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PubMed1985

Relationship between numbers of cortical argentophilic and congophilic senile plaques in the brains of elderly people with and without senile dementia of Alzheimer type.

Four neocortical regions (frontal, parietal, temporal, occipital) of 44 cases were impregnated by a silver stain to show neuritic plaques and stained with Congo red to show amyloid plaques. In 11 cases with large numbers of argentophilic plaques these plaques decreased significantly with age while the reverse appeared to be true for the congophilic plaques. In the remaining 34 cases which had few argentophilic plaques the numbers of congophilic plaques increased significantly with age in the parietal and occipital regions. These results suggest that the neuritic component of senile plaques precedes the amyloid cores in their pathogenesis although a causative relationship is not implied.

Aged↗
PubMed2000

Conversion of yeast phosphoglycerate kinase into amyloid-like structure.

Yeast phosphoglycerate kinase is a structurally well-characterized enzyme consisting of 415 amino acids without disulfide bonds. Anion-induced refolding from its acid-unfolded state gives rise to the formation of worm-like amyloid fibrils with a persistence length of 73 nm. Electron microscopy and small-angle X-ray scattering data indicate that the fibrils have an elliptical cross-section with dimensions of 10.2 nm x 5.1 nm. About half of all amino acids are organized in form of cross-beta structure which gives rise to typical infrared spectra, X-ray diffraction and yellow-green birefringence after Congo red staining. The kinetics of amyloid formation, monitored by infrared spectroscopy, dynamic light scattering and X-ray scattering, was found to be strongly dependent on protein concentration. The infrared data indicate that the formation of cross-beta structure practically comes to an end already after some hours, whereas the length-growth of the amyloid fibrils, monitored by small-angle X-ray scattering, was not yet completed after 1,300 hours.

Amyloid↗
PubMed2000

A possible model of senile plaques using synthetic amyloid beta-protein and rat glial culture.

The senile plaque (SP) is one of the pathological hallmarks in the brains of patients with Alzheimer's disease (AD), but the mechanism of its formation and its role in AD progression are not yet fully understood. Synthetic amyloid beta-protein (Abeta)1-40 is known to aggregate in vitro, and the aggregated Abeta has been widely used for in vitro experiments, in which its peculiar effects on neuronal and glial cells have been shown. To date, however, the formation of a SP-like structure in a culture system using synthetic Abeta has not been demonstrated. In this study, we established a possible SP model using synthetic Abeta1-40 and rat glial cultures as follows: (1) large spherical aggregates of synthetic Abeta (sAmys) were produced from synthetic Abeta1-40 (10-50 microm in diameter), (2) the sAmys were added to a glial culture, and (3) the characteristics of the sAmys and the reactions of glial cells (microglia and astrocytes) around the sAmys were analyzed. We found that the sAmys exhibited the same features as the dense amyloid core in SPs, including the intense green birefringence under polarized light with Congo red, and induced reactive features in glial cells, including induction of major histocompatibility complex class II antigen in the microglia and interleukin-1beta in the astrocytes, similar to those seen in SPs in the brain in AD. Given our findings, we consider that this glial culture system with the sAmys is a possible in vitro SP model and useful for investigating the effects of massive amyloid deposition on neuronal and glial cells.

Amyloid beta-Peptides↗
PubMed2003

Phenotypic and genotypic characterization of bovine mastitis isolates of Staphylococcus aureus for biofilm formation.

Staphylococcus aureus is one of the most common pathogens responsible for contagious mastitis in ruminants. The ability of S. aureus to form biofilm in vivo is considered to be a major virulence factor influencing its pathogenesis in mastitis. The objectives of the study were to examine in vitro slime production, biofilm formation, and the presence of the ica gene locus and icaA and icaD genes in S. aureus isolates from bovine mastitis. Thirty-two of the 35 isolates tested produced slime on Congo red agar, whereas only 24 of the isolates were found to produce biofilm in vitro. However, all the 35 isolates possessed the ica locus, icaA and icaD genes. This study indicates a high prevalence of the ica genes among S. aureus mastitis isolates, and their presence is not always associated with in vitro formation of slime or biofilm. A combination of phenotypic and genotypic tests is recommended for investigating biofilm formation in S. aureus.

