Related Experiment Video
Updated: May 24, 2026
Understanding the Development of Compensatory Pathways in a Mutant Malaria Parasite Harbouring Hypomorphic Allele of Plant-Like Kinases
Published on: November 22, 2024
Multiple determinants for selective inhibition of apicomplexan calcium-dependent protein kinase CDPK1
Eric T Larson1, Kayode K Ojo, Ryan C Murphy
1Department of Biochemistry, University of Washington, Seattle, Washington, United States.
Abstract:
Diseases caused by the apicomplexan protozoans Toxoplasma gondii and Cryptosporidium parvum are a major health concern. The life cycle of these parasites is regulated by a family of calcium-dependent protein kinases (CDPKs) that have no direct homologues in the human host. Fortuitously, CDPK1 from both parasites contains a rare glycine gatekeeper residue adjacent to the ATP-binding pocket. This has allowed creation of a series of C3-substituted pyrazolopyrimidine compounds that are potent inhibitors selective for CDPK1 over a panel of human kinases. Here we demonstrate that selectivity is further enhanced by modification of the scaffold at the C1 position. The explanation for this unexpected result is provided by crystal structures of the inhibitors bound to CDPK1 and the human kinase c-SRC. Furthermore, the insight gained from these studies was applied to transform an alternative ATP-competitive scaffold lacking potency and selectivity for CDPK1 into a low nanomolar inhibitor of this enzyme with no activity against SRC.
Insights
New drug compounds selectively inhibit parasite kinases (CDPK1) crucial for Toxoplasma gondii and Cryptosporidium parvum survival. Structural insights guided modifications, enhancing potency and selectivity against human kinases.
Area of Science:
- Parasitology
- Medicinal Chemistry
- Structural Biology
Background:
- Apicomplexan protozoan diseases like toxoplasmosis and cryptosporidiosis pose significant global health risks.
- Calcium-dependent protein kinases (CDPKs) regulate the life cycles of these parasites and are potential therapeutic targets.
- CDPK1 possesses a unique glycine gatekeeper residue, offering a potential target for selective inhibition.
Purpose of the Study:
- To develop potent and selective inhibitors of apicomplexan CDPK1.
- To explore structure-activity relationships for pyrazolopyrimidine-based CDPK1 inhibitors.
- To gain structural insights into inhibitor binding for rational drug design.
Main Methods:
- Synthesis of C3-substituted pyrazolopyrimidine compounds.
- Biochemical assays to determine enzyme inhibition and selectivity against human kinases.
- X-ray crystallography to elucidate the binding modes of inhibitors with CDPK1 and human c-SRC kinase.
Main Results:
- C3-substituted pyrazolopyrimidines demonstrated potent and selective inhibition of CDPK1.
- Modification at the C1 position further enhanced inhibitor selectivity.
- Crystal structures revealed the molecular basis for selectivity, highlighting interactions within the ATP-binding pocket.
- An alternative scaffold was successfully transformed into a potent, selective CDPK1 inhibitor.
Conclusions:
- Targeting apicomplexan CDPK1 with rationally designed inhibitors is a viable therapeutic strategy.
- Structural information is crucial for optimizing selectivity and potency of kinase inhibitors.
- These findings pave the way for developing new treatments against toxoplasmosis and cryptosporidiosis.
Related Concept Videos
01:25cAMP-dependent Protein Kinase Pathways
01:16Calmodulin-dependent Signaling
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
01:07MAPK Signaling Cascades