Citrullinated β-Catenin (human, recombinant)

β-Catenin is a transcriptional coactivator that is encoded by the CTNNB1 gene in humans.^1,2 It is a 781-amino acid protein comprised of an N-terminal domain containing glycogen synthase kinase 3β (GSK3β) phosphorylation sites, a C-terminal transactivation domain, and a central domain spanning amino acid residues 138-664.^3,4 The central domain consists of 12 armadillo repeats and is required for binding to cadherins, TCF/LEF transcription factors, and adenomatous polyposis coli (APC). β-Catenin has roles in cell adhesion, canonical Wnt signaling, regulation of stem cells, embryonic development, and adult tissue homeostasis, among others.^3,1 In the absence of Wnt, a complex consisting of axin, APC, GSK3β, and casein kinase 1 (CK1), binds to and phosphorylates β-catenin, targeting it for ubiquitination and proteasomal degradation.¹ In the presence of Wnt, phosphorylation of β-catenin is inhibited, allowing β-catenin to translocate into the nucleus, where it interacts with TCF/LEF to activate expression of Wnt target genes. Activating mutations in CTNNB1 that stabilize β-catenin have been associated with a variety of cancers, including hepatocellular and adrenocortical carcinomas, colorectal cancer, and pilomatricomas.^5,4,6,7 Citrullination of β-catenin by protein arginine deiminase 2 (PAD2) induces proteasomal degradation of β-catenin thus preventing Wnt signaling.⁸ PAD2 citrullination of β-catenin induced by the antiparasitic agent nitazoxanide (Item No. 13692) reduces the levels of β-catenin in tumor tissue from Apc^min/+ mice, a model of intestinal adenomatous polypsis, and decreases the number of adenomas.

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5. de La Coste, A., Romagnolo, B., Billuart, P., et al. Somatic mutations of the β-catenin gene are frequent in mouse and human hepatocellular carcinomas. Proc. Natl. Acad. Sci. USA 95(15), 8847-8851 (1998).

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7. Durand, J., Lampron, A., Mazzuco, T.L., et al. Characterization of differential gene expression in adrenocortical tumors harboring β-catenin (CTNNB1) mutations. J. Clin. Endocrinol. Metab. 96(7), E1206-E1211 (2011).

8. Qu, Y., Olsen, J.R., Yuan, X., et al. Small molecule promotes β-catenin citrullination and inhibits Wnt signaling in cancer. Nat. Chem. Biol. 14(1), 94-101 (2017).