The CK1α Activator Pyrvinium Enhances the Catalytic Efficiency (kcat/ Km) of CK1α

Chen Shen, Bin Li, Luisana Astudillo, Murray P. Deutscher, Melanie H. Cobb, Anthony J. Capobianco, Ethan Lee, David J. Robbins

Research output: Contribution to journalArticle

Abstract

The serine/threonine protein kinase casein kinase 1α (CK1α) functions as a negative regulator of Wnt signaling, phosphorylating β-catenin at serine 45 (P-S45) to initiate its eventual ubiquitin-mediated degradation. We previously showed that the repurposed, FDA-approved anthelminthic drug pyrvinium potently inhibits Wnt signaling in vitro and in vivo. Moreover, we proposed that pyrvinium's Wnt inhibitory activity was the result of its function as an activator of CK1α. An understanding of the mechanism by which pyrvinium activates CK1α is important because pyrvinium was given an orphan drug designation by the FDA to treat familial adenomatous polyposis, a precancerous condition driven by constitutive Wnt signaling. In the current study, we show that pyrvinium stimulates the phosphorylation of S45 β-catenin, a known CK1α substrate, in a cell-based assay, and does so in a dose- and time-dependent manner. Alternative splicing of CK1α results in four forms of the protein with distinct biological properties. We evaluated these splice products and identified the CK1α splice variant, CK1αS, as the form that exhibits the most robust response to pyrvinium in cells. Kinetic studies indicate that pyrvinium also stimulates the kinase activity of purified, recombinant CK1αS in vitro, increasing its catalytic efficiency (kcat/Km) toward substrates. These studies provide strong and clear mechanistic evidence that pyrvinium enhances CK1α kinase activity.

Original languageEnglish (US)
Pages (from-to)5102-5106
Number of pages5
JournalBiochemistry
Volume58
Issue number51
DOIs
StatePublished - Dec 24 2019

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ASJC Scopus subject areas

  • Biochemistry

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