1
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Mulazzani E, Kong K, Aróstegui JI, Ng AP, Ranathunga N, Abeysekera W, Garnham AL, Ng SL, Baker PJ, Jackson JT, Lich JD, Hibbs ML, Wicks IP, Louis C, Masters SL. G-CSF drives autoinflammation in APLAID. Nat Immunol 2023; 24:814-826. [PMID: 36997670 PMCID: PMC10154231 DOI: 10.1038/s41590-023-01473-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2022] [Accepted: 02/22/2023] [Indexed: 04/07/2023]
Abstract
Missense mutations in PLCG2 can cause autoinflammation with phospholipase C gamma 2-associated antibody deficiency and immune dysregulation (APLAID). Here, we generated a mouse model carrying an APLAID mutation (p.Ser707Tyr) and found that inflammatory infiltrates in the skin and lungs were only partially ameliorated by removing inflammasome function via the deletion of caspase-1. Also, deleting interleukin-6 or tumor necrosis factor did not fully prevent APLAID mutant mice from autoinflammation. Overall, these findings are in accordance with the poor response individuals with APLAID have to treatments that block interleukin-1, JAK1/2 or tumor necrosis factor. Cytokine analysis revealed increased granulocyte colony-stimulating factor (G-CSF) levels as the most distinct feature in mice and individuals with APLAID. Remarkably, treatment with a G-CSF antibody completely reversed established disease in APLAID mice. Furthermore, excessive myelopoiesis was normalized and lymphocyte numbers rebounded. APLAID mice were also fully rescued by bone marrow transplantation from healthy donors, associated with reduced G-CSF production, predominantly from non-hematopoietic cells. In summary, we identify APLAID as a G-CSF-driven autoinflammatory disease, for which targeted therapy is feasible.
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Affiliation(s)
- Elisabeth Mulazzani
- Inflammation Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Klara Kong
- Inflammation Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Juan I Aróstegui
- Department of Immunology, Hospital Clínic-IDIBAPS, Barcelona, Spain
| | - Ashley P Ng
- Blood Cells and Blood Cancer Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Clinical Haematology Department, Royal Melbourne Hospital, Melbourne, Victoria, Australia
- Peter MacCallum Cancer Centre, Parkville, Victoria, Australia
| | - Nishika Ranathunga
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
- Division of Bioinformatics, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Waruni Abeysekera
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
- Division of Bioinformatics, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Alexandra L Garnham
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
- Division of Bioinformatics, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Sze-Ling Ng
- Immunology Research Unit, GlaxoSmithKline, Collegeville, PA, USA
| | - Paul J Baker
- Inflammation Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Jacob T Jackson
- Division of Immunology, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - John D Lich
- Immunology Research Unit, GlaxoSmithKline, Collegeville, PA, USA
| | - Margaret L Hibbs
- Department of Immunology and Pathology, Monash University, Clayton, Victoria, Australia
| | - Ian P Wicks
- Inflammation Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
- Rheumatology Unit, Royal Melbourne Hospital, Parkville, Victoria, Australia
| | - Cynthia Louis
- Inflammation Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Seth L Masters
- Inflammation Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia.
