180-kDa Bullous Pemphigoid Antigen Research Articles

Basal Detachment of the Epidermis Using Dispase: Tissue Spatial Organization and Fate of Integrin α6β4 and Hemidesmosomes

Dispase has been utilized to produce basal detachment of the epidermis of human skin biopsies and to study the consequences induced afterwards during incubations of the detached tissue. Spatial reorganization of the epidermis is observed under these conditions and is characterized by disappearance of the typical basal keratinocyte layer. Immunofluorescent labelings reveal upward migration of several cells exhibiting the basal phenotype between suprabasal differentiating keratinocytes and demonstrate progressive intracellular expression of hemidesmosomal components: the integrin alpha 6 beta 4 and two plaque components, the 230-kDa bullous pemphigoid antigen and HD1, a 500-kDa protein. Using electron microscopy and immunogold techniques, we demonstrate that the hemidesmosome-containing basal membrane domains enter the cell cytoplasm after detachment of the epidermal tissue. Partial recycling of internalized hemidesmosomal components is also suggested. Our findings illustrate the processing of released hemidesmosomes in detached basal keratinocytes and suggest some heterogeneity between basal cells migrating towards a suprabasal position and those remaining in the basal layer. These results suggest that the dispase-detached epidermis is a self-remodeling tissue in which basal keratinocytes' and tissue's polarities observed in the anchored epidermis are progressively changing.

Identification of a DNA-binding protein (keratinocyte transcriptional protein-1) recognizing a keratinocyte-specific regulatory element in the 230-kDa bullous pemphigoid antigen gene.

We have recently cloned and characterized the entire human 230-kDa bullous pemphigoid antigen gene, which is expressed at a relatively high level in the basal keratinocytes. A putative AP2 binding sequence (KRE2), identified in the position -1786 to -1778, was cloned in front of a heterologous thymidine kinase chloramphenicol acetyltransferase construct, and transient transfections of normal human keratinocytes indicated a marked enhancement of the promoter activity. Normal human keratinocyte nuclear extracts contained a protein, designated as keratinocyte transcriptional protein-1 (KTP-1), which complexed with the KRE2 oligomer when examined by gel mobility shift assays. This protein was not detected in human skin fibroblast or HeLa cell nuclear extracts that did, however, contain AP2. UV cross-linking studies and Southwestern analyses suggested that KTP-1 binds to DNA as a single polypeptide of approximately 110 kDa. These data suggest that KTP-1 is a DNA-binding protein clearly distinct from AP2, and this protein may be responsible for the basal keratinocyte-specific expression of the bullous pemphigoid antigen gene.

Paraneoplastic pemphigus in a child with a T-cell lymphoblastic lymphoma

We report a child with a T-cell lymphoblastic lymphoma, and a widespread erosive mucocutaneous eruption, whose clinical and immunopathological features were consistent with a diagnosis of paraneoplastic pemphigus. Direct immunofluorescence showed deposition of C3 in the epidermal intercellular spaces, and in a linear pattern along the dermo-epidermal junction. Circulating autoantibodies binding in a pemphigus-like pattern to mouse urinary bladder epithelium were found. By Western immunoblotting, the patient's serum recognized two epidermal polypeptides with molecular weights of 210 and 190 kDa. No reactivity with the 230-kDa bullous pemphigoid antigen and the 250-kDa desmoplakin I antigen was found.

Cloning of type XVII collagen. Complementary and genomic DNA sequences of mouse 180-kilodalton bullous pemphigoid antigen (BPAG2) predict an interrupted collagenous domain, a transmembrane segment, and unusual features in the 5‘-end of the gene and the 3‘-untranslated region of the mRNA.

Thus far, 16 distinct vertebrate collagens (types I-XVI) have been delineated. In this study, we have cloned a mouse collagenous protein, the 180-kDa bullous pemphigoid antigen (BPAG2). Isolation of over-lapping clones, together with 5' and 3' rapid amplification of cDNA ends, allowed delineation of the entire coding sequence. The 5' and 3' ends of the mRNA transcripts were confirmed by primer extension and anchored reverse transcription polymerase chain reaction analyses. The deduced polypeptide contained 1,433 amino acids, including a collagenous domain that consisted of 13 separate segments. Computer analysis of the deduced amino acid sequence demonstrated the presence of a membrane-associated segment. Examination of the 5' end of the BPAG2 gene revealed that the 295-base pair (bp) exon 1 contained two segments of (T)13AA and TT(A)11, whereas exon 2 was shown to contain the translation initiation codon. The 3' end of the mRNA transcript identified two 6-bp inverted repeat sequences that could form a stem for a 30-bp hairpin loop followed by a series of U residues. Comparison of mouse and human BPAG2 sequences demonstrated 86% homology and the unit of evolutionary period of 4.2 million years. In summary, we have cloned full-length mouse BPAG2 cDNA sequences that encode a collagenous polypeptide. We propose that this polypeptide be designated as the alpha 1-chain of type XVII collagen.

