Biomedical subjects

J P Faure

Publications and source records attributed to J P Faure.

At least 19 recordsLinked to original sources

PubMed1996

The mineralocorticoid hormone receptor and action in the eye.

Immunoblotting with a polyclonal antibody, directed against the mineralocorticoid receptor protein purified from rat kidney in presence of the receptor-specific ligand RU 26752, labeled a single 98-102 kDa band in soluble extracts from bovine retina and from cultured bovine retinal pigment epithelial cells, identical to the receptor in several other tissues from the rat. The antibody also immunoprecipitated the receptor-3H-RU 26752 complex in bovine retinal extract. The growth of the isolated pigment epithelial cells was inhibited by RU 26752 and ZK91587, two ligands specific to the mineralocorticoid receptor. Successive passages in culture led to the disappearance of immunoreactivity in Western blots, concurrently with the refractoriness of the cells to growth inhibition by the two antagonists. On sections of the human eye, mineralocorticoid receptor-specific immunofluorescence was observed in retinal cone cells, pigment epithelium, epithelium of ciliary body, iris, cornea and lens. To our knowledge, this is the first ever demonstration of the mineralocorticoid receptor in ocular tissues.

Animals↗

PubMed1994

Differential tumor necrosis factor expression by resident retinal cells from experimental uveitis-susceptible and -resistant rat strains.

Experimental autoimmune uveoretinitis (EAU) and endotoxin-induced uveitis (EIU), models for human ocular immunopathological syndromes, result in ocular inflammation in susceptible, but not in resistant rat strains. Moreover rapid photoreceptor degeneration occurs in susceptible rats developing EAU. In order to see whether differences in local ocular immune regulation may account for changes in resistance or susceptibility, we have examined the in vitro production of the cytotoxic cytokine tumor necrosis factor (TNF) by two resident ocular cell types, retinal Müller glia (RMG) and retinal pigmented epithelium (RPE). These cells were isolated and cultured in vitro from Lewis (Lew) (highly susceptible), Lew x Brown-Norway (BN) F1 hybrid (susceptible), BN and Long-Evans (LE) (resistant or poorly susceptible) rats. Constitutive production of the cytokine TNF, or its liberation in response to either interferon-gamma (IFN-gamma) or lipopolysaccharide (LPS) alone, was very low in RMG and RPE cells, irrespective of the strain. It was strongly induced by combined treatment with IFN-gamma and LPS in Lew RMG and RPE cells (mean values of 140 and 150 pg/10(5) cells, respectively) and in Lew x BN F1 RMG and RPE cells (mean values of 125 and 190 pg/10(5) cells, respectively), much less so from BN RMG and RPE cells (30 and 20 pg/10(5) cells, respectively) and remained undetectable in LE RMG and RPE cells. Hence susceptibility to EAU and EIU in vivo is correlated with the extent of TNF production by these two cell types under in vitro conditions, which may play a key role in initiating or perpetuating local immune responses.

Animals↗

PubMed1994

Light-induced changes in S-antigen (arrestin) localization in retinal photoreceptors: differences between rods and cones and defective process in RCS rat retinal dystrophy.

The subcellular localization of S-antigen (arrestin), a protein regulating phototransduction in retinal rods, was studied by immunocytochemistry using monoclonal antibodies on sections of Swiss mouse, Lewis, Brown Norway (BN), Royal College of Surgeons (RCS) rdy-p+ (dystrophic) and RCS rdy(+)-p (non-dystrophic) rat retinas. In normal retinas, the topography of S-antigen immunoreactivity in photoreceptor cells varied according to the lighting environment of the animals. In dark-adapted eyes, outer segments did not display any S-antigen immunoreactivity while the inner segments, cell bodies and synaptic terminals were strongly labeled. A few minutes after light exposure, there was an inversion of the pattern of labeling: the label increased in the outer segment but was strongly reduced in the other compartments. After 1 h of light, S-antigen immunoreactivity remained only in outer segments and in a few synaptic terminals. We show that the kinetics of this change is slower in cone than in rod cells, and thus allows the transient visualization of the scarce cone photoreceptors. On the 17th day after birth, photoreceptor cells are well differentiated in all rat strains, including RCS rdy-p+ rats. At this time, the S-antigen shift phenomenon occurred in the non-dystrophic strains, but was not observed in rdy-p+ rats: after light exposure, the intracellular distribution of S-antigen remained the same as in the dark. We suggest that an abnormality in the mechanisms of intracellular protein transport could be a characteristic of this genetic disease.

