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Biomedical subjects

M Amagai

Publications and source records attributed to M Amagai.

At least 127 records · Page 7Linked to original sources
PubMed1995

Delayed assembly of desmosomes in keratinocytes with disrupted classic-cadherin-mediated cell adhesion by a dominant negative mutant.

We examined whether classic cadherins play a role in the formation of desmosomes using a mouse keratinocyte, PAMcN390 delta cell, which shows disrupted classic-cadherin-mediated cell adhesion by introduction of a dominant-negative mutant of N-cadherin. The expression of the mutant did not alter that of endogenous E-cadherin or desmoplakin. In control cells with functional classic cadherins, we observed redistribution of desmoplakin to cell-cell borders with insertions of keratin filaments at the contact sites as soon as 2 h after calcium elevation, after an earlier event of E-cadherin translocation to the cell-cell contact sites. In contrast, in the PAMcN390 delta cells, which showed retarded translocation of E-cadherin, the redistribution of desmoplakin and the rearrangement of keratin filaments were delayed as late as 24 h after the calcium elevation. The acquisition of Nonidet P-40 insolubility of desmoplakins also was found to be delayed in the PAMcN390 delta cells. These findings indicate that the disruption of classic cadherin affected the organization of desmosomes upon calcium elevation and suggest that the proper function of classic cadherins is a prerequisite for desmosome assembly in keratinocytes.

Animals↗
PubMed1995

Adhesion molecules. I: Keratinocyte-keratinocyte interactions; cadherins and pemphigus.

During the last few years, considerable progress has been made in our understanding of the structure and function of cadherins and of the pathophysiology of pemphigus. Cadherins are a multiple gene family of Ca(++)-dependent cell adhesion molecules with a typical single-spanning transmembrane structure. Cadherins have two major subfamilies, classic cadherin and desmosomal cadherin. Classic cadherins, including E-, P-, and N-cadherins, are characterized by a homophilic binding specificity. They localize at adherens junctions and mediate physiologic interaction with the involvement of cytoplasmic anchoring molecules, catenins, and the actin-based cytoskeleton network. Desmosomal cadherins, the desmocollins and desmogleins, localize at desmosomes and are linked to the intermediate keratin filaments network via plakoglobin and desmoplakin. Molecular cloning has demonstrated that the autoantigens of both pemphigus vulgaris and pemphigus foliaceus are members of the desmoglein subfamily of the cadherin supergene family. Thus, pemphigus is characterized as an anti-cadherin autoimmune disease. Furthermore, a baculovirus recombinant protein of pemphigus vulgaris antigen was capable of absorbing out the pathogenic autoantibodies from patients' sera, providing a possibility of antigen-specific therapeutic strategies for pemphigus.

Cadherins↗
PubMed1995

Lymphomatoid papulosis followed by Ki-1 positive anaplastic large cell lymphoma: proliferation of a common T-cell clone.

We report a case of lymphomatoid papulosis (LyP) followed by Ki-1 positive anaplastic large cell lymphoma (LCL). A 33-year-old man developed subcutaneous nodules in the left inguinal region and the left thigh after a seven-year-history of self-healing papulonecrotic lesions of LyP. Histological and immunohistochemical examination of the subcutaneous nodules revealed LCL. DNA was isolated from a nodule of the initial stage of LyP in 1988, a subcutaneous nodule of LCL in 1993, and a papule of LyP in 1993 which appeared after chemotherapy for LCL. T cell receptor gene rearrangement analysis demonstrated an identical rearranged pattern in all the three specimens, indicating that a common T cell clone proliferated throughout the course in both the LyP and LCL lesions.

Adult↗
PubMed1995

Detection of autoantibodies against bullous pemphigoid and pemphigus antigens by an enzyme-linked immunosorbent assay using the bacterial recombinant proteins.

To develop a new method to evaluate autoantibodies in various autoimmune bullous skin diseases, we examined reactivity of bullous pemphigoid (BP) and pemphigus vulgaris (PV) patients' sera with partial bacterial fusion proteins of the 230 kD BP antigen (BPAG1) and PV antigen, respectively, by an enzyme-linked immunosorbent assay (ELISA), and compared the results with those of immunoblotting. We used two fusion proteins derived from the mouse BPAG1 and a fusion protein derived from the amino-terminus (EC1-2) of PV antigen. For both BP and PV sera, the ELISA scores were well correlated with the reactivities on immunoblot assays. The present study indicates that ELISA using recombinant antigen proteins in various autoimmune bullous skin diseases will be a new useful technique to detect the autoantibodies. However, development of recombinant proteins with the entire molecule and correct conformation will be necessary to establish a perfect ELISA system in the future.

