Characterization of recombinant pectate lyase refolded from inclusion bodies generated in E. coli BL21(DE3).

Pectate lyase (EC 4.2.2.2) gene from Bacillus subtilis RCK was cloned and expressed in Escherichia coli to maximize its production. In addition to soluble fraction, bioactive pectate lyase was also obtained from inclusion body aggregates by urea solubilization and refolding under in vitro conditions. Enzyme with specific activity ∼3194IU/mg and ∼1493IU/mg were obtained from soluble and inclusion bodies (IBs) fraction with recovery of 56% and 74% in terms of activity, respectively. The recombinant enzyme was moderately thermostable (t1/2 60min at 50°C) and optimally active in wider alkaline pH range (7.0-10.5). Interaction of protein with its cofactor CaCl2 was found to stimulate the change in tertiary structure as revealed by near UV CD spectra. Intrinsic tryptophan fluorescence spectra indicated that tryptophan is involved in substrate binding and there might be independent binding of Ca(2+) and polygalacturonic acid to the active site. The recombinant enzyme was found to be capable of degrading pectin and polygalacturonic acid. The work reports novel conditions for refolding to obtain active recombinant pectate lyase from inclusion bodies and elucidates the effect of ligand and substrate binding on protein conformation by circular dichroism (CD) and fluorescence spectrofluorometry.

Protein aggregation and prionopathies.

Prion protein and prion-like proteins share a number of characteristics. From the molecular point of view, they are constitutive proteins that aggregate following conformational changes into insoluble particles. These particles escape the cellular clearance machinery and amplify by recruiting the soluble for of their constituting proteins. The resulting protein aggregates are responsible for a number of neurodegenerative diseases such as Creutzfeldt-Jacob, Alzheimer, Parkinson and Huntington diseases. In addition, there are increasing evidences supporting the inter-cellular trafficking of these aggregates, meaning that they are "transmissible" between cells. There are also evidences that brain homogenates from individuals developing Alzheimer and Parkinson diseases propagate the disease in recipient model animals in a manner similar to brain extracts of patients developing Creutzfeldt-Jacob's disease. Thus, the propagation of protein aggregates from cell to cell may be a generic phenomenon that contributes to the evolution of neurodegenerative diseases, which has important consequences on human health issues. Moreover, although the distribution of protein aggregates is characteristic for each disease, new evidences indicate the possibility of overlaps and crosstalk between the different disorders. Despite the increasing evidences that support prion or prion-like propagation of protein aggregates, there are many unanswered questions regarding the mechanisms of toxicity and this is a field of intensive research nowadays.

Expression and purification of a novel therapeutic single-chain variable fragment antibody against BNP from inclusion bodies of Escherichia coli.

Abnormal brain natriuretic peptide (BNP) secretion is regarded as the dominating mechanism of cerebral salt wasting syndrome (CSW), which results from a renal loss of sodium and water during intracranial disease leading to hyponatremia. Scale preparation of therapeutic single-chain variable fragment (scFv) that can neutralize elevated circulating BNP may have potential value for clinical use. In this report, we used a recently isolated humanized anti-BNP scFv fragment (3C1) as model antibody (Ab) to evaluate the potential of scale production of this therapeutic protein. The truncated gene encoding for scFv fragment cloned in pET22b (+) was mainly overexpressed as inclusion bodies in Escherichia coli (E. coli) Rosetta (DE3) pLysS cells. The insoluble fragment was solubilized and purified by Ni-NTA agarose resin under denaturation conditions, and recovered via an effective refolding buffer containing 50 mM Tris-HCl, pH 8.0, 0.15 M NaCl, 1 mM EDTA, 0.5 M arginine, 2 mM GSH, 1 mM GSSG, and 5% glycerol. The refolded scFv fragment was concentrated by PEG20000, and dialyzed in PBS (containing 5% glycerol, pH 7.4). The final yield was approximately 10.2 mg active scFv fragment per liter of culture (3.4 g wet weight cells). The scFv fragment was more than 95% pure assessed by SDS-PAGE assay. Recombinant scFv fragment with His tag displayed its immunoreactivity with anti-His tag Ab by western blotting. ELISA showed the scFv fragment specifically bound to BNP, and it displayed similar activity as the traditional anti-BNP monoclonal Ab (mAb). Thus, the current strategy allows convenient small-scale production of this therapeutic protein.

Characterization of oil bodies in adlay (Coix lachryma-jobi L).

