Biology subjects

Kalel, V. C.

Publications and source records attributed to Kalel, V. C..

4 recordsLinked to original sources

bioRxiv2025

Identification of small molecule inhibitors of Trypanosoma PEX15--PEX6 interaction

Trypanosomatid parasites that cause life threatening tropical diseases harbor specialized essential organelles, called glycosomes. Like other peroxisome-related organelles, the biogenesis of glycosomes is mediated by proteins known as peroxins (PEX). A cascade of PEX protein-protein interactions (PPIs) is essential for glycosome function and parasite survival. Accordingly, small molecule inhibitors of PEX proteins that disrupt glycosomal matrix or membrane protein import have been reported as potential therapies for trypanosomiasis. We recently identified the long sought-after Trypanosoma PEX15 (TbPEX15), which anchors the PEX1-PEX6 complex to the glycosomal membrane for recycling of the receptor PEX5. Defects in this process cause PEX5 degradation, mislocalization of glycosomal matrix proteins and parasite death. In this study, we targeted the interaction between TbPEX6 and TbPEX15. Recombinant TbPEX6 and TbPEX15 were purified, and their interaction was confirmed by in vitro pull-down assays and size exclusion chromatography. Furthermore, we established an AlphaScreen-based method to identify small molecule inhibitors of this PPI. Screening of a drug-repurposing library identified two inhibitors with trypanocidal activity against T. brucei in vitro and the amastigote stage of T. cruzi. Given its essentiality and low sequence similarity to its human homolog, parasite PEX15 and its interaction with PEX6 represent promising targets for the development of new therapies against trypanosomatid infections.

microbiology↗

bioRxiv2024

An inhibitor targeting glycosome membrane biogenesis kills Leishmania parasites

Leishmaniasis is a life-threatening neglected tropical disease caused by over 20 species of Leishmania parasites. Visceral leishmaniasis, also known as kala-azar, is particularly lethal, with a 95% mortality rate if left untreated. Currently, no vaccine is available, and chemotherapy remains the primary treatment option. However, these drugs have drawbacks such as high toxicities, the emergence of resistant strains, and high costs. Therefore, there is a need to develop new and safe treatments. Glycosomes are essential organelles for the survival of Leishmania parasites. They are maintained by peroxin (PEX) proteins, which are responsible for glycosome biogenesis, including targeting proteins to glycosomes. Previous studies have shown that blocking the interaction between the import receptor PEX19 and the docking factor PEX3 kills Trypanosoma brucei by disrupting glycosome biogenesis. In this study, we screened an FDA-approved drug repurposing library using an AlphaScreen based assay and identified inhibitors of LdPEX3-LdPEX19 interaction in vitro. The inhibitor effectively kills Leishmania parasites, including the challenging amastigote forms contained within the infected mammalian host cells. This study validates the inhibition of glycosome biogenesis in Leishmania as a potential approach for developing new anti-leishmanial therapies.

biochemistry↗

bioRxiv2023

High confidence glycosomal membrane protein inventory unveils trypanosomal Peroxin PEX15

Infections by trypanosomatid parasites cause Chagas disease, Human African Trypanosomiasis, and Leishmaniasis, affecting over 12 million people worldwide. Glycosomes, the unique peroxisome-related organelles of trypanosomes are essential for their survival, and hence their metabolic functions and biogenesis mediated by peroxins (PEX) are suitable as drug targets. Here we report on a comprehensive protein inventory of glycosomal membranes through advanced subcellular membrane protein profiling employing quantitative mass spectrometry. Our quantitative analysis resulted in the identification of 28 novel high confidence glycosomal membrane proteins. Our in-depth protein inventory of glycosomal membranes serves as an important resource for characterizing glycosome biology and drug development. We validated four so far unknown glycosomal membrane proteins, including two tail-anchored (TA) proteins, a homolog of human peroxisomal PXMP4, and a Macrodomain-containing protein. Using a structure-based approach, we identified one of the TA proteins as the long-sought Trypanosoma PEX15. Despite its low sequence similarity, Trypanosoma PEX15 exhibits structural and topological similarities with its yeast (Pex15) and human counterparts (PEX26). We show that PEX15 is an essential integral glycosomal membrane protein that interacts with PEX6. Accordingly, RNAi knockdown of PEX15 in bloodstream form trypanosomes demonstrates that it is essential for glycosome biogenesis and parasite survival. Considering the low degree of conservation with its human counterpart, PEX15 is a promising molecular target for drug development.

cell biology↗

bioRxiv2023

PEX1 is essential for the glycosome biogenesis and trypanosomatid parasite survival.

Trypanosomatid parasites are kinetoplastid protists that compartmentalize glycolytic enzymes in unique peroxisome-related organelles called glycosomes. The heterohexameric AAA-ATPase complex of PEX1-PEX6 is anchored to the peroxisomal membrane and functions in the export of matrix protein import receptor PEX5 from the peroxisomal membrane. Defects in PEX1, PEX6 or their membrane anchor causes dysfunction of peroxisomal matrix protein import cycle. In this study, we identified the Trypanosoma PEX1 orthologue using sequence and structural similarities. Using yeast two-hybrid analysis, we demonstrate that TbPEX1 can bind to TbPEX6. Endogenously tagged TbPEX1 localizes to glycosomes in the T. brucei parasites. Depletion of PEX1 gene expression by RNA interference causes lethality to bloodstream form trypanosomes, due to a partial mislocalization of glycosomal enzymes to the cytosol and ATP depletion. TbPEX1 RNAi leads to a selective proteasomal degradation of both matrix protein import receptors TbPEX5 and TbPEX7. Unlike in yeast, PEX1 depletion did not result in an accumulation of ubiquitinated TbPEX5 in trypanosomes. As PEX1 turned out to be essential for trypanosomatid parasites, it could provide a suitable drug target for parasitic diseases. The results also suggests that these parasites possess a highly efficient quality control mechanisms that export the import receptors from glycosomes to the cytosol, in the absence of a functional TbPEX1-TbPEX6 complex.

cell biology↗