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Biomedical subjects

R R Brentani

Publications and source records attributed to R R Brentani.

At least 19 recordsLinked to original sources
PubMed1991

Asn-linked oligosaccharide-dependent interaction between laminin and gp120/140. An alpha 6/beta 1 integrin.

Receptor-mediated recognition and adhesion to laminin, a specific glycoprotein from basement membranes, exert an important role in many biological phenomena. Studying cell surface proteins of B16-F10, a metastatic murine melanoma cell line, we identified a 120-140 kDa glycoprotein (gp120/140) that binds laminin. This glycoprotein was recognized by a polyclonal antibody raised against the human fibronectin receptor beta 1-integrin chain, as well as immunoprecipitated by an anti-alpha 6 chain (monoclonal antibody GoH3), characterizing it as an alpha 6/beta 1-integrin. Its binding to laminin was specific and displayed moderate affinity, as its apparent dissociation constant was 18 nM. To characterize the influence of carbohydrate moieties on the laminin-gp120/140 interaction, metaperiodate oxidation, metabolic inhibition of glycosylation, and enzymatic deglycosylation studies were performed. Our results indicate that gp120/140 Asn-linked oligosaccharides play a part in this interaction. Reciprocally, both metaperiodate and N-glycanase treatment of native laminin reduced its binding to gp120/140, characterizing the latter as a lectin-like molecule. These results point to glycosylation processes as a possible mechanism for variable binding specificity profiles among integrins.

Animals↗
PubMed1991

Nucleotide sequence of a variant protein A of Staphylococcus aureus suggests molecular heterogeneity among strains.

Protein A is a cell wall linked protein of Staphylococcus aureus that binds mammalian IgG. Although protein A displays high size heterogeneity among strains, cloning and sequencing of its gene from two strains had not shown a large difference in size. Here we report a third protein A gene sequence that shows a size variation relative to these two, due to deletions on both one IgG binding domain and a cell wall binding domain (region X). By analysis of the three sequences we were able to delineate a hypothetic model for region X domain evolution and discussed the origin of genetic variability within and without strains.

Amino Acid Sequence↗
PubMed1990

Independent prognostic value of laminin receptor expression in breast cancer survival.

We studied the possible prognostic role of laminin, estrogen (ER), and progesterone (PR) receptors and other pathological factors in relation to the disease-free interval and overall survival of female breast carcinoma patients. Multivariate analyses of clinical and pathological data with respect to the above survival time variables were performed by Cox regression. The statistical dependence of prognosis on ER, PR, and tumor size was based on the discriminant cutoff value that could best distinguish between survival curves. Axillary nodal status was the most significant independent factor in the prediction of both disease-free interval and overall survival of these patients. Use of the information on laminin receptor expression, PR concentration, tumor size, lymphocytic infiltrate, and tumor necrosis improved significantly the prediction of the risk of recurrence. Patients with tumors expressing laminin receptors had 40% less risk of recurrence (P = 0.0209) than those with no expression. On the other hand, four covariates were independently predictive of the risk of death: axillary nodal status, lymphocytic infiltrate, PR and ER concentration. There was a marginally significant (10% level) interaction between tumor size and lymphocytic infiltrate with respect to the prediction of the risk of recurrence. The above sets of variables were used to classify patients into risk groups for the prediction of recurrence and death.

Breast Neoplasms↗
PubMed1990

Are synthetic peptides suitable for the detection of continuous epitopes only?

Present-day methods for the definition of antibody binding sites on antigenic polypeptides show a strong bias toward identification of sequential epitopes. We have employed anti-sequence monoclonal antibodies raised against short synthetic peptides to screen a random-primed cDNA library constructed in an expression vector. Sequence data analysis performed on three clones thus isolated showed that the clones did not cross-hybridize and that the antigenic peptide sequence was found in none of them. Our findings suggest therefore that sequential epitopes may be preferentially identified because of an inherent bias in commonly used epitope mapping protocols which masks available conformational determinants.

Amino Acid Sequence↗
PubMed1990

Identification and characterization of highly conserved antigenic determinants in the laminin molecule.

1. Fragments P1 and E8, the result of two different enzymatic digestions of the laminin molecule, represent interaction sites of laminin with specific cell receptors. By using negative and positive affinity purification of a rabbit antiserum against mouse laminin we have generated antibodies to these two fragments. 2. Antibodies against P1 were able to immunoprecipitate fragment E8 from elastase-digested laminin. By liquid phase competition experiments we demonstrated that the epitopes shared by P1 and E8 are a minor portion of the antigenic determinants of P1. When we checked for the presence of these shared epitopes in the human laminin molecule, they were the major fraction of the interspecies antigenic conservation. 3. A similar approach using polyclonal antibodies against human laminin has confirmed these results. 4. The shared epitopes present in both mouse and human laminin molecules seem to be spatially determined, because antibodies against these sites did not bind to fully denatured laminin. 5. Since human and mouse laminin bind to cell receptors and to other extracellular matrix proteins from both species, we conclude that these antigenic determinants may represent the actual sites for at least some of these interactions.

Animals↗
PubMed1989

Determination of the putative binding site for fibronectin on platelet glycoprotein IIb-IIIa complex through a hydropathic complementarity approach.

