long-range signaling, and may reflect a general mechanism for potentiating signals in the shallow part of a morphogen gradient.
Baig-Lewis
Shahana
S
Oregon Health and Science University, Department of Cell and Developmental Biology, 3181 SW Sam Jackson Park Road/L215, Portland, OR 97239, USA.
Peterson-Nedry
Wynne
W
Wehrli
Marcel
M
D000818:Animals; D019281:Dimerization; D004330:Drosophila / Q000737:chemistry / Q000196:embryology* / Q000378:metabolism; D029721:Drosophila Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000378:metabolism; D051157:Frizzled Receptors / Q000378:metabolism; D008024:Ligands; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D015398:Signal Transduction; D014921:Wings, Animal / Q000196:embryology*; D051153:Wnt Proteins / Q000378:metabolism*; D051155:Wnt1 Protein
D029721:Drosophila Proteins; D051157:Frizzled Receptors; D008024:Ligands; D011518:Proto-Oncogene Proteins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D051153:Wnt Proteins; D051155:Wnt1 Protein; C474373:arr protein, Drosophila; C101703:fz2 protein, Drosophila; C074622:wg protein, Drosophila