title: Interactions between the mannose receptor and thyroid autoantigens.
abstract: Thyroid autoantigens require internalization and processing by antigen-presenting cells to induce immune responses. Besides pinocytosis, antigen uptake can be receptor-mediated. The mannose receptor (ManR) has a cysteine rich domain (CR) and eight carbohydrate recognition domains (CRD) that bind glycosylated proteins. The TSH receptor (TSHR), thyroid peroxidase (TPO) and thyroglobulin (Tg) are glycoproteins. To investigate a role for the ManR in thyroid autoimmunity, we tested the interaction between these autoantigens and chimeric ManRs. Plasmids encoding the CR-domain linked to IgG-Fc (CR-Fc) and CDR domains 4-7 linked to IgG-Fc (CDR4-7-Fc) were expressed and purified with Protein A. Enzyme-linked immunosorbent assay (ELISA) plates were coated with human thyroid autoantigens and CR-Fc or CRD4-7-Fc binding detected with peroxidase-conjugated anti-IgG-Fc. CRD4-7-Fc binding was highest for the TSHR, followed by Tg and was minimal for TPO. CR-Fc bound to Tg but not to TSHR or TPO. The interaction between the TSHR and CRD-Fc was calcium-dependent; it was inhibited by mannose (not galactose), and required a glycosylated TSHR A-subunit. Moreover, precomplexing the TSHR A-subunit with CRD-Fc (but not CR-Fc), or adding mannose (but not galactose), decreased in vitro responses of splenocytes from TSHR-immunized mice. Our data indicate that the ManR may participate in autoimmune responses to Tg and the TSHR but not to TPO. Most important, ManR binding of heavily glycosylated TSHR A-subunits suggests a mechanism by which the minute amounts of A-subunit protein shed from the thyroid may be captured by antigen-presenting cells located in the gland or in draining lymph nodes.
authors.affiliation: Autoimmune Disease Unit, Cedars-Sinai Research Institute and UCLA School of Medicine, Los Angeles, CA 90048, USA.
authors.forename: G D
authors.initials: GD
authors.lastname: Chazenbalk
authors.forename: P N
authors.initials: PN
authors.lastname: Pichurin
authors.forename: J
authors.initials: J
authors.lastname: Guo
authors.forename: B
authors.initials: B
authors.lastname: Rapoport
authors.forename: S M
authors.initials: SM
authors.lastname: McLachlan
mesh_terms: D000818:Animals; D017951:Antigen Presentation; D001324:Autoantigens / Q000378:metabolism*; D002241:Carbohydrates / Q000032:analysis; D002460:Cell Line; D005260:Female; D006801:Humans; D007453:Iodide Peroxidase / Q000737:chemistry / Q000276:immunology; D037181:Lectins, C-Type / Q000378:metabolism*; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011989:Receptors, Thyrotropin / Q000737:chemistry / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*; D013954:Thyroglobulin / Q000737:chemistry / Q000276:immunology; D013963:Thyroid Hormones / Q000276:immunology*; D013967:Thyroiditis, Autoimmune / Q000276:immunology*
chemical_list: D001324:Autoantigens; D002241:Carbohydrates; D037181:Lectins, C-Type; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D011956:Receptors, Cell Surface; D011989:Receptors, Thyrotropin; D013963:Thyroid Hormones; D013954:Thyroglobulin; D007453:Iodide Peroxidase