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2
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Jackson JT, Mulazzani E, Nutt SL, Masters SL. The role of PLCγ2 in immunological disorders, cancer, and neurodegeneration. J Biol Chem 2021; 297:100905. [PMID: 34157287 PMCID: PMC8318911 DOI: 10.1016/j.jbc.2021.100905] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Revised: 06/15/2021] [Accepted: 06/18/2021] [Indexed: 02/06/2023] Open
Abstract
Phosphatidylinositol-specific phospholipase Cγ2 (PLCγ2) is a critical signaling molecule activated downstream from a variety of cell surface receptors that contain an intracellular immunoreceptor tyrosine-based activation motif. These receptors recruit kinases such as Syk, BTK, and BLNK to phosphorylate and activate PLCγ2, which then generates 1D-myo-inositol 1,4,5-trisphosphate and diacylglycerol. These well-known second messengers are required for diverse membrane functionality including cellular proliferation, endocytosis, and calcium flux. As a result, PLCγ2 dysfunction is associated with a variety of diseases including cancer, neurodegeneration, and immune disorders. The diverse pathologies associated with PLCγ2 are exemplified by distinct genetic variants. Inherited mutations at this locus cause PLCγ2-associated antibody deficiency and immune dysregulation, in some cases with autoinflammation. Acquired mutations at this locus, which often arise as a result of BTK inhibition to treat chronic lymphocytic leukemia, result in constitutive downstream signaling and lymphocyte proliferation. Finally, a third group of PLCγ2 variants actually has a protective effect in a variety of neurodegenerative disorders, presumably by increased uptake and degradation of deleterious neurological aggregates. Therefore, manipulating PLCγ2 activity either up or down could have therapeutic benefit; however, we require a better understanding of the signaling pathways propagated by these variants before such clinical utility can be realized. Here, we review the signaling roles of PLCγ2 in hematopoietic cells to help understand the effect of mutations driving immune disorders and cancer and extrapolate from this to roles which may relate to protection against neurodegeneration.
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Affiliation(s)
- Jacob T Jackson
- Immunology Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia; Inflammation Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Elisabeth Mulazzani
- Inflammation Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia; Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Stephen L Nutt
- Immunology Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia; Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Seth L Masters
- Inflammation Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia; Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia; Immunology Laboratory, Guangzhou Institute of Paediatrics, Guangzhou Women and Children's Medical Centre, Guangzhou, Guangdong, China.
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3
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Novice T, Kariminia A, Del Bel KL, Lu H, Sharma M, Lim CJ, Read J, Lugt MV, Hannibal MC, O'Dwyer D, Hosler M, Scharnitz T, Rizzo JM, Zacur J, Priatel J, Abdossamadi S, Bohm A, Junker A, Turvey SE, Schultz KR, Rozmus J. A Germline Mutation in the C2 Domain of PLCγ2 Associated with Gain-of-Function Expands the Phenotype for PLCG2-Related Diseases. J Clin Immunol 2019; 40:267-276. [PMID: 31853824 PMCID: PMC7086538 DOI: 10.1007/s10875-019-00731-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Accepted: 12/02/2019] [Indexed: 10/25/2022]
Abstract
We report three new cases of a germline heterozygous gain-of-function missense (p.(Met1141Lys)) mutation in the C2 domain of phospholipase C gamma 2 (PLCG2) associated with symptoms consistent with previously described auto-inflammation and phospholipase Cγ2 (PLCγ2)-associated antibody deficiency and immune dysregulation (APLAID) syndrome and pediatric common variable immunodeficiency (CVID). Functional evaluation showed platelet hyper-reactivity, increased B cell receptor-triggered calcium influx and ERK phosphorylation. Expression of the altered p.(Met1141Lys) variant in a PLCγ2-knockout DT40 cell line showed clearly enhanced BCR-triggered influx of external calcium when compared to control-transfected cells. Our results further expand the molecular basis of pediatric CVID and phenotypic spectrum of PLCγ2-related defects.