We have applied the principle of complementary hydropathy to the prediction of the binding site for fibronectin (FN) and for the alpha-chain of fibrinogen in the platelet receptor complex glycoprotein (GP) IIb-IIIa. Since both ligands bind to it through their respective RGDS (Arg-Gly-Asp-Ser) domains and since both have been cloned, we were able to deduce the amino acid sequence of the binding site from the nucleotide sequence coding for RGDS in both proteins. The deduced peptides were very similar. Antibodies raised against a synthetic peptide WTVPTA (Trp-Thr-Val-Pro-Thr-Ala) deduced from the cloned rat FN RGDS domain block ADP-mediated platelet aggregation; this block can be overcome by additional fibrinogen. In Western blots of whole cell platelet extracts run under reducing conditions, this antibody binds to a 108-kDa band. It also binds to affinity-purified GP IIIa. Furthermore, it reacts strongly with GP IIIa immunoprecipitated by a commercially available anti-GP IIb-IIIa monoclonal antibody. Binding of affinity-purified GP IIb-IIIa complex to fibronectin is inhibited by the 110-kDa FN fragment. Similar inhibitions can be effected by WTVPTA (Trp-Thr-Val-Pro-Thr-Ala) and GAVSTA (Gly-Ala-Val-Ser-Thr-Ala) predicted from the rat and human fibronectin nucleotide sequences, respectively. GAGSTA (Gly-Ala-Gly-Ser-Thr-Ala) and GARSTA (Gly-Ala-Arg-Ser-Thr-Ala) related to the human peptide but with discrepant hydropathies are noninhibitory.

Adult↗
PubMed1988

Characterization of the cellular receptor for fibronectin through a hydropathic complementarity approach.

It has been shown that a significant correlation is seen when the hydropathy scores of amino acids encoded by the coding strand of double-helical DNA are plotted against those of the noncoding strand. Thus, peptides encoded by complementary DNA strands might form amphiphilic structures and bind one another. We have used this approach to study the interaction between fibronectin (FN) and its cell receptor. Taking into consideration the nucleotide sequence from published rat cDNA clones that corresponds to the cell binding site (Arg-Gly-Asp-Ser) in the FN molecule, the deduced amino acid sequence found for the putative receptor binding site was Trp-Thr-Val-Pro-Thr-Ala. This peptide was chemically synthesized and coupled to an AH-Sepharose column. FN bound appreciably to this column and was eluted much more efficiently by a solution of Arg-Gly-Asp-Ser-containing peptide than by a solution of related but inactive Arg-Gly-Glu-Ser-containing peptide. Binding of labeled FN to receptor-rich MG63 human osteosarcoma cells was inhibited by the hexapeptide. The hexapeptide Gly-Ala-Val-Ser-Thr-Ala predicted similarly from the nucleotide sequence of human FN was equally efficient in such inhibition. Antibodies produced against Trp-Thr-Val-Pro-Thr-Ala recognized with equal efficiency Gly-Ala-Val-Ser-Thr-Ala in an ELISA assay. Furthermore, they were able to recognize a single 140-kDa band in whole-cell extracts from Chinese hamster ovary cells, attesting to their specificity. Identification of the recognized protein was provided by showing that this antibody was also able to bind to affinity-purified FN receptor from human osteosarcoma MG63 cells.

Amino Acid Sequence↗
PubMed1988

Biology of metastasis.

1. Metastasis, i.e., dissemination of tumor cells throughout the organism, is the cause of death for most cancer patients. We discuss here the role of the interaction between basement membrane laminin and specific cell receptors in the process. We further show that such interaction is mediated by receptors not only in cancer cells but also in normal granulocytes, in a parasitic protozoan and even in an invasive prokaryote. 2. Metastatic potential has been correlated with the number of receptors/cell and preliminary results with a monoclonal antibody against the S. aureus laminin receptor suggest that the binding site at the receptor level might be conserved. This conclusion is supported by the facts that this monoclonal antibody can recognize the eukaryotic receptor and inhibit laminin binding.

Animals↗
PubMed1988

Evolutionary conservation of laminin-binding proteins.

1. The virulence of pathogens and metastatic capacity of cancer cells seems to correlate with the ability to adhere to cells and/or to basement membrane components. A key feature of this mechanism is the expression of specific receptors for the basement membrane protein laminin. Three different receptors have been already described in cells phylogenetically very distant, such as human white blood cells, Trichomonas vaginalis and Staphylococcus aureus, all recognizing laminin with the same range of affinity. 2. We have shown that laminin, which is also found in the circulation, enhances phagocytosis of S. aureus by macrophages in a species-specific fashion. Also, monoclonal antibodies (MAb) raised against the bacterial receptor inhibit the phagocytic enhancement mediated by laminin and recognize laminin-binding proteins in unicellular parasites and mammalian cells. The same Mab 1.H12 elutes a 52-kDa protein from bacterial extracts and a 67-kDa band from cancer cell extracts. Since the MAb is a monospecific reagent, results with 1.H12 strongly suggest an evolutionary conservation of the binding site of phylogenetically different laminin receptors.

Animals↗
PubMed1979

Picrosirius staining plus polarization microscopy, a specific method for collagen detection in tissue sections.

Sirius Red, a strong anionic dye, stains collagen by reacting, via its sulphonic acid groups, with basic groups present in the collagen molecule. The elongated dye molecules are attached to the collagen fibre in such a way that their long axes are parallel. This parallel relationship between dye and collagen results in an enhanced birefringency. Examination of tissue sections from 15 species of vertebrates suggests that staining with Sirius Red, when combined with enhancement of birefringency, may be considered specific for collagen. An improved and modified method of staining with Sirius Red is presented.

Animals↗