Proteomic analysis of human nasal mucosa: different expression profile in rhino-pathologic states.

BACKGROUND: Rhinitis comprises several diseases with varying causes and different clinical manifestations and pathological features, but treated as a single clinical disorder. As heterogeneous disease, proper differential diagnosis is useful to delineate appropriate therapeutic intervention. Comparative proteomic investigation was aimed to provide information for specific differentially expressed proteins in rhino pathologic state, that could be used for diagnostic purpose and therapeutic monitoring. METHODS: Proteins extracted from nasal mucosa cells of patients with different features of rhinitis and from control subjects, were separated by 2-DE. Proteins differentially expressed were identified by mass spectrometry (MS). RESULTS: Comparative proteomic analyses led to the identification of eighteen proteins differentially expressed in patients with rhinitis, mainly related to cell defense and innate and acquired immunity. From that, at least one protein can be a possible candidate as biomarker of disease.

Gastrokine 1 expression in patients with and without Helicobacter pylori infection.

BACKGROUND: To understand the molecular changes underlying Helicobacter pylori-related gastric diseases is mandatory to prevent gastric cancer. Proteomic technology is providing a rapid expansion of the basic knowledge, particularly in the discovery of new biomarkers involved in the tumourigenesis. AIM: To characterise changes in protein expression level of the gastric mucosa in H. pylori-infected patients. METHODS: The population enrolled comprised 41 dyspeptic patients. Proteins extracted from gastric mucosal specimens were analysed by 2-dimensional electrophoresis, sequenced by MALDI-TOF and identified by Edman's degradation. RESULTS: Twenty-one out of 41 patients had H. pylori infection of whom 17 had anti-CagA IgG antibodies. Several proteins were identified, of which Rho guanosine diphosphatase dissociation inhibitor alpha and heat shock protein 27 increased and glutathione transferase and antrum mucosa protein-18 decreased in H. pylori-positive in respect to H. pylori-negative patients. Interestingly, antrum mucosa protein-18, currently referred as gastrokine-1, showed two isoforms differing in the first N-terminal amino acid residue. Both gastrokine-1 isoforms were observed in the H. pylori-negative group whereas a lower expression or even absence of the gastrokine-1 basic isoform was found in a subgroup (7/21) of H. pylori-positive patients with moderate-severe gastritis. CONCLUSION: Our study demonstrated the presence of gastrokine-1 isoforms of which the basic isoform was reduced in a subset of patients with H. pylori infection.

Analysis of human serum albumin variants by mass spectrometric procedures.

A new strategy for the structural characterisation of human albumin variants has been developed which makes extensive use of mass spectrometric methodologies. The rationale behind the method is to provide a rapid and effective screening of the entire albumin structure. The first step in this strategy consists in the attempt to determine the accurate molecular mass of the intact variant by electrospray mass spectrometry often providing a first indication on the presence of the variant. An HPLC procedure has been developed io isolate all the seven fragments generated by CNBr hydrolysis of HSA in a single chromatographic step. A rapid screening of the entire albumin structure is achieved by the ESMS analysis of the peptide fragments and the protein region(s) carrying the structural abnormality is identified by its anomalous mass value(s). Mass mapping of the corresponding CNBr peptide, either by Fast Atom Bombardment Mass Spectrometry (FABMS) or by Matrix Assisted Laser Desorption Ionisation Mass Spectrometry (MALDIMS), leads to the definition of the site and the nature of the variation. This combined strategy was applied to the structural characterisation of three HSA genetic variants and provided to be an effective procedure for the rapid assessment of their structural modifications showing considerable advantages over the classical approach.

O-glycosylation mimics N-glycosylation in the 16-kDa fragment of bovine pro-opiomelanocortin. The major O-glycan attached to Thr-45 carries SO4-4GalNAc beta 1-4GlcNAc beta 1-, which is the archetypal non-reducing epitope in the N-glycans of pituitary glycohormones.