Oil bodies were observed in cells of both embryo and aleurone layers of mature adlay grains (Coix lachryma-jobi L. var. ma-yuen Stapf). Stable oil bodies were successfully isolated from the adlay grains. Thin-layer chromatography revealed that the contents stored in the adlay oil bodies were mainly neutral lipids (>90% triacylglycerols and about 5% diacylglycerols). The integrity of the isolated oil bodies was presumably maintained via electronegative repulsion and steric hindrance provided by their surface proteins. Immunological cross-recognition using antibodies against sesame oil-body proteins indicated that two oleosin isoforms (termed oleosin-H and oleosin-L) and one caleosin were present in the adlay oil bodies. Full-length cDNA fragments encoding these three unique oil-body proteins were obtained by PCR cloning. MALDI-MS analyses confirmed that the three full-length cDNA fragments encoded the two oleosin isoforms and one caleosin observed in the oil bodies isolated from the adlay grains.

Comparative analysis of Beggiatoa from hypersaline and marine environments.

The main criterion to classify a microorganism as belonging to the genus Beggiatoa is its morphology. All multicellular, colorless, gliding bacterial filaments containing sulfur globules described so far belong to this genus. At the ultrastructural level, they show also a very complex cell envelope structure. Here we describe uncultured vacuolated and non-vacuolated bacteria from two different environments showing all characteristics necessary to assign a bacterium to the genus Beggiatoa. We also intended to investigate whether narrow and vacuolate Beggiatoa do differ morphologically as much as they do phylogenetically. Both large, vacuolated trichomes and narrow filaments devoid of vacuoles were observed. We confirmed the identity of the narrow filaments by 16S rRNA phylogenetic analysis. The diameters of the trichomes ranged from 2.4 to 34 microm, and their lengths ranged from 10 microm to over 30 mm. Narrow trichomes moved by gliding at 3.0 microm/s; large filaments moved at 1.5 microm/s. Periplasmic sulfur inclusions were observed in both types of filaments, whereas phosphorus-rich bodies were found only in narrow trichomes. On the other hand, nitrate vacuoles were observed only in large trichomes. Ultra-thin section transmission electron microscopy showed differences between the cell ultrastructure of narrow (non-vacuolated) and large (vacuolated) Beggiatoa. We observed that cell envelopes from narrow Beggiatoa consist of five layers, whereas cell envelopes from large trichomes contain four layers.

Characterization of oil bodies in jelly fig achenes.

Thin-layer chromatography analysis revealed that the contents stored in oil bodies isolated from jelly fig (Ficus awkeotsang Makino) achenes were mainly neutral lipids (>90% triacylglycerols and approximately 5% diacylglycerols). Fatty acids released from the neutral lipids of achene oil bodies were highly unsaturated (62.65% alpha-linolenic acid, 18.24% linoleic acid, and 10.62% oleic acid). The integrity of isolated oil bodies was presumably maintained via electronegative repulsion and steric hindrance provided by their surface proteins. Immunological cross-recognition using antibodies against sesame oil-body proteins indicated that two oleosin isoforms and one caleosin were present in these oil bodies. MALDI-MS analyses confirmed that the three full-length cDNA fragments obtained by PCR cloning from maturing achenes encoded the two jelly fig oleosin isoforms and one caleosin identified by immunological screening.

Sorption of hydrophobic organic compounds (HOC) in rapeseed oil bodies.

Oil-bodies are minute plant organelles (0.5-2.0microm diameter) consisting of an oil core surrounded by a phospholipid monolayer/proteinaceous membrane. Oil-bodies have been isolated from rapeseed seeds and demonstrated to constitute a novel type of micro-capsule suitable for the extraction of hydrophobic organic compounds from aqueous environments. Three hydrophobic pesticides: atrazine (2-chlor-4-ethyl-amino-6-isopropylamino-1,3,5-triazine), carbaryl (1-naphthyl methylcarbamate) and parathion (O,O-diethyl O-(4-nitrophenyl) phosphorothioate), as well as naphthalene and 2-phenylethanol were successfully extracted from aqueous solutions, with absorption in the inner oily core of OB as sorption mechanism. The OB membrane does not represent a barrier for the mass transfer of the compound towards the inner oily core of OB. Moreover, due to very high surface area to volume ratio, oil-bodies exhibit very good mass transfer properties compared with larger synthetic microcapsules or two-phase liquid-liquid extraction (LLE) techniques, which diminishes the need for strong agitation and avoids the formation of difficult to separate stable emulsions.

