Jozef Van Damme

The CC chemokine CCL20 and its receptor CCR6.

CCL20, alternatively named liver and activation-regulated chemokine (LARC), macrophage inflammatory protein-3alpha (MIP-3alpha) or Exodus-1, is the only chemokine known to interact with CC chemokine receptor 6 (CCR6), a property shared with the antimicrobial beta-defensins. The ligand-receptor pair CCL20-CCR6 is responsible for the chemoattraction of immature dendritic cells (DC), effector/memory T-cells and B-cells and plays a role at skin and mucosal surfaces under homeostatic and inflammatory conditions, as well as in pathology, including cancer and rheumatoid arthritis. In this review, the discovery, the gene and protein structure, the in vitro biological activities, the cell and inducer specific expression and the tissue distribution of CCL20 and CCR6 are discussed.

Exploring proteomes and analyzing protein processing by mass spectrometric identification of sorted N-terminal peptides.

Current non-gel techniques for analyzing proteomes rely heavily on mass spectrometric analysis of enzymatically digested protein mixtures. Prior to analysis, a highly complex peptide mixture is either separated on a multidimensional chromatographic system or it is first reduced in complexity by isolating sets of representative peptides. Recently, we developed a peptide isolation procedure based on diagonal electrophoresis and diagonal chromatography. We call it combined fractional diagonal chromatography (COFRADIC). In previous experiments, we used COFRADIC to identify more than 800 Escherichia coli proteins by tandem mass spectrometric (MS/MS) analysis of isolated methionine-containing peptides. Here, we describe a diagonal method to isolate N-terminal peptides. This reduces the complexity of the peptide sample, because each protein has one N terminus and is thus represented by only one peptide. In this new procedure, free amino groups in proteins are first blocked by acetylation and then digested with trypsin. After reverse-phase (RP) chromatographic fractionation of the generated peptide mixture, internal peptides are blocked using 2,4,6-trinitrobenzenesulfonic acid (TNBS); they display a strong hydrophobic shift and therefore segregate from the unaltered N-terminal peptides during a second identical separation step. N-terminal peptides can thereby be specifically collected for further liquid chromatography (LC)-MS/MS analysis. Omitting the acetylation step results in the isolation of non-lysine-containing N-terminal peptides from in vivo blocked proteins.

The role of CXC chemokines and their receptors in cancer

Chemokines, or chemotactic cytokines, and their receptors have been discovered as essential and selective mediators in leukocyte migration to inflammatory sites and to secondary lymphoid organs. Besides their functions in the immune system, they also play a critical role in tumor initiation, promotion and progression. There are four subgroups of chemokines: CXC, CC, CX(3)C, and C chemokine ligands. The CXC or alpha subgroup is further subdivided in the ELR(+) and ELR(-) chemokines. Members that contain the ELR motif bind to CXC chemokine receptor 2 (CXCR2) and are angiogenic. In contrast, most of the CXC chemokines without ELR motif bind to CXCR3 and are angiostatic. An exception is the angiogenic ELR(-)CXC chemokine stromal cell-derived factor-1 (CXCL12/SDF-1), which binds to CXCR4 and CXCR7 and is implicated in tumor metastasis. This review is focusing on the role of CXC chemokines and their receptors in tumorigenesis, including angiogenesis, attraction of leukocytes to tumor sites and induction of tumor cell migration and homing in metastatic sites. Finally, their therapeutic use in cancer treatment is discussed.

Gelatinase B: a tuner and amplifier of immune functions

Gelatinase B (matrix metalloproteinase-9) is a secreted multidomain enzyme that is important for the remodeling of the extracellular matrix and the migration of normal and tumor cells. It cleaves denatured collagens (gelatins) and type IV collagen, which is present in basement membranes. In the immune system, this cleavage helps lymphocytes and other leukocytes to enter and leave the blood and lymph circulations. Gelatinase B also cleaves myelin basic protein and type II gelatins, and this clipping leads to remnant epitopes that generate autoimmunity, the so-called REGA model of autoimmunity. Recently, gelatinase B has been found to process cytokines and chemokines, resulting in skewed immune functions. Therefore, gelatinase B, often considered as a pure effector molecule, acts as a switch and catalyst in both innate and specific immunity, and constitutes a prototypic example of the regulation of immune functions by proteolysis.

Production of Interleukin-6 by Folliculo-Stellate Cells of the Anterior Pituitary Gland in a Histiotypic Cell Aggregate Culture System

Reaggregate cell cultures of mouse or rat anterior pituitary were found to produce interleukin-6 (IL-6), a cytokine known for its multiple actions in the immune system. Studies on aggregates prepared from differentially enriched pituitary cell populations revealed the presence of folliculo-stellate (FS) cells to be essential for IL-6 production. Aggregates that contained only hormone-secreting, but no FS cells, failed to produce IL-6. Furthermore, the yield of IL-6 increased with increasing proportions of FS cells present in the aggregates. It is suggested that IL-6 participates in the local regulation of the secretory function of the hypophysis and may constitute a link between events in the immune system and those in the endocrine system.