Amino Acid Sequence↗

PubMed1993

[Diagnostic and predictive importance of the blast transformation test and basophil activation test in retinal vasculitis].

22 patients suffering from Birdshot retinochoroidopathy (10), idiopathic vasculitis (6) and Behcet disease (6) and treated by cyclosporine were tested at regular intervals during 11 to 38 months by the lymphocyte stimulation test (LST) and basophil degranulation test (HBDT) with S retinal antigen. These two tests were found frequently positive especially during acute inflammation for the LST. However HBDT was positive in all the patients before relapse of acute inflammation which is in favor of its predictive value and its involvement in the triggering of inflammation at the basophiles or at the local mast cell level.

Basophil Degranulation Test↗

PubMed1992

Receptor-specific desensitization with purified proteins. Kinase dependence and receptor specificity of beta-arrestin and arrestin in the beta 2-adrenergic receptor and rhodopsin systems.

Homologous desensitization of beta-adrenergic receptors, as well as adaptation of rhodopsin, are thought to be triggered by specific phosphorylation of the receptor proteins. However, phosphorylation alone seems insufficient to inhibit receptor function, and it has been proposed that the inhibition is mediated, following receptor phosphorylation, by the additional proteins beta-arrestin in the case of beta-adrenergic receptors and arrestin in the case of rhodopsin. In order to test this hypothesis with isolated proteins, beta-arrestin and arrestin were produced by transient overexpression of their cDNAs in COS7 cells and purified to apparent homogeneity. Their functional effects were assessed in reconstituted receptor/G protein systems using either beta 2-adrenergic receptors with Gs or rhodopsin with Gt. Prior to the assays, beta 2-receptors and rhodopsin were phosphorylated by their specific kinases beta-adrenergic receptor kinase (beta ARK) and rhodopsin kinase, respectively. beta-Arrestin was a potent inhibitor of the function of beta ARK-phosphorylated beta 2-receptors. Half-maximal inhibition occurred at a beta-arrestin:beta 2-receptor stoichiometry of about 1:1. More than 100-fold higher concentrations of arrestin were required to inhibit beta 2-receptor function. Conversely, arrestin caused half-maximal inhibition of the function of rhodopsin kinase-phosphorylated rhodopsin when present in concentrations about equal to those of rhodopsin, whereas beta-arrestin at 100-fold higher concentrations had little inhibitory effect. The potency of beta-arrestin in inhibiting beta 2-receptor function was increased over 10-fold following phosphorylation of the receptors by beta ARK, but was not affected by receptor phosphorylation using protein kinase A. This suggests that beta-arrestin plays a role in beta ARK-mediated homologous, but not in protein kinase A-mediated heterologous desensitization of beta-adrenergic receptors. It is concluded that even though arrestin and beta-arrestin are similar proteins, they display marked specificity for their respective receptors and that phosphorylation of the receptors by the receptor-specific kinases serves to permit the inhibitory effects of the "arresting" proteins by allowing them to bind to the receptors and thereby inhibit their signaling properties. Furthermore, it is shown that this mechanism of receptor inhibition can be reproduced with isolated purified proteins.

Adrenergic beta-Antagonists↗

PubMed1992

Immunological characterization of an immunomodulatory epitope in S-antigen/arrestin with a sequence motif common to tumor necrosis factor alpha.

Some monoclonal antibodies (mAbs) to retinal S-antigen recognize a phylogenetically conserved epitope (S2) in the N-terminal part of the protein. These antibodies have been shown to inhibit the induction of experimental autoimmune uveoretinitis by S-antigen in rats. Using Pepscan method, we localized this epitope on the amino acid (aa) residues 40-50, i.e., PVDGVVLVDPE (peptide S2). MAb binding was confirmed by ELISA, competition-ELISA and dot blot. Other S-antigen peptides with homologies to epitope S2 and peptides exhibiting the pathogenic and T-cell proliferation inducing sites did not bind these mAbs. Epitope S2 displays an immunological crossreactivity with human tumor necrosis factor (TNF) alpha. Recent results indicate that both peptide S2 and a peptide from human TNF alpha (aa residues 31-53) containing the common sequence motif GVxLxD induce TNF alpha production in monocytes. We analyzed the fine structure of the common epitope by studying mAb binding in an amino acid residue exchange experiment.

