1
|
Degn SE, Tolar P. Towards a unifying model for B-cell receptor triggering. Nat Rev Immunol 2024:10.1038/s41577-024-01073-x. [PMID: 39256626 DOI: 10.1038/s41577-024-01073-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/16/2024] [Indexed: 09/12/2024]
Abstract
Antibodies are exceptionally versatile molecules with remarkable flexibility in their binding properties. Their natural targets range from small-molecule toxins, across viruses of different sizes, to bacteria and large multicellular parasites. The molecular determinants bound by antibodies include proteins, peptides, carbohydrates, nucleic acids, lipids and even synthetic molecules that have never existed in nature. Membrane-anchored antibodies also serve as receptors on the surface of the B cells that produce them. Despite recent structural insights, there is still no unifying molecular mechanism to explain how antibody targets (antigens) trigger the activation of these B-cell receptors (BCRs). After cognate antigen encounter, somatic hypermutation and class-switch recombination allow BCR affinity maturation and immunoglobulin class-specific responses, respectively. This raises the fundamental question of how one receptor activation mechanism can accommodate a plethora of variant receptors and ligands, and how it can ensure that individual B cells remain responsive to antigen after somatic hypermutation and class switching. There is still no definite answer. Here we give a brief historical account of the different models proposed to explain BCR triggering and discuss their merit in the context of the current knowledge of the structure of BCRs, their dynamic membrane distribution, and recent biochemical and cell biological insights.
Collapse
Affiliation(s)
- Søren E Degn
- Laboratory for Lymphocyte Biology, Department of Biomedicine, Aarhus University, Aarhus, Denmark.
- Centre for Cellular Signal Patterns (CellPAT), Aarhus University, Aarhus, Denmark.
| | - Pavel Tolar
- Institute of Immunity and Transplantation, Division of Infection and Immunity, University College London, London, UK
| |
Collapse
|
2
|
Kassis G, Palshikar MG, Hilchey SP, Zand MS, Thakar J. Discrete-state models identify pathway specific B cell states across diseases and infections at single-cell resolution. J Theor Biol 2024; 583:111769. [PMID: 38423206 PMCID: PMC11046450 DOI: 10.1016/j.jtbi.2024.111769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2023] [Revised: 02/10/2024] [Accepted: 02/17/2024] [Indexed: 03/02/2024]
Abstract
Oxygen (O2) regulated pathways modulate B cell activation, migration and proliferation during infection, vaccination, and other diseases. Modeling these pathways in health and disease is critical to understand B cell states and ways to mediate them. To characterize B cells by their activation of O2 regulated pathways we develop pathway specific discrete state models using previously published single-cell RNA-sequencing (scRNA-seq) datasets from isolated B cells. Specifically, Single Cell Boolean Omics Network Invariant-Time Analysis (scBONITA) was used to infer logic gates for known pathway topologies. The simplest inferred set of logic gates that maximized the number of "OR" interactions between genes was used to simulate B cell networks involved in oxygen sensing until they reached steady network states (attractors). By focusing on the attractors that best represented sequenced cells, we identified genes critical in determining pathway specific cellular states that corresponded to diseased and healthy B cell phenotypes. Specifically, we investigate the transendothelial migration, regulation of actin cytoskeleton, HIF1A, and Citrate Cycle pathways. Our analysis revealed attractors that resembled the state of B cell exhaustion in HIV+ patients as well as attractors that promoted anerobic metabolism, angiogenesis, and tumorigenesis in breast cancer patients, which were eliminated after neoadjuvant chemotherapy (NACT). Finally, we investigated the attractors to which the Azimuth-annotated B cells mapped and found that attractors resembling B cells from HIV+ patients encompassed a significantly larger number of atypical memory B cells than HIV- attractors. Meanwhile, attractors resembling B cells from breast cancer patients post NACT encompassed a reduced number of atypical memory B cells compared to pre-NACT attractors.
Collapse
Affiliation(s)
- George Kassis
- Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, USA
| | - Mukta G Palshikar
- Biophysics, Structural, and Computational Biology Program, University of Rochester School of Medicine and Dentistry, Rochester, USA
| | - Shannon P Hilchey
- Department of Medicine, Division of Nephrology, University of Rochester Medical Center, Rochester, NY, USA
| | - Martin S Zand
- Department of Medicine, Division of Nephrology, University of Rochester Medical Center, Rochester, NY, USA
| | - Juilee Thakar
- Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, USA; Biophysics, Structural, and Computational Biology Program, University of Rochester School of Medicine and Dentistry, Rochester, USA; Department of Biostatistics and Computational Biology, University of Rochester School of Medicine and Dentistry, Rochester, USA; Department of Biomedical Genetics, University of Rochester School of Medicine and Dentistry, Rochester, USA.
