Identification of the Wnt signaling activator leucine-rich repeat in Flightless interaction protein 2 by a genome-wide functional analysis

doi:10.1073/pnas.0409472102

Identification of the Wnt signaling activator leucine-rich repeat in Flightless interaction protein 2 by a genome-wide functional analysis

^*Department of Chemistry and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037; ^†The Salk Institute for Biological Studies, P.O. Box 85800, La Jolla, CA 92186; and ^‡Genomics Institute of The Novartis Research Foundation, 10675 John Jay Hopkins Drive, San Diego, CA 92121

Contributed by Peter G. Schultz, December 17, 2004

Abstract

The Wnt signaling pathway acts ubiquitously in metazoans to control various aspects of embryonic development. Wnt ligands bind their receptors Frizzled and low-density lipoprotein receptor-related protein 5/6 and function through Disheveled (Dvl), Axin, adenomatous polyposis coli, glycogen synthase kinase 3β, and casein kinase (CK) 1 to stabilize β-catenin and induce lymphocyte enhancer-binding factor (LEF)/T cell factor (TCF)-dependent transcriptional activities. To identify previously unrecognized Wnt signaling modulators, a genome-wide functional screen was performed using large-scale arrayed cDNA collections. From this screen, both known components and previously uncharacterized regulators of this pathway were identified, including β-catenin, Dvl1, Dvl3, Fbxw-1, Cul1, CK1ε, CK1δ, and γ-catenin. In particular, a previously unrecognized activator, LRRFIP2 (leucine-rich repeat in Flightless interaction protein 2), was found that interacts with Dvl to increase the cellular levels of β-catenin and activate β-catenin/LEF/TCF-dependent transcriptional activity. The function of LRRFIP2 is blocked when a dominant negative Dvl (Xdd1) is coexpressed. Expression of LRRFIP2 in Xenopus embryos induced double axis formation and Wnt target gene expression; a dominant negative form of LRRFIP2 suppresses ectopic Wnt signaling in Xenopus embryos and partially inhibits endogenous dorsal axis formation. These data suggest that LRRFIP2 plays an important role in transducing Wnt signals.

Footnotes

↵ § To whom correspondence should be addressed. E-mail: schultz{at}scripps.edu.
Author contributions: J.L. performed research; J.L., A.G.B., and C.K. analyzed data; J.L. wrote the paper; A.P.O., S.K.C., and S.D. contributed new reagents/analytic tools; and P.G.S. designed research and supervised.
Abbreviations: LRRFIP2, leucine-rich repeat in Flightless interaction protein 2; GSK-3β, glycogen synthase kinase 3β; CK, casein kinase; Dvl, Disheveled; LEF, lymphocyte enhancer-binding factor; TCF, T cell factor; HEK, human embryonic kidney.