The NH2-terminal domain of pro-opiomelanocortin, designated as the 16-kDa fragment, is highly conserved throughout the vertebrate family and is likely therefore to have an important functional role. Bovine 16-kDa fragment is a 77- residue glycopeptide, which has been found to be glycosylated at threonine 45 and asparagine 65. Available evidence suggests that glycoforms lacking glycans at the O-linked site are processed in the intermediate pituitary at -Arg49-Lys50- to give the residue 1-49 amino-terminal peptide and a carboxyl-terminal glycopeptide referred to as Lys1 gamma 3-melanotropin. Glycoforms carrying O-glycans remain unprocessed in the intermediate pituitary. Thus O-glycosylation is likely to play an important role in controlling the fate of the NH2-terminal portion of pro-opiomelanocortin, thereby affecting the biological events that are influenced by peptides and glycopeptides derived from this domain. In a recent study (Siciliano, R. A., Morris, H. R., McDowell, R. A., Azadi, P., Rogers, M. E., Bennett, H. P. J., and Dell, A. (1993) Glycobiology 3, 225-239), we sequenced the N-glycans attached to Asn-65 of bovine 16-kDa fragment and demonstrated that the acidic components contain, in addition to neutral antennae, a single SO4-4GalNAc beta 1-4GlcNAc beta 1- antenna, which is characteristic of the pituitary glycohormone N-glycans (Baenziger, J. U., and Green, E. D. (1988) Biochim. Biophys. Acta 947, 287-306). We now report the structural characterization of the O-linked oligosaccharides found in bovine 16-kDa fragment. The major component, which constitutes about 80% of the O-glycan population, is a novel sulfated tetrasaccharide, which carries the same sulfated epitope as the N-glycans. This is the first time that the SO4-4GalNAc beta 1-4GlcNAc beta 1- moiety has been observed in O-glycans, and it raises the interesting possibility that the beta-N-acetylgalactosaminyltransferase responsible for the addition of N-acetylgalactosamine to the pituitary glycohormones (Smith, P. L., and Baenziger, J. U. (1988) Science, 242, 930-933) might be capable of glycosylating both N- and O-linked acceptors.

Assignment of the complete disulphide bridge pattern in the human recombinant follitropin beta-chain.

The chemical assessment of the complete disulphide bridge pattern in the beta-chain of human recombinant follicotropin (betaFSH) was accomplished by integrating classical biochemical methodologies with mass spectrometric procedures. A proteolytic strategy consisting of a double digestion of native betaFSH using the broad-specificity protease subtilisin first, followed by trypsin, was employed. The resulting peptide mixture was directly analysed by FAB-MS, leading to the assignment of the first three disulphide bridges. The remaining S-S bridges were determined by HPLC fractionation of the proteolytic digest followed by ESMS analysis of the individual fractions. The pattern of cysteine couplings in betaFSH was determined as: Cys3-Cys5l, Cys17-Cys66, Cys20-Cys104, Cys28-Cys82, Cys32-Cys84 and Cys87-Cys94, confirming the arrangement inferred from the crystal structure of the homologous betaCG. A subset of the S-S bridge pattern comprising Cys3-Cys51, Cys28-Cys82 and Cys32-Cys84 constitutes a cysteine knot motif similar to that found in the growth factor superfamily.

The Lewis x epitope is a major non-reducing structure in the sulphated N-glycans attached to Asn-65 of bovine pro-opiomelanocortin.

