CD147 monoclonal antibodies induce homotypic cell aggregation of monocytic cell line U937 via LFA-1/ICAM-1 pathway. (1/318)

CD147 is a 50 000-60 000 MW glycoprotein of the immunoglobulin superfamily broadly expressed on haemopoietic cell lines and peripheral blood cells. In the present study, six monoclonal antibodies (mAbs) directed against the CD147 protein were generated. The antigen defined by the generated CD147 mAbs is widely expressed on haemopoietic cell lines, peripheral blood cells and is a lymphocyte activation-associated cell surface molecule. The generated CD147 mAbs precipitated a broad protein band from U937 cells of 45 000-65 000 MW under reducing conditions. Functional analysis indicated that the CD147 mAbs markedly induced homotypic cell aggregation of U937 cells, but not K562 cells. The CD147 mAb-induced cell aggregation was inhibited by leucocyte function-antigen-1 (LFA-1) and intercellular adhesion molecule-1 (ICAM-1) mAbs. However, the expression of LFA-1 and ICAM-1 molecules on U937 was not altered by CD147 mAb treatment. The U937 cell aggregation induced by CD147 mAb was also inhibited by ethylenediamine tetra-acetic acid (EDTA), sodium azide and when incubated at 4 degrees. We therefore propose that the binding of CD147 mAb to CD147 molecule, which mimics the natural ligand binding, may generate intracellular signals that activate LFA-1/ICAM-1 intercellular adhesion pathway.  (+info)

T cell activation-associated epitopes of CD147 in regulation of the T cell response, and their definition by antibody affinity and antigen density. (2/318)

CD147 is a broadly expressed cell surface glycoprotein of the Ig superfamily whose expression is up-regulated upon T cell activation. In order to elucidate a possible role of CD147 in T cell biology, we established 15 specific mAb. Seven distinct epitopes were defined by the mAb panel. Most of the mAb bound only to phytohemagglutinin (PHA)-activated but not resting T cells. We demonstrate that this was not because of true expression of activation-dependent neoepitopes but rather due to bivalent binding of the relatively low-affinity mAb (affinity constant KA values between 2.25 x 10(8) and 7 x 10(9) M-1) to the more densely expressed and/or more clustered CD147 molecules on the activated T cells. In contrast, the mAb with higher affinity (KA > 7 x 10(9) M-1) could stably bind in a monovalent fashion even to the relatively low dense CD147 molecules on resting T cells. This model might more generally explain the nature of 'activation epitopes' described previously in other leukocyte surface molecules. Finally, we provide evidence that induction of ordered dimerization of CD147 by a mAb directed to a unique epitope results in strong inhibition of CD3-mediated T cell activation.  (+info)

Differential expression of novel abundant and highly regionalized mRNAs of the canine epididymis. (3/318)

Three novel gene products have been cloned by differential screening of a dog epididymis cDNA library as part of a global appraisal of specific gene expression in the epididymis. The predicted proteins were provisionally named CE8-CE10 (for canine epididymal gene products 8-10). Northern blot analyses and in situ transcript hybridization confirmed that the cDNAs were all derived from tissue-specific, moderately to highly abundant mRNAs of the epididymal epithelium, showing a distinct regionalized expression pattern within the epididymal duct. Their sequences predict (i) a novel 19 kDa member of the Ly-6-domain protein superfamily (CE8), (ii) an approximately 30 kDa protein with multiple membrane-spanning regions (CE9), and (iii) a novel approximately 13 kDa single whey acidic protein domain protein (CE10). Closely related, cross-hybridizing gene products were abundant in the epididymis of stallions and bulls, but not in rodents or men. Changes in mRNA frequency were observed that specifically correlated with a cryptorchid situation and with the age of the dogs. Gene products restricted to the caput epididymidis were affected by both conditions, while those with a wider regional distribution were not.  (+info)

Increased expression of extracellular matrix metalloproteinase inducer in rheumatoid synovium. (4/318)

OBJECTIVE: To investigate the expression of extracellular matrix metalloproteinase inducer (EMMPRIN) in the synovial membrane of patients with rheumatoid arthritis (RA) and osteoarthritis (OA). METHODS: Mouse monoclonal antibody against human EMMPRIN was applied according to an avidin-biotin-peroxidase complex method to reveal EMMPRIN expression. Western blotting and reverse transcriptase-polymerase chain reaction (RT-PCR) were performed to check for the presence of EMMPRIN protein and messenger RNA (mRNA). RESULTS: EMMPRIN immunoreactivity was more intense in RA than in OA synovial membrane (P < 0.01). EMMPRIN staining was more widespread in RA than in OA, especially in association with macrophage infiltrates. RT-PCR of synovial membrane samples disclosed the presence of EMMPRIN mRNA. Nucleotide sequencing of the PCR amplification products confirmed the identity of the amplified bands. Immunoblot analysis revealed 55-kd glycosylated EMMPRIN bands, which were particularly prominent in RA samples. CONCLUSION: The expression of EMMPRIN is upregulated in the rheumatoid synovial membrane. EMMPRIN can induce local production of at least MMPs 1, 2, and 3, and can thereby play a role in joint destruction in RA.  (+info)

EMMPRIN (CD147), an inducer of matrix metalloproteinase synthesis, also binds interstitial collagenase to the tumor cell surface. (5/318)