| |
Collapse
|
3
|
Wheaton BJ, Sena J, Sundararajan A, Umale P, Schilkey F, Miller RD. Identification of regenerative processes in neonatal spinal cord injury in the opossum (Monodelphis domestica): A transcriptomic study. J Comp Neurol 2021; 529:969-986. [PMID: 32710567 PMCID: PMC7855507 DOI: 10.1002/cne.24994] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 07/08/2020] [Accepted: 07/09/2020] [Indexed: 12/20/2022]
Abstract
This study investigates the response to spinal cord injury in the gray short‐tailed opossum (Monodelphis domestica). In opossums spinal injury early in development results in spontaneous axon growth through the injury, but this regenerative potential diminishes with maturity until it is lost entirely. The mechanisms underlying this regeneration remain unknown. RNA sequencing was used to identify differential gene expression in regenerating (SCI at postnatal Day 7, P7SCI) and nonregenerating (SCI at Day 28, P28SCI) cords +1d, +3d, and +7d after complete spinal transection, compared to age‐matched controls. Genes showing significant differential expression (log2FC ≥ 1, Padj ≤ 0.05) were used for downstream analysis. Across all time‐points 233 genes altered expression after P7SCI, and 472 genes altered expression after P28SCI. One hundred and forty‐seven genes altered expression in both injury ages (63% of P7SCI data set). The majority of changes were gene upregulations. Gene ontology overrepresentation analysis in P7SCI gene‐sets showed significant overrepresentations only in immune‐associated categories, while P28SCI gene‐sets showed overrepresentations in these same immune categories, along with other categories such as “cell proliferation,” “cell adhesion,” and “apoptosis.” Cell‐type–association analysis suggested that, regardless of injury age, injury‐associated gene transcripts were most strongly associated with microglia and endothelial cells, with strikingly fewer astrocyte, oligodendrocyte and neuron‐related genes, the notable exception being a cluster of mostly downregulated oligodendrocyte‐associated genes in the P7SCI + 7d gene‐set. Our findings demonstrate a more complex transcriptomic response in nonregenerating cords, suggesting a strong influence of non‐neuronal cells in the outcome after injury and providing the largest survey yet of the transcriptomic changes occurring after SCI in this model.
Collapse
Affiliation(s)
- Benjamin J Wheaton
- Department of Integrative Medical Biology, University of Umeå, Umeå, Sweden.,Center for Evolutionary and Theoretical Immunology, Department of Biology, University of New Mexico, Albuquerque, New Mexico, USA
| | - Johnny Sena
- National Center for Genome Resources, Santa Fe, New Mexico, USA
| | | | - Pooja Umale
- National Center for Genome Resources, Santa Fe, New Mexico, USA
| | - Faye Schilkey
- National Center for Genome Resources, Santa Fe, New Mexico, USA
| | - Robert D Miller
- Center for Evolutionary and Theoretical Immunology, Department of Biology, University of New Mexico, Albuquerque, New Mexico, USA
| |
Collapse
|
4
|
Karslake JD, Donarski ED, Shelby SA, Demey LM, DiRita VJ, Veatch SL, Biteen JS. SMAUG: Analyzing single-molecule tracks with nonparametric Bayesian statistics. Methods 2020; 193:16-26. [PMID: 32247784 DOI: 10.1016/j.ymeth.2020.03.008] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 03/27/2020] [Accepted: 03/30/2020] [Indexed: 02/08/2023] Open
Abstract
Single-molecule fluorescence microscopy probes nanoscale, subcellular biology in real time. Existing methods for analyzing single-particle tracking data provide dynamical information, but can suffer from supervisory biases and high uncertainties. Here, we develop a method for the case of multiple interconverting species undergoing free diffusion and introduce a new approach to analyzing single-molecule trajectories: the Single-Molecule Analysis by Unsupervised Gibbs sampling (SMAUG) algorithm, which uses nonparametric Bayesian statistics to uncover the whole range of information contained within a single-particle trajectory dataset. Even in complex systems where multiple biological states lead to a number of observed mobility states, SMAUG provides the number of mobility states, the average diffusion coefficient of single molecules in that state, the fraction of single molecules in that state, the localization noise, and the probability of transitioning between two different states. In this paper, we provide the theoretical background for the SMAUG analysis and then we validate the method using realistic simulations of single-particle trajectory datasets as well as experiments on a controlled in vitro system. Finally, we demonstrate SMAUG on real experimental systems in both prokaryotes and eukaryotes to measure the motions of the regulatory protein TcpP in Vibrio cholerae and the dynamics of the B-cell receptor antigen response pathway in lymphocytes. Overall, SMAUG provides a mathematically rigorous approach to measuring the real-time dynamics of molecular interactions in living cells.
