The direct binding of collagen XVII and collagen IV is disrupted by pemphigoid autoantibodies

• Published in: Laboratory investigation 2019-01, Vol.99 (1), p.48-57
• Main Authors: Kamaguchi, Mayumi, Iwata, Hiroaki, Nishie, Wataru, Toyonaga, Ellen, Ujiie, Hideyuki, Natsuga, Ken, Kitagawa, Yoshimasa, Shimizu, Hiroshi
• Format: Article
• Language: English
• Subjects: 13/1; 631/250/38; 692/699/249/1313; Adhesive strength; Amino acids; Autoantibodies; Autoantibodies - metabolism; Autoantigens - metabolism; Binding sites; Blistering; Bullous pemphigoid; C-Terminus; Cells, Cultured; Collagen; Collagen (type IV); Collagen Type IV - metabolism; Collagen Type XVII; Extracellular matrix; Hemidesmosomes; Humans; Immunoglobulin G; Immunoprecipitation; Inflammation; Keratinocytes; Keratinocytes - metabolism; Laboratory Medicine; Lesions; Medicine; Medicine & Public Health; Mouth Mucosa - pathology; Mucosa; Mucous membrane; Non-Fibrillar Collagens - metabolism; Pathology; Pemphigoid, Benign Mucous Membrane - immunology; Pemphigoid, Benign Mucous Membrane - metabolism; Pemphigoid, Benign Mucous Membrane - pathology; Pemphigoid, Bullous - immunology; Pemphigoid, Bullous - metabolism; Pemphigoid, Bullous - pathology; Protein interaction; Proteins
• ISSN: 0023-6837; 1530-0307
• DOI: 10.1038/s41374-018-0113-9

The basement membrane zone (BMZ) is framed by hemidesmosomes and extracellular matrix (ECM) including collagen IV (COL4). Hemidesmosomes are multiprotein complexes that include collagen XVII (COL17). BMZ proteins can be targeted in autoimmune subepidermal blistering diseases, e.g., pemphigoid targeting COL17. The blistering mechanisms in pemphigoid have not been fully elucidated, especially in mucous membrane pemphigoid (MMP), which mainly affects the mucosa. In this study, we showed that oral lesions in pemphigoid may be attributed to the inhibition of protein–protein interactions by autoantibodies. Using immunoprecipitation, we revealed that COL17 directly binds to COL4 in normal human keratinocytes and normal human oral keratinocytes. In particular, the C-terminus of COL17 is binding site to COL4 in oral keratinocytes. The precise COL4-binding region on COL17 was determined by protein–protein binding assay to be from amino acid Gly1175 to Asp1340 on the C-terminus. MMP-IgG or mAb recognizing the C-terminus hindered the interaction of COL17 with COL4 in oral keratinocytes. Furthermore, keratinocyte adhesion strength to COL4-coated plates was significantly reduced by the treatment of mAb against the C-terminus. In addition, the inflammatory infiltrates around perilesions were significantly less in MMP compared to BP. These results indicate that pemphigoid IgG targeting the C-terminus plays a pathogenic role in blister formation in the oral mucosa to inhibit protein interactions with less inflammation. Collagen XVII directly binds to collagen IV at the basement membrane zone in both skin and oral mucosa. Mucous membrane pemphigoid autoantibodies targeting the C-terminus of collagen XVII hinder this binding and induce the detachment of basal cells in the oral mucosa. This mechanism leads to oral lesions that show less inflammation than the skin lesions show.