title: Effect of Antimuscarinic Autoantibodies in Primary Sjögren's Syndrome.
abstract: The presence of functional autoantibodies against the muscarinic type 3 receptor (M3R) has been reported in primary Sjögren's syndrome (pSS). However, the pathogenic role of these autoantibodies in pSS development remains to be elucidated. In this experiment, we investigated a pathologic role of pSS autoantibodies (pSS IgG) associated with downregulation of the major histocompatibility complex I (MHC I) molecule with M3R through internalization. Anti-M3R autoantibodies in purified control and pSS IgG were detected using 4 synthesized cyclic M3R peptides by enzyme-linked immunosorbent assay. The binding reactivity of pSS IgG to M3R in situ was analyzed by a dual immunostaining method. Surface expression, interaction, and internalization of M3R with MHC I were analyzed by immunofluorescence confocal microscopy and biochemical assays. Synthetic cyclic peptides M3RP(205-221) and M3RP(520-527) showed significantly high reactivity with pSS IgG compared to the control IgG or the other 3 peptides (P < 0.05). Significantly high reactivity of pSS IgG to M3R in situ was observed. PSS IgG increased the interaction of membrane M3R with MHC I and induced their internalization in primary human submandibular gland cells. The pSS IgG-induced internalization of M3R with MHC I was significantly inhibited by the cholesterol-sequestering drug filipin. Our novel finding-namely, strong downregulation of the membrane MHC I with M3R through internalization of the cholesterol-rich microdomain associating with anti-M3R autoantibodies-could be an important mechanism contributing to the impaired salivation seen in pSS and linking secretory hypofunction to autoimmune pathogenesis.
authors.affiliation: Department of Physiology, School of Dentistry, Seoul National University and Dental Research Institute, Seoul, Republic of Korea.
authors.forename: N
authors.initials: N
authors.lastname: Kim
authors.affiliation: Department of Physiology, School of Dentistry, Seoul National University and Dental Research Institute, Seoul, Republic of Korea.
authors.forename: Y
authors.initials: Y
authors.lastname: Shin
authors.affiliation: Department of Physiology, School of Dentistry, Seoul National University and Dental Research Institute, Seoul, Republic of Korea.
authors.forename: S
authors.initials: S
authors.lastname: Choi
authors.affiliation: Department of Physiology, School of Dentistry, Seoul National University and Dental Research Institute, Seoul, Republic of Korea.
authors.forename: E
authors.initials: E
authors.lastname: Namkoong
authors.affiliation: Department of Physiology, School of Dentistry, Seoul National University and Dental Research Institute, Seoul, Republic of Korea.
authors.forename: M
authors.initials: M
authors.lastname: Kim
authors.affiliation: Oral and Maxillofacial Surgery, School of Dentistry, Seoul National University and Dental Research Institute, Seoul, Republic of Korea.
authors.forename: J
authors.initials: J
authors.lastname: Lee
authors.affiliation: Internal Medicine, College of Medicine, Seoul National University, Seoul, Republic of Korea.
authors.forename: Y
authors.initials: Y
authors.lastname: Song
authors.affiliation: Department of Physiology, School of Dentistry, Seoul National University and Dental Research Institute, Seoul, Republic of Korea kppark@snu.ac.kr.
authors.forename: K
authors.initials: K
authors.lastname: Park
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001323:Autoantibodies / Q000276:immunology*; D018929:Cell Culture Techniques; D002462:Cell Membrane / Q000276:immunology; D002478:Cells, Cultured; D003600:Cytosol / Q000276:immunology; D015536:Down-Regulation; D004705:Endocytosis / Q000187:drug effects / Q000276:immunology; D005260:Female; D005372:Filipin / Q000494:pharmacology; D015395:Histocompatibility Antigens Class I / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000187:drug effects / Q000276:immunology; D008285:Major Histocompatibility Complex / Q000276:immunology; D008297:Male; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008875:Middle Aged; D043587:Receptor, Muscarinic M3 / Q000187:drug effects / Q000276:immunology*; D012859:Sjogren's Syndrome / Q000276:immunology*; D013363:Submandibular Gland / Q000166:cytology / Q000276:immunology; D055815:Young Adult
chemical_list: D001323:Autoantibodies; D015395:Histocompatibility Antigens Class I; D007074:Immunoglobulin G; D043587:Receptor, Muscarinic M3; D005372:Filipin
keywords: MHC class I; down-regulation; endocytosis; humans; receptors; salivary glands