Animals↗
PubMed2006

The indirect generation of long-distance structural changes in antibodies upon their binding to antigen.

An allosteric mechanism for the generation of long-distance structural alterations in Fab fragments of antibodies in immune complexes has been postulated and tested in theoretical and experimental analysis. The flexing and/or torsion-derived forces exerted on the elbow region in Fab arms of bivalent antibodies upon binding to antigen were assumed to drive the disruption of hydrogen bonds which stabilize N- and C-terminal chain fragments in V-domains. This allows an extra movement in the elbow followed by a relaxation in the Fab arm and may generate long-distance effects if, in particular, the structural changes are generated asymmetrically involving one chain of the Fab arm only. This mechanism was studied by simulation of molecular dynamics. The local instability in the area involving the site of packing of the N-terminal chain fragment allows penetration and binding of the supramolecular dye Congo red that hence becomes an indicator of the initiated relaxation process and is also the prospective ligand in studies of designing drugs. The susceptibility to dye binding was observed in complexation of bivalent antibodies only, supplying the evidence that constraints associating the interaction with randomly distributed antigenic determinants drive the local structural changes in the V-domain followed by long-distance effects.

Allosteric Regulation↗
PubMed2000

Papillary carcinoma in amyloid goitre.

Amyloid goitre is a rare lesion characterized by a diffuse and bilateral enlargement of the thyroid gland due to amyloid deposition. It is uncommon that a massive and widespread amount of adipose tissue deposition is found within these lesions and only in exceptional cases a differentiated carcinoma can develop. We describe the third example of thyroid carcinoma, arising in a 74-year old female who had also massive adipose thyroidal metaplasia, within amyloid goitre. The Congo red stain confirmed the diagnosis of amyloid goitre. Immunohistochemistry showed reactivity with MoAb against amyloid fibril protein A. The patient suffered from renal failure of undetermined aetiology for three years, but neither systemic amyloidosis nor risk factors for its development were found. It is important to correctly diagnose amyloid goitre both to rule out the presence of a differentiated thyroidal carcinoma and to search for amyloid infiltration in other organs in view of an early appropriate therapy.

Aged↗
PubMed2000

An improved method of preparing the amyloid beta-protein for fibrillogenesis and neurotoxicity experiments.

Synthetic amyloid beta-protein (A beta) is used widely to study fibril formation and the physiologic effects of low molecular weight and fibrillar forms of the peptide on cells in culture or in experimental animals. Not infrequently, conflicting results have arisen in these studies, in part due to variation in the starting conformation and assembly state of A beta. To avoid these problems, we sought a simple, reliable means of preparing A beta for experimental use. We found that solvation of synthetic peptide with sodium hydroxide (A beta x NaOH), followed by lyophilization, produced stocks with superior solubility and fibrillogenesis characteristics. Solubilization of the pretreated material with neutral buffers resulted in a pH transition from approximately 10.5 to neutral, avoiding the isoelectric point of A beta (pI approximately 5.5), at which A beta precipitation and aggregation propensity are maximal. Relative to trifluoroacetate (A beta x TFA) or hydrochloric acid (A beta x HCl) salts of A beta, yields of "low molecular weight A beta" (monomers and/or dimers) were improved significantly by NaOH pretreatment. Time-dependent changes in circular dichroism spectra and Congo red dye-binding showed that A beta x NaOH formed fibrils more readily than did the other A beta preparations and that these fibrils were equally neurotoxic. NaOH pretreatment thus offers advantages for the preparation of A beta for biophysical and physiologic studies.

Amino Acid Sequence↗
PubMed2001

A novel action of alzheimer's amyloid beta-protein (Abeta): oligomeric Abeta promotes lipid release.