Collapse
Affiliation(s)
- Joshua D Karslake
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48104 USA
| | - Eric D Donarski
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48104 USA
| | - Sarah A Shelby
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48104 USA
| | - Lucas M Demey
- Department of Microbiology & Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA
| | - Victor J DiRita
- Department of Microbiology & Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA
| | - Sarah L Veatch
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48104 USA
| | - Julie S Biteen
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48104 USA; Department of Chemistry, University of Michigan, Ann Arbor, MI 48104 USA.
| |
Collapse
|
5
|
Halova I, Bambouskova M, Draberova L, Bugajev V, Draber P. The transmembrane adaptor protein NTAL limits mast cell chemotaxis toward prostaglandin E2. Sci Signal 2018; 11:11/556/eaao4354. [DOI: 10.1126/scisignal.aao4354] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Chemotaxis of mast cells is one of the crucial steps in their development and function. Non–T cell activation linker (NTAL) is a transmembrane adaptor protein that inhibits the activation of mast cells and B cells in a phosphorylation-dependent manner. Here, we studied the role of NTAL in the migration of mouse mast cells stimulated by prostaglandin E2 (PGE2). Although PGE2 does not induce the tyrosine phosphorylation of NTAL, unlike IgE immune complex antigens, we found that loss of NTAL increased the chemotaxis of mast cells toward PGE2. Stimulation of mast cells that lacked NTAL with PGE2 enhanced the phosphorylation of AKT and the production of phosphatidylinositol 3,4,5-trisphosphate. In resting NTAL-deficient mast cells, phosphorylation of an inhibitory threonine in ERM family proteins accompanied increased activation of β1-containing integrins, which are features often associated with increased invasiveness in tumors. Rescue experiments indicated that only full-length, wild-type NTAL restored the chemotaxis of NTAL-deficient cells toward PGE2. Together, these data suggest that NTAL is a key inhibitor of mast cell chemotaxis toward PGE2, which may act through the RHOA/ERM/β1-integrin and PI3K/AKT axes.
Collapse
|
6
|
|
7
|
Adler LN, Jiang W, Bhamidipati K, Millican M, Macaubas C, Hung SC, Mellins ED. The Other Function: Class II-Restricted Antigen Presentation by B Cells. Front Immunol 2017; 8:319. [PMID: 28386257 PMCID: PMC5362600 DOI: 10.3389/fimmu.2017.00319] [Citation(s) in RCA: 87] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 03/07/2017] [Indexed: 12/31/2022] Open
Abstract
Mature B lymphocytes (B cells) recognize antigens using their B cell receptor (BCR) and are activated to become antibody-producing cells. In addition, and integral to the development of a high-affinity antibodies, B cells utilize the specialized major histocompatibility complex class II (MHCII) antigen presentation pathway to process BCR-bound and internalized protein antigens and present selected peptides in complex with MHCII to CD4+ T cells. This interaction influences the fate of both types of lymphocytes and shapes immune outcomes. Specific, effective, and optimally timed antigen presentation by B cells requires well-controlled intracellular machinery, often regulated by the combined effects of several molecular events. Here, we delineate and summarize these events in four steps along the antigen presentation pathway: (1) antigen capture and uptake by B cells; (2) intersection of internalized antigen/BCRs complexes with MHCII in peptide-loading compartments; (3) generation and regulation of MHCII/peptide complexes; and (4) exocytic transport for presentation of MHCII/peptide complexes at the surface of B cells. Finally, we discuss modulation of the MHCII presentation pathway across B cell development and maturation to effector cells, with an emphasis on the shaping of the MHCII/peptide repertoire by two key antigen presentation regulators in B cells: HLA-DM and HLA-DO.
