Purified Wnt 5a protein activates or inhibits
description
Transcript of Purified Wnt 5a protein activates or inhibits
Purified Wnt 5a protein activates or inhibits β-catenin-TCF signaling depending on receptor context
Mikels et al., 2006, PLOS Biology
Mouselimb bud
Over-expression of Wnt 5 blocks the ability of Wnt 8 to promote dorsal cell fate in Xenopus. - Torres et al., 2003, J. Cell Biol.
In the distal tip of mouse limb buds, Wnt 5a antagonizes b-catenin signaling, since in Wnt 5a -/-limbs higher levels of b-catenin can be detected in the distal tip. - Topol et al., 2003, J. Cell Biol.
Removal of maternal and zygotic functions of zebrafish Wnt 5 result in variable degrees of dorsalization, including formation of secondary axis. - Westfall et al., 2003, Dev. Biol.
Wnts antagonize Wnts
Dominant negative Wnt 11 and CaMK II promotes dorsal cell fates. - Kuhl et al., 2000, J. Biol. Chem.
Over-expression of Wnt 5 can activate Nemo-like kinase, which in C. elegans and mammalian cellsInhibit Tcf transcription factors to which b-catenin binds to regulate gene expression. - Ishitani et al., 2003, Mol. Cell. Biol.
Siah 2 (b-catenin destruction complex) is transcriptionally activated by Wnt 5a. - Topol et al., 2003, J. Cell Biol.
How to inhibit the canonical signaling…?
SuperTopflash in 293 cells
Purified Wnt 5a protein inhibits canonical Wnt signaling
wnt 3a wnt 5a (after 1, 3hr)wnt 5a 6hr after washing wnt 3a
Wnt 5a does not affect b-catenin protein stabilization
Wnt 5a protein competes with Wnt 3a for Fz receptor context.
Siah 2, which targets b-catenin for b-TrCP independent proteasomal degradation, is transcriptionally activated by Wnt 5a. - Topol et al., 2003, J. Cell Biol.
293 cells
Cytosolic fraction of 293 cells
Wnt 5a - mediated inhibition of canonical signaling is not associated with Wnt- stimulated Ca++ flux
* PTX (pertussis toxin) : inhibition of G protein binding with membrane receptor
* LPA (lysophosphatidic acid) : agonist of G protein signaling
wnt 5a
Ca ++
CaMKII
TAK/NLK mitogen activatedSignaling cascade
TCF/LEF - phosphorylation
DNA
b-cat
G-protein
* Ionomycin :raises the intracellular level of Ca2+
Wnt stimulatedcalcium flux
Wnt 5a protein activates b-catenin signaling depending on receptor context
XWnt 5a RNA with Xfz4 RNA leads to the synergistic activation of Wnt/b-cat target genes in Xenopus animal caps. - Umbhauer et al., 2000, EMBO J
An alternative Wnt receptor, mRor2, mediates Wnt 5a’s inhibitory activity
Expression of mRor2 is required for Wnt 5a- mediated inhibition of canonical Wnt signaling
SuperTopflashLRPcotransfection
Membrane tethered form(no transmembrane & cytoplasmic domain)
293
Transmembrane domain : OCytoplasmic domain : X
A member of the Fz protein family (hFz5) mediating axis induction by Wnt 5a. - He et al., 1997, Scinece.