A growth-based assay using fluorescent protein emission to screen for S-adenosylmethionine synthetase inhibitors.

The use of cell growth-based assays to identify inhibitory compounds is straightforward and inexpensive, but is also inherently insensitive and somewhat nonspecific. To overcome these limitations and develop a sensitive, specific cell-based assay, two different approaches were combined. To address the sensitivity limitation, different fluorescent proteins have been introduced into a bacterial expression system to serve as growth reporters. To overcome the lack of specificity, these protein reporters have been incorporated into a plasmid in which they are paired with different orthologs of an essential target enzyme, in this case l-methionine S-adenosyltransferase (MAT, AdoMet synthetase). Screening compounds that serve as specific inhibitors will reduce the growth of only a subset of strains, because these strains are identical, except for which target ortholog they carry. Screening several such strains in parallel not only reveals potential inhibitors but the strains also serve as specificity controls for one another. The present study makes use of an existing Escherichia coli strain that carries a deletion of metK, the gene for MAT. Transformation with these plasmids leads to a complemented strain that no longer requires externally supplied S-adenosylmethionine for growth, but its growth is now dependent on the activity of the introduced MAT ortholog. The resulting fluorescent strains provide a platform to screen chemical compound libraries and identify species-selective inhibitors of AdoMet synthetases. A pilot study of several chemical libraries using this platform identified new lead compounds that are ortholog-selective inhibitors of this enzyme family, some of which target the protozoal human pathogen Cryptosporidium parvum.

Research progress on phosphatidylinositol 4-kinase inhibitors.

Phosphatidylinositol 4-kinases (PI4Ks) could phosphorylate phosphatidylinositol (PI) to produce phosphatidylinositol 4-phosphate (PI4P) and maintain its metabolic balance and location. PI4P, the most abundant monophosphate inositol in eukaryotic cells, is a precursor of higher phosphoinositols and an essential substrate for the PLC/PKC and PI3K/Akt signaling pathways. PI4Ks regulate vesicle transport, signal transduction, cytokinesis, and cell unity, and are involved in various physiological and pathological processes, including infection and growth of parasites such as Plasmodium and Cryptosporidium, replication and survival of RNA viruses, and the development of tumors and nervous system diseases. The development of novel drugs targeting PI4Ks and PI4P has been the focus of the research and clinical application of drugs, especially in recent years. In particular, PI4K inhibitors have made great progress in the treatment of malaria and cryptosporidiosis. We describe the biological characteristics of PI4Ks; summarize the physiological functions and effector proteins of PI4P; and analyze the structural basis of selective PI4K inhibitors for the treatment of human diseases in this review. Herein, this review mainly summarizes the developments in the structure and enzyme activity of PI4K inhibitors.

Cryptosporidium parvum maintains intracellular survival by activating the host cellular EGFR-PI3K/Akt signaling pathway.

Autophagy is a critical cellular mechanism in helping infected cells remove intracellular pathogens and is countered by pathogens maintaining intracellular survival by regulating autophagy through the manipulation of the host cellular signal transduction pathway. Cryptosporidium parvum is a zoonotic intracellular but extracytoplasmic protozoon that causes diarrhea in infants and young children worldwide. However, it is still unclear how Cryptosporidium adapts to intracellular survival. In the present study, we demonstrated that C. parvum could activate the EGFR-PI3K/Akt signaling pathway to promote intracellular survival in HCT-8 cells. The western blot results showed that C. parvum induced EGFR and Akt phosphorylation in HCT-8 cells. The EGFR inhibitor AG1478 decreased EGFR and Akt phosphorylation, and the PI3K inhibitor LY294002 impaired Akt phosphorylation induced by C. parvum in HCT-8 cells. Inhibition of EGFR or Akt decreased the number of intracellular parasites. Second, low-dose infection of C. parvum triggered complete autophagy and enhanced autophagic flux in HCT-8 cells. The expressions of mTOR and p62 were decreased, and the expressions of LC3 and Beclin1 were increased in C. parvum-infected HCT-8 cells. Transfection with siBeclin1 or siATG7 reduced LC3 accumulation, while lysosome inhibitor E64d+pepA increased LC3 accumulation induced by C. parvum in HCT-8 cells. Intracellular parasite proliferation was decreased when treated with autophagy inducer rapamycin, whereas autophagy inhibitor 3-MA, E64d+pep A, siBeclin1 or siATG7 increased intracellular parasites. Third, C. parvum inhibited autophagy killing to promote its own intracellular survival by activating EGFR-Akt signaling pathway. The EGFR inhibitor AG1478 enhanced autophagic flux, and Akt inhibitor IV increased LC3 accumulation and inhibited C. parvum proliferation in HCT-8 cells. Akt inhibitor IV-inhibited C. parvum proliferation was attenuated by E64d+pepA. In summary, C. parvum could maintain intracellular survival by inhibiting autophagy via EGFR-PI3K/Akt pathway. These results revealed a new mechanism for the interaction of C. parvum with host cells.

