Structure determination of glycogen synthase kinase-3 from Leishmania major and comparative inhibitor structure–activity relationships with Trypanosoma brucei GSK-3

Glycogen synthase kinase-3 (GSK-3) is a drug target under intense investigation in pharmaceutical companies and constitutes an attractive piggyback target for eukaryotic pathogens. Two different GSKs are found in trypanosomatids, one about 150 residues shorter than the other. GSK-3 short (GeneDB: Tb927.10.13780) has previously been validated genetically as a drug target in Trypanosoma brucei by RNAi induced growth retardation; and chemically by correlation between enzyme and in vitro growth inhibition. Here, we report investigation of the equivalent GSK-3 short enzymes of L. major (LmjF18.0270) and L. infantum (LinJ18_V3.0270, identical in amino acid sequences to LdonGSK-3 short) and a crystal structure of LmajGSK-3 short at 2 Å resolution. The inhibitor structure–activity relationships (SARs) of L. major and L. infantum are virtually identical, suggesting that inhibitors could be useful for both cutaneous and visceral leishmaniasis. Leishmania spp. GSK-3 short has different inhibitor SARs than TbruGSK-3 short, which can be explained mostly by two variant residues in the ATP-binding pocket. Indeed, mutating these residues in the ATP-binding site of LmajGSK-3 short to the TbruGSK-3 short equivalents results in a mutant LmajGSK-3 short enzyme with SAR more similar to that of TbruGSK-3 short. The differences between human GSK-3β (HsGSK-3β) and LmajGSK-3 short SAR suggest that compounds which selectively inhibit LmajGSK-3 short may be found.

Graphical abstractThis study presents the first solved structure of a parasitic protozoan GSK-3 enzyme and concluded that LmajGSK-3 short structure reported here will aid in the design and development of potent GSK-3 inhibitors for all Leishmania species.Figure optionsDownload full-size imageDownload high-quality image (122 K)Download as PowerPoint slideResearch highlights▶ First structure of a parasite GSK-3 enzyme is presented, i.e. L. major GSK-3 short. ▶ Biochemical, structural, and inhibitor SAR of Leishmania GSK-3 enzymes described. ▶ The inhibitor SARs of L. major and L. infantum are virtually identical. ▶ GSK-3 inhibitors may be useful therapy for cutaneous and visceral leishmaniasis. ▶ Leishmania and T. brucei GSK-3 have different SAR due to 2 variant aminoacids.