BackgroundHuntington's disease (HD) is a fatal inherited neurodegenerative disease, caused by a

We have used mRNA differential display PCR to search for genes induced in activated T cells and have found the LGALS1 (lectin, galactoside-binding, soluble) gene to be strongly up-regulated in effector T cells. The protein coded by the LGALS1 gene is a g-galactoside-binding protein (g GBP), which is released by cells as a monomeric negative growth factor but which can also associate into homodimers (galectin-1) with lectin properties. Northern blot analysis revealed that ex vivo isolated CD8 + effector T cells induced by a viral infection expressed high amounts of LGALS1 mRNA, whereas LGALS1 expression was almost absent in resting CD8 + T cells. LGALS1 expression could be induced in CD4 + and CD8 + T cells upon activation with the cognate peptide antigen and high levels of LGALS1 expression were found in concanavalin A-activated T cells but not in lipopolysaccharide-activated B cells. Gel filtration and Western blot analysis revealed that only monomeric g GBP was released by activated CD8 + T cells and in vitro experiments further showed that recombinant g GBP was able to inhibit antigen-induced proliferation of naive and antigen-experienced CD8 + T cells. Thus, these data indicate a role of g GBP as an autocrine negative growth factor for CD8 + T cells.

Human meprin (N-benzoyl-l-tyrosyl-p-aminobenzoic acid hydrolase, EC 3.4.24.18), an astacin-type metalloprotease, is expressed by intestinal epithelial cells as a dimeric protein complex of a and b subunits. In transfected cells, intracellular proteolytic removal of the membrane anchor from the a subunit results in its secretion, while the b subunit and a/b heterodimers are retained at the cell membrane. We investigated the consequence of differential intracellular processing of a and b subunits in the human small and large intestine using subunit-specific immunohistochemistry, in situ hybridization and biosynthetic studies in organ culture. In the ileum, both subunits localize to the brush-border membrane of villus enterocytes. In contrast, the b subunit is not expressed in the colon, which leads to the secretion of the a subunit. We conclude that differential expression of meprin a and b subunits is a unique means of targeting the proteolytic activity of the a subunit either to the brush-border membrane in the ileum or to the lumen in the colon, suggesting dual functions of cell-associated and luminal meprin. Meprin a and b subunits are also coexpressed in distinct lamina propria leukocytes, suggesting an additional role for this protease in leukocyte function in the intestinal mucosa.Keywords: astacin family; meprin; intestine; leukocytes; protein processing.Meprins, membrane-bound Zn-metalloendopeptidases of the astacin family [1,2], were first identified in brush-border preparations of kidney and intestinal epithelial cells in rodents and humans [3±5]. They are dimeric and tetrameric protein complexes composed of varying ratios of a and b subunits (meprin a, meprin b) [6±8]. The corresponding mRNAs are transcribed from two independent gene loci [9].Human meprin (endopeptidase 3.4.24.18, N-benzoyl-l-tyrosyl-p-aminobenzoic acid hydrolase) in analogy with the rodent enzymes is a multidomain protein that includes an N-terminal protease domain with the astacin consensus sequence (Fig. 1) [10±15]. 17] (see Fig. 1 for definitions) are thought to mediate protein±protein interactions. The MAM domain of the rodent enzyme has been shown to mediate dimerization of both subunits via disulfide bonds [18,19]. An epidermal-growth-factor-like domain is followed by the transmembrane region and a C-terminal cytosolic tail.In heterologous expression studies of wild-type and mutant subunits, the biosynthesis of a and b subunits has been found to be different [11,20±24]. In mammalian cells transfected with single subunits, the b subunit accumulates at the cell surface. On the other hand, an a-specific`inserted-domain' and the transmembrane region mediate retention and proteolytic processing of the a subunit in the endoplasmic reticulum. This processing step is essential for subsequent intracellular transport. Having lost its membrane anchor, the a subunit is released into the extracellular medium. However, in cells cotransfected with both subunits, the a subunit is retained at the cell surface via association with the transmembra...

We have exmied the expression of the recombination activating gene RAG-I by in situ hybridization to thymi from mice bearing transgenes for the T-cell receptor (TCR) a chain, TCR 13 chain, or both TCR a and 13 chains. RAG-i transcription was found in the thymic cortex of transgenic mice carrying a sngle TCR a-or TCR 1-chain transgene, comparable to normal mice. However, RAG-i a tion was strikingly reduced in the thymic cortex from transgenic mice carrying both TCR a-and 1-chain genes and expressing major histocompatibility complex (MHC) class I (H-2b) molecules necessary for positive selection of the transgenic TCR. In contrast, thymi of transgenic mice also carrying both TCR a-and 1-chain genes but expre MHC molecules (H-2d) that did not positively select the tagenic TCR displayed high levels of RAG-I transcription. The low thymic RAG-I expression coincided with high transgenic TCR a-chain surface expression and with inhibition of endogenous TCR a-chain rearrangement. Our rindings suggest that binding of the TCR to self MHC molecules during positive selection down-regulates RAG-i transcription in cortical thymocytes and thereby prevents further TCR a-chain rearrangements.

Mouse ´Macrophage ´CD163 ´Scavenger receptor ´DexamethasoneCD163 is a glycoprotein belonging to the scavenger receptor cysteine-rich superfamily (SRCR) expressed on cells of the monocyte/macrophage lineage. The protein is induced by the anti-inflammatory mediator, dexamethasone, and is proposed to be associated with the downregulatory phase of inflammatory reactions. However, the biological properties of the protein are poorly characterized. In the present report, the mouse CD163 cDNA (mCD163) was cloned from dexamethasone-treated peritoneal macrophages using a reverse transcription-PCR-based screening method. The predicted polypeptide sequence of the type I transmembrane glycoprotein consists of a 38-amino acid signal peptide, nine SRCR domains, one transmembrane domain, and a short cytoplasmic tail. Sequence variance analysis of all mouse and human CD163-SRCR D.J. Schaer ( ) ) ´P. Linnscheid ´H. Staege ´G. Schoedon