Autoantibodies↗
PubMed1995

Immunofluorescence and immunoblot studies on the reactivity of pemphigus vulgaris and pemphigus foliaceus sera with desmoglein 3 and desmoglein 1.

We have investigated expression of pemphigus vulgaris (PV) antigen, desmoglein 3 (Dsg3), and pemphigus foliaceus (PF) antigen, desmoglein 1 (Dsg1), in various tissues. Immunofluorescence studies suggested that Dsg1 and Dsg3 are preferentially expressed in the upper and lower epidermis, respectively. With immunoblotting of human epidermal extracts, all PV sera reacted with Dsg3 but not with Dsg1. By contrast, only half of PF sera reacted with Dsg1 but none reacted with Dsg3. These results confirm the distinct antibody specificity between PV and PF sera. They also suggest that PV sera contain antibodies against linear epitopes present even on the denatured antigen, while some PF sera contain antibodies only against conformational epitopes present on the native antigen. With immunoblotting of bovine desmosome preparations, certain PV sera and an anti-Dsg monoclonal antibody reacted with both Dsg1 and Dsg3. Affinity-purification of these PV antibodies suggested that the simultaneous reactivity with Dsg1 and Dsg3 was produced by two different subsets of antibodies and not by cross-reactivity of single antibodies. This study indicates that pemphigus serum is a useful probe with which we learn various aspects of keratinocyte biology.

Animals↗
PubMed1994

The human genes for desmogleins (DSG1 and DSG3) are located in a small region on chromosome 18q12.

Desmoglein is a transmembrane glycoprotein component of desmosomes in vertebrate epithelial cells. Two of the three currently known desmogleins are the autoantigens of autoimmune skin blistering diseases, pemphigus vulgaris and pemphigus foliaceus, in which autoantibodies cause the loss of cell adhesion of keratinocytes with resultant blister formation. In this study, the genes for two autoantigens (DSG1 for pemphigus foliaceus and DSG3 for pemphigus vulgaris) were mapped on band q12 of human chromosome 18 by fluorescence in situ hybridization. Furthermore, both genes were localized on a 320-kb genomic fragment separated by pulsed-field gel electrophoresis. These results suggest the possibility of a cluster for the desmoglein gene family on chromosome 18.

Animals↗
PubMed1994

Extracellular domain of pemphigus vulgaris antigen (desmoglein 3) mediates weak homophilic adhesion.

Pemphigus vulgaris antigen is in the cadherin supergene family. We hypothesized that the extracellular domain of pemphigus vulgaris antigen might mediate homophilic cell adhesion because 1) the originally described cadherins (e.g., E-cadherin) mediate this type of adhesion, 2) pemphigus vulgaris antigen is localized in desmosomes that are cell adhesion junctions, and 3) autoantibodies in pemphigus vulgaris patients cause loss of cell adhesion. To test this hypothesis we used a system developed for E-cadherin that, when transfected into L cells (mouse fibroblasts), has been shown to cause aggregation. Because this aggregation requires the cytoplasmic domain of E-cadherin to bind to catenins, we made a chimeric cDNA construct that encodes the extracellular domain of pemphigus vulgaris antigen and the cytoplasmic domain of E-cadherin. Analysis by immunofluorescence and flow cytometry with pemphigus vulgaris sera indicated that the pemphigus vulgaris antigen extracellular domain of this chimeric molecule (PVEC) was expressed on the cell surface of transiently transfected cells and permanently transfected L-cell clones. Immunoprecipitation of the chimeric molecule from extracts of these clones showed that the E-cadherin cytoplasmic domain bound catenins. Surprisingly, these L-cell clones displayed only slight aggregation compared to an L-cell clone transfected with E-cadherin. This weak aggregation was, however, specific and homophilic, as determined by cell sorting of only PVEC transfectants into aggregates from mixtures of PVEC and neomycin resistance gene transfectants, one of which was labeled with a fluorescent dye. We conclude that the extracellular domain of pemphigus vulgaris antigen mediates weak homophilic adhesion and is not interchangeable in function with the extracellular domain of E-cadherin.

Animals↗
PubMed1994

Pemphigus vulgaris antigen lacks biochemical properties characteristic of classical cadherins.