Purification and protective efficacy of monomeric and modified Yersinia pestis capsular F1-V antigen fusion proteins for vaccination against plague.

The F1-V vaccine antigen, protective against Yersinia pestis, exhibits a strong tendency to multimerize that affects larger-scale manufacture and characterization. In this work, the sole F1-V cysteine was replaced with serine by site-directed mutagenesis for characterization of F1-V non-covalent multimer interactions and protective potency without participation by disulfide-linkages. F1-V and F1-V(C424S) proteins were overexpressed in Escherichia coli, recovered using mechanical lysis/pH-modulation and purified from urea-solubilized soft inclusion bodies, using successive ion-exchange, ceramic hydroxyapatite, and size-exclusion chromatography. This purification method resulted in up to 2mg/g of cell paste of 95% pure, mono-disperse protein having < or =0.5 endotoxin units per mg by a kinetic chromogenic limulus amoebocyte lysate reactivity assay. Both F1-V and F1-V(C424S) were monomeric at pH 10.0 and progressively self-associated as pH conditions decreased to pH 6.0. Solution additives were screened for their ability to inhibit F1-V self-association at pH 6.5. An L-arginine buffer provided the greatest stabilizing effect. Conversion to >500-kDa multimers occurred between pH 6.0 and 5.0. Conditions for efficient F1-V adsorption to the cGMP-compatible alhydrogel adjuvant were optimized. Side-by-side evaluation for protective potency against subcutaneous plague infection in mice was conducted for F1-V(C424S) monomer; cysteine-capped F1-V monomer; cysteine-capped F1-V multimer; and a F1-V standard reported previously. After a two-dose vaccination with 2 x 20 microg of F1-V, respectively, 100%, 80%, 80%, and 70% of injected mice survived a subcutaneous lethal plague challenge with 10(8) LD(50)Y. pestis CO92. Thus, vaccination with F1-V monomer and multimeric forms resulted in significant, and essentially equivalent, protection.

Cloning, expression, and identification of immunological activity of an allergenic protein in tartary buckwheat.

A cDNA fragment encoding a 24 kDa allergenic protein in tartary buckwheat was obtained using reverse transcription PCR, 3'-rapid amplification of cDNA ends (RACE), and nest PCR. The cDNA clone contained 768 nucleotides, including 588 nucleotides in the open reading frame (ORF) and 180 nucleotides in the 3'-terminal sequence. The ORF encoded a functional protein of 195 amino acids. It shared 95% and 93% nucleotide homology with the allergenic storage protein and a legumin-like protein from common buckwheat respectively. The encoding region was expressed in host strain Escherichia coli BL21 (DE3) induced by IPTG at 28 degrees C. The inclusion bodies of recombinant protein obtained were analyzed by western blot and purified by affinity chromatography. The purity of target protein reached above 95%. After they were refolded by step-wise dialysis, 68% of the inclusion bodies reached soluble state. An analysis of immunological activity showed that the recombinant protein had a specific IgE binding activity. This is the first report of the molecular cloning and expression of the major allergen from tartary buckwheat.

Lack of protective effect of D-003, a mixture of high-molecular-weight primary acids from sugar cane wax, on liver damage induced by galactosamine in rats.

D-003 is a mixture of very-high-molecular-weight aliphatic primary acids purified from sugar cane wax, wherein octacosanoic acid is the most abundant. Experimental and clinical studies have shown that D-003 lowers cholesterol and prevents plasma lipoprotein peroxidation (LP). D-003 has protected against the histological changes characteristic of CCl4- and paracetamol-induced hepatic injury in rats, in which LP plays a pivotal role for explaining the resulting hepatotoxicity. Galactosamine induces hepatotoxicity associated with depressed RNA and protein synthesis, not with LP. The aim of this study was to evaluate whether D-003 could prevent hepatoxicity induced by mechanisms others than increased LP. We investigated the effects on galactosamine hepatotoxicity in rats distributed into five groups: a negative control group, a positive control group, and three groups treated with galactosamine and D-003 (5, 25, and 100 mg/kg). To induce liver damage, galactosamine (800 mg/kg) was injected intraperitoneally 30 minutes after dosing with vehicle or D-003. Twenty-four hours later, rats were sacrificed, and livers were immediately removed for histopathological studies. Livers from positive controls showed the characteristic pattern of galactosamine-induced damage. Galactosamine significantly reduced the percentage of normal hepatocytes, increasing both necrotic or lipid-rich hepatocytes compared with negative controls. D-003, however, did not increase the percentage of normal hepatocytes compared with positive controls, indicating that treatment was not effective for preventing the hepatic injury induced with galactosamine. Likewise, D-003 failed to change the content of necrotic and lipid-rich hepatocytes relative to positive controls. It is concluded that D-003 did not protect against the histological changes of galactosamine-induced hepatotoxicity.

