PEX1 is essential for glycosome biogenesis and trypanosomatid parasite survival
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PROVIDER: S-EPMC10952002 | biostudies-literature | 2024 Jan
REPOSITORIES: biostudies-literature
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Project description:BackgroundMutations in PEX1 are the most common primary cause of Zellweger syndrome. In addition to exonic mutations, deletions and splice site mutations two 5' polymorphisms at c.-137 and c.-53 with a potential influence on PEX1 protein levels have been described in the 5' untranslated region (UTR) of the PEX1 gene.MethodsWe used RACE and in silico promoter prediction analysis to study the 5' UTR of PEX1. We determined the distribution of PEX1 5' polymorphisms in a cohort of 30 Zellweger syndrome patients by standard DNA sequencing. 5' polymorphisms were analysed in relation to the two most common mutations in PEX1 and were incorporated into a novel genotype-phenotype analysis by correlation of three classes of PEX1 mutations with patient survival.ResultsWe provide evidence that the polymorphism 137 bp upstream of the ATG codon is not part of the UTR, rendering it a promoter polymorphism. We show that the first, but not the second most common PEX1 mutation arose independently of a specific upstream polymorphic constellation. By genotype-phenotype analysis we identified patients with identical exonic mutation and identical 5' polymorphisms, but strongly differing survival.ConclusionsOur study suggests that two different types of PEX1 5' polymorphisms have to be distinguished: a 5' UTR polymorphism at position c.-53 and a promoter polymorphism 137 bp upstream of the PEX1 start codon. Our results indicate that the exonic PEX1 mutation correlates with patient survival, but the two 5' polymorphisms analysed in this study do not have to be considered for diagnostic and/or prognostic purposes.
| S-EPMC3167756 | biostudies-literature
Project description:Apicomplexan parasites are the cause of numerous important human diseases including malaria and AIDS-associated opportunistic infections. Drug treatment for these diseases is not satisfactory and is threatened by resistance. The discovery of the apicoplast, a chloroplast-like organelle, presents drug targets unique to these parasites. The apicoplast-localized fatty acid synthesis (FAS II) pathway, a metabolic process fundamentally divergent from the analogous FAS I pathway in humans, represents one such target. However, the specific biological roles of apicoplast FAS II remain elusive. Furthermore, the parasite genome encodes additional and potentially redundant pathways for the synthesis of fatty acids. We have constructed a conditional null mutant of acyl carrier protein, a central component of the FAS II pathway in Toxoplasma gondii. Loss of FAS II severely compromises parasite growth in culture. We show FAS II to be required for the activation of pyruvate dehydrogenase, an important source of the metabolic precursor acetyl-CoA. Interestingly, acyl carrier protein knockout also leads to defects in apicoplast biogenesis and a consequent loss of the organelle. Most importantly, in vivo knockdown of apicoplast FAS II in a mouse model results in cure from a lethal challenge infection. In conclusion, our study demonstrates a direct link between apicoplast FAS II functions and parasite survival and pathogenesis. Our genetic model also offers a platform to dissect the integration of the apicoplast into parasite metabolism, especially its postulated interaction with the mitochondrion.
| S-EPMC1559775 | biostudies-literature
Project description:Zellweger syndrome (ZS), neonatal adrenoleukodystrophy (NALD), and infantile Refsum disease (IRD) are clinically overlapping syndromes, collectively called "peroxisome biogenesis disorders" (PBDs), with clinical features being most severe in ZS and least pronounced in IRD. Inheritance of these disorders is autosomal recessive. The peroxisome biogenesis disorders are genetically heterogeneous, having at least 12 different complementation groups (CGs). The gene affected in CG1 is PEX1. Approximately 65% of the patients with PBD harbor mutations in PEX1. In the present study, we used SSCP analysis to evaluate a series of patients belonging to CG1 for mutations in PEX1 and studied phenotype-genotype correlations. A complete lack of PEX1 protein was found to be associated with severe ZS; however, residual amounts of PEX1 protein were found in patients with the milder phenotypes, NALD and IRD. The majority of these latter patients carried at least one copy of the common G843D allele. When patient fibroblasts harboring this allele were grown at 30 degrees C, a two- to threefold increase in PEX1 protein levels was observed, associated with a recovery of peroxisomal function. This suggests that the G843D missense mutation results in a misfolded protein, which is more stable at lower temperatures. We conclude that the search for the factors and/or mechanisms that determine the stability of mutant PEX1 protein by high-throughput procedures will be a first step in the development of therapeutic strategies for patients with mild PBDs.