[miRNA Expression Profile in Ileocecal Adenocarcinoma Cells Infected with Cryptosporidium]. / Cryptosporidium ile Enfekte Edilmis Ileoçekal Adenokarsinom Hücrelerindeki miRNA Ekspresyon Profili.

Cryptosporidium spp. is an opportunistic protozoan transmitted by fecal-oral route via oocysts. The agent may cause severe infection especially in individuals with suppressed immune system, due to its intracellular location and ability to cause auto-infection. MicroRNAs (miRNAs) are non-translated endogenous RNA molecules with an average of 22 nucleotides in length that regulate the expression of genes involved in important biological functions such as proliferation, differentiation, apoptosis and immune response. Recent studies have focused on the role of miRNAs in pathogenesis of infectious diseases and their potential to be used as biomarkers. The aim of this study was to determine the miRNA profile of human ileocecal adenocarcinoma (HCT-8) cells at 24 hours of infection with Cryptosporidium spp. In the study, the HCT-8 cell line was infected with Cryptosporidium spp. that were isolated from infected human stool samples and RNA was isolated from the cells 24 hours after infection. After this process, cDNA synthesis was performed and the expression of 95 human miRNA profiles were investigated by polymerase chain reaction (PCR) method. Fold changes of expression were determined by comparison with Cryptosporidium spp. uninfected cell lines. Sequence information of miRNAs and their target genes were performed via TargetScanHuman7.1 and miRDB websites, while gene ontology (GO) pathways of target genes were analyzed with the mirPath v.3 program. It was detected that the expression of 10 miRNAs were upregulated and 11 of them were downregulated compared with the control group. It was observed that, this 21 differentially expressed miRNAs were mainly associated with apoptosis, mitotic cell cycle, and immune response. Hsa-miR-612, hsa-miR-6763-5p, hsa-miR-188-5p, hsa-miR-664b-3p, hsa-miR-210-3p, hsa-let-7e-5p hsa-let-7b-3p, hsa-miR-4787-3p, hsa-miR-548ab, hsa-miR-3714 and hsamiR-4803 were found to be associated with apoptosis; and hsa-miR-612, hsa-miR-664b-3p, hsa-miR210-3p, hsa-let-7e-5p, hsa-let-7b-3p, hsa-miR-548ab, and hsa-miR4803 were found to be associated with mitotic cell cycle. The balance of proliferation and apoptosis is very significant in the development of infection and cancer. It is thought that determination of the effect of miRNAs on proliferation-apoptosis balance could provide information related to the etiopathogenesis and prognosis of infections, and on the role of microorganisms in carcinogenesis. In this study, 12 differentially expressed miRNAs were found to be associated with immune response. This may emphasize the role of miRNAs in the prevention and treatment of infections. It was concluded that, miRNAs could be used in the diagnosis, treatment and prevention of infections with the determination of miRNA's role in the infection mechanism as a result of the increasing number of studies.

Emerging roles for extracellular vesicles in parasitic infections.

Extracellular vesicles (EVs) are released by cells and contain a complex mixture of proteins, genetic information and lipids. EVs mediate cell:cell communication by transferring their molecular cargo between cells. EVs, initially discovered in mammalian systems, have been demonstrated to play critical role in immunology and cancer biology. More recently, EVs have been identified in a broad range of both unicellular and multicellular parasites. In this review we focus on the emerging roles for EVs in parasitic infections. Parasite-derived EVs can transfer virulence factors and drug-resistance markers, modify host cell gene expression and promote parasite adherence and host cell proliferation. EVs can also suppress or stimulate host immune responses. Thus, EVs are likely important in determining the outcome of parasitic infections.

Glycoproteins and Gal-GalNAc cause Cryptosporidium to switch from an invasive sporozoite to a replicative trophozoite.