Intracellular inclusions of uncultured magnetotactic bacteria.

Magnetotactic bacteria produce magnetic crystals in organelles called magnetosomes. The bacterial cells may also have phosphorus-containing granules, sulfur globules, or polyhydroxyalkanoate inclusions. In the present study, the ultrastructure and elemental composition of intracellular inclusions from uncultured magnetotactic bacteria collected in a marine environment are described. Magnetosomes contained mainly defect-free, single magnetite crystals with prismatic morphologies. Two types of phosphorus-containing granules were found in magnetotactic cocci. The most common consisted of phosphorus-rich granules containing P, O, and Mg; and sometimes also C, Na, Al, K, Ca, Mn, Fe, Zn, and small amounts of S and Cl were also found. In phosphorus-sulfur-iron granules, P, O, S, Na, Mg, Ca, Fe, and frequently Cl, K, and Zn, were detected. Most cells had two phosphorus-rich granules, which were very similar in elemental composition. In rod-shaped bacteria, these granules were positioned at a specific location in the cell, suggesting a high level of intracellular organization. Polyhydroxyalkanoate granules and sulfur globules were less commonly seen in the cells and had no fixed number or specific location. The presence and composition of these intracellular structures provide clues regarding the physiology of the bacteria that harbor them and the characteristics of the microenvironments where they thrive.

Effects of dietary restriction and metal supplementation on the accumulation of iron-laden glial inclusions in the aging rat hippocampus.

The mechanisms responsible for the pathological deposition of iron and other redox-active metals in the aging and degenerating mammalian CNS remain poorly understood. We previously demonstrated that normal aging and pharmacological (oxidative) stressors promote the transformation of astroglial mitochondria to iron-laden, diaminobenzidine (DAB)-positive cytoplasmic inclusions in sub-cortical regions of the rat brain. In the current study, we demonstrate that (1) numbers of DAB-positive glial granules in the rat dorsal hippocampus, an area implicated in learning and memory, progressively increase between 3, 12 and 22 months of age; (2) dietary restriction (40%), a manipulation that attenuates many mammalian aging processes, has no effect on the age-related accumulation of these gliosomes in the rat hippocampus; and (3) the latter can be accelerated by dietary supplementation of iron and copper. Our data support the view that dietary exposure to iron and/or copper in adult life can impact the sequestration of redox-active metals in aging hippocampal astroglia.

Acute pulmonary inflammation induced by lung overloading with selenium particles: leukocyte response and in situ detection of selenium at high resolution.

The kinetics of the acute inflammatory response of the lung was triggered in CD-1 mice by a single intratracheal instillation of a large amount of Se (10 mg); it was studied by quantitative cytology of bronchoalveolar lavage samples, light microscopy, and scanning electron microscopy coupled with x-ray elemental microanalysis. Bronchoalveolar lavage leukocytes were mostly neutrophils and increased from 12 to 24 h of Se treatment and decreased at 72 h. Only less than half of the granulocytes showed ingested Se particles; in contrast, virtually all BAL macrophages contained Se particles. Scanning electron microscopy coupled with X-ray elemental microanalysis revealed that the intracellular Se particles were heterogeneous in size (diameters from 0.4 and up to 14 microm), and that Se inclusions were sometimes accumulated at a pole of the cell. At 72 h after instillation of the particles, Se-loaded alveolar macrophages were migrated in the interstitial space of the alveoli. Se-positive regions had a focal distribution in the lung; accumulation of inflammatory cells erased the alveolar architecture of these areas of the deep lung. Our data indicates that Se overloading of the lung results in: (1) an acute inflammatory response that is dominated by neutrophils; (2) early removal of Se done mostly by alveolar macrophages, and (3) formation of focal areas of invasion of the lung parenchyma by inflammatory infiltrates.

A rapid cellular FRET assay of polyglutamine aggregation identifies a novel inhibitor.

