title: Roles of N-glycosylation and lipidation in Wg secretion and signaling.
abstract: Wnt members act as morphogens essential for embryonic patterning and adult homeostasis. Currently, it is still unclear how Wnt secretion and its gradient formation are regulated. In this study, we examined the roles of N-glycosylation and lipidation/acylation in regulating the activities of Wingless (Wg), the main Drosophila Wnt member. We show that Wg mutant devoid of all the N-glycosylations exhibits no major defects in either secretion or signaling, indicating that N-glycosylation is dispensable for Wg activities. We demonstrate that lipid modification at Serine 239 (S239) rather than that at Cysteine 93 (C93) plays a more important role in regulating Wg signaling in multiple developmental contexts. Wg S239 mutant exhibits a reduced ability to bind its receptor, Drosophila Frizzled 2 (dFz2), suggesting that S239 is involved in the formation of a Wg/receptor complex. Importantly, while single Wg C93 or Wg S239 mutants can be secreted, removal of both acyl groups at C93 and S239 renders Wg incapable of reaching the plasma membrane for secretion. These data argue that lipid modifications at C93 and S239 play major roles in Wg secretion. Further experiments demonstrate that two acyl attachment sites in the Wg protein are required for the interaction of Wg with Wntless (Wls, also known as Evi or Srt), the key cargo receptor involved in Wg secretion. Together, our data demonstrate the in vivo roles of N-glycosylation and lipid modification in Wg secretion and signaling.
authors.affiliation: Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, and The Graduate Program in Molecular and Developmental Biology, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA.
authors.forename: Xiaofang
authors.initials: X
authors.lastname: Tang
authors.forename: Yihui
authors.initials: Y
authors.lastname: Wu
authors.forename: Tatyana Y
authors.initials: TY
authors.lastname: Belenkaya
authors.forename: Qinzhu
authors.initials: Q
authors.lastname: Huang
authors.forename: Lorraine
authors.initials: L
authors.lastname: Ray
authors.forename: Jia
authors.initials: J
authors.lastname: Qu
authors.forename: Xinhua
authors.initials: X
authors.lastname: Lin
mesh_terms: D000818:Animals; D002460:Cell Line; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000196:embryology* / Q000235:genetics / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000378:metabolism; D051157:Frizzled Receptors / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006031:Glycosylation; D050356:Lipid Metabolism; D009154:Mutation; D011485:Protein Binding; D015398:Signal Transduction; D051155:Wnt1 Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D029721:Drosophila Proteins; D051157:Frizzled Receptors; D051155:Wnt1 Protein; C074622:wg protein, Drosophila