Isolation of a laminin-binding protein from the protozoan parasite Leishmania donovani that may mediate cell adhesion.
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ABSTRACT:
SUBMITTER: Ghosh A
PROVIDER: S-EPMC1220009 | biostudies-other | 1999 Feb
REPOSITORIES: biostudies-other
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Project description:The ability of Leishmania to survive in their insect or mammalian host is dependent upon an ability to sense and adapt to changes in the microenvironment. However, little is known about the molecular mechanisms underlying the parasite response to environmental changes, such as nutrient availability. To elucidate nutrient stress response pathways in Leishmania donovani, we have used purine starvation as the paradigm. The salvage of purines from the host milieu is obligatory for parasite replication; nevertheless, purine-starved parasites can persist in culture without supplementary purine for over 3 months, indicating that the response to purine starvation is robust and engenders parasite survival under conditions of extreme scarcity. To understand metabolic reprogramming during purine starvation we have employed global approaches. Whole proteome comparisons between purine-starved and purine-replete parasites over a 6-48 h span have revealed a temporal and coordinated response to purine starvation. Purine transporters and enzymes involved in acquisition at the cell surface are upregulated within a few hours of purine removal from the media, while other key purine salvage components are upregulated later in the time-course and more modestly. After 48 h, the proteome of purine-starved parasites is extensively remodeled and adaptations to purine stress appear tailored to deal with both purine deprivation and general stress. To probe the molecular mechanisms affecting proteome remodeling in response to purine starvation, comparative RNA-seq analyses, qRT-PCR, and luciferase reporter assays were performed on purine-starved versus purine-replete parasites. While the regulation of a minority of proteins tracked with changes at the mRNA level, for many regulated proteins it appears that proteome remodeling during purine stress occurs primarily via translational and post-translational mechanisms.
2014-02-01 | GSE48394 | GEO
Project description:Leishmaniasis represents a serious health problem worldwide and drug resistance is a growing concern. Leishmania parasites use unusual mechanisms to control their gene expression. In contrast to many other species, they do not have transcriptional regulation. The lack of transcriptional control is mainly compensated by post-transcriptional mechanisms, including tight translational control and regulation of mRNA stability/translatability by RNA-binding proteins. Modulation of translation plays a major role in parasite survival and adaptation to dramatically different environments during change of host; however, our knowledge of fine molecular mechanisms of translation in Leishmania remains limited. Here, we review the current progress in our understanding of how changes in the translational machinery promote parasite differentiation during transmission from a sand fly to a mammalian host, and discuss how translational reprogramming can contribute to the development of drug resistance.
| S-EPMC7215931 | biostudies-literature
Project description:The ability of Leishmania to survive in their insect or mammalian host is dependent upon an ability to sense and adapt to changes in the microenvironment. However, little is known about the molecular mechanisms underlying the parasite response to environmental changes, such as nutrient availability. To elucidate nutrient stress response pathways in Leishmania donovani, we have used purine starvation as the paradigm. The salvage of purines from the host milieu is obligatory for parasite replication; nevertheless, purine-starved parasites can persist in culture without supplementary purine for over three months, indicating that the response to purine starvation is robust and engenders parasite survival under conditions of extreme scarcity. To understand metabolic reprogramming during purine starvation we have employed global approaches. Whole proteome comparisons between purine-starved and purine-replete parasites over a 6-48 h span have revealed a temporal and coordinated response to purine starvation. Purine transporters and enzymes involved in acquisition at the cell surface are upregulated within a few hours of purine removal from the media, while other key purine salvage components are upregulated later in the time-course and more modestly. After 48 h, the proteome of purine-starved parasites is extensively remodeled and adaptations to purine stress appear tailored to deal with both purine deprivation and general stress. To probe the molecular mechanisms affecting proteome remodeling in response to purine starvation, comparative RNA-seq analyses, qRT-PCR, and luciferase reporter assays were performed on purine-starved versus purine-replete parasites. While the regulation of a minority of proteins tracked with changes at the mRNA level, for many regulated proteins it appears that proteome remodeling during purine stress occurs primarily via translational and/or post-translational mechanisms.
| S-EPMC3937319 | biostudies-literature
Project description:Treatments against leishmaniasis are limited and the development of new molecules is crucial. One class of developmental drug that has shown activity against the parasite Leishmania are thiophene derivatives. Here we synthetized thirty-eight novel thiophene compounds and characterized their activity and potential for resistance against L. infantum. Half of the molecules had an EC50 in the low micromolar range, the piperidine derivatives being more potent than the tetramethylpyran derivatives. Resistance was challenging to select for, and resistant cells could only be raised against one (GC1-19) of the four most active compounds. Using chemogenomic screens we show that a gene conversion event at the ABCG2 locus as well as the overexpression of a tryparedoxin peroxidase are responsible for a weak but significant resistance to the GC1-19 drug candidate. Together, our results suggest that thiophene is a scaffold of interest for further drug development against leishmaniasis.