The apicomplexan parasite Cryptosporidium causes cryptosporidiosis, a diarrheal disease that can become chronic and life threatening in immunocompromised and malnourished people. There is no effective drug treatment for those most at risk of severe cryptosporidiosis. The disease pathology is due to a repeated cycle of host cell invasion and parasite replication that amplifies parasite numbers and destroys the intestinal epithelium. This study aimed to better understand the Cryptosporidium replication cycle by identifying molecules that trigger the switch from invasive sporozoite to replicative trophozoite. Our approach was to treat sporozoites of Cryptosporidium parvum and Cryptosporidium hominis, the species causing most human cryptosporidiosis, with various media under axenic conditions and examine the parasites for rounding and nuclear division as markers of trophozoite development and replication, respectively. FBS had a concentration-dependent effect on trophozoite development in both species. Trophozoite development in C. parvum, but not C. hominis, was enhanced when RPMI supplemented with 10% FBS (RPMI-FBS) was conditioned by HCT-8 cells for 3h. The effect of non-conditioned and HCT-8 conditioned RPMI-FBS on trophozoite development was abrogated by proteinase K and sodium metaperiodate pretreatment, indicating a glycoprotein trigger. Cryptosporidium parvum and C. hominis trophozoite development also was triggered by Gal-GalNAc in a concentration-dependent manner. Cryptosporidium parvum replication was greatest following treatments with Gal-GalNAc, followed by conditioned RPMI-FBS and non-conditioned RPMI-FBS (P<0.05). Cryptosporidium hominis replication was significantly less than that in C. parvum for all treatments (P<0.05), and was greatest at the highest tested concentration of Gal-GalNAc (1mM).

A novel stereo bioactive metabolite isolated from an endophytic fungus induces caspase dependent apoptosis and STAT-3 inhibition in human leukemia cells.

The present study describes the anti-leukemic potential of a novel stereo bioactive secondary metabolite, (R)-5-hydroxy-2-methylchroman-4-one (HMC) isolated from a novel endophytic fungus source (Cryptosporiopsis sp. H2-1, NFCCI-2856), associated with Clidemia hirta. HMC inhibited cell proliferation of different cancer cell lines with IC50 values in the range of 8-55 µg/ml. The cytotoxicity window of HMC was 6-12 times lower in normal cells as compared to susceptible leukemic HL-60, MOLT-4 and K-562 cells. It persuades apoptosis through both intrinsic and extrinsic pathways in above leukemic cell lines, which was evident through Hoechst staining, Annexin-V binding, cell cycle analysis, loss of mitochondrial membrane potential (Δψm), release of cytochrome c, Bax, Bid, over-expression of apical death receptors, activation of caspase-3,-8,-9 and PARP (poly ADP ribose polymerase) cleavage. HMC induced caspase dependent apoptosis and robustly attenuate transcription factor, p-STAT-3 in myeloid and lymphoid leukemia cells. The mechanism of HMC arbitrated inhibition of p-STAT-3 was due to the activation of ubiquitin dependent degradation of p-STAT-3. Therefore, our study not only describes the anti-leukemic potential of HMC but also provides insights into how endophytes can be useful in discovery and development of novel anticancer therapeutics.

Two COWP-like cysteine rich proteins from Eimeria nieschulzi (coccidia, apicomplexa) are expressed during sporulation and involved in the sporocyst wall formation.

BACKGROUND: The family of cysteine rich proteins of the oocyst wall (COWPs) originally described in Cryptosporidium can also be found in Toxoplasma gondii (TgOWPs) localised to the oocyst wall as well. Genome sequence analysis of Eimeria suggests that these proteins may also exist in this genus and led us to the assumption that these proteins may also play a role in oocyst wall formation. METHODS: In this study, COWP-like encoding sequences had been identified in Eimeria nieschulzi. The predicted gene sequences were subsequently utilized in reporter gene assays to observe time of expression and localisation of the reporter protein in vivo. RESULTS: Both investigated proteins, EnOWP2 and EnOWP6, were expressed during sporulation. The EnOWP2-promoter driven mCherry was found in the cytoplasm and the EnOWP2, respectively EnOWP6, fused to mCherry was initially observed in the extracytoplasmatic space between sporoblast and oocyst wall. This, so far unnamed compartment was designated as circumplasm. Later, the mCherry reporter co-localised with the sporocyst wall of the sporulated oocysts. This observation had been confirmed by confocal microscopy, excystation experiments and IFA. Transcript analysis revealed the intron-exon structure of these genes and confirmed the expression of EnOWP2 and EnOWP6 during sporogony. CONCLUSIONS: Our results allow us to assume a role, of both investigated EnOWP proteins, in the sporocyst wall formation of E. nieschulzi. Data mining and sequence comparisons to T. gondii and other Eimeria species allow us to hypothesise a conserved process within the coccidia. A role in oocyst wall formation had not been observed in E. nieschulzi.

Cloning and Iron Transportation of Nucleotide Binding Domain of Cryptosporidium andersoni ATP-Binding Cassette (CaABC) Gene.

