Closantel is an allosteric inhibitor of human Taspase1

• Published in: iScience 2021-12, Vol.24 (12), p.103524-103524, Article 103524
• Main Authors: Luciano, Vanessa, Proschak, Ewgenij, Langer, Julian D., Knapp, Stefan, Heering, Jan, Marschalek, Rolf
• Format: Article
• Language: English
• Subjects: Biochemistry; Biophysical chemistry; Structural biology
• ISSN: 2589-0042; 2589-0042
• DOI: 10.1016/j.isci.2021.103524

Dimerization of Taspase1 activates an intrinsic serine protease function that leads to the catalytic Thr234 residue, which allows to catalyze the consensus sequence Q−3X−2D−1⋅G1X2D3D4, present in Trithorax family members and TFIIA. Noteworthy, Taspase1 performs only a single hydrolytic step on substrate proteins, which makes it impossible to screen for inhibitors in a classical screening approach. Here, we report the development of an HTRF reporter assay that allowed the identification of an inhibitor, Closantel sodium, that inhibits Taspase1 in a noncovalent fashion (IC50 = 1.6 μM). The novel inhibitor interferes with the dimerization step and/or the intrinsic serine protease function of the proenzyme. Of interest, Taspase1 is required to activate the oncogenic functions of the leukemogenic AF4-MLL fusion protein and was shown in several studies to be overexpressed in many solid tumors. Therefore, the inhibitor may be useful for further validation of Taspase1 as a target for cancer therapy. [Display omitted] ⋅Taspase1 hydrolyzes members of the Trithorax family and TFIIA⋅Taspase1 acts in a stoichiometric fashion, performing only a single cleavage reaction⋅HTFR assay allowed the identification of an allosteric inhibitor⋅The inhibitor can be used for target validation and as a lead substance for drug design Biochemistry, Structural biology, and Biophysical chemistry