Analysis of human lymphocyte protein expression. I. Identification of subpopulation markers by two-dimensional polyacrylamide gel electrophoresis

Analysis of porcine peripheral blood mononuclear cells proteome by 2-DE and MS: Analytical and biological variability in the protein expression level and protein identification

In this paper, we present the protein map corresponding to the porcine peripheral blood mononuclear cells (PBMC) to better understand the role of these cells in the pig immune system. To conform the map, the proteins were separated by 2-DE using a 5-8 range pH gradient in IEF and approximately 800 spots were detected. Due to the high level of indeterminate variability associates to the 2-DE, analytical and biological variances were analyzed. The analytical variance was calculated for 50 proteins in three replicate 2-DE gels from the same protein extract whereas the biological variance was determined by comparison of the patterns obtained for the same 50 proteins in different animals. Values of 15.13 and 33.70% were determined for analytical and biological variances, respectively. These average variances will provide a quantified and statistical basis for future proteomic studies directed to evaluate relevant quantitative changes in the biological response. A representative set of the major proteins was subjected to MALDI-TOF analysis and over 75% of the proteins were identified on the basis of their similarity with its human homologue proteins. A large number of cytoskeletal and metabolic proteins were found as well as some proteins related to cell mobility and immunological functions. Finally, other proteins implicated in the cell signaling process, transport or apoptosis were also identified giving a wide overview of the porcine PBMC protein map.

LMP2+ proteasomes are required for the presentation of specific antigens to cytotoxic T lymphocytes

BACKGROUND

Major histocompatibility complex (MHC) class I molecules present short peptides generated by intracellular protein degradation to cytotoxic T lymphocytes (CTL). The multisubunit, non-lysosomal proteinases known as proteasomes have been implicated in the generation of these peptides. Two interferon-gamma (IFN-gamma)-inducible proteasome subunits, LMP2 and LMP7, are encoded within the MHC gene cluster in a region associated with antigen presentation. The incorporation of these LMP subunits into proteasomes may alter their activity so as to favour the generation of peptides able to bind to MHC class I molecules. It has been difficult, however, to demonstrate a specific requirement for LMP2 or LMP7 in the presentation of peptide epitopes to CTL.

RESULTS

We describe a T-cell lymphoma, termed SP3, that displays a novel selective defect in MHC class I-restricted presentation of influenza virus antigens. Of the MHC-encoded genes implicated in the class I pathway, only LMP2 is underexpressed in SP3 cells. Expression of IFN-gamma in transfected SP3 cells simultaneously restores LMP2 expression and antigen presentation to CTL. Expression of antisense-LMP2 mRNA in these IFN-gamma-transfected cells selectively represses antigen recognition and the induction of surface class I MHC expression. Moreover, the expression of this antisense-LMP2 mRNA in L929 fibroblast cells, which constitutively express LMP2 and have no presentation defect, blocks the presentation of the same influenza virus antigens that SP3 cells are defective in presenting.

CONCLUSIONS

Our results show that the LMP2 proteasome subunit can directly influence both MHC class I-restricted antigen presentation and class I surface expression.

Specific polypeptide markers in chronic B cell malignancies detected by two-dimensional gel electrophoresis

Two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) analysis of silver stained polypeptides was used to discriminate the cell protein profiles in chronic B cell malignancies. We identified 5 distinct polypeptides (H1 to H5) present in hairy cell leukemia (HCL) (14 cases) and absent in most chronic lymphocytic leukemia (CLL) and normal B lymphocytes. Two polypeptides, H2 and H5, were absolutely specific of HCL. The 2-D PAGE profiles found in 3 splenic lymphoma with villous lymphocytes (SLVL) and 2 HCL variants (HCL-V) were similar to HCL with a unique additional peptide present in 3/3 SLVL and 1/2 HCL-V. When HCL and SLVL were assessed for the CLL stage-specific 2-D PAGE patterns, HCL was related to stage A/B while SLVL was related to stage C. In conclusion, 2-D PAGE analysis of the molecular pattern of B lymphocytes provides a new means to recognize the leukemic origin of the sample and distinguish HCL from CLL and SLVL.

Biomedical relevance of two-dimensional protein mapping

State-of-the-art and future perspectives are discussed for the application of two-dimensional protein maps to basic medical research and routine clinical chemistry problems. Despite the technical advances that allow effective processing of a large number of samples and the refinement of devices and procedures for image analysis, at present two-dimensional maps are mostly confined to research purposes, i.e. to the inventory of normal constituents of body fluids and tissues on the one hand, and to qualitative-quantitative alterations of some protein spots in a number of instances (genetic, degenerative, infectious or xenobiotic diseases) on the other. It is hoped that in some instances a single primarily affected component will be able to be identified and then specifically tested (for instance by immunological means) as a diagnostic marker, but complex pathological patterns would still require the analysis of a large number of peptides at the resolution level only afforded by two dimensions. Further simplification of the protocols, for example with ready-made gels, and data reduction systems might then allow the application of the technique to be extended to general clinical laboratories.

