title: The autoinhibitory C-terminal SH2 domain of phospholipase C-γ2 stabilizes B cell receptor signalosome assembly.
abstract: The binding of antigen to the B cell receptor (BCR) stimulates the assembly of a signaling complex (signalosome) composed initially of the kinases Lyn, spleen tyrosine kinase (Syk), and Bruton's tyrosine kinase (Btk), as well as the adaptor protein B cell linker (BLNK). Together, these proteins recruit and activate phospholipase C-γ2 (PLC-γ2), a critical effector that stimulates increases in intracellular Ca(2+) and activates various signaling pathways downstream of the BCR. Individuals with one copy of a mutant PLCG2 gene, which encodes a variant PLC-γ2 that lacks the autoinhibitory C-terminal Src homology 2 (cSH2) domain, exhibit PLC-γ2-associated antibody deficiency and immune dysregulation (PLAID). Paradoxically, although COS-7 cells expressing the variant PLC-γ2 show enhanced basal and stimulated PLC-γ2 activity, B cells from PLAID patients show defective intracellular Ca(2+) responses upon cross-linking of the BCR. We found that the cSH2 domain of PLC-γ2 played a critical role in stabilizing the early signaling complex that is stimulated by BCR cross-linking. In the presence of the variant PLC-γ2, Syk, Btk, and BLNK were only weakly phosphorylated and failed to stably associate with the BCR. Thus, BCRs could not form stable clusters, resulting in dysregulation of downstream signaling and trafficking of the BCR. Thus, the cSH2 domain functions not only to inhibit the active site of PLC-γ2 but also to directly or indirectly stabilize the early BCR signaling complex.
authors.affiliation: Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.affiliation: Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA.
authors.forename: Haewon
authors.initials: H
authors.lastname: Sohn
authors.affiliation: Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Guangping
authors.initials: G
authors.lastname: Sun
authors.affiliation: Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Milner
authors.affiliation: Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA. spierce@nih.gov.
authors.forename: Susan K
authors.initials: SK
authors.lastname: Pierce
mesh_terms: D000077329:Agammaglobulinaemia Tyrosine Kinase; D000704:Analysis of Variance; D000818:Animals; D019556:COS Cells; D002118:Calcium / Q000378:metabolism; D002522:Chlorocebus aethiops; D005434:Flow Cytometry; D006801:Humans; D007153:Immunologic Deficiency Syndromes / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008051:Lipid Bilayers / Q000378:metabolism; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D046912:Multiprotein Complexes / Q000378:metabolism*; D051966:Phospholipase C gamma / Q000378:metabolism*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D000072377:Syk Kinase; D018909:src Homology Domains / Q000502:physiology*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D008051:Lipid Bilayers; D046912:Multiprotein Complexes; D011947:Receptors, Antigen, B-Cell; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625949:BTK protein, human; C000606896:SYK protein, human; D000072377:Syk Kinase; D051966:Phospholipase C gamma; D002118:Calcium