Collapse
Affiliation(s)
- Lital N Adler
- Department of Pediatrics, Stanford University, Stanford, CA, USA; Program in Immunology, Stanford University, Stanford, CA, USA
| | - Wei Jiang
- Department of Pediatrics, Stanford University, Stanford, CA, USA; Program in Immunology, Stanford University, Stanford, CA, USA
| | | | | | - Claudia Macaubas
- Department of Pediatrics, Stanford University, Stanford, CA, USA; Program in Immunology, Stanford University, Stanford, CA, USA
| | - Shu-Chen Hung
- Department of Pediatrics, Stanford University, Stanford, CA, USA; Program in Immunology, Stanford University, Stanford, CA, USA
| | - Elizabeth D Mellins
- Department of Pediatrics, Stanford University, Stanford, CA, USA; Program in Immunology, Stanford University, Stanford, CA, USA
| |
Collapse
|
8
|
Stone MB, Shelby SA, Núñez MF, Wisser K, Veatch SL. Protein sorting by lipid phase-like domains supports emergent signaling function in B lymphocyte plasma membranes. eLife 2017; 6. [PMID: 28145867 PMCID: PMC5373823 DOI: 10.7554/elife.19891] [Citation(s) in RCA: 138] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Accepted: 01/31/2017] [Indexed: 12/19/2022] Open
Abstract
Diverse cellular signaling events, including B cell receptor (BCR) activation, are hypothesized to be facilitated by domains enriched in specific plasma membrane lipids and proteins that resemble liquid-ordered phase-separated domains in model membranes. This concept remains controversial and lacks direct experimental support in intact cells. Here, we visualize ordered and disordered domains in mouse B lymphoma cell membranes using super-resolution fluorescence localization microscopy, demonstrate that clustered BCR resides within ordered phase-like domains capable of sorting key regulators of BCR activation, and present a minimal, predictive model where clustering receptors leads to their collective activation by stabilizing an extended ordered domain. These results provide evidence for the role of membrane domains in BCR signaling and a plausible mechanism of BCR activation via receptor clustering that could be generalized to other signaling pathways. Overall, these studies demonstrate that lipid mediated forces can bias biochemical networks in ways that broadly impact signal transduction. DOI:http://dx.doi.org/10.7554/eLife.19891.001 Membranes made of molecules called lipids surround every living cell to protect the cell's contents. Cells also communicate with the outside environment via their membranes. Proteins in the membrane receive information from the environment and trigger signaling pathways inside the cell to relay this information to the center of cell. The way in which proteins are organized on the membrane has a major influence on their signaling activity. Some areas of the membrane are more crowded with certain lipids and signaling proteins than others. Lipid and protein molecules of particular types can come together and form distinct areas called “ordered” and “disordered” domains. The lipids in ordered domains are more tightly packed than disordered domains and it is thought that this difference allows domains to selectively exclude or include certain proteins. Ordered domains are also known as "lipid rafts". Lipid rafts and disordered domains may help cells to control the activities of signaling pathways, however, technical limitations have made it difficult to study the roles of these domains. The membranes surrounding immune cells called B cells contain a protein called the B cell receptor, which engages with proteins from microbes and other foreign invaders. When the B cell receptor binds to a foreign protein it forms clusters with other B cell receptors and becomes active, triggering a signaling pathway that leads to immune responses. Stone, Shelby et al. examined lipid rafts and disordered domains in B cells from mice using a technique called super-resolution fluorescence microscopy. The results show that clusters of B cell receptors are present within lipid rafts. These clusters made the lipid rafts larger and more stable. A protein that is needed during the early stages of B cell receptor signaling was also found in the same lipid rafts. Another protein that terminates signaling was excluded because it prefers disordered domains. Together, this provides a local environment in certain areas of the membrane that favors receptor activity and supports the subsequent immune response. Future work is needed to understand how cells control the make-up of lipids and proteins within their membranes, and how defects in this regulation can alter signaling activity and lead to disease. DOI:http://dx.doi.org/10.7554/eLife.19891.002
Collapse
Affiliation(s)
- Matthew B Stone
- Department of Biophysics, University of Michigan, Ann Arbor, United States
| | - Sarah A Shelby
- Department of Biophysics, University of Michigan, Ann Arbor, United States
| | - Marcos F Núñez
- Department of Biophysics, University of Michigan, Ann Arbor, United States
| | - Kathleen Wisser
- Department of Biophysics, University of Michigan, Ann Arbor, United States
| | - Sarah L Veatch
- Department of Biophysics, University of Michigan, Ann Arbor, United States
| |
Collapse
|
9
|
Allen JC, Talab F, Slupsky JR. Targeting B-cell receptor signaling in leukemia and lymphoma: how and why? Int J Hematol Oncol 2016; 5:37-53. [PMID: 30302202 DOI: 10.2217/ijh-2016-0003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 05/13/2016] [Indexed: 01/04/2023] Open
Abstract
B-lymphocytes are dependent on B-cell receptor (BCR) signaling for the constant maintenance of their physiological function, and in many B-cell malignancies this signaling pathway is prone to aberrant activation. This understanding has led to an ever-increasing interest in the signaling networks activated following ligation of the BCR in both normal and malignant cells, and has been critical in establishing an array of small molecule inhibitors targeting BCR-induced signaling. By dissecting how different malignancies signal through BCR, researchers are contributing to the design of more customized therapeutics which have greater efficacy and lower toxicity than previous therapies. This allows clinicians access to an array of approaches to best treat patients whose malignancies have BCR signaling as a driver of pathogenesis.
