| Wnt signaling is involved in a variety of developmental processes including cell fate determination, cell polarity, tissue patterning and control of cell proliferation. Members of the Frizzled family of proteins serve as receptors for the Wnt signaling pathway. The founding member of this family was identified in Drosophilia based on its role in tissue polarity in the adult cuticle and named for the disorganized appearance of bristle hairs on the mutant. Mouse Frizzled-4 (mFrz-4) was originally cloned in a PCR screen to identify additional Frizzled family members in vertebrates. There are nine murine Frizzled genes and 10 human Frizzled genes identified to date. The predicted structure of Frizzled proteins is similar among all family members, containing a divergent N-terminal signal peptide, a highly conserved extracellular cysteine-rich domain, a variable-length linker region, a seven-pass transmembrane region, and a variable-length C-terminal tail. The most conserved regions of the Frizzled proteins are the extracellular cysteine-rich domain (CRD) which spans approximately 120 amino acid (aa) residues and contains 10 invariant cysteines, and the seven transmembrane domains. Mouse Frizzled-4 is 537aa long and shows 97% and 93% aa identity to human and Xenopus Frizzled-4, respectively. Two distinct Wnt signal transduction pathways have been characterized. One is the canonical Wnt/beta-catenin pathway that is involved in diverse biological mechanisms such as dorsal/ventral development in Xenopus embryos and mammalian tumor formation. Frizzled-4 is implicated in this pathway based on its ability to induce beta-catenin target genes in the presence of ligand. However, Frizzled-4 is also implicated in the Wnt/Ca2+ flux pathway, another mechanism for Wnt signal transduction that does not rely on beta-catenin activity, but on intracellular calcium fluxes. Since the CRD of mFrz-4, like mFrz-8, binds cell-surface Xenopus Wnt-8 (Xwnt-8) protein, this product is tested to antagonize Wnt signaling in the same way as mFrz-8/Fc: for inhibition of secondary axes induced by Xwnt-8 mRNA (Wan, Y. et al., 1996, J. Biol. Chem. 271:4468, Hsieh, J-C. et al., 1999, Proc. Natl. Acad. Sci. USA 96:3546, Sheldahl, L. et al., 1999, Curr. Biol. 9:695, Kirikoshi, et al., 1999, BBRC 264:955). Source: N- Frizzled 4 (Met1-Glu180)- IEGRMD- IgG1 (Pro100-Lys330)- C A DNA sequence encoding amino acid residues 1-180 of the extracellular Cysteine-Rich Domain (CRD) of mouse Frizzled-4 (Wang, Y. et al., 1996, J. Biol. Chem. 271: 4468-4476) was fused to the Fc region of human IgG1 via a polypeptide linker. The chimeric protein was expressed in a mouse myeloma cell line, NS0. Activity: Measured by its ability to interfere with the axis-inducing activity of Xwnt-8 mRNA in early Xenopus embryos. In a population of embryos, addition of 1ng of mFrizzled-4/Fc protein pre embryo resulted in 50-100% reduction in the number of secondary axes produced by 10-20pg of Xwnt-8 mRNA. Storage: Lyophilized samples are stable for greater than six months at -20C to -70C. Upon reconstitution, this cytokine can be stored under sterile conditions at 2-8 C for one month or at -20C to -70C in a manual defrost freezer for three months without detectable loss of activity. Avoid repeated freeze-thaw cycles. |