Cryptosporidium andersoni ATP-binding cassette (CaABC) is an important membrane protein involved in substrate transport across the membrane. In this research, the nucleotide binding domain (NBD) of CaABC gene was amplified by PCR, and the eukaryotic expression vector of pEGFP-C1-CaNBD was reconstructed. Then, the recombinant plasmid of pEGFP-C1-CaNBD was transformed into the mouse intestinal epithelial cells (IECs) to study the iron transportation function of CaABC. The results indicated that NBD region of CaABC gene can significantly elevate the transport efficiency of Ca(2+), Mg(2+), K(+), and HCO3 (-) in IECs (P<0.05). The significance of this study is to find the ATPase inhibitors for NBD region of CaABC gene and to inhibit ATP binding and nutrient transport of CaABC transporter. Thus, C. andersoni will be killed by inhibition of nutrient uptake. This will open up a new way for treatment of cryptosporidiosis.

Evidence for a structural role for acid-fast lipids in oocyst walls of Cryptosporidium, Toxoplasma, and Eimeria.

UNLABELLED: Coccidia are protozoan parasites that cause significant human disease and are of major agricultural importance. Cryptosporidium spp. cause diarrhea in humans and animals, while Toxoplasma causes disseminated infections in fetuses and untreated AIDS patients. Eimeria is a major pathogen of commercial chickens. Oocysts, which are the infectious form of Cryptosporidium and Eimeria and one of two infectious forms of Toxoplasma (the other is tissue cysts in undercooked meat), have a multilayered wall. Recently we showed that the inner layer of the oocyst walls of Toxoplasma and Eimeria is a porous scaffold of fibers of ß-1,3-glucan, which are also present in fungal walls but are absent from Cryptosporidium oocyst walls. Here we present evidence for a structural role for lipids in the oocyst walls of Cryptosporidium, Toxoplasma, and Eimeria. Briefly, oocyst walls of each organism label with acid-fast stains that bind to lipids in the walls of mycobacteria. Polyketide synthases similar to those that make mycobacterial wall lipids are abundant in oocysts of Toxoplasma and Eimeria and are predicted in Cryptosporidium. The outer layer of oocyst wall of Eimeria and the entire oocyst wall of Cryptosporidium are dissolved by organic solvents. Oocyst wall lipids are complex mixtures of triglycerides, some of which contain polyhydroxy fatty acyl chains like those present in plant cutin or elongated fatty acyl chains like mycolic acids. We propose a two-layered model of the oocyst wall (glucan and acid-fast lipids) that resembles the two-layered walls of mycobacteria (peptidoglycan and acid-fast lipids) and plants (cellulose and cutin). IMPORTANCE: Oocysts, which are essential for the fecal-oral spread of coccidia, have a wall that is thought responsible for their survival in the environment and for their transit through the stomach and small intestine. While oocyst walls of Toxoplasma and Eimeria are strengthened by a porous scaffold of fibrils of ß-1,3-glucan and by proteins cross-linked by dityrosines, both are absent from walls of Cryptosporidium. We show here that all oocyst walls are acid fast, have a rigid bilayer, dissolve in organic solvents, and contain a complex set of triglycerides rich in polyhydroxy and long fatty acyl chains that might be synthesized by an abundant polyketide synthase. These results suggest the possibility that coccidia build a waxy coat of acid-fast lipids in the oocyst wall that makes them resistant to environmental stress.

IVICAT for the masses: an improved technique for permethylation of peptides.

To determine the levels of post-translational modifications, we needed a quantitative technique that would allow comparison of the amounts of acetylated versus mono-, di-, and tri-methylated lysines in histones. One method, IVICAT, generates trimethyl-amines and could be used, but is technically challenging. We have modified this technique to be used with standard laboratory equipment so that this chemistry is accessible to most proteomics laboratories.

Fate of Cryptosporidium oocysts and Giardia cysts in the Norwegian aquatic environment over winter.

We investigated the survival of Cryptosporidium oocysts and Giardia cysts during winter in an aquatic environment (approximate temperature measurements between 1 and 7 degrees C) in Norway, using morphology and uptake of dyes as indicators of viability. Previous research has shown that in the terrestrial environment, shear forces caused by freeze and thaw cycles probably cause the parasites to be inactivated. Such forces occurred infrequently in the aquatic environment, as freezing of the water around the parasites was not observed during the study period (although freezing of the water surface did occur). The rate of decline in viability (log(10) N (t)/N (0)) was similar in control and experimental environments for both parasites; no Cryptosporidium oocysts with viable morphology were detected after approximately 20 weeks and no Giardia cysts with apparently viable morphology could be detected after 1 month. These results suggest that infection with these parasites in Norway is not usually from transmission stages that have over-wintered in the Norwegian environment.

