microheterogeneity
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BACKGROUND AND AIMS: Proteolytic enzymes contribute to the progression of various cancers. We previously reported increased expression of the proline specific peptidases dipeptidyl peptidase-IV (DPP-IV) and its closest paralogue fibroblast activation protein (FAP) in human glioblastomas. Here we analyze the molecular heterogeneity of DPP-IV and FAP in glioblastomas. METHODS: ELISA, isoelectric focusing, 1D and 2D electrophoresis followed by WB or enzyme overlay assay were utilized to analyze DPP-IV and FAP isoforms. Cell fractionation using a Percoll gradient and deglycosylation with PNGase F were performed to analyze the possible basis of DPP-IV and FAP microheterogeneity. RESULTS: Molecular forms of DPP-IV with an estimated molecular weight of 140-160 kDa and a pI predominantly 5.8 were detected in human glioblastoma; in some tumors additional isoforms with a more acidic (3.5-5.5) as well as alkaline (8.1) pI were revealed. Using 2D electrophoresis, two to three molecular forms of FAP with an alkaline (7.0-8.5) pI and an estimated MW of 120-140 kDa were identified in glioblastoma tissues. In glioma cell lines in vitro, several isoforms of both enzymes were expressed, however the alkalic forms present in glioblastoma tissues were not detected. Removal of N-linked oligosaccharides decreased the estimated molecular weight of both enzymes; the overall pattern of molecular forms nevertheless remained unchanged. CONCLUSION: Several isoforms of DPP-IV and FAP are present in glioblastoma tissue. The absence of alkaline isoforms of both enzymes in glioma cell lines however suggests that isoforms from other, most likely stromal, cell types contribute to the overall pattern seen in glioblastoma tissues.
- MeSH
- dipeptidylpeptidasa 4 fyziologie MeSH
- elektroforéza MeSH
- ELISA MeSH
- frakcionace buněk MeSH
- genetická heterogenita MeSH
- glioblastom enzymologie MeSH
- imunohistochemie MeSH
- isoelektrická fokusace MeSH
- lidé MeSH
- membránové proteiny fyziologie MeSH
- mozek enzymologie patologie MeSH
- nádorové buňky kultivované MeSH
- serinové endopeptidasy fyziologie MeSH
- stabilita enzymů MeSH
- želatinasy fyziologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Chronic liver diseases are a serious health problem worldwide. One of the frequently reported glycan alterations in liver disease is aberrant fucosylation, which was suggested as a marker for noninvasive serologic monitoring. We present a case study that compares site specific glycoforms of four proteins including haptoglobin, complement factor H, kininogen-1, and hemopexin isolated from the same patient. Our exoglycosidase-assisted LC-MS/MS analysis confirms the high degree of fucosylation of some of the proteins but shows that microheterogeneity is protein- and site-specific. MSn analysis of permethylated detached glycans confirms the presence of LeY glycoforms on haptoglobin, which cannot be detected in hemopexin or complement factor H; all three proteins carry Lewis and H epitopes. Core fucosylation is detectable in only trace amounts in haptoglobin but with confidence on hemopexin and complement factor H, where core fucosylation of the bi-antennary glycans on select glycopeptides reaches 15-20% intensity. These protein-specific differences in fucosylation, observed in proteins isolated from the same patient source, suggest that factors other than up-regulation of enzymatic activity regulate the microheterogeneity of glycoforms. This has implications for selection of candidate proteins for disease monitoring and suggests that site-specific glycoforms have structural determinants, which could lead to functional consequences for specific subsets of proteins or their domains.
- MeSH
- glykoproteiny krev sekrece MeSH
- glykosylace MeSH
- hepatitida C krev MeSH
- jaterní cirhóza krev virologie MeSH
- játra sekrece MeSH
- konformace sacharidů MeSH
- lidé středního věku MeSH
- lidé MeSH
- molekulární sekvence - údaje MeSH
- posttranslační úpravy proteinů * MeSH
- sacharidové sekvence MeSH
- sekvence aminokyselin MeSH
- Check Tag
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
UNLABELLED: Determining disease-associated changes in protein glycosylation provides a better understanding of pathogenesis. This work focuses on human immunoglobulin A1 (IgA1), where aberrant O-glycosylation plays a key role in the pathogenesis of IgA nephropathy (IgAN). Normal IgA1 hinge region carries 3 to 6 O-glycans consisting of N-acetylgalactosamine (GalNAc) and galactose (Gal); both sugars may be sialylated. In IgAN patients, some O-glycans on a fraction of IgA1 molecules are Gal-deficient. Here we describe a sample preparation protocol with optimized cysteine alkylation of a Gal-deficient polymeric IgA1 myeloma protein prior to in-gel digestion and analysis of the digest by MALDI-TOF/TOF mass spectrometry (MS). Following a novel strategy, IgA1 hinge-region O-glycopeptides were fractionated by reversed-phase liquid chromatography using a microgradient device and identified by MALDI-TOF/TOF tandem MS (MS/MS). The acquired MS/MS spectra were interpreted manually and by means of our own software. This allowed assigning up to six O-glycosylation sites and demonstration, for the first time, of the distribution of isomeric O-glycoforms having the same molecular mass, but a different glycosylation pattern. The most abundant Gal-deficient O-glycoforms were GalNAc4Gal3 and GalNAc5Gal4 with one Gal-deficient site and GalNAc5Gal3 and GalNAc4Gal2 with two Gal-deficient sites. The most frequent Gal-deficient sites were at Ser230 and/or Thr236. BIOLOGICAL SIGNIFICANCE: In this work, we