HD4, a 180 kDa Bullous Pemphigoid Antigen, Is a Major Transmembrane Glycoprotein of the Hemidesmosome1

Hemidesmosomes (HDs) constitute a major cellular apparatus for substratum adhesion in stratified and complex epithelia. A large number of components participate in their construction. HD4, a 180 kDa polypeptide, which is one of the major constituents of the isolated HD fraction, has been suggested to be a glycoprotein, is probably identical to the 180 kDa bullous pemphigoid (BP) antigen [Owaribe, K., Nishizawa, Y., & Franke, W.W. (1991) Exp. Cell Res. 192, 622-630]. By using a sensitive method for detection of glycoproteins, HD4 was confirmed to be a major glycoprotein in cytoskeletal fractions of certain cultured epithelial cells as well as in the HD fraction. To further characterize HD4, we prepared two groups of monoclonal antibodies (mAbs), one recognizing extracellular parts of the HD4 molecule (group I) and the other recognizing intracellular ones (group II). In cultured keratinocytes, type I mAbs, as well as BP autoantibodies that recognize both 230 and 180 kDa polypeptides, stained living cells while type II mAbs did not. The two mAbs exhibited identical staining patterns in fixed cells. HD4 molecules proved partially susceptible to collagenase and Dispase digestion, which removed epitopes of type I mAbs but not those of type II. Immunoelectron microscopy revealed the epitopes of group I mAbs to be localized in the extracellular region of HDs, whereas those of group II were on the cytoplasmic side. These results indicate that the HD4 (BP180) molecule is a major transmembrane glycoprotein with collagen domains in its extracellular portion.

IgE and its related phenomena in bullous pemphigoid.

This study was designed to analyse IgE and its related phenomena in bullous pemphigoid (BP). We analysed 17 BP sera by indirect immunofluorescence (IIF) and immunoblotting (IB) using a monoclonal antibody to IgE. In addition, inflammatory cells in lesional skin from 11 patients with BP were analysed by the alkaline phosphatase-anti-alkaline phosphatase (APAAP) technique using monoclonal antibodies to IgE and Fc epsilon RII/CD23. IgE class anti-basement membrane zone (BMZ) autoantibody was detected in nine of 17 sera (52.9%) by IIF. IgG class anti-BMZ antibody could block the BMZ-binding reactivity of IgE class antibody. Titres of IgE class autoantibody in the sera ranged from 1:40 to 1:320, and statistically correlated with serum IgE levels. Two of 11 sera contained an IgE class autoantibody which recognized a 230-kDa BP antigen by IB. By radio-allergosorbent test (RAST), IgE-specific antibodies to an extended series of common inhalant and food allergens were detectable in six sera with high concentrations of total IgE (over 3,300 IU/ml). IgE-bearing and Fc epsilon RII-expressing cells were demonstrated in the upper dermis and along the BMZ in seven of 11 biopsy specimens by the APAAP technique. The distribution and number of IgE-bearing cells in the lesions were similar to those of the Fc epsilon RII-expressing cells. These results suggest that both IgE-mediated immune responses and autoimmunity characterize BP as distinctive features.

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.

Phorbol ester- and calcium-induced reorganization of 180-kDa bullous pemphigoid antigen on the ventral surface of cultured human keratinocytes as studied by immunofluorescence and immunoelectron microscopy