Effects of the Norwegian winter environment on Giardia cysts and Cryptosporidium oocysts.

The structural integrity of Cryptosporidium oocysts and Giardia cysts in the Norwegian winter environment was investigated. During winter 2001/2002, Cryptosporidium oocysts and Giardia cysts were placed in the upper layers of soil in different matrices contained in chambers and exposed to the Norwegian climate. Morphological characteristics and inclusion/exclusion of vital dyes were monitored and compared to refrigerated controls. Reduction in parasite numbers was recorded for all parasites, geographical locations, and matrices. Shear forces generated during freeze-thaw cycles are postulated to have disintegrated the parasites exposed to the Norwegian winter and retrospective laboratory studies support this theory. Increased dye inclusion, possibly indicative of viability loss, was also noted. The refrigerated control parasites exhibited no decline in numbers, and alteration in dye inclusion characteristics for refrigerated parasites was slower. Cryptosporidium oocysts were apparently more robust than Giardia cysts; differences between isolates were also noted. These results suggest Cryptosporidium oocysts and Giardia cysts do not persist in the Norwegian terrestrial environment over winter, and when detected, will have been excreted since the previous winter. Differences in the morphological characteristics, matrix effects, and the possible relationship of the dye data to parasite survival are discussed in relation to further studies.

Evaluation of an internal positive control for Cryptosporidium and Giardia testing in water samples.

AIMS: An internal positive control for Cryptosporidium and Giardia monitoring was evaluated for use in routine water monitoring quality control. The control, known as ColorSeed C&G (BTF Pty Ltd, Sydney, Australia), is a suspension containing exactly 100 Cryptosporidium oocysts and 100 Giardia cysts that have been modified by attachment of Texas Red to the cell wall, allowing them to be differentiated from unmodified oocysts and cysts. The control enables recovery efficiencies to be determined for every water sample analysed. METHODS AND RESULTS: A total of 494 water samples were seeded with ColorSeed C&G and with unlabelled Cryptosporidium and Giardia and then analysed. Additionally, the robustness of the ColorSeed labelling was challenged with various chemical treatments. Recoveries were significantly lower for the ColorSeed Texas Red labelled Cryptosporidium and Giardia than recoveries of unlabelled Cryptosporidium and Giardia. However, the differences in recoveries were small. On average ColorSeed Cryptosporidium recoveries were 3.3% lower than unlabelled Cryptosporidium, and ColorSeed Giardia recoveries were 4% lower than unlabelled Giardia. CONCLUSIONS: ColorSeed C&G is suitable for use as an internal positive control for routine monitoring of both treated and raw water samples. SIGNIFICANCE AND IMPACT OF THE STUDY: The small differences in recoveries are unlikely to limit the usefulness of ColorSeed C&G as an internal positive control. The ColorSeed labelling was found to be robust after different treatments.

Detection of respiratory enzyme activity in Giardia cysts and Cryptosporidium oocysts using redox dyes and immunofluorescence techniques.

The fluorescent redox dye 5-cyano-2,3-ditolyl tetrazolium chloride (CTC), combined with fluorescein-labeled antibodies, was tested for the simultaneous detection of the respiratory electron transport system (ETS) activity and enumeration of Giardia cysts and Cryptosporidium oocysts by spectral microfluorometry and epifluorescence microscopy. The reduction of CTC and p-iodonitrotetrazolium violet (INT), a non-fluorescent redox dye, was compared with propidium iodide (PI) and fluorescein diacetate (FDA) for the measurements of Giardia cyst viability over time. According to the PI and FDA staining techniques, nearly 60% of the cysts tested viable at the beginning of the observations; after 21 days their viability decreased to 5%. The redox dyes indicated that approximately 4-10% of the cysts were metabolically active 48 h after they were shed, followed by a decline in enzyme activity to near undetectable levels after 4 days. Spectral analysis on individual cysts indicated that the fluorescence emission of the reduced CTC and the fluorescein-labeled antibodies is distinctive for each compound and suitable for their simultaneous determination by microphotometry, flow cytometry and epifluorescence microscopy. The fluorescence signal remained without alteration when the cysts were transferred onto microscope slides coated with an optical embedding medium and stored at -20 degrees C. The fluorescence intensity of the reduced CTC, when properly standardized, can provide quantitative measurements of ETS activity of the cysts. This is the first report of a method to determine enzyme redox activity on intact cysts applicable to water, laboratory and animal samples.