Biochemical characterization by two-dimensional electrophoresis of lymphocyte antigens involved in cell-to-cell or cell-to-matrix adhesion

We have exemplified three cases of application of two-dimensional (2-D) electrophoresis to the characterization of lymphocyte membrane antigens. We could show that the proteins recognized by two monoclonal antibodies, LAK1 and LAK2, on the surface of large granular cells mediating natural- and lymphokine-activated killing are distinct molecules. LAK1 is expressed without any structural modification, even on the surface of endothelial cells. Another membrane antigen, recognized by the monoclonal antibody FB12, was shown to have the overall structure of the integrins of the very late activation (VLA) class, being composed of an alpha and of a beta subunit. The latter corresponded to the beta 1 type as already characterized for other VLAs, whereas the alpha chain was different from alpha 1 through alpha 6. The 2-D protocol using immobilized pH gradients for the first dimension allows reliable assessment of the identity of individual components because of the reproducibility of the absolute coordinates for spot position.

Quantitation of human leukocyte proteins after silver staining: a study with two-dimensional electrophoresis

The quantitative attributes of human leukocyte proteins detected by silver staining two-dimensional electrophoresis (2-DE) gels were studied by using computer-assisted data analysis. Experiments included (a) analysis of replicate patterns of the same sample, (b) analysis of different dilutions of the same sample, and (c) analysis of samples from different individuals. Over 200 proteins were observed to have coefficients of variation (CV) less than or equal to 15% when data from replicate patterns were analyzed. In contrast, 8 proteins had CV values of less than or equal to 15% when data from different samples were analyzed. The dilution experiment showed that a majority of the proteins detected with some consistency (i.e., observed in at least 80% of the patterns) have a linear relationship between the amount of protein loaded onto a 2-DE gel and the spot volume in the final 2-DE pattern. The slope of the curves and the deviation from linearity were found to be quite protein-specific. These results indicate that optimization of sample purity and minimization of staining protocol variables are required to limit the background quantitative variability between and within 2-DE runs to a level that will allow detection of quantitative changes indicative of biological responses.

Molecular analysis of genetically determined target organ abnormalities in spontaneous autoimmune thyroiditis

We have shown in earlier studies, that the development of spontaneous autoimmune thyroiditis (SAT) in chickens of the Obese strain (OS) depends on the presence of both, two dominant genes coding for an altered immune regulation and one recessive gene responsible for the susceptibility of the target organ for the autoimmune attack. The product(s) of the latter is (are) still not known. The present study was aimed at identifying possible candidates of cellular components of the thyroid gland of OS chicken and its SAT susceptible parental Cornell C-strain (CS) by high resolution 2-dimensional (2D) gel electrophoresis. For this purpose organ cultures of the thyroid, bursa, thymus and liver were established and the synthesized polypeptides were labelled by 35S-methionine. OS and CS organs were compared with those of healthy normal White Leghorn (NWL) controls. The autoradiographs of the 2D-gels obtained from individual samples after various labelling periods were subjected to comparative analysis. We have found both quantitative and qualitative differences of polypeptide spots between OS/CS and NWL organ samples, some of them specific for the thyroid gland. Although one has to be aware that in this multidimensional analytical approach numerous, still elusive pattern differences are revealed, the thyroid specific phenomena will be further scrutinized.

A specific defect in CD3 gamma-chain gene transcription results in loss of T-cell receptor/CD3 expression late after human immunodeficiency virus infection of a CD4+ T-cell line

Sequential effects on cellular protein expression following human immunodeficiency virus (type 1) infection of a CD4+ T-cell line in vitro were investigated. Events in the human interleukin 2-dependent helper T-cell line WE17/10 are similar in several respects to the clinical progression in acquired immunodeficiency syndrome. WE17/10 cell infection is characterized by an extended period during which viral replication occurs without accompanying cytotoxicity and with a maximum 30% decrease in surface CD4. Cellular protein expression generally remains unaffected during this first phase of infection. However, after 2-3 months, a severe defect in the expression of the T-cell receptor/CD3 complex both on the cell surface and inside the cell becomes apparent. Other cell membrane markers, such as CD2 and CD25, remain constant throughout the course of infection; after its initial decrease, CD4 remains at 70% of control values. Lack of surface expression of the TCR/CD3 complex is correlated with a specific defect in transcription of the CD3 gamma-chain gene.