Amino Acid Sequence↗

PubMed1992

Immunodetection and localization of protein(s) related to retinal S-antigen (arrestin) in kidney.

S-antigen (arrestin) is a cytosolic protein which regulates phototransduction in retinal rods. A protein immunologically related to S-antigen was identified in fractions from soluble extract of bovine kidney enriched by gel filtration or by immunoaffinity chromatography using a polyclonal antibody to retinal S-antigen. On immunoblots, this protein was recognized by a panel of monoclonal antibodies (mAbs S2D2, S1A3 and S9E2) directed against different S-antigen epitopes and displayed the same apparent molecular mass (48 kDa) as retinal S-antigen. All three mAbs revealed a specific immunoreactivity by indirect immunocytochemical technique on rat kidney sections. The three mAbs recognized some but not all glomerular cells, identified as epithelial cells by immunoelectron microscopy using the mAb S9E2. Both mAbs S2D2 and S1A3 gave a diffuse cytoplasmic staining in all tubule cells. Proximal tubule cells exhibited a weak immunoreactivity, whereas distal and collecting tubule cells were strongly labeled. In contrast, the mAb S9E2 immunoreaction was restricted to a cell subpopulation from distal and collecting tubules corresponding to intercalated cells identified by immunoelectron microscopy. With the mAb S9E2, the labeling of proximal tubule cells was localized in the apical region of the cytoplasm. These results suggest that two or more 48-kDa proteins immunologically cross-reactive with retinal S-antigen are present in kidney. The observed pattern of distribution is in keeping with the hypothesis that such proteins could play a role in the regulation of G-protein-related receptors present in renal glomerulus and tubule epithelial cells.

Amino Acid Sequence↗

PubMed1992

Humoral immune response against the S-antigen/TNF alpha common epitope in rat EAU suppressed by the monoclonal antibody S2D2.

S-antigen (S-Ag)-induced experimental autoimmune uveoretinitis (EAU) in rats can be suppressed by injecting the mouse monoclonal antibody (mAb) S2D2 or a polyclonal rat anti-idiotype S2D2 (anti-Id S2D2) antibody, the internal image of the epitope of S-Ag recognized by mAb S2D2. This epitope located in amino acids 40-50 of bovine S-Ag (peptide S2), displays an homology with a sequence of human tumor necrosis factor alpha (hTNF alpha) (peptide RRAN) which is also recognized by S2D2. (Stiemer et al., this symposium). We show that one injection of S2D2 at the time of immunization with S-Ag suppressed EAU and modulated the production of antibodies against peptides of bovine or human S-Ag containing the S2 epitope and against peptide RRAN. Immunization against anti-Id S2D2 stimulated antibody production to peptide S2 and RRAN and inhibited EAU. These data suggest that disease suppression could be related to the production of antibodies against the S-Ag/TNF alpha common epitope.

Amino Acid Sequence↗

PubMed1992

Cytokine induction by immunomodulatory epitopes in S-antigen and tumor necrosis factor alpha.

Common epitopes on S-antigen (arrestin), a potent autoantigen inducing experimental autoimmune uveoretinitis (EAU), and on human tumor necrosis factor alpha (hTNF alpha) are revealed with monoclonal antibodies (mAb) to S-antigen, which inhibit EAU induction. The minimal common sequence for mAb recognition is GVxLxD in the S-antigen/hTNF alpha amino acid (aa) sequences. Peptides containing this sequence motif exhibit monocyte activating capacity analogous to the autocrine stimulatory capacity of hTNF alpha itself. In S-antigen this activity is located at epitope S2 (aa residues 40 to 50), corresponding to the peptide PVDGVVLVDPE (peptide S2). In hTNF alpha the monocyte activating capacity correlates to aa residue 31 to 53, corresponding to the peptide RRANALLANGVELRDNQLVVPSE (peptide RRAN). Peptide S2 but not peptide RRAN is competing for mAbs S6H8 and S2D2 binding to S-antigen. Anti-idiotypic antibodies to S2D2 compete with peptide S2 but not peptide RRAN for binding to mAbs S2D2 and S6H8. In human retinal S-antigen epitope S2 is localized at the aa residues 44-54 and is cleaved in the human peptide 4 (aa 31-50). Competition experiments with peptide 4 (aa 31-50) and peptide 5 (aa 41-60) indicate that the C-terminal aa residues VDPD in the epitope S2 play an important role for internal image recognition of the anti-idiotypic antibodies. Peptide S2 and peptide RRAN define common functional structures in the autoantigen and hTNF alpha molecules. The data suggest regulatory functions of the peptides in cytokine expression, network regulation and in autoimmunity.

