Fc gamma receptor IIb modulates the molecular Grb2 interaction network in activated B cells.
B cells require signals transduced by the B cell antigen receptor (BCR) to provide humoral adaptive immunity. These signals are modulated by co-receptors like the Fcγ receptor IIb (FcγRIIb) that prevents activation of B cells after co-ligation with the BCR. Positive and negative effectors need to be precisely organized into signaling complexes, which requires adapter proteins like the growth factor receptor-bound protein 2 (Grb2). Here, we address the question how Grb2-mediated signal integration is affected by FcγRIIb. Our data reveal that concomitant engagement of BCR and FcγRIIb leads to markedly increased Grb2-mediated formation of ternary protein complexes comprising downstream of kinase-3 (Dok-3), Grb2, and the SH2 domain-containing inositol phosphatase (SHIP). Consistently, we found Grb2 to be required for full FcγRIIb-mediated negative regulation. To investigate how FcγRIIb influences the entire Grb2 interactions, we utilized quantitative mass spectrometry to make a differential interactome analysis. This approach revealed a shift of Grb2 interactions towards negative regulators like Dok-3, SHIP and SHP-2 and reduced binding to other proteins like CD19. Hence, we provide evidence that Grb2-mediated signal integration is a dynamic process that is important for the crosstalk between the BCR and its co-receptor FcγRIIb.
Georg August University of Göttingen, Institute of Cellular and Molecular Immunology, Humboldtallee 34, 37073 Göttingen, Germany.
Konstantin
K
Neumann
Thomas
T
Oellerich
Ines
I
Heine
Henning
H
Urlaub
Michael
M
Engelke
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D051380:GRB2 Adaptor Protein / Q000378:metabolism*; D013058:Mass Spectrometry; D051379:Mice; D008954:Models, Biological; D011485:Protein Binding; D017452:Receptors, IgG / Q000378:metabolism*; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; C406768:Dok3 protein, mouse; C080571:Fc gamma receptor IIB; D051380:GRB2 Adaptor Protein; D017452:Receptors, IgG; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases; D002118:Calcium