| S-EPMC1226046 | biostudies-literature
Project description:Human pathogenic trypanosomatid parasites harbor a unique form of peroxisomes termed glycosomes that are essential for parasite viability. We and others previously identified and characterized the essential Trypanosoma brucei ortholog TbPEX3, which is the membrane-docking factor for the cytosolic receptor PEX19 bound to the glycosomal membrane proteins. Knockdown of TbPEX3 expression leads to mislocalization of glycosomal membrane and matrix proteins, and subsequent cell death. As an early step in glycosome biogenesis, the PEX3-PEX19 interaction is an attractive drug target. We established a high-throughput assay for TbPEX3-TbPEX19 interaction and screened a compound library for small-molecule inhibitors. Hits from the screen were further validated using an in vitro ELISA assay. We identified three compounds, which exhibit significant trypanocidal activity but show no apparent toxicity to human cells. Furthermore, we show that these compounds lead to mislocalization of glycosomal proteins, which is toxic to the trypanosomes. Moreover, NMR-based experiments indicate that the inhibitors bind to PEX3. The inhibitors interfering with glycosomal biogenesis by targeting the TbPEX3-TbPEX19 interaction serve as starting points for further optimization and anti-trypanosomal drug development.
| S-EPMC8721105 | biostudies-literature
Project description:In Leishmania, de novo polyamine synthesis is initiated by the cleavage of L-arginine to urea and L-ornithine by the action of arginase (ARG, E.C. 3.5.3.1). Previous studies in L. major and L. mexicana showed that ARG is essential for in vitro growth in the absence of polyamines and needed for full infectivity in animal infections. The ARG protein is normally found within the parasite glycosome, and here we examined whether this localization is required for survival and infectivity. First, the localization of L. amazonensis ARG in the glycosome was confirmed in both the promastigote and amastigote stages. As in other species, arg(-) L. amazonensis required putrescine for growth and presented an attenuated infectivity. Restoration of a wild type ARG to the arg(-) mutant restored ARG expression, growth and infectivity. In contrast, restoration of a cytosol-targeted ARG lacking the glycosomal SKL targeting sequence (argΔSKL) restored growth but failed to restore infectivity. Further study showed that the ARGΔSKL protein was found in the cytosol as expected, but at very low levels. Our results indicate that the proper compartmentalization of L. amazonensis arginase in the glycosome is important for enzyme activity and optimal infectivity. Our conjecture is that parasite arginase participates in a complex equilibrium that defines the fate of L-arginine and that its proper subcellular location may be essential for this physiological orchestration.
| S-EPMC3316525 | biostudies-literature
Project description:Trypanosomatid parasites are infectious agents for diseases such as African sleeping sickness, Chagas disease, and leishmaniasis that threaten millions of people, mostly in the emerging world. Trypanosomes compartmentalize glycolytic enzymes to an organelle called the glycosome, a specialized peroxisome. Functionally intact glycosomes are essential for trypanosomatid viability, making glycosomal proteins as potential drug targets against trypanosomatid diseases. Peroxins (Pex), of which Pex3 is the master regulator, control glycosome biogenesis. Although Pex3 has been found throughout the eukaryota, its identity has remained stubbornly elusive in trypanosomes. We used bioinformatics predictive of protein secondary structure to identify trypanosomal Pex3. Microscopic and biochemical analyses showed trypanosomal Pex3 to be glycosomal. Interaction of Pex3 with the peroxisomal membrane protein receptor Pex19 observed for other eukaryotes is replicated by trypanosomal Pex3 and Pex19. Depletion of Pex3 leads to mislocalization of glycosomal proteins to the cytosol, reduced glycosome numbers, and trypanosomatid death. Our findings are consistent with Pex3 being an essential gene in trypanosomes.
