Mu-surrogate light chain physicochemical interactions of the human preB cell receptor: implications for VH repertoire selection and cell signaling at the preB cell stage.
The surrogate light chain (SL) composed of the A-like and VpreB polypeptides is organized as two Ig domains and an extra-loop structure. It associates to the mu-chain in preB cells. We have produced human VpreB, SL, two Fdmu (VH-CH1), and the two corresponding Fab-like (Fdmu-SL) recombinant proteins in baculovirus. The correctness of the general conformation of the proteins was assessed by epitope mapping and affinity measurements using a new batch of anti-VpreB mAbs. Plasmon resonance analysis showed that both VpreB and the entire SL associated with the Fdmu fragments, with Kd values of 3x10(-8) M for VpreB-Fdmu and of 10(-9) to 10(-10) M, depending upon the V(H), for SL-Fdmu. These results indicate that the A-like chain, in addition to be covalently bound to the Cmu1 domain, also interacts with the VH domain. Therefore, a dual role of the SL emerges: 1) interaction of the C-domain of A-like would release the mu-chain from its interaction with binding protein in the endoplasmic reticulum, and 2) interaction of a part of A-like and most of VpreB would bind to VH, ensuring a "quality control" of the native heavy chain that represents the first step of selection of the B cell repertoire. We also demonstrated that two Fab-like fragments did not interact with each other, suggesting that activation of the cell surface preB receptor does not involve aggregation neither in cis nor in trans of the Fab-like structures.
Gauthier
L
L
Centre d'Immunologie de Marseille-Luminy, Marseille, France.
Lemmers
B
B
Guelpa-Fonlupt
V
V
Fougereau
M
M
Schiff
C
C
D000911:Antibodies, Monoclonal / Q000737:chemistry; D016175:B-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D016367:Baculoviridae / Q000235:genetics; D002460:Cell Line; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D005822:Genetic Vectors / Q000138:chemical synthesis; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry / Q000378:metabolism; D007143:Immunoglobulin Heavy Chains / Q000096:biosynthesis / Q000378:metabolism*; D007147:Immunoglobulin Light Chains; D054444:Immunoglobulin Light Chains, Surrogate; D007135:Immunoglobulin Variable Region / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D007148:Immunoglobulin mu-Chains / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D011487:Protein Conformation; D011947:Receptors, Antigen, B-Cell / Q000276:immunology / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification; D015398:Signal Transduction / Q000276:immunology*; D013234:Stem Cells / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D007140:Immunoglobulin Fab Fragments; D007143:Immunoglobulin Heavy Chains; D007147:Immunoglobulin Light Chains; D054444:Immunoglobulin Light Chains, Surrogate; D007135:Immunoglobulin Variable Region; D007148:Immunoglobulin mu-Chains; D008562:Membrane Glycoproteins; D011947:Receptors, Antigen, B-Cell; D011994:Recombinant Proteins