The hemidesmosome is an adhesion structure of the epidermal-dermal junction in keratinocytes. When keratinocytes migrate laterally or upward to differentiate, they must control the formation and disintegration of the hemidesmosomes. When keratinocytes are cultured in low-calcium (below 0.1 m M) medium, all cells behave like basal cells, adhere to the culture dish, and proliferate without differentiation. The calcium addition induces the differentiation. A bullous pemphigoid antigen, 180-kDa BPA, has been shown to be a component of the hemidesmosome. Using a monoclonal antibody to the 180-kDa BPA and a human squamous cell carcinoma cell line (DJM-1 cells), the fate of hemidesmosomes was studied after the addition of calcium to low-calcium-grown cells and 12-tetradecanoylphorbol13-acetate (TPA) to high-calcium (1.87 m M) grown cells by immunofluorescence and immunoelectron microscopy. The antigen was distributed evenly as fine dots on the entire ventral surface of low-calcium cells, whereas they formed a peculiar, concentric ring or arch arrangement on the ventral surface of high-calcium cells. Immunoelectron microscopy revealed the deposits of gold particles at sites on the membrane surface, where some filamentous or electron-dense materials were associated, although the complete structure of hemidesmosomes was not formed. They deposited directly onto the membrane surface in low-calcium cells and with a distance of 20–50 nm from the membrane surface in high-calcium cells. The calcium addition caused a profound reduction of the 180-kDa BPA-positive area for 30 to 120 min and then formed the high-calcium-ring pattern after 4 to 6 h. A similar calcium response was seen in normal human keratinocytes. TPA (16 n M) treatment caused disintegration of the ring pattern in high-calcium DJM-1 cells. This was inhibited with a protein kinase C (PKC) inhibitor. H7 (20 μ M). These results suggest that the hemidesmosome is a dynamic structure and PKC can be one of the major factors in controling the hemidesmosome, since it is known that the low-high calcium shift induces a calcium influx and a PKC activation, and TPA activates PKC in keratinocytes.

Cloning of Partial cDNA for Mouse 180-kDa Bullous Pemphigoid Antigen (BPAG2), a Highly Conserved Collagenous Protein of the Cutaneous Basement Membrane Zone

One-hundred-eighty kilodalton bullous pemphigoid antigen (BPAG2) is recognized by autoantibodies in the sera of patients with blistering skin diseases, bullous pemphigoid (BP), and herpes gestationis (HG). In this study, we have screened a mouse epidermal keratinocyte cDNA library with a 1.0-kb human BPAG2 cDNA, which has been shown to correspond to two collagenous domains (Giudice et al: J Clin Invest 87:734-738, 1991). Screening of the mouse library identified two cDNA clones, the larger one being 1.8 kb in size. Comparison of the mouse amino acid sequences, as deduced from cDNA, with the corresponding human sequences revealed 86% homology. Furthermore, Northern hybridizations of mouse epidermal RNA with these cDNA revealed the presence of an mRNA transcript of approximately 6 kb, the size of the human BPAG2 mRNA. Elucidation of the deduced amino-acid sequences revealed the presence of definitely one and possibly two putative membrane-associated segments, suggesting that the 180-kDa BP antigen is a transmembrane protein. The sequence analysis also identified a 7-amino-acid segment that was predicted by computer analysis to be antigenic. Elucidation of the divergence between the mouse and previously published human and chicken BPAG2 sequences indicated that this protein segment was relatively well conserved. These data suggest, therefore, that the 180-kDa bullous pemphigoid antigen associated with hemidesmosomes is a well-conserved transmembrane protein that may play a critical role in the attachment of epidermis to the underlying basement membrane.

Recent advances on the 180-kDa epidermal antigen in autoimmune subepidermal bullous skin diseases

The blistering skin disease bullous pemphigoid (BP) is an example of how autoantibodies from patients can be used as tools to improve our knowledge of the molecular structure of normal skin. BP autoantibodies bind to the basement membrane zone of normal human skin and usually react with two main epidermal antigens of approximately 230-kDa and 180-kDa. From recent studies, it is now established that the 180-kDa polypeptide is distinct from the 230-kDa BP antigen and is a major component of hemidesmosome. In this article, the recent data regarding the localization and structure of the epidermal 180-kDa BP antigen are reviewed in detail, together with its clinical significance, since it appears to be also a target antigen for pemphigoid (herpes) gestationis and, perhaps, cicatricial pemphigoid autoantibodies.

Genomic organization of collagenous domains and chromosomal assignment of human 180-kDa bullous pemphigoid antigen-2, a novel collagen of stratified squamous epithelium.

We have recently isolated a 1.0-kilobase (kb) cDNA encoding 180-kDa bullous pemphigoid antigen (BPAG2), an autoantigen in blistering skin disease, bullous pemphigoid (Giudice, G. J., Squiquera, H. L., Elias, P. M., and Diaz, L. (1991) J. Clin. Invest. 87, 734-738). The deduced amino acid sequence identified two collagenous domains characterized by Gly-X-Y repeats. In this study we have elucidated the genomic organization of the corresponding segment in the human BPAG2 gene. Screening of a genomic lambda-phage DNA library yielded six overlapping clones, and the sequences corresponding to the 1.0-kb cDNA spanned approximately 12 kb of genomic DNA. The coding segment consisted of 19 separate exons varying in size from 27 to 222 base pairs. The organization of these exons and the splice sites at the intron-exon junctions were clearly different from other fibrillar and nonfibrillar collagen genes described to date. The BPAG2 gene was mapped by chromosomal in situ hybridization to the long arm of human chromosome 10, at locus 10q24.3; this location is distinct from any previously mapped collagens, and it also distinguishes BPAG2 from BPAG1, a 230-kDa bullous pemphigoid antigen, which has been mapped to chromosome 6p (Sawamura, D., Nomura, K., Sugita, Y., Mattei, M.-G., Chu, M.-L., Knowlton, R.G., and Uitto, J. (1990) Genomics 8, 722-726). These data suggest that BPAG2 is a novel collagen present in stratified squamous epithelia.