studied the O-glycosylation in the hinge region of human immunoglobulin A1 (IgA1). Aberrant glycosylation of the protein plays a key role in the pathogenesis of IgA nephropathy. Thus identification of the O-glycan composition of IgA1 is important for a deeper understanding of the disease mechanism, biomarker discovery and validation, and implementation and monitoring of disease-specific therapies. We developed a new procedure for elucidating the heterogeneity of IgA1 O-glycosylation. After running a polyacrylamide gel electrophoresis under denaturing conditions, the heavy chain of IgA1 was subjected to in-gel digestion by trypsin. O-glycopeptides were separated from the digest on capillary columns using a microgradient chromatographic device (replacing commonly used liquid chromatographs) and subjected to MALDI-TOF/TOF mass spectrometry (MS) and tandem mass spectrometry (MS/MS) involving post-source decay fragmentation. We show that the complete modification of cysteines by iodoacetamide prior to electrophoresis is critical for successful MS/MS analyses on the way to deciphering the microheterogeneity of O-glycosylation in IgA1. Similarly, the removal of the excess of the reagent is equally important. The acquired MS/MS allowed assigning up to six O-glycosylation sites and identification of isomeric O-glycoforms. We show that our simplified approach is efficient and has a high potential to provide a method for the rapid assessment of IgA1 heterogeneity that is a less expensive and yet corroborating alternative to LC-(high-resolution)-MS protocols. The novelty and biological significance reside in the demonstration, for the first time, of the distribution of the most abundant isoforms of HR O-glycopeptides of IgA1. As another new feature, we introduce a software solution for the interpretation of MS/MS data of O-glycopeptide isoforms, which provides the possibility of fast and easier data processing. This article is part of a Special Issue entitled: Posttranslational Protein modifications in biology and Medicine.
- MeSH
- alkylace MeSH
- cystein krev chemie MeSH
- glykosylace MeSH
- IgA nefropatie krev MeSH
- imunoglobulin A krev chemie MeSH
- lidé MeSH
- odběr biologického vzorku * MeSH
- spektrometrie hmotnostní - ionizace laserem za účasti matrice metody MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
BACKGROUND: Participation of protein polymorphism is often considered in the pathogenesis of various diseases. Aberrant protein glycosylation has been recognized to play major roles in human disorders, including neurodegenerative diseases. OBJECTIVE: The aim of the study was to examine possible involvement of protein genetic variants and degree of glycosylation of some serum glycoproteins in the manifestation of neurodegenerative disorders in a Czech population sample. METHODS: Apolipoprotein (Apo) E and three main serum markers of glycosylation defects (transferrin, Tf, alpha1-antitrypsin, aAT and ApoCIII) in patients with Alzheimer's dementia (AD), Parkinson's disease (PD) and vascular dementia (n=62, 139 and 44, respectively) were analyzed by isoelectric focusing. Children with serious neurological symptoms (n=55) and three age-matched control groups (n=45, 45 and 42) were examined for comparison. RESULTS: Of the supposedly pathognomonic protein variants Tf C2, aAT ZM and ApoE e4 only the latter was detected with higher frequency in AD patients; significant synergy of the C2/e4 allelic combination was not confirmed. The most prominent finding among PD adults was an increased appearance of Tf C2 allele and significant mean hypoglycosylation of ApoCIII, besides a C2/e4 positive correlation in PD seniors. Laboratory signs of Tf hypoglycosylation and a pattern of Tf/ApoCIII hyperglycosylation have been occasionally found.
- MeSH
- alely MeSH
- alfa-1-antitrypsin krev genetika MeSH
- Alzheimerova nemoc krev genetika MeSH
- apolipoprotein C-III krev genetika MeSH
- apolipoproteiny E krev genetika MeSH
- dítě MeSH
- dospělí MeSH
- frekvence genu MeSH
- glykoproteiny krev genetika MeSH
- glykosylace MeSH
- isoelektrická fokusace MeSH
- lidé středního věku MeSH
- lidé MeSH
- neurodegenerativní nemoci krev epidemiologie genetika MeSH
- Parkinsonova nemoc krev genetika MeSH
- senioři MeSH
- sexuální faktory MeSH
- stárnutí fyziologie MeSH
- transferin genetika metabolismus MeSH
- vaskulární demence krev genetika MeSH
- věkové faktory MeSH
- Check Tag
- dítě MeSH
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- senioři MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Česká republika MeSH
The plasma membrane of various mammalian cell types is heterogeneous in structure and may contain microdomains, which can impose constraints on the lateral diffusion of its constituents. Fluorescence correlation spectroscopy (FCS) can be used to investigate the dynamic properties of the plasma membrane of living cells. Very recently, Wawrezinieck et al. (Wawrezinieck, L., H. Rigneault, D. Marguet, and P. F. Lenne. 2005. Biophys. J. 89:4029-4042) described a method to probe the nature of the lateral microheterogeneities of the membrane by varying the beam size in the FCS instrument. The dependence of the width of the autocorrelation function at half-maximum, i.e., the diffusion time, on the transverse area of the confocal volume gives information on the nature of the imposed confinement. We describe an alternative approach that yields essentially the same information, and can readily be applied on commercial FCS instruments by measuring the diffusion time and the particle number at various relative positions of the cell membrane with respect to the waist of the laser beam, i.e., by performing a Z-scan.