| S-EPMC6658674 | biostudies-literature
Project description:Telomeres define the ends of chromosomes protecting eukaryotic cells from chromosome instability and eventual cell death. The complex regulation of telomeres involves various proteins including telomerase, which is a specialized ribonucleoprotein responsible for telomere maintenance. Telomeres of chromosomes of malaria parasites are kept at a constant length during blood stage proliferation. The 7-bp telomere repeat sequence is universal across different Plasmodium species (GGGTTT/CA), though the average telomere length varies. The catalytic subunit of telomerase, telomerase reverse transcriptase (TERT), is present in all sequenced Plasmodium species and is approximately three times larger than other eukaryotic TERTs. The Plasmodium RNA component of TERT has recently been identified in silico. A strategy to delete the gene encoding TERT via double cross-over (DXO) homologous recombination was undertaken to study the telomerase function in P. berghei. Expression of both TERT and the RNA component (TR) in P. berghei blood stages was analysed by Western blotting and Northern analysis. Average telomere length was measured in several Plasmodium species using Telomere Restriction Fragment (TRF) analysis. TERT and TR were detected in blood stages and an average telomere length of ? 950 bp established. Deletion of the tert gene was performed using standard transfection methodologies and we show the presence of tert- mutants in the transfected parasite populations. Cloning of tert- mutants has been attempted multiple times without success. Thorough analysis of the transfected parasite populations and the parasite obtained from extensive parasite cloning from these populations provide evidence for a so called delayed death phenotype as observed in different organisms lacking TERT. The findings indicate that TERT is essential for P. berghei cell survival. The study extends our current knowledge on telomere biology in malaria parasites and validates further investigations to identify telomerase inhibitors to induce parasite cell death.
| S-EPMC4183507 | biostudies-literature
Project description:A recent model for peroxisome biogenesis postulates that peroxisomes form de novo continuously in wild-type cells by heterotypic fusion of endoplasmic reticulum-derived vesicles containing distinct sets of peroxisomal membrane proteins. This model proposes a role in vesicle fusion for the Pex1/Pex6 complex, which has an established role in matrix protein import. The growth and division model proposes that peroxisomes derive from existing peroxisomes. We tested these models by reexamining the role of Pex1/Pex6 and dynamin-related proteins in peroxisome biogenesis. We found that induced depletion of Pex1 blocks the import of matrix proteins but does not affect membrane protein delivery to peroxisomes; markers for the previously reported distinct vesicles colocalize in pex1 and pex6 cells; peroxisomes undergo continued growth if fission is blocked. Our data are compatible with the established primary role of the Pex1/Pex6 complex in matrix protein import and show that peroxisomes in Saccharomyces cerevisiae multiply mainly by growth and division.
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Project description:Fever is a part of the human innate immune response that contributes to limiting microbial growth and development in many infectious diseases. For the parasite Plasmodium falciparum, survival of febrile temperatures is crucial for its successful propagation in human populations as well as a fundamental aspect of malaria pathogenesis. This review discusses recent insights into the biological complexity of the malaria parasite's heat-shock response, which involves many cellular compartments and essential metabolic processes to alleviate oxidative stress and accumulation of damaged and unfolded proteins. We highlight the overlap between heat-shock and artemisinin resistance responses, while also explaining how the malaria parasite adapts its fever response to fight artemisinin treatment. Additionally, we discuss how this systemic and essential fight for survival can also contribute to parasite transmission to mosquitoes.
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Project description:Genome sequences were determined for a novel RNA virus, Leptomonas seymouri Narna-like virus 1 (LepseyNLV1). A 2.9-kb segment encodes an RNA-dependent RNA polymerase (RdRp), while a smaller 1.5-kb segment showed no database search matches. This is the first report of bisegmented Narnaviridae from insect trypanosomatids.
| S-EPMC4974305 | biostudies-literature