Localization of the 230-kilodalton bullous pemphigoid antigen in cultured keratinocytes: Formation of a prehemidesmosome

The hemidesmosome is the major attachment structure of the epidermal basal cell visible ultrastructurally in skin. The importance of its components to cultured cell attachment to substratum is not understood, however. A component of the hemidesmosome, the 230-kDa bullous pemphigoid antigen (p230), has been shown to be present in an insoluble or particulate fraction of cultured cells. In order to more fully characterize its potential importance for cell-matrix adhesion in cultured keratinocytes, specific antibodies were raised to the C-terminal region of p230 expressed as a bacterial fusion protein. Such antibodies recognize the hemidesmosome of epidermis, binding on the cytoplasmic region of its plaque. In addition, keratinocytes cultured in a 0.15 m M Ca 2+-defined medium contain a detergent-resistant pool of p230 which appears to lie in the same focal plane as the culture substrate and has a patchy or irregular distribution by indirect immunofluorescence. Treatment of cultured cells at 4 °C with trypsin or pronase sufficient to release keratinocytes from the culture dish does not affect the electrophoretic migration of p230 on SDS-gels, suggesting that p230 is not exposed to the extracellular space. In cells cultured in 0.15 m MCa 2+, 230-kDa BP antigen is localized to discrete clusters resting near the basal plasma membrane of the cell by immunogold staining following brief detergent treatment and fixation. These clusters are approximately 0.1 μm in diameter, which is similar in size to the in vivo hemidesmosome. Fully formed electron dense hemidesmosomal plaques are not observed under the same culture conditions, however. It appears that these clusters are early precursors of the hemidesmosome.

Western blot analysis of the antigen in pemphigoid gestationis

Using an immunoblotting technique, sera from 25 patients with pemphigoid gestationis were examined and tested against epidermal and dermal extracts of normal skin. The major antigen recognized by seven patients' sera was a molecule of 180 kDa, pemphigoid gestationis antigen, extractable only from the epidermis. Sera from 18 patients with bullous pemphigoid were studied as positive controls and the major antigen recognized was a larger molecule of 220 kDa. There was some degree of shared recognition of antigens with three patients with pemphigoid gestationis recognizing the 220 kDa bullous pemphigoid antigen. In addition one bullous pemphigoid serum recognized the 180 kDa pemphigoid gestationis antigen. The dominant pemphigoid gestationis antigen, however, differs from bullous pemphigoid antigen.

Structure of the human desmoplakins. Implications for function in the desmosomal plaque.

Desmoplakins (DPs) I and II are two major related proteins located in the innermost portion of the desmosomal plaque where it is thought they may play a role in attaching intermediate filaments (IF) to the cell surface. We have isolated and sequenced human cDNA clones encoding two major DP domains and a portion of a third. These clones can be divided into two classes that we believe to represent DPI and DPII cDNAs; our evidence suggests that the DPII message is derived at least in part from the processing of a larger transcript encoded by a single gene. Computer-aided analysis of the DPI-predicted amino acid sequence indicates that the central domain, which contains the heptad repeat characteristic of many alpha-fibrous proteins, will participate in the formation of a coiled coil dimer approximately 130 nm in length. The periodicity of acidic and basic residues in the rod suggests that DPI will aggregate with itself or similar molecules into higher order filamentous structures. The carboxyl terminus contains three regions with significant homology, each of which comprises almost five repeats of a 38-residue motif. It is likely that these regions each fold into a compact globular conformation stabilized by intrachain ionic interactions. Comparison of the predicted amino acid sequence of a cDNA encoding a portion of the 230-kDa bullous pemphigoid antigen (Stanley, J. R., Tanaka, T., Mueller, S., Klaus-Kovtun, V., and Roop, D. (1988) J. Clin. Invest. 82, 1864-1870) with DP revealed the presence of a 38-residue repeat with striking similarity to that of the DPs. Significantly, the periodicity in acidic and basic residues of these domains is the same as that found in the 1B rod domain of IF proteins. This suggests the possibility that the DPs might interact with IF via their common periodicity of charged residues.