Pemphigus vulgaris antigen (PVA) is a member of the desmoglein subfamily of the cadherin supergene family. PVA has homology to the classical cadherins (e.g., E-cadherin), both in its extracellular and cytoplasmic domains. Classical cadherins possess certain well-defined and characteristic biochemical properties of both domains. The cytoplasmic domain binds alpha-, beta-, and gamma-catenins. The extracellular domain is protected by calcium from degradation by trypsin. In this study we show that PVA does not share these characteristic biochemical features. Immunoprecipitation of E-cadherin and PVA from human keratinocytes shows that under the same conditions in which the catenins co-precipitate with E-cadherin, only plakoglobin (which co-migrates with gamma-catenin) co-precipitates with PVA. Treatment of keratinocytes with 0.01% trypsin in 1 mM calcium (T/C) does not degrade the extracellular region of E-cadherin, but does partially degrade that of PVA. This increased T/C susceptibility of PVA is not due to its cytoplasmic domain, as the same sensitivity of the extracellular domain of PVA to T/C was observed in L cell clones transfected with a chimeric cDNA that encoded for the extracellular domain of PVA and the cytoplasmic domain of E-cadherin. These data demonstrate that although the desmogleins and classical cadherins share striking amino acid homologies in both the cytoplasmic and extracellular domains, they do not exhibit identical biochemical properties and, by extension, may not subserve identical cell biologic functions.

Amino Acid Sequence↗
PubMed1994

The extracellular aminoterminal domain of bovine desmoglein 1 (Dsg1) is recognized only by certain pemphigus foliaceus sera, whereas its intracellular domain is recognized by both pemphigus vulgaris and pemphigus foliaceus sera.

The major antibody binding regions of desmoglein 1 (Dsg1) in pemphigus foliaceus and pemphigus vulgaris were examined using cDNA-encoded fusion proteins combining glutathione S-transferase with various domains of bovine Dsg1, namely, the extracellular regions EC1-2, EC3-5, EC1-5, and the entire intracellular region IC. In immunoblot analyses using these fusion proteins, EC1-2, as well as EC1-5, which comprises EC1-2, were recognized by 50% of the sporadic pemphigus foliaceus sera and 45% of Brazilian pemphigus foliaceus sera that reacted with Dsg1 in immunoblotting of bovine desmosome preparations. None of these fusion proteins reacted with any sera of pemphigus vulgaris. None of these sera showed reactivity with EC3-5. In contrast, the IC domain was recognized by 91% of pemphigus vulgaris sera reactive with Dsg1 in bovine desmosome preparations, and by certain pemphigus foliaceus and Brazilian pemphigus foliaceus sera. These results indicate that major epitopes of Dsg1 recognized by pemphigus foliaceus and Brazilian pemphigus foliaceus sera are located in the extracellular amino-terminal domain EC1-2, and that sera of the Dsg1-positive pemphigus vulgaris contain antibodies against the intracellular domain, which may not play a pathogenic role. Possible reasons for this selectivity of antigen binding site are discussed.

Animals↗
PubMed1994

Extracellular domain of pemphigus vulgaris antigen (desmoglein 3) mediates weak homophilic adhesion.

Pemphigus vulgaris antigen is in the cadherin supergene family. We hypothesized that the extracellular domain of pemphigus vulgaris antigen might mediate homophilic cell adhesion because 1) the originally described cadherins (e.g., E-cadherin) mediate this type of adhesion, 2) pemphigus vulgaris antigen is localized in desmosomes that are cell adhesion junctions, and 3) autoantibodies in pemphigus vulgaris patients cause loss of cell adhesion. To test this hypothesis we used a system developed for E-cadherin that, when transfected into L cells (mouse fibroblasts), has been shown to cause aggregation. Because this aggregation requires the cytoplasmic domain of E-cadherin to bind to catenins, we made a chimeric cDNA construct that encodes the extracellular domain of pemphigus vulgaris antigen and the cytoplasmic domain of E-cadherin. Analysis by immunofluorescence and flow cytometry with pemphigus vulgaris sera indicated that the pemphigus vulgaris antigen extracellular domain of this chimeric molecule (PVEC) was expressed on the cell surface of transiently transfected cells and permanently transfected L-cell clones. Immunoprecipitation of the chimeric molecule from extracts of these clones showed that the E-cadherin cytoplasmic domain bound catenins. Surprisingly, these L-cell clones displayed only slight aggregation compared to an L-cell clone transfected with E-cadherin. This weak aggregation was, however, specific and homophilic, as determined by cell sorting of only PVEC transfectants into aggregates from mixtures of PVEC and neomycin resistance gene transfectants, one of which was labeled with a fluorescent dye. We conclude that the extracellular domain of pemphigus vulgaris antigen mediates weak homophilic adhesion and is not interchangeable in function with the extracellular domain of E-cadherin.