Amino Acid Sequence↗

PubMed1991

Immunopurification of an S-antigen-like protein from human platelets.

S-antigen (also named arrestin or 48K protein) is a protein abundant in photoreceptor cells of vertebrates and invertebrates. The presently known function of this protein in retina is to arrest the enzymatic cascade of phototransduction in retinal rods, through its binding to photoactivated and phosphorylated rhodopsin. Proteins closely related to S-antigen were recently demonstrated in several non photosensitive cells. In this work, we demonstrated the presence of a protein similar to retinal S-antigen with regards to its immunoreactivity with a panel of monoclonal antibodies and its molecular weight in soluble extracts of human platelets. This protein was purified by immunoaffinity chromatography using a rabbit antibody to retinal S-antigen. This S-antigen-like protein could have a regulatory function in G-protein-mediated transduction of chemical signals in platelets, similar to arrestin function in phototransduction.

Antibodies, Monoclonal↗

PubMed1991

Distribution of arrestin-like protein and beta-subunit of GTP-binding proteins in quail choroid plexuses.

Monoclonal antibodies (Mabs) directed against retinal arrestin (S-antigen) were used to detect and characterize this protein in choroid plexus (CP) of quails maintained during eight days, either under long-day photoperiods or in constant darkness. Immunocytochemistry and Western blotting confirmed the presence and the distribution of an arrestin-like protein in quail CP. Arrestin-like immunoreactivities in CP were compared with those obtained with Mabs to beta 36-subunit of G proteins (G beta), alpha-subunit of transducin and rhodopsin. Rhodopsin-like and transducin-like proteins could not be detected in choroidal cells, whereas intense positive reactions were observed with anti-G beta and anti-arrestin Mabs. The strongest immunoreactivities were found in choroidal ependymocytes of the lateral and IIIrd ventricles. In CP epithelial cells lining the IVth ventricle, very weak or no immunoreactivity could be detected with Mabs to arrestin, while Mab against G beta subunit always provided a positive reaction. In quails maintained in constant darkness, arrestin- and G beta-immunoreactivities of CP epithelial cells displayed changes in cellular distribution and intensity (decrease or disappearance of the immunoreactions). The strong arrestin-like immunoreaction located in the apical region of ependymocytes suggests the preferential association of the protein with choroidal microvilli and a possible role in cerebrospinal fluid production assumed by CP cells.

Animals↗

PubMed1991

Early disappearance of alpha-transducin in light-induced photoreceptor degeneration in albino rats.

Progressive degeneration of retinal photoreceptor cells occurs in albino rats when exposed to continuous lighting. Three proteins involved in the phototransduction cascade were immunodetected in these cells after various durations of continuous illumination. We found that S-antigen (arrestin) and rhodopsin immunoreactivities persisted for 1-2 months during the degenerative process, whilst immunoreactivity of the alpha subunit of transducin totally disappeared between day 2 and day 4 of continuous light exposure. This suggests that continuous illumination could impair alpha-transducin synthesis, a possible causal factor of photoreceptor damage.

Animals↗

PubMed1991

[Presence of arrestin (S-antigen)-like proteins in vegetable cells].

Arrestin (or S-antigen) is a protein that regulates phototransduction in photoreceptor cells of the retina. Homologous proteins have been recently detected in other, non-photosensitive, cells of vertebrates, where they are thought to be associated with other systems of signal transduction. Proteins crossreactive with retinal arrestin were detected in soluble cell extracts from Nicotiana tabacum and Chlamydomonas reinhardtii by immunoblotting using several antibodies against arrestin. Variations of the immunoreactive protein pattern were associated with the growth cycle of tobacco cells. These observations suggest that analogs of arrestin exist in the vegetal kingdom, where they could be involved in transduction processes.

Animals↗

PubMed1990

Arrestin from nucleated red blood cells binds to bovine rhodopsin in a light-dependent manner.