Collapse
Affiliation(s)
- John C Allen
- Department of Molecular & Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, L69 3GE, UK.,Department of Molecular & Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, L69 3GE, UK
| | - Fatima Talab
- Redx Oncology Plc, Duncan Building, Royal Liverpool University Hospital, Daulby Street, Liverpool, L69 3GA, UK.,Redx Oncology Plc, Duncan Building, Royal Liverpool University Hospital, Daulby Street, Liverpool, L69 3GA, UK
| | - Joseph R Slupsky
- Department of Molecular & Clinical Cancer Medicine, Institute of Translational Medicine, University of Liverpool, Ashton Street, Liverpool, L69 3GE, UK.,Department of Molecular & Clinical Cancer Medicine, Institute of Translational Medicine, University of Liverpool, Ashton Street, Liverpool, L69 3GE, UK
| |
Collapse
|
10
|
LRRK1 is critical in the regulation of B-cell responses and CARMA1-dependent NF-κB activation. Sci Rep 2016; 6:25738. [PMID: 27166870 PMCID: PMC4863158 DOI: 10.1038/srep25738] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Accepted: 04/21/2016] [Indexed: 12/12/2022] Open
Abstract
B-cell receptor (BCR) signaling plays a critical role in B-cell activation and humoral immunity. In this study, we discovered a critical function of leucine-rich repeat kinase 1 (LRRK1) in BCR-mediated immune responses. Lrrk1−/− mice exhibited altered B1a-cell development and basal immunoglobulin production. In addition, these mice failed to produce IgG3 antibody in response to T cell–independent type 2 antigen due to defects in IgG3 class-switch recombination. Concomitantly, B cells lacking LRRK1 exhibited a profound defect in proliferation and survival upon BCR stimulation, which correlated with impaired BCR-mediated NF-κB activation and reduced expression of NF-κB target genes including Bcl-xL, cyclin D2, and NFATc1/αA. Furthermore, LRRK1 physically interacted and potently synergized with CARMA1 to enhance NF-κB activation. Our results reveal a critical role of LRRK1 in NF-κB signaling in B cells and the humoral immune response.
Collapse
|
11
|
Vaughn SE, Foley C, Lu X, Patel ZH, Zoller EE, Magnusen AF, Williams AH, Ziegler JT, Comeau ME, Marion MC, Glenn SB, Adler A, Shen N, Nath S, Stevens AM, Freedman BI, Tsao BP, Jacob CO, Kamen DL, Brown EE, Gilkeson GS, Alarcón GS, Reveille JD, Anaya JM, James JA, Moser KL, Criswell LA, Vilá LM, Alarcón-Riquelme ME, Petri M, Scofield RH, Kimberly RP, Ramsey-Goldman R, Binjoo Y, Choi J, Bae SC, Boackle SA, Vyse TJ, Guthridge JM, Namjou B, Gaffney PM, Langefeld CD, Kaufman KM, Kelly JA, Harley ITW, Harley JB, Kottyan LC. Lupus risk variants in the PXK locus alter B-cell receptor internalization. Front Genet 2015; 5:450. [PMID: 25620976 PMCID: PMC4288052 DOI: 10.3389/fgene.2014.00450] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Accepted: 12/09/2014] [Indexed: 01/17/2023] Open
Abstract
Genome wide association studies have identified variants in PXK that confer risk for humoral autoimmune diseases, including systemic lupus erythematosus (SLE or lupus), rheumatoid arthritis and more recently systemic sclerosis. While PXK is involved in trafficking of epidermal growth factor Receptor (EGFR) in COS-7 cells, mechanisms linking PXK to lupus pathophysiology have remained undefined. In an effort to uncover the mechanism at this locus that increases lupus-risk, we undertook a fine-mapping analysis in a large multi-ancestral study of lupus patients and controls. We define a large (257kb) common haplotype marking a single causal variant that confers lupus risk detected only in European ancestral populations and spans the promoter through the 3′ UTR of PXK. The strongest association was found at rs6445972 with P < 4.62 × 10−10, OR 0.81 (0.75–0.86). Using stepwise logistic regression analysis, we demonstrate that one signal drives the genetic association in the region. Bayesian analysis confirms our results, identifying a 95% credible set consisting of 172 variants spanning 202 kb. Functionally, we found that PXK operates on the B-cell antigen receptor (BCR); we confirmed that PXK influenced the rate of BCR internalization. Furthermore, we demonstrate that individuals carrying the risk haplotype exhibited a decreased rate of BCR internalization, a process known to impact B cell survival and cell fate. Taken together, these data define a new candidate mechanism for the genetic association of variants around PXK with lupus risk and highlight the regulation of intracellular trafficking as a genetically regulated pathway mediating human autoimmunity.