Extracellular matrix metalloproteinase inducer (EMMPRIN), also known as basigin or CD147, is a glycoprotein that is enriched on the surface of tumor cells and stimulates production of several matrix metalloproteinases by adjacent stromal cells. In this study, we have found that EMMPRIN not only stimulates the production of interstitial collagenase (MMP-1) but also forms a complex with MMP-1 at the tumor cell surface. Complex formation was demonstrated by phage display, affinity chromatography, and immunocytochemistry. Presentation of MMP-1 complexed to EMMPRIN at the tumor cell surface may be important in modifying the tumor cell pericellular matrix to promote invasion.  (+info)

The expression and cellular localization of the sperm flagellar protein MC31/CE9 in the rat testis: possible posttranscriptional regulation during rat spermiogenesis. (6/318)

We isolated the MC31 cDNA clone coding the antigen specifically recognized by the monoclonal antibody mMC31, and found that MC31 was identical to rat CE9. Therefore, this molecule is called MC31/CE9. MC31/CE9, a member of the immunoglobulin superfamily molecules, was localized on the rat sperm flagellar plasma membrane. We analyzed the expression and cellular localization of MC31/CE9 mRNA and protein in the adult rat testis by use of Northern hybridization, in situ hybridization, and immunohistochemical analyses. In the course of spermatogenesis, MC31/CE9 mRNA first appeared in type B spermatogonia. The mRNA signal intensity increased progressively to pachytene spermatocytes and remained constantly at a considerable level throughout the subsequent phases of spermatocytes and round spermatids, and then decreased gradually from step-11 spermatids to disappear in step-15 spermatids. On the other hand, MC31/CE9 protein expression showed a bimodal pattern. Immunohistochemical analysis for the MC31/CE9 protein revealed its most intense immunoreactivity on the flagella of step-8 to step-19 elongated spermatids. The cytoplasmic immunoreactivity of the MC31/CE9 protein also appeared in preleptotene to early pachytene spermatocytes and elongated spermatids, with particularly intense immunoreactivity in the Golgi complexes of zygotene and early pachytene spermatocytes (stage XIII to III) as well as step-8 to step-13 spermatids. Between these two phases, the MC31/CE9 protein proved undetectable in the cytoplasm of any spermatogenic cells. Sertoli cells and Leydig cells were devoid of MC31/CE9 mRNA and its protein. Therefore, the production of MC31/CE9 is thought to be posttranscriptionally regulated during spermiogenesis.  (+info)

Expression patterns of chondrocyte genes cloned by differential display in tibial dyschondroplasia. (7/318)

Tibial dyschondroplasia (TD) appears to involve a failure of the growth plate chondrocytes within growing long bones to differentiate fully to the hypertrophic stage, resulting in a mass of prehypertrophic chondrocytes which form the avascular TD lesion. Many biochemical and molecular markers of chondrocyte hypertrophy are absent from the lesion, or show reduced expression, but the cause of the disorder remains to be identified. As differentiation to the hypertrophic state is impaired in TD, we hypothesised that chondrocyte genes that are differentially expressed in the growth plate should show altered expression in TD. Using differential display, four genes, B-cadherin, EF2, HT7 and Ex-FABP were cloned from chondrocytes stimulated to differentiate to the hypertrophic stage in vitro, and their differential expression confirmed in vivo. Using semi-quantitative RT-PCR, the expression patterns of these genes were compared in chondrocytes from normal and TD growth plates. Surprisingly, none of these genes showed the pattern of expression that might be expected in TD lesion chondrocytes, and two of them, B-cadherin and Ex-FABP, were upregulated in the lesion. This indicates that the TD phenotype does not merely reflect the absence of hypertrophic marker genes, but may be influenced by more complex developmental mechanisms/defects than previously thought.  (+info)

Homo-oligomer formation by basigin, an immunoglobulin superfamily member, via its N-terminal immunoglobulin domain. (8/318)

Basigin (Bsg) is a highly glycosylated transmembrane protein with two immunoglobulin (Ig)-like domains. A number of studies, including gene targeting, have demonstrated that Bsg plays pivotal roles in spermatogenesis, implantation, neural network formation and tumor progression. In the present study, to understand the mechanism of action of Bsg, we determined its expression status on the plasma membrane. Cotransfection of Bsg expression vectors with two different tags clarified that Bsg forms homo-oligomers in a cis-dependent manner on the plasma membrane. If the disulfide bond of the more N-terminally located Ig-like domain was destroyed by mutations, Bsg could not form oligomers. In contrast, the mutations of the C-terminal Ig-like domain or N-glycosylation sites did not affect the association. The association of mouse and human Bsgs, which exhibit high homology in the transmembrane and intracellular domains but low homology in the extracellular domain, was very weak as compared with that within the same species, suggesting the importance of the extracellular domain in the association. If the extracellular domain of the human Ret protein was replaced with the N-terminal Ig-like domain of Bsg, the resulting chimera protein was associated with intact wild-type Bsg, but not if the C-terminal Ig-like domain, instead of the N-terminal one, of Bsg was used. No oligomer formation took place between the intact wild-type Ret and Bsg proteins. In conclusion, these data indicate that the N-terminal Ig-like domain is necessary and sufficient for oligomer formation by Bsg on the plasma membrane.  (+info)

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