Interactions between amyloid beta-protein (Abeta) and lipids have been suggested to play important roles in the pathogenesis of Alzheimer's disease. However, the molecular mechanism underlying these interactions has not been fully understood. We examined the effect of Abeta on lipid metabolism in cultured neurons and astrocytes and found that oligomeric Abeta, but not monomeric or fibrillar Abeta, promoted lipid release from both types of cells in a dose- and time-dependent manner. The main components of lipids released after the addition of Abeta were cholesterol, phospholipids, and monosialoganglioside (GM1). Density-gradient and electron microscopic analyses of the conditioned media demonstrated that these Abeta and lipids formed particles and were recovered from the fractions at densities of approximately 1.08-1.18 g/ml, which were similar to those of high-density lipoprotein (HDL) generated by apolipoproteins. The lipid release mediated by Abeta was abolished by concomitant treatment with Congo red and the PKC inhibitor, H7, whereas it was not inhibited with N-acetyl-l-cysteine. These Abeta-lipid particles were not internalized into neurons, whereas HDL-like particles produced by apolipoprotein E were internalized. Our findings indicate that oligomeric Abeta promotes lipid release from neuronal membrane, which may lead to the disruption of neuronal lipid homeostasis and the loss of neuronal function.

Alzheimer Disease↗
PubMed2002

In catheter infections by Staphylococcus epidermidis the intercellular adhesion (ica) locus is a molecular marker of the virulent slime-producing strains.

Recently, it has been shown that S. epidermidis includes the ica operon responsible for slime production. In the operon, coexpression of icaA and icaD genes is required for full slime synthesis. In this study, the presence of icaA and icaD genes was searched for in a collection of 100 Staphylococcus epidermidis strains from catheter-associated infections by an original PCR method. Another 51 strains of S. epidermidis isolated from the skin or mucosa of healthy volunteers (26 of which derived from the hospital staff) were also investigated. Slime-forming ability was phenotypically tested on Congo red agar plates. Sixty-one percent of the strains isolated from catheters were icaA- icaD-positive and produced slime. The results indicate that detection of ica genes by a PCR method is a useful tool for prompt identification of S. epidermidis slime-forming strains isolated from catheter-related infections. Also, three saprophytic strains from the hospital staff were positive for slime synthesis and presence of ica genes, suggesting a potential diffusion of slime-forming strains in hospital personnel.

Biomarkers↗
PubMedDate not supplied

Inhibition of scrapie-associated PrP accumulation. Probing the role of glycosaminoglycans in amyloidogenesis.

Accumulation of an abnormal, protease-resistant form of an endogenous protein, PrP, is a characteristic feature of scrapie and related transmissible spongiform encephalopathies. This abnormal isoform is also present in the amyloid plaques that are often observed in these diseases. In mouse neuroblastoma cells persistently infected with scrapie, the abnormal protease-resistant isoform of PrP is derived from an operationally normal protease-sensitive precursor. Conversion of PrP to the protease-resistant state occurs either on the plasma membrane or along an endocytic pathway by an unknown mechanism. Inhibitors of protease-resistant PrP accumulation have been identified, and these include the amyloid-binding dye Congo red and certain sulfated glycans. The similarity of these compounds to sulfated glycosaminoglycans, which are components of all natural amyloids, has led to the hypothesis that the inhibitors act by competitively blocking an interaction between endogenous glycosaminoglycan(s) and PrP that is critical for amyloidogenic PrP accumulation. The proven prophylactic effect of these sulfated glycans in animal models of scrapie suggests that they represent a group of compounds that might interfere with the pathogenic formation of amyloid in a variety of diseases, such as Alzheimer's disease.

Amyloid↗
PubMed1986

Fluorescence activated cell sorting (FACS) as a separation method for neurofibrillary tangles in Alzheimer's disease.

We have developed a fluorescence cell sorting (FACS) method for the separation of neurofibrillary tangles from post-mortem brain from cases of Alzheimer's disease and Down's syndrome. Neurofibrillary tangles in brain homogenate were selectively labelled with the fluorescent dye congo red. Using FACS the tangles were separated from other tissue components on the basis of fluorescence and forward-angle light scatter to give a fraction highly enriched in tangles, which were identified by light and crossed polarisation microscopy. Tangles were not observed in a comparison fraction, collected at the same time, of weakly fluorescent particles of similar size to the tangles. Thus FACS provides a non-denaturing method for obtaining preparations of neurofibrillary tangles for purposes of further analysis.

Aged↗
PubMed1995

Sulfonated dyes attenuate the toxic effects of beta-amyloid in a structure-specific fashion.