Animals↗
PubMed1994

Autoantibodies against cell adhesion molecules in pemphigus.

cDNA cloning has demonstrated that pemphigus autoantigens of both pemphigus vulgaris (PV) and pemphigus foliaceus are members of the desmoglein subfamily of the cadherin supergene family. The availability of these cDNAs allowed us to utilize molecular engineering to attempt to understand the pathophysiology of pemphigus. Transfection study with a chimeric molecule containing the extracellular domain of PV antigen (PVA) and the cytoplasmic domain of E-cadherin demonstrated that the extracellular domain of PVA mediates weak homophilic cell adhesion. Bacterial fusion proteins representing different parts of PVA showed that the major immunogenic domains are EC1, EC2, and EC4 and that at least one pathogenic epitope is located on the amino-terminal region of PVA, an area thought to be important for classic cadherin homophilic interaction. Further, a secreted form of PVA recombinant protein, PVIg, was produced by baculovirus expression. Immunoabsorption assay has demonstrated that PVIg is capable of absorbing pathogenic autoantibodies from patients' sera and preventing blister formation in neonatal mice.

Animals↗
PubMed1994

Pemphigus vulgaris antigen is a desmosomal desmoglein.

Because pemphigus vulgaris antigen (PVA) is homologous to desmogleins which are in desmosomes, we asked whether PVA is also localized to desmosomes. Immunogold electron microscopy was used to localize binding of PV antibodies. Rabbit antibodies raised against fusion proteins containing the extracellular portion of PVA bound to desmosomes of cultured keratinocytes. PV patient serum affinity-purified on one of these fusion proteins and injected into neonatal mice localized to separating desmosomes. These results show that PVA belongs to the desmoglein subfamily of cadherins according to sequence, localization and, presumably, function.

Cadherins↗
PubMed1994

Absorption of pathogenic autoantibodies by the extracellular domain of pemphigus vulgaris antigen (Dsg3) produced by baculovirus.

Pemphigus vulgaris (PV) is an autoimmune blistering disease, in which autoantibodies against PV antigen (PVA or Dsg3) play a pathogenic role in inducing blister formation. Bacterial fusion proteins of PVA failed to absorb pathogenic autoantibodies from PV patients' sera probably because they did not represent the proper conformation. Therefore, a chimeric protein, PVIg, consisting of the whole extracellular domain of PVA and the constant region of human IgG1, was produced in either in COS7 or in insect Sf9 eucaryotic cells. Both PVIg-COS7 and PVIg-Sf9 were recognized by all of the 35 PV sera tested, but not by any of 10 pemphigus foliaceus (PF), 16 Brazilian PF, 10 bullous pemphigoid, or five normal control sera. Incubation of PV patients' sera with PVIg-Sf9 removed heterogeneous autoantibodies and significantly reduced their immunofluorescence titers on normal human epidermis, although PVIg-Sf9 did not affect the titers of PF sera at all. Furthermore, PVIg-Sf9 absorbed pathogenic autoantibodies from patients' sera and prevented gross blister formation in a neonatal mouse model for pemphigus. These results indicate that this baculovirus product has the proper conformation of the authentic PVA and that its conformation is important in pathogenicity of pemphigus.

Animals↗
PubMed1993

Natural occurrence of Nuc in the sera of autoimmune-prone MRL/lpr mice.

We previously established a clone of cells termed KML1-7 which produces a soluble factor that boosts anti-DNA antibody production both in vitro and in vivo across the H-2 barrier. By using the purified protein, termed nucleobindin (Nuc), we cloned cDNA and produced recombinant(r) Nuc in E.coli. Although the purified rNuc showed biological activities such as anti-DNA antibody boosting and DNA binding, there was no evidence that Nuc is really associated with autoimmune status in lupus-prone MRL/lpr mice. Here we report that identification of Nuc was successful from the sera of MRL/lpr mice, but not from those of the substrain MRL/n mice, which show no apparent autoimmune syndrome at the same age of MRL/lpr mice, by means of immunochemical as well as N-terminal amino-acid sequencing methods.