Many neurodegenerative diseases, including tauopathies, Parkinson's disease, amyotrophic lateral sclerosis, and the polyglutamine diseases, are characterized by intracellular aggregation of pathogenic proteins. It is difficult to study modifiers of this process in intact cells in a high-throughput and quantitative manner, although this could facilitate molecular insights into disease pathogenesis. Here we introduce a high-throughput assay to measure intracellular polyglutamine protein aggregation using fluorescence resonance energy transfer (FRET). We screened over 2800 biologically active small molecules for inhibitory activity and have characterized one lead compound in detail. Y-27632, an inhibitor of the Rho-associated kinase p160ROCK, diminished polyglutamine protein aggregation (EC(50) congruent with 5 microM) and reduced neurodegeneration in a Drosophila model of polyglutamine disease. This establishes a novel high-throughput approach to study protein misfolding and aggregation associated with neurodegenerative diseases and implicates a signaling pathway of previously unrecognized importance in polyglutamine protein processing.

Expression, purification, and characterization of human enteropeptidase catalytic subunit in Escherichia coli.

Enteropeptidase (synonym:enterokinase, EC 3.4.21.9) is a heterodimeric serine protease of the intestinal brush border that activates trypsinogen by highly specific cleavage of the trypsinogen activation peptide following the sequence (Asp)(4)-Lys. The DNA sequence encoding the light chain (catalytic subunit) of human enteropeptidase (GenBank Accession No. U09860) was synthesized from 26 oligonucleotides by polymerase chain reaction and cloned into plasmid pET-32a downstream to the gene of fusion partner thioredoxin immediately after the DNA sequence encoding enteropeptidase recognition site. The fusion protein thioredoxin/human enteropeptidase light chain was expressed in Escherichia coli BL21(DE3) strain in both soluble and insoluble forms. The soluble recombinant fusion protein failed to undergo autocatalytic cleavage and activation; however, autocatalytic cleavage and activation of recombinant human enteropeptidase light chain (L-HEP) were achieved by solubilization and renaturation of the fusion protein from inclusion bodies and the active L-HEP was purified on agarose-linked soybean trypsin inhibitor. The purified L-HEP cleaved the synthetic peptide substrate Gly-Asp-Asp-Asp-Asp-Lys-beta-naphthylamide with kinetic parameters K(m)=0.16 mM and k(cat)=115 s(-1) and small ester Z-Lys-SBzl with K(m)=140 microM, k(cat)=133 s(-1). L-HEP associated with soybean trypsin inhibitor slowly and small ester Z-Lys-SBzl cleavage was inhibited with K(i)(*)=2.3 nM. L-HEP digested thioredoxin/human epidermal growth factor fusion protein five times faster than equal activity units of bovine recombinant light chain (EKMax, Invitrogen) at the same conditions.

Intracellular lipophilic inclusions of mycobacteria in vitro and in sputum.

Although most mycobacterial lipids are thought to be associated with the cell envelope, the authors previously observed substantial deposits of intracellular lipophilic material. A Nile-red-based cytological assay was used to determine factors which affect the presence and natural history of intracellular lipophilic inclusions (ILIs) in Mycobacterium smegmatis. Development of ILIs was associated with stationary-phase cultures in broth and with aged (6 days) colonies on agar. Using variants of Youmans' defined medium, the frequency and size of ILIs was observed to be minimal in carbon-poor medium. ILIs were observed to form within 15 min after provision of fatty acids to the medium and after a period of several days in nitrogen-poor medium. Analysis of the non-polar lipid extracts of ILI-rich and -poor preparations indicated that the triacylglycerols (TAGs) were a major component of the inclusions. The acyl substituents of the TAGs varied according to whether they were formed in Middlebrook 7H9 broth, in low-nitrogen Youmans' broth or rapidly after oleic acid supplementation of Youmans' broth. These studies support a storage function for TAGs in mycobacteria in addition to their previously suggested occurrence as components of the cell envelope. To assess a possible role for ILIs in Mycobacterium tuberculosis, a combined acid-fast (Auramine)/Nile red assay was applied to heavily positive sputum samples from patients with tuberculosis. Strong intracellular Nile red signals were obtained from acid-fast cells, indicating that ILI occur in M. tuberculosis in vivo. This may reflect a distinct physiological state of these cells, which it has not been possible to reproduce in vitro. These findings indicate that the uptake of long-chain fatty acids and TAG biosynthetic and degradative pathways are important aspects of mycobacterial lipid metabolism, meriting further investigation.

Experimental lead nephropathy: treatment with calcium disodium ethylenediaminetetraacetate.

