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

Two-dimensional electrophoresis of membrane proteins using immobilized pH gradients

Two-dimensional electrophoresis (2-DE) is a highly resolving technique for arraying proteins by isoelectric point and molecular mass. To date, the resolving ability of 2-DE for protein separation is unsurpassed, thus ensuring its use as the fundamental separation method for proteomics. When immobilized pH gradients (IPGs) are used for isoelectric focusing in the first dimension, excellent reproducibility and high protein load capacity can be achieved. While this has been beneficial for separations of soluble and mildly hydrophobic proteins, separations of membrane proteins and other hydrophobic proteins with IPGs have often been poor. Stimulated by the growing interest in proteomics, recent developments in 2-DE methodology have been aimed at rectifying this situation. Improvements have been made in the area of protein solubilization and sample fractionation, leading to a revamp of traditional approaches for 2-DE of membrane proteins. This review explores these developments.

A functional monoclonal antibody recognizing the human alpha 1-integrin I-domain

Alpha 1 beta 1 heterodimer is a member of the integrin receptor superfamily that has been described to be involved in cell-matrix binding through its interaction with collagens, fibronectin and laminin. The alpha 1 integrin belongs to a subset of I-domain containing integrins that includes alpha M, alpha L, alpha X and alpha 2. In this study we describe an anti-alpha 1 mAb (FB12) that recognizes an epitope located in the human alpha 1 I-domain, since the mAb can bind to human, but not to rat, recombinant I-domain GST fusion protein. FB12 mAb efficiently and specifically inhibits the binding of activated human lymphocytes to laminin, collagen and fibronectin. These data support the notion that the alpha 1 I-domain itself has an important role in receptor-ligand binding. In particular, we show that alpha 1 integrin-dependent lymphocyte adhesion to fibronectin is I-domain mediated, at variance with the RGD-dependent adhesion which seems to be mediated by the beta 1 rather than the alpha 1 integrin chain. Lastly, the overexpression of the alpha 1-integrin by stromal cells and blood vessels of solid tumors may suggest a role for this integrin in tumor biology.

Differential expression of nucleophosmin and stathmin in human T lymphoblastic cell lines, CCRF-CEM and JURKAT analyzed by two-dimensional gel electrophoresis

Two-dimensional gel electrophoresis was used to study the expression of intracellular proteins in adherent cells of human T lymphoblastic cell line, CCRF-CEM. The adherent cells grown in monolayer on a culture plate decreased the amount of proteins of M(r) 37,000 and pI 4.7-4.9, and of 17,000 and pI 5.7. The proteins were identified to be nucleophosmin for the 37,000 protein and stathmin for the 17,000 protein by microsequencing their CNBr fragments. The amount of proteins was increased in CCRF-CEM cells grown in floating mass to a comparable level of JURKAT cells which grew in floating mass throughout the culture. The adherent cells decreased their growth rate as compared with the cells in the floating mass. These results suggest that the adhesion of human T lymphoblastic cells modulates their morphology and proliferation via a concomitant decrease in the amount of nucleophosmin and stathmin.