Amino Acid Sequence↗
PubMed1993

Adhesion of epidermal Langerhans cells to keratinocytes mediated by E-cadherin.

Langerhans cells (LC) are the principal accessory cells present in epidermis. Because LC have limited capacity for self-renewal, epidermis is continually repopulated by as-yet uncharacterized bone marrow-derived LC progenitors. In addition, although LC persist in epidermis for extended periods, LC are induced to migrate from skin to regional lymph nodes after antigen exposure. To begin to elucidate mechanisms involved in LC trafficking, we characterized LC-keratinocyte (KC) interactions. Here we report that fresh murine LC express cadherins, and that LC adhere to KC in vitro through E-cadherin. Cultured LC (which may bear a phenotypic and functional relationship to LC that have migrated to lymph nodes) express lower levels of E-cadherin and exhibit decreased affinity for KC. These results suggest that expression of E-cadherin by LC promotes persistence of these cells in epidermis, and that cadherins may play important and unanticipated roles in interactions between leukocytes and epithelia.

Animals↗
PubMed1993

Pemphigus vulgaris antigen, a desmoglein type of cadherin, is localized within keratinocyte desmosomes.

Pemphigus vulgaris antigen (PVA) is a member of the desmoglein subfamily of cadherin cell adhesion molecules. Because autoantibodies in this disease cause blisters due to loss of epidermal cell adhesion, and because desmoglein is found in the desmosome cell adhesion junction, we wanted to determine if PVA is also found in desmosomes. By immunofluorescence, PV IgG bound, in a dotted pattern, to the cell surface of cultured human keratinocytes induced to differentiate with calcium, suggesting junctional staining. However, by preembedding, immunogold electron microscopic studies only slight labeling could be detected in desmosomes, presumably because of difficulty in gold penetration of intact desmosomes. We therefore treated the keratinocytes with 0.01% trypsin in 1 mM calcium, conditions known to preserve cadherin antigenicity but that caused slight separation of desmosomes, before immunogold staining. In this case there was extensive labeling of the extracellular part of desmosomes but not of the interdesmosomal cell membrane which was stained with anti-beta 2-microglobulin antibodies. To confirm the specificity of this binding we showed that antibodies raised in rabbits against the extracellular portions of PVA also bound desmosomes in these cultures. In intact mouse epidermis we could also show slight, but specific, immunogold desmosomal labeling with PV IgG. Furthermore, neonatal mice injected with PV IgG affinity purified on PVA showed desmosomal separation with the IgG localized to desmosomal cores. These results indicate that PVA is organized and concentrated within the desmosome where it presumably functions to maintain the integrity of stratifying epithelia.

Animals↗
PubMed1993

Further analyses of epitopes for human monoclonal anti-basement membrane zone antibodies produced by stable human hybridoma cell lines constructed with Epstein-Barr virus transformants.

We previously established Epstein-Barr virus (EBV)-transformed bullous pemphigoid (BP) patient lymphoblastoid cell lines, which produced human monoclonal anti-basement membrane zone antibodies. In the present study, we established two independent human-human hybridomas by fusion of these EBV transformants with a human B-cell line. These hybridomas, designated 5E-HY-4B and 10D-HY-8B, were very stable and showed a high yield of monoclonal antibody (MoAb) secretion. Each cell line was tetraploid and showed combined rearranged segments of immunoglobulin heavy-chain gene derived from both an EBV transformant and a parent cell. Immunoblot analysis showed that the 5E-HY-4B MoAb recognized the 230-kDa BP antigen but that the 10D-HY-8B MoAb did not show any reactivity. In contrast, both MoAbs precipitated the 230-kDa BP antigen with immunoprecipitation. These results indicate that the two MoAbs reacted with different epitopes on the 230-kDa BP antigen: a continuous epitope for the 5E-HY-4B MoAb and a conformation-dependent epitope for the 10D-HY-8B MoAb. This speculation was confirmed at the molecular level by the result that the fusion protein produced by a partial cDNA for the 230-kDa mouse BP antigen reacted with the 5E-HY-4B MoAb but not with the 10D-HY-8B MoAb. Furthermore, the study of the reactivity with fusion proteins of a series of deleted clones restricted the epitope for the 5E-HY-4B MoAb within the region with 114 amino acid residues in the C-terminal domain of the 230-kDa BP antigen.

Antibodies, Monoclonal↗