Chronic lead poisoning may cause hypertension, gout, and renal insufficiency. Most experimental poisoning studies have involved the use of high doses over short periods (ie, acute poisoning). Although chelating treatment leads to remission of acute lead nephropathy, its effects in the treatment of chronic poisoning are unclear. The aims of this study were to evaluate renal alterations produced during chronic lead poisoning and their progression when poisoning was over and to determine the efficiency of chelating treatment with calcium disodium ethylenediaminetetraacetate (EDTA). In this study, 56 male Wistar rats were administered lead in drinking water (500 ppm lead acetate) over 90 days. The control group consisted of 21 nonexposed rats. Seven rats from each group were killed on days 60 and 90. At the end of the 90-day period, 21 of the lead-exposed rats were treated with disodium monocalcium EDTA (50 mg/kg/d x 5 days) intraperitoneally, and 21 were administered serum saline by the same route. Three treatment courses were given separated by 9 days free of treatment. Seven rats from each subgroup were sacrificed at the end of each treatment course. Main findings related to poisoning were hypertrophy and vacuolization of medium and small arteries; mucoid edema and muscular hypertrophy in arterioles; loss of cell brush borders, cell loss, and intranuclear inclusion bodies in the proximal tubule; and fibrosis and the presence of infiltrates in the interstitial component. Treatment with EDTA slowed the progression of most alterations. No damage associated with the use of the chelating agent was observed. Longer term studies of the effects of this drug are required to establish whether the damage caused by lead poisoning may be reversed.

Ultrastructure and composition of asteroid bodies.

PURPOSE: Asteroid hyalosis is a disease of the vitreous, characterized by brilliant reflecting particles, termed asteroid bodies, which are surrounded by a tightly adhering network of fibrils. The composition and mode of formation of asteroid bodies is not yet understood in detail. The purpose of this study was to investigate the ultrastructure of asteroid bodies and to identify the intrinsic inorganic and organic components that contribute to the nature and development of asteroid bodies. METHODS: Electron energy loss spectroscopy and energy-filtered transmission electron microscopy were used for the elemental analysis of asteroid bodies. The ultrastructural localization of glycosaminoglycans was investigated, using lectin and antibody conjugates in conjunction with transmission electron microscopy and epifluorescence microscopy. Anionic sites of glycosaminoglycans were detected with 15 nm cationic colloidal gold at low pH, applied as a postembedding technique. Ultrastructural details of asteroid bodies were documented using fast Fourier transform analysis of zero-loss filtered images. RESULTS: Element mapping of asteroid bodies by electron spectroscopic imaging revealed a homogeneous distribution of calcium, phosphorus, and oxygen. The electron energy loss spectra of these elements showed details similar to those found for hydroxyapatite. Additionally, high contrast and sensitivity against a calcium-specific chelator highlighted the crystalline, apatite-like nature of asteroid bodies. Immunofluorescence microscopy revealed the presence of chondroitin-6-sulfate at the periphery of asteroid bodies, which is in agreement with the ultrastructural colocalization of anionic sites. Fast Fourier transform analysis revealed that each 7-nm periodicity of asteroid lamellar stacks is divided by a fine, parallel-oriented line, separating each 7-nm layer into two halves of 3.5-nm thickness. Carbohydrates specific for hyaluronic acid were observed by lectin-gold labeling to be part of the inner matrix of asteroid bodies. CONCLUSIONS: The results of this study demonstrate the structural and elemental similarity of asteroid bodies with hydroxyapatite. Proteoglycans and their glycosaminoglycan side chains are implicated in playing a role in regulating the biomineralization process.

Impairment of sterol biosynthesis leads to phosphorus and calcium accumulation in Leishmania acidocalcisomes.

The induction of the formation of inclusion vesicles in Leishmania amazonensis by the sterol biosynthesis inhibitors (SBI) ketoconazole and terbinafine has been reported previously. These compartments were recently identified as acidocalcisomes. By the use of electron spectroscopic imaging and energy loss spectroscopy, the presence of calcium, phosphorus and oxygen in the electron-dense inclusions located within the acidocalcisomes has been demonstrated. Endoplasmic reticulum cisternae formed membrane whorls which enclosed large portions of the cytoplasm and sometimes circumscribed acidocalcisomes. In addition, acid phosphatase activity, as well as the endocytic tracers horseradish peroxidase and gold-labelled transferrin and cystatin C were detected within these organelles in both SBI-treated and untreated parasites. These data suggest that impairment of sterol biosynthesis induces the biogenesis of acidocalcisomes and triggers an autophagic process that leads to intersection of the endosomal/lysosomal system with the acidocalcisomes.