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Affiliation(s)
- Taylor Novice
- University of Michigan Medical School, University of Michigan, Ann Arbor, MI, USA
| | - Amina Kariminia
- Michael Cuccione Childhood Cancer Research Program, BC Children's Hospital Research Institute, Vancouver, Canada
| | - Kate L Del Bel
- Department of Pediatrics, BC Children's Hospital Research Institute, Vancouver, Canada
| | - Henry Lu
- Department of Pediatrics, BC Children's Hospital Research Institute, Vancouver, Canada
| | - Mehul Sharma
- Department of Pediatrics, BC Children's Hospital Research Institute, Vancouver, Canada
| | - Chinten J Lim
- Michael Cuccione Childhood Cancer Research Program, BC Children's Hospital Research Institute, Vancouver, Canada
| | - Jay Read
- Department of Pediatrics, Mott Children's Hospital, University of Michigan, Ann Arbor, MI, USA
| | - Mark Vander Lugt
- Division of Pediatric Hematology/Oncology, Department of Pediatrics, Mott Children's Hospital, University of Michigan, Ann Arbor, MI, USA
| | - Mark C Hannibal
- Division of Pediatric Genetics, Metabolism & Genomic Medicine, Mott Children's Hospital, University of Michigan, Ann Arbor, MI, USA
| | - David O'Dwyer
- Division of Pulmonary and Critical Care Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Mirie Hosler
- Division of Allergy and Clinical Immunology, University of Michigan, Ann Arbor, MI, USA
| | - Thomas Scharnitz
- Department of Dermatology, University of Michigan, Ann Arbor, MI, USA
| | - Jason M Rizzo
- Department of Dermatology, University of Michigan, Ann Arbor, MI, USA
| | - Jennifer Zacur
- Department of Dermatology, University of Michigan, Ann Arbor, MI, USA
| | - John Priatel
- Department of Pediatrics, BC Children's Hospital Research Institute, Vancouver, Canada
| | - Sayeh Abdossamadi
- Michael Cuccione Childhood Cancer Research Program, BC Children's Hospital Research Institute, Vancouver, Canada
| | - Alexandra Bohm
- Michael Cuccione Childhood Cancer Research Program, BC Children's Hospital Research Institute, Vancouver, Canada
| | - Anne Junker
- Division of Clinical Immunology & Allergy, Department of Pediatrics, BC Children's Hospital, University of British Columbia, Vancouver, Canada
| | - Stuart E Turvey
- Division of Clinical Immunology & Allergy, Department of Pediatrics, BC Children's Hospital, University of British Columbia, Vancouver, Canada
| | - Kirk R Schultz
- Michael Cuccione Childhood Cancer Research Program, BC Children's Hospital Research Institute, Vancouver, Canada
- Division of Pediatric Hematology/Oncology and Bone Marrow Transplant, Department of Pediatrics, BC Children's Hospital, University of British Columbia, 4480 Oak Street, Vancouver, Canada
| | - Jacob Rozmus
- Michael Cuccione Childhood Cancer Research Program, BC Children's Hospital Research Institute, Vancouver, Canada.
- Division of Pediatric Hematology/Oncology and Bone Marrow Transplant, Department of Pediatrics, BC Children's Hospital, University of British Columbia, 4480 Oak Street, Vancouver, Canada.
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4
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Krishnamoorthy M, Wasim L, Buhari FHM, Zhao T, Mahtani T, Ho J, Kang S, Deason-Towne F, Perraud AL, Schmitz C, Treanor B. The channel-kinase TRPM7 regulates antigen gathering and internalization in B cells. Sci Signal 2018; 11:11/533/eaah6692. [PMID: 29871912 DOI: 10.1126/scisignal.aah6692] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Members of the transient receptor potential (TRP) family of ion channels are cellular sensors involved in numerous physiological and pathological processes. We identified the TRP subfamily M member 7 (TRPM7) channel-kinase as a previously uncharacterized regulator of B cell activation. We showed that TRPM7 played a critical role in the early events of B cell activation through both its ion channel and kinase functions. DT40 B cells deficient in TRPM7 or expressing a kinase-deficient mutant of TRPM7 showed defective gathering of antigen and prolonged B cell receptor (BCR) signaling. We showed that lipid metabolism was altered in TRPM7-deficient cells and in cells expressing a kinase-deficient mutant of TRPM7 and suggest that PLC-γ2 may be a target of the kinase activity of TRPM7. Primary B cells that expressed less TRPM7 or were treated with a pharmacological inhibitor of TRPM7 also displayed defective antigen gathering and increased BCR signaling. Finally, we demonstrated that blocking TRPM7 function compromised antigen internalization and presentation to T cells. These data suggest that TRPM7 controls an essential process required for B cell affinity maturation and the production of high-affinity antibodies.