We recently reported that several sulfate-containing glycosaminoglycans, a class of compounds associated with the beta-amyloid plaques of Alzheimer's disease, attenuate the toxic effects of beta-amyloid fragments beta 25-35 and beta 1-40. The amyloid-binding sulfonated dye Congo Red was shown to have a similar effect. Using two clonal cell lines, we now demonstrate that several sulfonated dyes attenuate beta-amyloid toxicity and that the protective effect appears specific for compounds whose sulfonate groups can interact with the beta-pleated structure of aggregated amyloid. These results suggest that by binding beta-amyloid these compounds may prevent toxic interactions of the peptide with cells.

Amyloid beta-Peptides↗
PubMed2003

Isolation of the MNN9 gene of Yarrowia lipolytica (YlMNN9) and phenotype analysis of a mutant ylmnn9 Delta strain.

In this work we describe the isolation of the Yarrowia lipolytica homologue of Saccharomyces cerevisiae MNN9 gene, which we have named YlMNN9, and the phenotype analysis of a Y. lipolytica strain containing the disrupted YlMNN9 allele. YlMNN9 was cloned using degenerate consensus oligonucleotides to generate specific probes that were in turn used to screen mini-gene libraries. The gene is defined by a 1014 bp ORF predicted to encode a protein 337 amino acids long that shares significant homology with the Mnn9ps of S. cerevisiae, Candida albicans and Hansenula polymorpha, including a putative N-terminal transmembrane domain. Disruption of YlMNN9 leads to phenotypes such as resistance to sodium orthovanadate and sensitivity to hygromycin B, compatible with a glycosylation defect, and hypersensitivity to Calcofluor white, Congo red or zymolyase, characteristic of cell wall defects. Analysis of cell wall proteins present in beta-mercaptoethanol and zymolyase extracts showed significant differences between the parental and the ylmnn9 Delta strain. These results suggest that, as has been the case with the mnn9 strain of S. cerevisiae, the ylmnn9 Delta strain we present in this work, could be used to study the cell wall proteins of Y. lipolytica and how they are organized into the cell wall.

Amino Acid Sequence↗
PubMed2001

The hydrophobin EAS is largely unstructured in solution and functions by forming amyloid-like structures.

BACKGROUND: Fungal hydrophobin proteins have the remarkable ability to self-assemble into polymeric, amphipathic monolayers on the surface of aerial structures such as spores and fruiting bodies. These monolayers are extremely resistant to degradation and as such offer the possibility of a range of biotechnological applications involving the reversal of surface polarity. The molecular details underlying the formation of these monolayers, however, have been elusive. We have studied EAS, the hydrophobin from the ascomycete Neurospora crassa, in an effort to understand the structural aspects of hydrophobin polymerization. RESULTS: We have purified both wild-type and uniformly 15N-labeled EAS from N. crassa conidia, and used a range of physical methods including multidimensional NMR spectroscopy to provide the first high resolution structural information on a member of the hydrophobin family. We have found that EAS is monomeric but mostly unstructured in solution, except for a small region of antiparallel beta sheet that is probably stabilized by four intramolecular disulfide bonds. Polymerised EAS appears to contain substantially higher amounts of beta sheet structure, and shares many properties with amyloid fibers, including a characteristic gold-green birefringence under polarized light in the presence of the dye Congo Red. CONCLUSIONS: EAS joins an increasing number of proteins that undergo a disorder-->order transition in carrying out their normal function. This report is one of the few examples where an amyloid-like state represents the wild-type functional form. Thus the mechanism of amyloid formation, now thought to be a general property of polypeptide chains, has actually been applied in nature to form these remarkable structures.

Amino Acid Sequence↗
PubMed2005

Candida albicans Pmr1p, a secretory pathway P-type Ca2+/Mn2+-ATPase, is required for glycosylation and virulence.

