Allosteric Inhibition of Trypanosomatid Pyruvate Kinases by a Camelid Single-Domain Antibody

Основные понятия

A camelid single-domain antibody (sdAb42) selectively binds and stabilizes the inactive T-state conformation of trypanosomatid pyruvate kinases, thereby inhibiting their enzymatic activity through an allosteric mechanism.

Аннотация

The content describes the discovery and characterization of a camelid single-domain antibody (sdAb42) that selectively inhibits the enzymatic activity of trypanosomatid pyruvate kinases (PYKs) through an allosteric mechanism.
Key highlights:

sdAb42 was originally identified as a diagnostic tool for detecting active Trypanosoma congolense infections, as its target TcoPYK is a reliable biomarker.
Enzyme kinetics, biophysics, and structural biology analyses reveal that sdAb42 selectively binds and stabilizes the inactive T-state conformation of trypanosomatid PYKs, thereby preventing their transition to the active R-state.
Perturbation analysis shows that the sdAb42 epitope contains residues that are critical for the allosteric communication between the PYK effector and active sites.
The sdAb42 epitope is highly conserved among Trypanosoma and Leishmania PYKs, and the antibody can inhibit the enzymatic activity of PYKs from these different trypanosomatid species, albeit with varying potencies.
The production of sdAb42 as an "intrabody" (intracellularly expressed sdAb) in transgenic Trypanosoma brucei parasites induces a growth defect, demonstrating the potential of targeting trypanosomatid PYKs for therapeutic development.

Статистика

Trypanosomatid PYKs display a high degree of sequence identity (at least 70%).
The binding affinity of sdAb42 for TcoPYK is in the low nanomolar range (KD = 0.90 ± 0.07 nM), while the affinity for TbrPYK and LmePYK is roughly 40-fold lower (KD = 37.16 ± 14.80 nM and 42.54 ± 10.81 nM, respectively).
The IC50 values for the inhibition of TcoPYK, LmePYK, and TbrPYK by sdAb42 are approximately 350 nM, 700 nM, and 1400 nM, respectively.

Цитаты

"The binding of sdAb42 to this AA' intersubunit site is proposed to prevent TcoPYK from "rocking and locking" into its active R state conformation."
"The results presented here subscribe to the potential of antibodies (or fragments thereof) as drug discovery tools. Antibodies (and camelid sdAbs especially) are known for their ability to "freeze out" specific conformations of highly dynamic antigens, thereby exposing target sites of interest, which could be exploited for rational drug design."

Ключевые выводы из

Allosteric inhibition of trypanosomatid pyruvate kinases by a camelid single-domain antibody

by Pinto Torres... в www.biorxiv.org 06-15-2024

https://www.biorxiv.org/content/10.1101/2024.06.14.598993v1

Дополнительные вопросы

How could the insights gained from the allosteric inhibition mechanism of sdAb42 be leveraged to develop small-molecule inhibitors that target the same "allosteric hotspot" on trypanosomatid PYKs?

The insights obtained from the allosteric inhibition mechanism of sdAb42 provide a valuable starting point for the development of small-molecule inhibitors that target the same "allosteric hotspot" on trypanosomatid PYKs. By understanding the specific residues and structural features of the allosteric site targeted by sdAb42, researchers can design small molecules that mimic the binding interactions and stabilizing effects of the antibody.
One approach could involve structure-based drug design, where the crystal structure of the sdAb42:TcoPYK complex is used as a template to identify potential small molecule inhibitors that can bind to the same site on the enzyme. Computational methods, such as molecular docking and virtual screening, can be employed to screen large chemical libraries for compounds that have the potential to interact with the allosteric hotspot and inhibit enzyme activity.
Additionally, medicinal chemistry strategies can be utilized to optimize the identified lead compounds, enhancing their potency, selectivity, and pharmacokinetic properties. By iteratively designing, synthesizing, and testing small molecules based on the allosteric site targeted by sdAb42, researchers can develop novel inhibitors with therapeutic potential for targeting trypanosomatid PYKs.

What other glycolytic enzymes or metabolic pathways in trypanosomatid parasites could be targeted using a similar approach of exploiting allosteric regulatory mechanisms for therapeutic development?

In addition to pyruvate kinases, other glycolytic enzymes and metabolic pathways in trypanosomatid parasites could be targeted using a similar approach of exploiting allosteric regulatory mechanisms for therapeutic development. Some potential targets include enzymes involved in key steps of glycolysis, such as phosphofructokinase (PFK), hexokinase, and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). These enzymes play crucial roles in the glycolytic pathway and are essential for the survival and proliferation of trypanosomatid parasites.
By identifying allosteric sites on these enzymes and designing small molecule inhibitors that can modulate their activity, researchers can disrupt the glycolytic pathway and impair the energy metabolism of the parasites. This approach could lead to the development of novel chemotherapeutic agents that selectively target trypanosomatid parasites while minimizing off-target effects on host cells.
Furthermore, metabolic pathways beyond glycolysis, such as the pentose phosphate pathway, fatty acid metabolism, and nucleotide biosynthesis, could also be explored as potential targets for allosteric inhibition. By understanding the allosteric regulation of key enzymes in these pathways, researchers can uncover new opportunities for therapeutic intervention and the development of innovative treatments for trypanosomatid infections.

Given the potential for parasites to develop resistance mechanisms against intrabody-based interventions, how could the sdAb42-mediated inhibition of trypanosomatid PYKs be combined with other anti-parasitic strategies to achieve more durable and effective disease control?

To address the potential for parasites to develop resistance against intrabody-based interventions targeting trypanosomatid PYKs, a multi-faceted approach combining sdAb42-mediated inhibition with other anti-parasitic strategies can be implemented to achieve more durable and effective disease control.
One strategy could involve the use of combination therapy, where sdAb42-mediated inhibition is combined with conventional anti-parasitic drugs targeting different metabolic pathways or essential cellular processes in trypanosomatid parasites. By targeting multiple vulnerabilities in the parasites simultaneously, the likelihood of developing resistance is reduced, and the overall efficacy of the treatment is enhanced.
Furthermore, the integration of sdAb42-mediated inhibition with immunotherapeutic approaches, such as vaccination or immune modulation, can help bolster the host immune response against the parasites. By enhancing the immune system's ability to recognize and eliminate the parasites, the treatment efficacy can be improved, and the risk of parasite resistance minimized.
Additionally, continuous monitoring of parasite populations for the emergence of resistance mutations and the development of alternative treatment strategies based on new insights into parasite biology and drug resistance mechanisms is essential. By staying ahead of potential resistance mechanisms and adapting treatment approaches accordingly, more durable and effective disease control can be achieved in the long term.