Involvement of Sialoadhesin in Entry of Porcine Reproductive and Respiratory Syndrome Virus into Porcine Alveolar Macrophages

ABSTRACT Porcine reproductive and respiratory syndrome virus (PRRSV) shows a very restricted tropism for cells of the monocyte/macrophage lineage. It enters cells via receptor-mediated endocytosis. A monoclonal antibody (MAb) that is able to block PRRSV infection of porcine alveolar macrophages (PAM) and that recognizes a 210-kDa protein (p210) was described previously (MAb41D3) (X. Duan, H. Nauwynck, H. Favoreel, and M. Pensaert, J. Virol. 72:4520-4523, 1998). In the present study, the p210 protein was purified from PAM by immunoaffinity using MAb41D3 and was subjected to internal peptide sequencing after tryptic digestion. Amino acid sequence identities ranging from 56 to 91% with mouse sialoadhesin, a macrophage-restricted receptor, were obtained with four p210 peptides. Using these peptide data, the full p210 cDNA sequence (5,193 bp) was subsequently determined. It shared 69 and 78% amino acid identity, respectively, with mouse and human sialoadhesins. Swine (PK-15) cells resistant to viral entry were transfected with the cloned p210 cDNA and inoculated with European or American PRRSV strains. Internalized virus particles were detected only in PK-15 cells expressing the recombinant sialoadhesin, demonstrating that this glycoprotein mediated uptake of both types of strains. However, nucleocapsid disintegration, like that observed in infected Marc-145 cells as a result of virus uncoating after fusion of the virus with the endocytic vesicle membrane, was not observed, suggesting a block in the fusion process. The ability of porcine sialoadhesin to mediate endocytosis was demonstrated by specific internalization of MAb41D3 into PAM. Altogether, these results show that sialoadhesin is involved in the entry process of PRRSV in PAM.

The MCP/eotaxin subfamily of CC chemokines

Migration of leukocytes from the bone marrow to the circulation, the primary lymphoid organs and inflammatory sites is directed by chemokines and specific receptor interactions. Besides the role of this group of low molecular weight cytokines in leukocyte attraction and activation, anti-HIV and hematopoietic activities were also attributed to chemokines. On the basis of the number and arrangement of the conserved cysteines, chemokines are subdivided in two multi-member families, namely the CXC and CC chemokines, whereas fractalkine (CX3C) and lymphotactin (C) are unique relatives. The CC chemokines possess four cysteines of which the first two are adjacent. Functionally, they form a rather heterogeneous family. Here, the focus is on the monocyte chemotactic proteins and eotaxin which, on a structural basis, can be considered as a CC chemokine subfamily. Not only the protein sequences, but also the gene structures, chromosomal location, biological activities and receptor usage exhibit considerable similarities. The review is complemented with a comparison of the biological functions of the MCP/eotaxin-subfamily in physiology and pathology.

Cytokine-regulated proteases in autoimmune diseases

Progress in the research of cellular and humoral immunity has been exponential during the past decade, although it is still insufficient to explain fully the pathogenesis of autoimmunity. Over the same period, an understanding of the cytokine network and the extracellular proteolysis cascades has grown considerably. Here, Ghislain Opdenakker and Jo Van Damme propose the REGA-model (Remnant Epitope Generates Autoimmunity) to explain the generation of autoantigens and their interaction with the T-cell receptor complex. Although this model may be applied to all known autoimmune diseases, multiple sclerosis has been used as the specific example here.

HUMAN MONOCYTE CHEMOTACTIC PROTEINS-2 AND -3 : STRUCTURAL AND FUNCTIONAL COMPARISON WITH MCP-1

Structurally, the monocyte chemotactic proteins MCP‐1, ‐2, and ‐3 form a subfamily of the C‐C or β‐chemokines. Like other chemokines, MCPs are produced by a variety of cells on stimulation with cytokines (interleukin‐1, tumor necrosis factor‐α, interferon‐γ), bacterial and viral products or mitogens. MCP‐1 levels are enhanced during infection and inflammation, which are characterized by leukocyte infiltration. In vitro, MCPs are chemotactic for a distinct spectrum of target cells and show different specific biological activities depending on the cell type and the chemokine tested. MCP‐3 has the broadest range in that it activates monocytes, dendritic cells, lymphocytes, natural killer cells, eosinophils, basophils, and neutrophils. The most sensitive cells to all three MCPs are lymphocytes and monocytes. MCP‐1 is a potent basophil activator but does not attract eosinophils, whereas, at higher concentrations, MCP‐2 also stimulates both eosinophils and basophils. The signal transduction of MCPs on monocytes involves at least two G protein‐linked C‐C chemokine receptors: C‐C CKR‐1 binds MCP‐3 and C‐C CKR‐2 binds MCP‐1 and MCP‐3 but not MCP‐2. Receptor binding leads to enhanced [Ca2+]i for all chemokines except for MCP‐2.

Caspase-specific and nonspecific in vivo protein processing during Fas-induced apoptosis

We generated a comprehensive picture of protease substrates in anti-Fas–treated apoptotic human Jurkat T lymphocytes. We used combined fractional diagonal chromatography (COFRADIC) sorting of protein amino-terminal peptides coupled to oxygen-16 or oxygen-18 differential labeling. We identified protease substrates and located the exact cleavage sites within processed proteins. Our analysis yielded 1,834 protein identifications and located 93 cleavage sites in 71 proteins. Indirect evidence of apoptosis-specific cleavage within 21 additional proteins increased the total number of processed proteins to 92. Most cleavages were at caspase consensus sites; however, other cleavage specificities suggest activation of other proteases. We validated several new processing events by immunodetection and by an in vitro assay using recombinant caspases and synthetic peptides containing presumed cleavage sites. The spliceosome complex appeared a preferred target, as 14 of its members were processed. Differential isotopic labeling further revealed specific release of nucleosomal components from apoptotic nuclei.