The cell surface of Candida albicans is the immediate point of contact with the host. The outer layer of the cell wall is enriched in highly glycosylated mannoproteins that are implicated in many aspects of the host-fungus interaction. Glycosylation of cell wall proteins is initiated in the endoplasmic reticulum and then elaborated in the Golgi as the protein passes through the secretory pathway. Golgi-bound mannosyltransferases require Mn(2+) as an essential cofactor. In Saccharomyces cerevisiae, the P-type ATPase Pmr1p transports Ca(2+) and Mn(2+) ions into the Golgi. To determine the effect of a gross defect in glycosylation on host-fungus interactions of C. albicans, we disrupted the PMR1 homolog, CaPMR1. This mutation would simultaneously inhibit many Golgi-located, Mn(2+)-dependent mannosyltransferases. The Capmr1Delta null mutant was viable in vitro and had no growth defect even on media containing low Ca(2+)/Mn(2+) ion concentrations. However, cells grown in these media progressively lost viability upon entering stationary phase. Phosphomannan was almost completely absent, and O-mannan was severely truncated in the null mutant. A defect in N-linked outer chain glycosylation was also apparent, demonstrated by the underglycosylation of surface acid phosphatase. Consistent with the glycosylation defect, the null mutant had a weakened cell wall, exemplified by hypersensitivity to Calcofluor white, Congo red, and hygromycin B and constitutive activation of the cell integrity pathway. In a murine model of systemic infection, the null mutant was severely attenuated in virulence. These results demonstrate the importance of glycosylation for cell wall structure and virulence of C. albicans.

Acid Phosphatase↗
PubMed2003

Diseases of protein conformation: what do in vitro experiments tell us about in vivo diseases?

Certain human diseases are associated with proteins that misfold and exhibit decreased solubility under physiological conditions. They result either from mutations that change the amino acid sequence of a protein, or from misfolded wild-type proteins, such as in Parkinson's disease and Alzheimer's disease. One subset--the amyloidoses--cause extracellular deposits that stain with the dye Congo red. Another subset is associated with intracellular deposits with non-Congophilic nuclear or cytoplasmic inclusions. Purified, recombinantly produced versions of some of the proteins that form intracellular aggregates can also display Congophilia, as well as other properties associated with the in vivo amyloidoses when examined under non-physiological conditions in vitro. Some of these purified proteins or protein fragments have never been identified as pathogenic in humans or animals. Despite potentially shared thermodynamic and kinetic processes involving the target molecules, the biology of these two subsets differs significantly.

Amyloid↗
PubMed1998

Induction of type III secretion in Shigella flexneri is associated with differential control of transcription of genes encoding secreted proteins.

Shigella, the etiological agent of human bacillary dysentery, invades the colonic epithelium where it induces an intense inflammatory response. Entry of Shigella into epithelial cells involves a type III secretion machinery, encoded by the mxi and spa operons, and the IpaA-D secreted proteins. In this study, we have identified secreted proteins of 46 and 60 kDa as the products of virA and ipaH9.8, respectively, the latter being a member of the ipaH multigene family. Inactivation of virA did not affect entry into epithelial cells. Using lacZ transcriptional fusions, we found that transcription of virA and four ipaH genes, but not that of the ipaBCDA and mxi operons, was markedly increased during growth in the presence of Congo red and in an ipaD mutant, two conditions in which secretion through the Mxi-Spa machinery is enhanced. Transcription of the virA and ipaH genes was also transiently activated upon entry into epithelial cells. These results suggest that transcription of the virA and ipaH genes is regulated by the type III secretion machinery and that a regulatory cascade differentially controls transcription of genes encoding secreted proteins, some of which, like virA, are not required for entry.

Amino Acid Sequence↗
PubMed2002

Ile-Lys-Val-Ala-Val (IKVAV)-containing laminin alpha1 chain peptides form amyloid-like fibrils.

The Ile-Lys-Val-Ala-Val (IKVAV) sequence derived from laminin-1 promotes cell adhesion, neurite outgrowth, and tumor growth and metastasis. Here, we examined amyloid formation of an IKVAV-containing peptide (LAM-L: AASIKVAVSADR, mouse laminin alpha1 chain 2097-2108). The LAM-L peptide was stained with Congo red and exhibited fibrils in electron microscopy with a characteristic cross-beta X-ray diffraction pattern. Further, infrared spectra of LAM-L suggested a beta-sheet structure. These results indicate that LAM-L forms amyloid-like fibrils. We also examined amyloid-like fibril formation of LAM-L analogs. The neurite outgrowth activity of the LAM-L analogs was closely related to their amyloid-like fibril formation.

Amyloid↗