| S-EPMC9772499 | biostudies-literature
Project description:The ability of Leishmania to survive in their insect or mammalian host is dependent upon an ability to sense and adapt to changes in the microenvironment. However, little is known about the molecular mechanisms underlying the parasite response to environmental changes, such as nutrient availability. To elucidate nutrient stress response pathways in Leishmania donovani, we have used purine starvation as the paradigm. The salvage of purines from the host milieu is obligatory for parasite replication; nevertheless, purine-starved parasites can persist in culture without supplementary purine for over 3 months, indicating that the response to purine starvation is robust and engenders parasite survival under conditions of extreme scarcity. To understand metabolic reprogramming during purine starvation we have employed global approaches. Whole proteome comparisons between purine-starved and purine-replete parasites over a 6-48 h span have revealed a temporal and coordinated response to purine starvation. Purine transporters and enzymes involved in acquisition at the cell surface are upregulated within a few hours of purine removal from the media, while other key purine salvage components are upregulated later in the time-course and more modestly. After 48 h, the proteome of purine-starved parasites is extensively remodeled and adaptations to purine stress appear tailored to deal with both purine deprivation and general stress. To probe the molecular mechanisms affecting proteome remodeling in response to purine starvation, comparative RNA-seq analyses, qRT-PCR, and luciferase reporter assays were performed on purine-starved versus purine-replete parasites. While the regulation of a minority of proteins tracked with changes at the mRNA level, for many regulated proteins it appears that proteome remodeling during purine stress occurs primarily via translational and post-translational mechanisms. One mRNA sample from each of Purine-Starved and Purine-Replete cells were analyzed using SL RNA-Seq methodology
2014-02-01 | E-GEOD-48394 | biostudies-arrayexpress
Project description:Adenine aminohydrolase (AAH) is an enzyme that is not present in mammalian cells and is found exclusively in Leishmania among the protozoan parasites that infect humans. AAH plays a paramount role in purine metabolism in this genus by steering 6-aminopurines into 6-oxypurines. Leishmania donovani AAH is 38 and 23% identical to Saccharomyces cerevisiae AAH and human adenosine deaminase enzymes, respectively, catalyzes adenine deamination to hypoxanthine with an apparent K(m) of 15.4 μM, and does not recognize adenosine as a substrate. Western blot analysis established that AAH is expressed in both life cycle stages of L. donovani, whereas subcellular fractionation and immunofluorescence studies confirmed that AAH is localized to the parasite cytosol. Deletion of the AAH locus in intact parasites established that AAH is not an essential gene and that Δaah cells are capable of salvaging the same range of purine nucleobases and nucleosides as wild type L. donovani. The Δaah null mutant was able to infect murine macrophages in vitro and in mice, although the parasite loads in both model systems were modestly reduced compared with wild type infections. The Δaah lesion was also introduced into a conditionally lethal Δhgprt/Δxprt mutant in which viability was dependent on pharmacologic ablation of AAH by 2'-deoxycoformycin. The Δaah/Δhgprt/Δxprt triple knock-out no longer required 2'-deoxycoformycin for growth and was avirulent in mice with no persistence after a 4-week infection. These genetic studies underscore the paramount importance of AAH to purine salvage by L. donovani.
| S-EPMC3293595 | biostudies-literature
Project description:The importance of autophagy in parasites with a digenetic life cycle like Leishmania spp. is significant. The parasite survives as promastigotes in the insect gut and as immotile amastigotes in mammals. This study demonstrates increased autophagy in Leishmania parasite during progression of in vitro life cycle and upon exposure to stress stimuli like starvation, oxidative stress, and drugs. Autophagy inhibition during stress exposure increased cell death, indicating the importance of autophagy in cellular defense against adverse conditions. Atg8 protein, a homolog of mammalian autophagy protein LC3 is expressed in Leishmania parasite but its function remains unknown. Overexpression of Atg8 (Atg8-OE) rendered the parasites resistant to stress and capable of infecting macrophages in substantial numbers; however, disruption of the Atg8 gene (?Atg8) resulting in suppression of Atg8 protein expression, increased susceptibility to stress and reduced the capability to cause infection. A critical event in the Leishmania parasite lifecycle is the differentiation of promastigote forms to the disease causing amastigote forms. The failure of ?Atg8 parasites lacking Atg8 protein to differentiate into amastigotes, unlike the Atg8-OE and vector-transfected parasites, clearly indicated Atg8 involvement in a crucial event. The inability of ?Atg8 parasites to infect macrophages in vitro was verified in an in vivo mouse model of leishmaniases where infection could not be induced by the ?Atg8 parasites. Autophagy is known to be involved in the remodeling of damaged organelles. The accumulation of Atg8 around damaged mitochondria suggested increase of autophagy in the vicinity of the organelle. This buildup was prevented when mitochondria generated reactive oxygen species that were quenched, suggesting them as possible signaling molecules for sensing mitochondrial instability. In summary, our study provides new evidences for a crucial role of Atg8 protein in sustaining Leishmania parasite survival during life cycle and stress exposure, differentiation to amastigotes, and their infective abilities.