Using a panel of monoclonal antibodies, it has previously been demonstrated that the cytosol of nucleated red cells (trout and turkey) contains a protein similar to arrestin, a soluble protein found so far only in the photosensitive cells and which, by binding to photoexcited rhodopsin, inhibits the phototransduction process. The role of this arrestin-like protein in non-photosensitive cells is questionable. In this report we present evidence that partially purified red blood cell arrestin (RBC arrestin) behaves functionally like bovine retinal arrestin: it binds to phosphorylated bovine rhodopsin only when this receptor has been photoactivated. Thus RBC arrestin and bovine retinal arrestin are closely related both structurally and functionally. By analogy with the function of retinal arrestin, it is proposed that RBC arrestin is involved in desensitization of membrane transport proteins and/or adrenergic receptors.

Animals↗

PubMed1990

Free radicals and antioxidants in the pathogenesis of eye diseases.

There is fairly convincing evidence that free radical mechanisms are involved in the pathogenesis of cataracts and uveitis and that antioxidants may be protective. Studies on retinal degeneration are almost entirely limited to dietary manipulation of vitamins C and D. Unfortunately, antioxidant properties are not easily isolated from other metabolic effects of vitamins. Cataracts, uveitis, and retinal degeneration cause nearly one-third of all blindness. The evidence that free radical mechanisms are important in the pathogenesis of these diseases is compelling incentive to encourage more extensive and detailed investigation.

Animals↗

PubMed1990

Severe retinochoroidopathy: variations of humoral and cellular immunity to S-antigen in a longitudinal study.

Ten patients with birdshot retinochoroidopathy, six with isolated retinal vasculitis and eight with Behçet's disease were treated with cyclosporine for one to three years. Autoantibodies to several retinal proteins, circulating lymphocyte subsets and cellular reactivity to S-antigen were evaluated repeatedly during this period. Autoantibody titers were similar in patients and in controls. However the serum content of antibodies to IRBP or S-antigen was lessened during inflammatory periods in some patients. In some sera, antibodies reacted with enzyme digested S-antigen preparations by immunoblot, whereas the same sera were negative for the native protein. A decrease of the CD4+ subpopulation of peripheral blood lymphocytes was associated with relapses of ocular inflammation in birdshot retinochoroidopathy. In this disease and in idiopathic retinal vasculitis, the positive lymphocyte stimulation test and basophil degranulation test with S-antigen were significantly most frequent in the period preceding a relapse of ocular inflammation. These tests could therefore be of predictive value for relapses occurring within the next few months.

Adult↗

PubMed1990

S-antigen in non ocular tissues.

S-antigen has been considered a specific protein of photoreactive cells by immunohistochemical criteria. It was observed in the retina and pineal gland of all examined vertebrates as well as in photoreceptors of invertebrates, but not currently in other organs. However, contrary to pineal cells of poikilotherms and birds which are true or modified photoreceptors, mammalian pinealocytes are not photosensitive. Recent experiments demonstrated that S-antigen-like proteins are present in low amount in many other cells in the body. These proteins are characterized by the same migration pattern (the same molecular weight) as retinal S-antigen in SDS-electrophoresis and by their immunoreactivity with a panel of monoclonal and polyclonal antibodies to S-antigen. These cells are not photosensitive, but are controlled by beta adrenergic, G-protein mediated adenylate cyclase system, a transduction system that shares many structural and functional homologies with visual transduction. S-antigen (arrestin) plays a regulatory role in phototransduction in rods by desensitizing rhodopsin. In the mammalian pineal and in other cells or tissues, S-antigen, or a family of structurally related proteins, could similarly be involved in the regulation of chemical signal transduction. Whether any systemic pathology is associated with uveoretinitis and pinealitis after S-antigen immunization deserves further investigations.

Animals↗

PubMed1989

Immunological detection of arrestin, a phototransduction regulatory protein, in the cytosol of nucleated erythrocytes.

Cytosolic extracts of trout and turkey erythrocytes were tested for their immunoreactivity with polyclonal and monoclonal antibodies to retinal arrestin (S-antigen), a cytosolic protein of photoreceptor cells involved in the desensitization of rhodopsin. After adsorption or immunoaffinity chromatography of the extracts, these antibodies specifically recognized a protein having a molecular weight similar to that of retinal arrestin. Because the G-protein-mediated transduction systems, such as visual and beta-adrenergic systems, display a high degree of structural and functional homology, the presence of arrestin-like proteins in non-photosensitive cells suggests that these proteins are involved in the transduction of chemical signals, with a possible role in receptor desensitization.

Animals↗