Collapse
Affiliation(s)
- Samuel E Vaughn
- Immunology Graduate Program and Medical Scientist Training Program, University of Cincinnati College of Medicine Cincinnati, OH, USA ; Center for Autoimmune Genomics and Etiology, Cincinnati Children's Hospital Medical Center Cincinnati, OH, USA
| | | | - Xiaoming Lu
- Center for Autoimmune Genomics and Etiology, Cincinnati Children's Hospital Medical Center Cincinnati, OH, USA
| | - Zubin H Patel
- Immunology Graduate Program and Medical Scientist Training Program, University of Cincinnati College of Medicine Cincinnati, OH, USA ; Center for Autoimmune Genomics and Etiology, Cincinnati Children's Hospital Medical Center Cincinnati, OH, USA
| | - Erin E Zoller
- Center for Autoimmune Genomics and Etiology, Cincinnati Children's Hospital Medical Center Cincinnati, OH, USA
| | - Albert F Magnusen
- Center for Autoimmune Genomics and Etiology, Cincinnati Children's Hospital Medical Center Cincinnati, OH, USA
| | - Adrienne H Williams
- Center for Public Health Genomics and the Department of Biostatistical Sciences, Wake Forest School of Medicine Winston-Salem, NC, USA
| | - Julie T Ziegler
- Center for Public Health Genomics and the Department of Biostatistical Sciences, Wake Forest School of Medicine Winston-Salem, NC, USA
| | - Mary E Comeau
- Center for Public Health Genomics and the Department of Biostatistical Sciences, Wake Forest School of Medicine Winston-Salem, NC, USA
| | - Miranda C Marion
- Center for Public Health Genomics and the Department of Biostatistical Sciences, Wake Forest School of Medicine Winston-Salem, NC, USA
| | - Stuart B Glenn
- Arthritis and Clinical Immunology Research Program, Oklahoma Medical Research Foundation Oklahoma City, OK, USA
| | - Adam Adler
- Arthritis and Clinical Immunology Research Program, Oklahoma Medical Research Foundation Oklahoma City, OK, USA
| | - Nan Shen
- Immunology Graduate Program and Medical Scientist Training Program, University of Cincinnati College of Medicine Cincinnati, OH, USA ; Joint Molecular Rheumatology Laboratory of the Institute of Health Sciences and Shanghai Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Institutes for Biological Sciences, and Chinese Academy of Sciences Shanghai, China
| | - Swapan Nath
- Arthritis and Clinical Immunology Research Program, Oklahoma Medical Research Foundation Oklahoma City, OK, USA
| | - Anne M Stevens
- Center for Immunity and Immunotherapies, Seattle Children's Research Institute Seattle, WA, USA ; Division of Rheumatology, Department of Pediatrics, University of Washington Seattle, WA, USA
| | - Barry I Freedman
- Department of Internal Medicine, Section on Nephrology, Wake Forest School of Medicine Winston-Salem, NC, USA
| | - Betty P Tsao
- Division of Rheumatology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles Los Angeles, CA, USA
| | - Chaim O Jacob
- Department of Medicine, Keck School of Medicine, University of Southern California Los Angeles, CA, USA
| | - Diane L Kamen
- Division of Rheumatology, Medical University of South Carolina Charleston, SC, USA
| | - Elizabeth E Brown
- Department of Epidemiology, University of Alabama at Birmingham Birmingham, AL, USA ; Department of Medicine, University of Alabama at Birmingham Birmingham, AL, USA
| | - Gary S Gilkeson
- Division of Rheumatology, Medical University of South Carolina Charleston, SC, USA
| | - Graciela S Alarcón
- Department of Medicine, University of Alabama at Birmingham Birmingham, AL, USA
| | - John D Reveille
- Rheumatology and Clinical Immunogenetics, University of Texas Health Science Center at Houston Houston, TX, USA
| | - Juan-Manuel Anaya
- Center for Autoimmune Disease Research, Universidad del Rosario Bogota, Colombia
| | - Judith A James
- Arthritis and Clinical Immunology Research Program, Oklahoma Medical Research Foundation Oklahoma City, OK, USA ; Department of Medicine, University of Oklahoma Health Sciences Center Oklahoma City, OK, USA
| | - Kathy L Moser
- Arthritis and Clinical Immunology Research Program, Oklahoma Medical Research Foundation Oklahoma City, OK, USA
| | - Lindsey A Criswell
- Rosalind Russell/Ephraim P Engleman Rheumatology Research Research Center, Department of Medicine, University of California, San Francisco San Francisco, CA, USA
| | - Luis M Vilá
- Division of Rheumatology, Department of Medicine, University of Puerto Rico Medical Sciences Campus San Juan, PR, USA
