Gene Profiling of Frizzled-1 and Frizzled-2 Signaling: Expression of G-Protein-Coupled Receptor Chimeras in Mouse F9 Teratocarcinoma Embryonal Cells

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Abstract
Wnt-Frizzled signaling via heterotrimeric G-proteins controls various aspects of early development. Because Wnts may activate more than one Frizzled, understanding the downstream signaling mechanisms and target genes for Frizzled activation has been a challenge. We constructed functional, chimeric receptors with the ligand-binding and transmembrane segments from the β2-adrenergic receptor and the cytoplasmic domains from either rat Frizzled-1 (Rfz1) or Frizzled-2 (Rfz2). Activation with β-agonist enables stimulation of only a single Frizzled pathway and profiling of genes targeted by this Frizzled-specific approach. Genes activated in mouse totipotent F9 teratocarcinoma cells solely by activation of the Rfz1 chimera include Lefty1, STAM, JAB, Erk1, MyD118, Fcer Ig, and follistatin, genes implicated in development. Stimulation of Rfz2 chimera, but not Rfz1, leads to activation of a smaller set of genes, including those for REST/NRSF, Groucho, nucleophosmin, and Ubc4/5E2. Activation of either Rfz1- or Rfz2-specific chimera leads, in these totipotent stem cells, to some differential activation of a common set of genes, including those for Msx-1, Msx-2, CBP/P300-associated factor, ephrin A3, and Nip-3. We demonstrate the utility of β2-adrenergic receptor-Frizzled chimeras to provide the tools with which to activate and to probe Frizzled-specific downstream signaling to gene activation.