| S-EPMC6813314 | biostudies-literature
Project description:BackgroundGene expression analysis in Leishmania donovani (Ld) identified an orthologue of the urea cycle enzyme, argininosuccinate synthase (LdASS), that was more abundantly expressed in amastigotes than in promastigotes. In order to characterize in detail this newly identified protein in Leishmania, we determined its enzymatic activity, subcellular localization in the parasite and affect on virulence in vivo.Methodology/principal findingsTwo parasite cell lines either over expressing wild type LdASS or a mutant form (G128S) associated with severe cases of citrullinemia in humans were developed. In addition we also produced bacterially expressed recombinant forms of the same proteins. Our results demonstrated that LdASS has argininosuccinate synthase enzymatic activity that is abolished using an ASS specific inhibitor (MDLA: methyl-D-L-Aspartic acid). However, the mutant form of the protein is inactive. We demonstrate that though LdASS has a glycosomal targeting signal that binds the targeting apparatus in vitro, only a small proportion of the total cellular ASS is localized in a vesicle, as indicated by protection from protease digestion of the crude organelle fraction. The majority of LdASS was found to be in the cytosolic fraction that may include large cytosolic complexes as indicated by the punctate distribution in IFA. Surprisingly, comparison to known glycosomal proteins by IFA revealed that LdASS was located in a structure different from the known glycosomal vesicles. Significantly, parasites expressing a mutant form of LdASS associated with a loss of in vitro activity had reduced virulence in vivo in BALB/c mice as demonstrated by a significant reduction in the parasite load in spleen and liver.Conclusion/significanceOur study suggests that LdASS is an active enzyme, with unique localization and essential for parasite survival and growth in the mammalian host. Based on these observations LdASS could be further explored as a potential drug target.
| S-EPMC3475689 | biostudies-literature
Project description:Leishmania donovani is an intracellular protozoan parasite that causes visceral leishmaniasis (VL). Antimonials (SSG) have long been the first-line treatment against VL, but have now been replaced by miltefosine (MIL) in the Indian subcontinent due to the emergence of SSG-resistance. Our previous study hypothesised that SSG-resistant L. donovani might have increased in vivo survival skills which could affect the efficacy of other treatments such as MIL. The present study attempts to validate these hypotheses. Fourteen strains derived from Nepalese clinical isolates with documented SSG-susceptibility were infected in BALB/c mice to study their survival capacity in drug free conditions (non-treated mice) and in MIL-treated mice. SSG-resistant parasites caused a significant higher in vivo parasite load compared to SSG-sensitive parasites. However, this did not seem to affect the strains' response to MIL-treatment since parasites from both phenotypes responded equally well to in vivo MIL exposure. We conclude that there is a positive association between SSG-resistance and in vivo survival skills in our sample of L. donovani strains which could suggest a higher virulence of SSG-R strains compared to SSG-S strains. These greater in vivo survival skills of SSG-R parasites do not seem to directly affect their susceptibility to MIL. However, it cannot be excluded that repeated MIL exposure will elicit different adaptations in these SSG-R parasites with superior survival skills compared to the SSG-S parasites. Our results therefore highlight the need to closely monitor drug efficacy in the field, especially in the context of the Kala-azar elimination programme ongoing in the Indian subcontinent.
| S-EPMC3148249 | biostudies-literature
Project description:Members of the Bcl-2 family are major regulators of apoptosis in mammalian cells, and hence infection-induced perturbations in their expression could result into elimination of the parasites or creation of a niche favoring survival. In this investigation, we uncover a novel role of host Bcl-2 in sustaining Leishmania donovani infection. A rapid twofold increase in Bcl-2 expression occurred in response to parasite challenge. Downregulation of post infection Bcl-2 increase using siRNA or functional inhibition using Bcl-2 small molecule inhibitors interfered with intracellular parasite survival confirming the necessity of elevated Bcl-2 during infection. An increased nitric oxide (NO) response and reduced parasitic burden was observed upon Bcl-2 inhibition, where restitution of the NO response accounted for parasite mortality. Mechanistic insights revealed a major role of elevated Th2 cytokine IL-13 in parasite-induced Bcl-2 expression via the transcription factor STAT-3, where blocking at the level of IL-13 receptor or downstream kinase JAK-2 dampened Bcl-2 induction. Increase in Bcl-2 was orchestrated through Toll like receptor (TLR)-2-MEK-ERK signaling, and changes in TLR-2 levels affected parasite uptake. In a mouse model of visceral leishmaniasis (VL), Bcl-2 inhibitors partially restored the antimicrobial NO response by at least a twofold increase that resulted in significantly reduced parasite burden. Interestingly, monocytes derived from the peripheral blood of six out of nine human VL subjects demonstrated Bcl-2 expression at significantly higher levels, and sera from these patients showed only marginally quantifiable nitrites. Collectively, our study for the first time reveals a pro-parasitic role of host Bcl-2 and the capacity of host-derived IL-13 to modulate NO levels during infection via Bcl-2. Here, we propose Bcl-2 inhibition as a possible therapeutic intervention for VL.
| S-EPMC5078497 | biostudies-literature