title: Identification of disulfide bonds in the Ig-alpha/Ig-beta component of the B cell antigen receptor using the Drosophila S2 cell reconstitution system.
abstract: Structural information about immune receptor complexes is important for understanding signal transduction mechanisms. We have used the Drosophila S2 cell reconstitution system for identification of disulfide bonds within and between CD79a (Ig-alpha) and CD79b (Ig-beta), the heterodimeric signal transducing element of the B cell antigen receptor (BCR). Cysteines 113 and 135 of Ig-alpha and Ig-beta, respectively, form the intermolecular disulfide bridge stabilizing the Ig-alpha/Ig-beta heterodimer in both S2 cells and the B cell line J558L. Furthermore, using transfected S2 cells, two putative intramolecular disulfide bonds in the Ig-like domain of Ig-beta were identified. Ig-betaC65 and Ig-betaC120 form the canonical Ig fold disulfide bond. In addition, Ig-betaC43 and Ig-betaC124 also bind covalently. Individual cysteine to serine mutations in Ig-alpha had no influence on membrane-bound Ig (mIg)-M expression on the surface of S2 cells. In contrast, mIgM expression on the surface of B cells expressing Ig-alphaC113S was reduced, indicating that this intermolecular bond is prerequisite for efficient IgM-BCR formation. Our data also suggest that the Ig-alpha/Ig-beta heterodimer can assemble into oligomers.
authors.affiliation: Max Planck-Institut für Immunbiologie and University of Freiburg, Biologie III Stübeweg 51, 79108 Freiburg, Germany.
authors.forename: Gabrielle M
authors.initials: GM
authors.lastname: Siegers
authors.forename: Jianying
authors.initials: J
authors.lastname: Yang
authors.forename: Claudia U
authors.initials: CU
authors.lastname: Duerr
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Nielsen
authors.forename: Michael
authors.initials: M
authors.lastname: Reth
authors.forename: Wolfgang W A
authors.initials: WW
authors.lastname: Schamel
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D015153:Blotting, Western; D051925:CD79 Antigens / Q000737:chemistry*; D004330:Drosophila / Q000276:immunology; D005434:Flow Cytometry; D007075:Immunoglobulin M / Q000737:chemistry; D051379:Mice; D011947:Receptors, Antigen, B-Cell / Q000737:chemistry*; D015398:Signal Transduction / Q000276:immunology*; D014161:Transduction, Genetic; D014162:Transfection
chemical_list: D051925:CD79 Antigens; D007075:Immunoglobulin M; D011947:Receptors, Antigen, B-Cell