Xnr2 and Xnr5 unprocessed proteins inhibit Wnt signaling upstream of dishevelled.
Nodal and Nodal-related proteins activate the Activin-like signal pathway and play a key role in the formation of mesoderm and endoderm in vertebrate development. Recent studies have shown additional activities of Nodal-related proteins apart from the canonical Activin-like signal pathway. Here we report a novel function of Nodal-related proteins using cleavage mutants of Xenopus nodal-related genes (cmXnr2 and cmXnr5), which are known to be dominant-negative inhibitors of nodal family signaling. cmXnr2 and cmXnr5 inhibited both BMP signaling and Wnt signaling without activating the Activin-like signal in animal cap assays. Pro region construct of Xnr2 and Xnr5 did not inhibit Xwnt8, and pro/mature region chimera mutant cmActivin-Xnr2 and cmActivin-Xnr5 also did not inhibit Xwnt8 activity. These results indicate that the pro domains of Xnr2 and Xnr5 are necessary, but not sufficient, for Wnt inhibition, by Xnr family proteins. In addition, Western blot analysis and immunohistochemistry analysis revealed that the unprocessed Xnr5 protein is stably produced and secreted as effectively as mature Xnr5 protein, and that the unprocessed Xnr5 protein diffused in the extracellular space. These results suggest that unprocessed Xnr2 and Xnr5 proteins may be involved in inhibiting both BMP and Wnt signaling and are able to be secreted to act on somewhat distant target cells, if these are highly produced.
Onuma
Yasuko
Y
Department of Life Sciences (Biology), Graduate School of Arts and Sciences, The University of Tokyo, Japan.
Takahashi
Shuji
S
Haramoto
Yoshikazu
Y
Tanegashima
Kousuke
K
Yokota
Chika
C
Whitman
Malcolm
M
Asashima
Makoto
M
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D000072261:Dishevelled Proteins; D004625:Embryo, Nonmammalian / Q000378:metabolism; D007150:Immunohistochemistry; D055456:Nodal Signaling Ligands; D010750:Phosphoproteins / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D051153:Wnt Proteins / Q000378:metabolism*; D014981:Xenopus / Q000196:embryology* / Q000235:genetics / Q000378:metabolism; D029867:Xenopus Proteins / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D000072261:Dishevelled Proteins; D055456:Nodal Signaling Ligands; D010750:Phosphoproteins; C485173:STK38L protein, Xenopus; D051153:Wnt Proteins; D029867:Xenopus Proteins; C418882:nodal5 protein, Xenopus; C495248:wnt8a protein, Xenopus