Negative feedback regulation of Wnt signaling via N-linked fucosylation in zebrafish

Abstract

Summary L-fucose, a monosaccharide widely distributed in eukaryotes and certain bacteria, is a determinant of many functional glycans that play central roles in numerous biological processes. The molecular mechanism, however, by which fucosylation mediates these processes remains largely elusive. To study how changes in fucosylation impact embryonic development, we up-regulated N-linked fucosylation via over-expression of a key GDP-Fucose transporter, Slc35c1, in zebrafish. We show that Slc35c1 overexpression causes elevated N-linked fucosylation and disrupts embryonic patterning in a transporter activity dependent manner. We demonstrate that patterning defects associated with enhanced N-linked fucosylation are due to diminished canonical Wnt signaling. Chimeric analyses demonstrate that elevated Slc35c1 expression in receiving cells decreases the signaling range of Wnt8a during zebrafish embryogenesis. Moreover, we provide biochemical evidence that this decrease is associated with degradation of Wnt8 ligand and elevated Lrp6 coreceptor, which we show are both substrates for N-linked fucosylation in zebrafish embryos. Strikingly, slc35c1 expression is regulated by canonical Wnt signaling. These results suggest that Wnt limits its own signaling activity in part via up-regulation of a transporter, slc35c1 that promotes terminal fucosylation and thereby limits Wnt activity.

Down‐regulation of SLC35C1 induces colon cancer through over‐activating Wnt pathway

“…We have been suggested that the reduction of the SLC35C1 level could increase the nuclear translocation of β‐catenin, which activates the signalling cascade and eventually results in the development of tumours. This is supported by the Feng group who found that strong nuclear β‐catenin was absent in the marginal blastoderm cells in GDP‐Fuc and mSlc35c1 expressing Zebrafish embryos …”

“…Meanwhile, Feng et al reported that during the development of zebrafish, SLC35C1 negatively regulated Wnt signalling through N‐fucosylation of Wnt8a and Lrp6, and overexpression of SLC35C1 disrupts embryonic patterning in a transporter activity‐dependent manner. Interestingly, this group also found that at the same time, SLC35C1 expression is modulated by canonical Wnt . This suggests that the Wnt signalling pathway is a carefully regulated system and it may limit its activity via elevated expression of SLC35C1.…”

“…23,24 The current study implicates SLC35C1 as a negative regulator for the canonical Wnt pathway during this process. We dis- 26 This suggests that the Wnt signalling pathway is a carefully regulated system and it may limit its activity via elevated expression of SLC35C1.…”

Modulating Cell‐Surface Receptor Signaling and Ion Channel Functions by In Situ Glycan Editing

“…[6] To our knowledge there has been only one report from our previous study where MOE was employed to control a specific signaling pathway, in which we discovered that enhanced fucosylation on N-glycans inhibits Wnt signaling. [7] …”

Modulating Cell‐Surface Receptor Signaling and Ion Channel Functions by In Situ Glycan Editing

“…[5] MOE remodels glycan structures by supplementing the growth media with carbohydrate analogues that get incorporated into glycans by the endogenous biosynthetic machinery. [7] Nevertheless,m odification of cell-surface glycans using genetic or MOE approaches are not free of limitations:due to the functional redundancyo fm any glycosyltransferases, typically more than one gene needs to be knocked out in order to produce ap henotype, [8] and gene editing of glycosyltransferases may also introduce unexpected side effects,f or example,c haperone functions. [7] Nevertheless,m odification of cell-surface glycans using genetic or MOE approaches are not free of limitations:due to the functional redundancyo fm any glycosyltransferases, typically more than one gene needs to be knocked out in order to produce ap henotype, [8] and gene editing of glycosyltransferases may also introduce unexpected side effects,f or example,c haperone functions.…”