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Affiliation(s)
- Mithunah Krishnamoorthy
- Department of Cell and Systems Biology, University of Toronto, 24 Harbord Street, Toronto, Ontario M5S 3G5, Canada
| | - Laabiah Wasim
- Department of Immunology, University of Toronto, 1 King's College Circle, Toronto, Ontario M5S 1A8, Canada
| | - Fathima Hifza Mohamed Buhari
- Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada
| | - Tiantian Zhao
- Department of Immunology, University of Toronto, 1 King's College Circle, Toronto, Ontario M5S 1A8, Canada
| | - Trisha Mahtani
- Department of Cell and Systems Biology, University of Toronto, 24 Harbord Street, Toronto, Ontario M5S 3G5, Canada
| | - Josephine Ho
- Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada
| | - Sohee Kang
- Department of Computer and Mathematical Sciences, University of Toronto Scarborough, Toronto, Ontario M1C 1A4, Canada
| | - Francina Deason-Towne
- Department of Immunology and Microbiology, University of Colorado, Denver, CO 80206, USA
| | - Anne-Laure Perraud
- Department of Immunology and Microbiology, University of Colorado, Denver, CO 80206, USA
| | - Carsten Schmitz
- Department of Immunology and Microbiology, University of Colorado, Denver, CO 80206, USA.,Department of Biomedical Research, National Jewish Health, Denver, CO 80206, USA
| | - Bebhinn Treanor
- Department of Cell and Systems Biology, University of Toronto, 24 Harbord Street, Toronto, Ontario M5S 3G5, Canada. .,Department of Immunology, University of Toronto, 1 King's College Circle, Toronto, Ontario M5S 1A8, Canada.,Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada
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5
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Unperturbed Immune Function despite Mutation of C-Terminal Tyrosines in Syk Previously Implicated in Signaling and Activity Regulation. Mol Cell Biol 2017; 37:MCB.00216-17. [PMID: 28760774 DOI: 10.1128/mcb.00216-17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 07/26/2017] [Indexed: 11/20/2022] Open
Abstract
The nonreceptor tyrosine kinase Syk, a central regulator of immune cell differentiation and activation, is a promising drug target for treatment of leukemia and allergic and inflammatory diseases. The clinical failure of Syk inhibitors underscores the importance of understanding the regulation of Syk function and activity. A series of previous studies emphasized the importance of three C-terminal tyrosines in Syk for kinase activity regulation, as docking sites for downstream effector molecules, and for Ca2+ mobilization. Here, we investigated the roles of these C-terminal tyrosines in the mouse. Surprisingly, expression of a triple tyrosine-to-phenylalanine human Syk mutant, SYK(Y3F), was not associated with discernible signaling defects either in reconstituted DT40 cells or in B or mast cells from mice expressing SYK(Y3F) instead of wild-type Syk. Remarkably, lymphocyte differentiation, calcium mobilization, and 2,4,6-trinitrophenyl (TNP)-specific immune responses were unperturbed in SYK(Y3F) mice. These results emphasize the capacity of immune cells to compensate for specific molecular defects, likely using redundant intermolecular interactions, and highlight the importance of in vivo analyses for understanding cellular signaling mechanisms.
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6
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Budzyńska PM, Niemelä M, Sarapulov AV, Kyläniemi MK, Nera KP, Junttila S, Laiho A, Mattila PK, Alinikula J, Lassila O. IRF4 Deficiency Leads to Altered BCR Signalling Revealed by Enhanced PI3K Pathway, Decreased SHIP Expression and Defected Cytoskeletal Responses. Scand J Immunol 2016; 82:418-28. [PMID: 26173778 DOI: 10.1111/sji.12343] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 07/07/2015] [Indexed: 12/13/2022]
Abstract
The graded expression of transcription factor interferon regulatory factor 4 (IRF4) regulates B cell development and is critical for plasma cell differentiation. However, the mechanisms, by which IRF4 elicits its crucial tasks, are largely unknown. To characterize the molecular targets of IRF4 in B cells, we established an IRF4-deficient DT40 B cell line. We found that in the absence of IRF4, the expression of several molecules involved in BCR signalling was altered. For example, the expression of B cell adaptor for PI3K (BCAP) was upregulated, whereas the SHIP (SH2-containing Inositol 5?-Phosphatase) expression was downregulated. These molecular unbalances were accompanied by increased BCR-induced calcium signalling, attenuated B cell linker protein (BLNK) and ERK activity and enhanced activity of PI3K/protein kinase B (Akt) pathway. Further, the IRF4-deficient cells showed dramatically diminished cytoskeletal responses to anti-IgM cross-linking. Our results show that IRF4 has an important role in the regulation of BCR signalling and help to shed light on the molecular mechanisms of B cell development and germinal centre response.
