Vitamin A Research Today is a free monthly online journal that collates and summarizes the latest research about Vitamin A, including details on retinol, benefits, dosage, supplements, deficiency, information.

Retinoic acid-inducible G protein-coupled receptors bind to frizzled receptors and may activate non-canonical Wnt signaling.

Harada Y, Yokota C, Habas R, Slusarski DC, He X

Neurobiology Program, Children's Hospital Boston, Department of Neurology, Harvard Medical School, Boston, MA 02115, USA.

Frizzled (Fz) seven-pass transmembrane receptors are Wnt receptors and function in a variety of developmental pathways. Here we identify retinoic acid-inducible gene-1, 2, 3, and 4 (RAIG1, 2, 3, and 4) as potential Fz binding proteins. RAIG proteins are seven-pass transmembrane receptors, and Xenopus RAIG2, 3, and 4 are expressed in early gastrula. XRAIG2 can activate small GTPases, such as RhoA, Rac, and Cdc42, and c-jun N-terminal kinase, thus exhibit activities that overlap with non-canonical Wnt/Fz signaling. Injection of XRAIG2 mRNA into Xenopus embryo causes a severe shortened and bent body axis due to defective gastrulation movements, reminiscent of abnormal non-canonical Wnt signaling. XRAIG2 affects convergent extension in activin-treated animal caps, which can be partially rescued by co-injection of a dominant-negative form of Cdc42. In zebrafish embryo, XRAIG2 also causes Ca(2+) flux, one of the consequences of non-canonical Wnt signaling. These results suggest a possible crosstalk/integration between Wnt/Frizzled and RAIG signal transduction pathways.

Published 4 June 2007 in Biochem Biophys Res Commun, 358(4): 968-75.
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