The N-terminal glycopeptide of pro-opiomelanocortin (POMC), designated as the 16K fragment, is highly conserved throughout vertebrates from amphibians to mammals and is likely therefore to have an important functional role. In this paper, we report the first structural characterization of N-glycans attached to asparagine-65 of a 16K glycopeptide. The 16K fragment was isolated from bovine pituitaries and the N-glycans were analysed using fast atom bombardment mass spectrometry together with sugar and linkage analysis. Sulphated-N-acetylgalactosamine-capped antennae, typical of the pituitary glycohormones, were present in the major acidic components. The POMC oligosaccharides are distinct from those of the pituitary glycohormones because the sulphate is exclusively located on the 3-arm of biantennary structures and, in addition, a significant proportion of the molecules carry the Lewis x epitope. It is probable that these differences reflect the absence of a tripeptide motif in POMC which fully conforms to the criteria previously defined for the recognition sequence for the N-acetylgalactosamine transferase that is specific for the pituitary glycohormones [Smith and Baenziger (1992) Proc. Natl. Acad. Sci. USA, 89, 329-333]. It remains to be seen whether the Lewis x epitope is involved in selectin-mediated events, but previous studies suggest that the sulphated moieties are unlikely to play a major role in clearance. The Lewis x epitope is also present in the neutral N-linked oligosaccharides, together with a variety of other antennae including a rarely found fucosylated GalNAc-GlcNAc structure.

Structural characterization and independent folding of a chimeric glycoprotein comprising granulocyte-macrophage colony stimulating factor and erythropoietin sequences.

MEN 11300 is a hybrid glycoprotein of 297 amino acids obtained by fusion of the cDNA encoding GM-CSF with the cDNA encoding EPO followed by transfection of the hybrid gene into CHO cells. The oligonucleotide construct incorporated a spacing sequence between the two individual cDNAs which encodes eight amino acids constituting a linker peptide intended to separate the GM-CSF and EPO moieties. The recombinant MEN 11300 protein was submitted to a detailed structural characterization including the verification of the entire amino acid sequence, the assignment of the disulfide bridges pattern, the identification of the glycosylation sites and the definition of the glycosidic moiety, including site-specificity. Partial processing of the C-terminal Arg residue and the occurrence of N-glycosylation sites at Asn27, Asn155, Asn169, Asn214 were established. Moreover, O-glycosylation at Ser257 and at the N-terminal region was also detected. A large heterogeneity was observed in the N-glycans due to the presence of differently sialylated and fucosylated branched complex type oligosaccharides whereas O-linked glycans were constituted by GalGalNAc chains with a different number of sialic acids. The disulfide bridges pattern was established by direct FABMS analysis of the proteolytic digests or by ESMS analysis of HPLC purified fractions. Pairing of the eight cysteine residues resulted in Cys54-Cys96, Cys88-Cys121, Cys138-Cys292, and Cys160-Cys164. This S-S bridges pattern is identical to that occurring in the individual natural GM-CSF and EPO, thus showing that the two protein moieties in MEN 11300 can independently acquire their native three-dimensional structure.

Intranasal administration of one alpha gliadin can downregulate the immune response to whole gliadin in mice.

The mucosal lesion present in coeliac disease is an immune-mediated injury triggered by gliadin and restricted by a particular assortment of major histocompatibility complex genes. In view of this, an immunomodulatory approach that induces tolerance to this antigen appears to be a possible alternative to a strict gluten-free diet in treating coeliac disease. We have shown that intranasal administration of multiple doses of whole gliadin is required to specifically inhibit T helper 1-like T-cell reactivity in BALB/c mice immunized parenterally with whole gliadin. However, T-cell activation to multiple antigens, as a consequence of the chemical complexity shown by the antigen gliadin, could hamper efforts to identify single component(s) useful for tolerance induction. In this study, gliadin fractions were purified and administered intranasally to study their ability to induce tolerance to whole gliadin in our animal model. We found that the alpha fraction was particularly effective in downregulating both the in vitro gliadin-specific T-cell proliferation and interferon-gamma production to whole gliadin. In particular, a purified alpha-gliadin was able to suppress the immune response to the entire gliadin mixture. These results demonstrate how an immune response to a complex antigen may be controlled by treatment with a purified component and specifically indicate alpha-gliadin to be a good candidate for further identification of short peptides to be used as tolerogens in this model.