Toxoplasma Calcium-Dependent Protein Kinase 1 Inhibitors: Probing Activity and Resistance Using Cellular Thermal Shift Assays
| Autor: | Kayode K. Ojo, Jennifer A. Geiger, Amy E. DeRocher, Ryan Choi, Wesley C. Van Voorhis, Ethan A. Merritt, Marilyn Parsons, Rama Subba Rao Vidadala, Lynn K. Barrett, Dustin J. Maly, Suzanne Scheele, Tess R. Smith, Matthew A. Hulverson |
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| Rok vydání: | 2018 |
| Předmět: |
0301 basic medicine
Gene isoform 030106 microbiology Mutant Drug Resistance Protozoan Proteins Naphthalenes 03 medical and health sciences chemistry.chemical_compound Piperidines Animals Humans Pharmacology (medical) Protein kinase A Protein Kinase Inhibitors Mechanisms of Action: Physiological Effects Pharmacology chemistry.chemical_classification Chemistry Point mutation Focal Adhesion Kinase 2 030104 developmental biology Infectious Diseases Enzyme Protein kinase domain Biochemistry Pyrazoles Growth inhibition Toxoplasma Toxoplasmosis |
| Zdroj: | Antimicrobial Agents and Chemotherapy. 62 |
| ISSN: | 1098-6596 0066-4804 |
| Popis: | In Toxoplasma gondii , calcium-dependent protein kinase 1 (CDPK1) is an essential protein kinase required for invasion of host cells. We have developed several hundred CDPK1 inhibitors, many of which block invasion. Inhibitors with similar 50% inhibitory concentrations (IC 50 s) were tested in thermal shift assays for their ability to stabilize CDPK1 in cell lysates, in intact cells, or in purified form. Compounds that inhibited parasite growth stabilized CDPK1 in all assays. In contrast, two compounds that showed poor growth inhibition stabilized CDPK1 in lysates but not in cells. Thus, cellular exclusion could explain exceptions in the correlation between the action on the target and cellular activity. We used thermal shift assays to examine CDPK1 in two clones that were independently selected by growth in the CDPK1 inhibitor RM-1-132 and that had increased 50% effective concentrations (EC 50 s) for the compound. The A and C clones had distinct point mutations in the CDPK1 kinase domain, H201Q and L96P, respectively, residues that lie near one another in the inactive isoform. Purified mutant proteins showed RM-1-132 IC 50 s and thermal shifts similar to those shown by wild-type CDPK1. Reduced inhibitor stabilization (and a presumed reduced interaction) was observed only in cellular thermal shift assays. This highlights the utility of cellular thermal shift assays in demonstrating that resistance involves reduced on-target engagement (even if biochemical assays suggest otherwise). Indeed, similar EC 50 s were observed upon overexpression of the mutant proteins, as in the corresponding drug-selected parasites, although high levels of CDPK1(H201Q) only modestly increased resistance compared to that achieved with high levels of wild-type enzyme. |
| Databáze: | OpenAIRE |
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