Mutant Frizzled 4 associated with vitreoretinopathy traps wild-type Frizzled in the endoplasmic reticulum by oligomerization

Article metrics


nt signalling pathways regulate cell proliferation, cell fate and morphogenetic movements. Here, we demonstrate that the Frizzled (Fz) family of Wnt receptors1,2,3,4, similarly to G-protein-coupled receptors (GPCRs)5,6,7, form specific homo- and hetero-oligomers. Two lines of evidence suggest that oligomerization occurs in the endoplasmic reticulum: first, a mutant allele of Fz4, encoding a truncated protein that is retained in the endoplasmic reticulum, is linked to the autosomal-dominant retinal degenerative disease, familial exudative vitreoretinopathy (FEVR)8. We show that this mutant form of Fz4 oligomerizes with wild-type Fz4, retains it in the endoplasmic reticulum and inhibits its signalling. Second, a derivative of Fz1 targeted to the endoplasmic reticulum traps wild-type Fz1 in the endoplasmic reticulum and blocks its signalling. These data support the hypothesis that oligomerization of mutant and wild-type Fz proteins occurs in the endoplasmic reticulum and may explain the genetic dominance of this FEVR allele.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Fzs homo- and hetero-oligomerize.
Figure 2: The heptahelical domain of Fz is sufficient for oligomerization.
Figure 3: Fzs oligomerize in the endoplasmic reticulum.
Figure 4: Mutant Fz4 inhibits wild-type Fz4.


  1. 1

    Slusarski, D.C., Corces, V.G. & Moon, R.T. Interaction of Wnt and a Frizzled homologue triggers G-protein-linked phosphatidylinositol signalling. Nature 390, 410–413 (1997).

  2. 2

    Sumanas, S. & Ekker, S.C. Xenopus frizzled-7 morphant displays defects in dorsoventral patterning and convergent extension movements during gastrulation. Genesis 30, 119–122 (2001).

  3. 3

    Winklbauer, R., Medina, A., Swain, R.K. & Steinbeisser, H. Frizzled-7 signalling controls tissue separation during Xenopus gastrulation. Nature 413, 856–860 (2001).

  4. 4

    Kuhl, M., Sheldahl, L.C., Park, M., Miller, J.R. & Moon, R.T. The Wnt/Ca2+ pathway: a new vertebrate Wnt signaling pathway takes shape. Trends Genet. 16, 279–283 (2000).

  5. 5

    Salahpour, A., Angers, S. & Bouvier, M. Functional significance of oligomerization of G-protein-coupled receptors. Trends Endocrinol. Metab. 11, 163–168 (2000).

  6. 6

    Angers, S., Salahpour, A. & Bouvier, M. Dimerization: an emerging concept for G protein-coupled receptor ontogeny and function. Annu. Rev. Pharmacol. Toxicol. 42, 409–435 (2002).

  7. 7

    Rios, C.D., Jordan, B.A., Gomes, I. & Devi, L.A. G-protein-coupled receptor dimerization: modulation of receptor function. Pharmacol. Ther. 92, 71–87 (2001).

  8. 8

    Robitaille, J. et al. Mutant frizzled-4 disrupts retinal angiogenesis in familial exudative vitreoretinopathy. Nature Genet. 32, 326–330 (2002).

  9. 9

    Rossi, F.M., Blakely, B.T., Charlton, C.A. & Blau, H.M. Monitoring protein-protein interactions in live mammalian cells by beta-galactosidase complementation. Methods Enzymol. 328, 231–251 (2000).

  10. 10

    Rossi, F., Charlton, C.A. & Blau, H.M. Monitoring protein–protein interactions in intact eukaryotic cells by β-galactosidase complementation. Proc. Natl Acad. Sci. USA 94, 8405–8410 (1997).

  11. 11

    Mercier, J.F., Salahpour, A., Angers, S., Breit, A. & Bouvier, M. Quantitative assessment of β1- and β2-adrenergic receptor homo- and heterodimerization by bioluminescence resonance energy transfer. J. Biol. Chem. 277, 44925–44931 (2002).

  12. 12

    Schlessinger, J. Ligand-induced, receptor-mediated dimerization and activation of EGF receptor. Cell 110, 669–672 (2002).

  13. 13

    Dann, C.E. et al. Insights into Wnt binding and signalling from the structures of two Frizzled cysteine-rich domains. Nature 412, 86–90 (2001).

  14. 14

    Bafico, A. et al. Interaction of frizzled related protein (FRP) with Wnt ligands and the frizzled receptor suggests alternative mechanisms for FRP inhibition of Wnt signaling. J. Biol. Chem. 274, 16180–16187 (1999).

  15. 15

    Carron, C. et al. Frizzled receptor dimerization is sufficient to activate the Wnt/β-catenin pathway. J. Cell Sci. 116, 2541–2550 (2003).

  16. 16

    Zhang, Z., Sun, S., Quinn, S.J., Brown, E.M. & Bai, M. The extracellular calcium-sensing receptor dimerizes through multiple types of intermolecular interactions. J. Biol. Chem. 276, 5316–5322 (2001).

  17. 17

    Rivera, V.M. et al. Regulation of protein secretion through controlled aggregation in the endoplasmic reticulum. Science 287, 826–830 (2000).

  18. 18

    Ou, W. & Silver, J. Role of a conserved amino-terminal sequence in the ecotropic MLV receptor mCAT1. Virology 308, 101–113 (2003).

  19. 19

    Sheldahl, L.C., Park, M., Malbon, C.C. & Moon, R.T. Protein kinase C is differentially stimulated by Wnt and Frizzled homologs in a G-protein-dependent manner. Curr. Biol. 9, 695–698 (1999).

  20. 20

    Kuhl, M., Sheldahl, L.C., Malbon, C.C. & Moon, R.T. Ca(2+)/calmodulin-dependent protein kinase II is stimulated by Wnt and Frizzled homologs and promotes ventral cell fates in Xenopus. J. Biol. Chem. 275, 12701–12711 (2000).

  21. 21

    Gomes, I. et al. G protein coupled receptor dimerization: implications in modulating receptor function. J. Mol. Med. 79, 226–242 (2001).

  22. 22

    Goodwin, A.M. & D'Amore, P.A. Wnt signaling in the vasculature. Angiogenesis 5, 1–9 (2002).

  23. 23

    Veeman, M.T., Slusarski, D.C., Kaykas, A., Louie, S.H. & Moon, R.T. Zebrafish prickle, a modulator of noncanonical Wnt/Fz signaling, regulates gastrulation movements. Curr. Biol. 13, 680–685 (2003).

Download references


We thank M. MacDonald and P. Goldberg of Xenon Genetics for the Fz4 constructs, H. Blau of Stanford for the β-Gal complementation constructs and S. Angers for helpful comments. A.K. was supported in part by a National Institutes of Health reproductive biology training grant. R.T.M is an Investigator, and A.K. and J.Y.S. are associates, of the Howard Hughes Medical Institute. M.B. and M.H. were supported in part by the Canadian Institute for Health Research, and M.H. holds a studentship from the Fonds de la recherche en Santé du Québec.

Author information

Correspondence to Randall T. Moon.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information, Fig. S1

Supplementary Information, Fig. S2 (PDF 1844 kb)

Supplementary Information, Fig. S3

Supplementary Information, Fig. S4

Rights and permissions

Reprints and Permissions

About this article

Further reading