| | - Marta E Alarcón-Riquelme
- Arthritis and Clinical Immunology Research Program, Oklahoma Medical Research Foundation Oklahoma City, OK, USA ; Center for Genomics and Oncological Research, Pfizer-University of Granada-Junta de Andalucia Granada, Spain
| | - Michelle Petri
- Department of Medicine, Johns Hopkins University School of Medicine Baltimore, MD, USA
| | - R Hal Scofield
- Arthritis and Clinical Immunology Research Program, Oklahoma Medical Research Foundation Oklahoma City, OK, USA ; Department of Medicine, University of Oklahoma Health Sciences Center Oklahoma City, OK, USA ; United States Department of Veterans Affairs Medical Center Oklahoma City, OK, USA
| | - Robert P Kimberly
- Department of Medicine, University of Alabama at Birmingham Birmingham, AL, USA
| | - Rosalind Ramsey-Goldman
- Division of Rheumatology, Feinberg School of Medicine, Northwestern University Chicago, IL, USA
| | - Young Binjoo
- Department of Rheumatology, Hanyang University Hospital for Rheumatic Diseases Seoul, Korea
| | - Jeongim Choi
- Department of Rheumatology, Hanyang University Hospital for Rheumatic Diseases Seoul, Korea
| | - Sang-Cheol Bae
- Department of Rheumatology, Hanyang University Hospital for Rheumatic Diseases Seoul, Korea
| | - Susan A Boackle
- Division of Rheumatology, University of Colorado School of Medicine Aurora, CO, USA
| | - Timothy J Vyse
- Divisions of Genetics and Molecular Medicine and Immunology, King's College London London, UK
| | - Joel M Guthridge
- Arthritis and Clinical Immunology Research Program, Oklahoma Medical Research Foundation Oklahoma City, OK, USA
| | - Bahram Namjou
- Center for Autoimmune Genomics and Etiology, Cincinnati Children's Hospital Medical Center Cincinnati, OH, USA
| | - Patrick M Gaffney
- Arthritis and Clinical Immunology Research Program, Oklahoma Medical Research Foundation Oklahoma City, OK, USA
| | - Carl D Langefeld
- Center for Public Health Genomics and the Department of Biostatistical Sciences, Wake Forest School of Medicine Winston-Salem, NC, USA
| | - Kenneth M Kaufman
- Center for Autoimmune Genomics and Etiology, Cincinnati Children's Hospital Medical Center Cincinnati, OH, USA ; United States Department of Veterans Affairs Medical Center Cincinnati, OH, USA
| | - Jennifer A Kelly
- Arthritis and Clinical Immunology Research Program, Oklahoma Medical Research Foundation Oklahoma City, OK, USA
| | - Isaac T W Harley
- Immunology Graduate Program and Medical Scientist Training Program, University of Cincinnati College of Medicine Cincinnati, OH, USA ; Center for Autoimmune Genomics and Etiology, Cincinnati Children's Hospital Medical Center Cincinnati, OH, USA
| | - John B Harley
- Center for Autoimmune Genomics and Etiology, Cincinnati Children's Hospital Medical Center Cincinnati, OH, USA ; United States Department of Veterans Affairs Medical Center Cincinnati, OH, USA
| | - Leah C Kottyan
- Center for Autoimmune Genomics and Etiology, Cincinnati Children's Hospital Medical Center Cincinnati, OH, USA ; United States Department of Veterans Affairs Medical Center Cincinnati, OH, USA
| |
Collapse
|
12
|
Hoogeboom R, Tolar P. Molecular Mechanisms of B Cell Antigen Gathering and Endocytosis. Curr Top Microbiol Immunol 2015; 393:45-63. [PMID: 26336965 DOI: 10.1007/82_2015_476] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Generation of high-affinity, protective antibodies requires B cell receptor (BCR) signaling, as well as antigen internalization and presentation to helper T cells. B cell antigen internalization is initiated by antigen capture, either from solution or from immune synapses formed on the surface of antigen-presenting cells, and proceeds via clathrin-dependent endocytosis and intracellular routing to late endosomes. Although the components of this pathway are still being discovered, it has become clear that antigen internalization is actively regulated by BCR signaling at multiple steps and, vice versa, that localization of the BCR along the endocytic pathway modulates signaling. Accordingly, defects in BCR internalization or trafficking contribute to enhanced B cell activation in models of autoimmune diseases and in B cell lymphomas. In this review, we discuss how BCR signaling complexes regulate each of the steps of this endocytic process and why defects along this pathway manifest as hyperactive B cell responses in vivo.