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Affiliation(s)
- P M Budzyńska
- Department of Medical Microbiology and Immunology, University of Turku, Turku, Finland.,Turku Doctoral Programme of Biomedical Sciences, University of Turku, Turku, Finland
| | - M Niemelä
- Department of Medical Microbiology and Immunology, University of Turku, Turku, Finland
| | - A V Sarapulov
- Institute of Biomedicine, Department of Pathology, University of Turku, Turku, Finland
| | - M K Kyläniemi
- Department of Medical Microbiology and Immunology, University of Turku, Turku, Finland
| | - K-P Nera
- Department of Medical Microbiology and Immunology, University of Turku, Turku, Finland
| | - S Junttila
- The Finnish Microarray and Sequencing Center, Turku Centre for Biotechnology, Turku, Finland
| | - A Laiho
- The Finnish Microarray and Sequencing Center, Turku Centre for Biotechnology, Turku, Finland
| | - P K Mattila
- Institute of Biomedicine, Department of Pathology, University of Turku, Turku, Finland
| | - J Alinikula
- Department of Medical Microbiology and Immunology, University of Turku, Turku, Finland
| | - O Lassila
- Department of Medical Microbiology and Immunology, University of Turku, Turku, Finland
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7
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Devkota S, Joseph RE, Min L, Bruce Fulton D, Andreotti AH. Scaffold Protein SLP-76 Primes PLCγ1 for Activation by ITK-Mediated Phosphorylation. J Mol Biol 2015; 427:2734-47. [PMID: 25916191 DOI: 10.1016/j.jmb.2015.04.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Revised: 04/04/2015] [Accepted: 04/06/2015] [Indexed: 11/25/2022]
Abstract
Activation of the phospholipase, PLCγ1, is critical for proper T cell signaling following antigen receptor engagement. In T cells, the Tec family kinase, interleukin-2-induced tyrosine kinase (ITK), phosphorylates PLCγ1 at tyrosine 783 (Y783) leading to activation of phospholipase function and subsequent production of the second messengers inositol 1,4,5-trisphosphate and diacylglycerol. In this work, we demonstrate that PLCγ1 can be primed for ITK-mediated phosphorylation on Y783 by a specific region of the adaptor protein, SLP-76. The SLP-76 phosphotyrosine-containing sequence, pY(173)IDR, does not conform to the canonical recognition motif for an SH2 domain yet binds with significant affinity to the C-terminal SH2 domain of PLCγ1 (SH2C). The SLP-76 pY(173) motif competes with the autoinhibited conformation surrounding the SH2C domain of PLCγ1 leading to exposure of the ITK recognition element on the PLCγ1 SH2 domain and release of the target tyrosine, Y783. These data contribute to the evolving model for the molecular events occurring early in the T cell activation process.
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Affiliation(s)
- Sujan Devkota
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA
| | - Raji E Joseph
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA
| | - Lie Min
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19711, USA
| | - D Bruce Fulton
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA
| | - Amy H Andreotti
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA.
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8
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Wang J, Sohn H, Sun G, Milner JD, Pierce SK. The autoinhibitory C-terminal SH2 domain of phospholipase C-γ2 stabilizes B cell receptor signalosome assembly. Sci Signal 2014; 7:ra89. [PMID: 25227611 DOI: 10.1126/scisignal.2005392] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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.
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Affiliation(s)
- Jing Wang
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA
| | - Haewon Sohn
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA
| | - Guangping Sun
- Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Joshua D Milner
- Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Susan K Pierce
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA.
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