Collapse
Affiliation(s)
- Robbert Hoogeboom
- Division of Immune Cell Biology, National Institute for Medical Research, Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, London, NW7 1AA, UK
| | - Pavel Tolar
- Division of Immune Cell Biology, National Institute for Medical Research, Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, London, NW7 1AA, UK.
| |
Collapse
|
13
|
Wan YJ, Yang Y, Leng QL, Lan B, Jia HY, Liu YH, Zhang CZ, Cao Y. Vav1 increases Bcl-2 expression by selective activation of Rac2-Akt in leukemia T cells. Cell Signal 2014; 26:2202-9. [PMID: 24880064 DOI: 10.1016/j.cellsig.2014.05.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Revised: 05/21/2014] [Accepted: 05/23/2014] [Indexed: 01/06/2023]
Abstract
Vav proteins are guanine nucleotide exchange factors (GEFs) that activate a group of small G proteins (GTPases). Vav1 is predominantly expressed in hematopoietic cells, whereas Vav2 and Vav3 are ubiquitously distributed in almost all human tissues. All three Vav proteins contain conserved structural motifs and associate with a variety of cellular activities including proliferation, migration, and survival. Previous observation with Jurkat leukemia T cells showed that Vav1 possessed anti-apoptotic activity by enhancing Bcl-2 transcription. However the mechanism has not been unveiled. Here, we explored the effectors of Vav1 in promoting Bcl-2 expression in Jurkat cells and revealed that Rac2-Akt was specifically evoked by the expression of Vav1, but not Vav2 or Vav3. Although all three Vav isoforms existed in Jurkat cells, Rac2 was distinguishably activated by Vav1 and that led to enhanced Bcl-2 expression and cell survival. Akt was modulated downstream of Vav1-Rac2, and the activation of Akt was indispensable in the enhanced transcription of Bcl-2. Intriguingly, neither Vav2 nor Vav3 was able to activate Rac2-Akt pathway as determined by gene silencing approach. Our data illustrated a unique role of Vav1 in T leukemia survival by selectively triggering Rac2-Akt axis and elevating the expression of anti-apoptotic Bcl-2.
Collapse
Affiliation(s)
- Ya-Juan Wan
- Key Laboratory of Microbial Functional Genomics of Ministry of Education, College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, PR China
| | - Yin Yang
- Key Laboratory of Microbial Functional Genomics of Ministry of Education, College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, PR China
| | - Qian-Li Leng
- Key Laboratory of Microbial Functional Genomics of Ministry of Education, College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, PR China
| | - Bei Lan
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, PR China
| | - Hui-Yan Jia
- Key Laboratory of Microbial Functional Genomics of Ministry of Education, College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, PR China
| | - Yao-Hui Liu
- Key Laboratory of Microbial Functional Genomics of Ministry of Education, College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, PR China
| | - Cui-Zhu Zhang
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, PR China
| | - Youjia Cao
- Key Laboratory of Microbial Functional Genomics of Ministry of Education, College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, PR China; State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, PR China.
| |
Collapse
|
14
|
Mele S, Devereux S, Ridley AJ. Rho and Rap guanosine triphosphatase signaling in B cells and chronic lymphocytic leukemia. Leuk Lymphoma 2014; 55:1993-2001. [PMID: 24237579 DOI: 10.3109/10428194.2013.866666] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Chronic lymphocytic leukemia (CLL) cells proliferate predominantly in niches in the lymph nodes, where signaling from the B cell receptor (BCR) and the surrounding microenvironment are critical for disease progression. In addition, leukemic cells traffic constantly from the bloodstream into the lymph nodes, migrate within lymphatic tissues and egress back to the bloodstream. These processes are driven by chemokines and their receptors, and depend on changes in cell migration and integrin-mediated adhesion. Here we describe how Rho and Rap guanosine triphosphatases (GTPases) contribute to both BCR signaling and chemokine receptor signaling, particularly by regulating cytoskeletal dynamics and integrin activity. We propose that new inhibitors of BCR-activated kinases are likely to affect CLL cell trafficking via Rho and Rap GTPases, and that upstream regulators or downstream effectors could be good targets for therapeutic intervention in CLL.
Collapse
Affiliation(s)
- Silvia Mele
- Randall Division of Cell and Molecular Biophysics, King's College London , London , UK
| | | | | |
Collapse
|
15
|
Hauser JT, Lindner R. Coalescence of B cell receptor and invariant chain MHC II in a raft-like membrane domain. J Leukoc Biol 2014; 96:843-55. [PMID: 25024398 DOI: 10.1189/jlb.2a0713-353r] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The BCR binds antigen for processing and subsequent presentation on MHC II molecules. Polyvalent antigen induces BCR clustering and targeting to endocytic processing compartments, which are also accessed by Ii-MHC II. Here, we report that clustered BCR is able to team up with Ii-MHC II already at the plasma membrane of mouse B-lymphocytes. Colocalization of BCR and Ii-MHC II on the cell surface required clustering of both types of molecules. The clustering of only one type did not trigger the recruitment of the other. Ii-bound MIF (a ligand of Ii) also colocalized with clustered BCR upon oligomerization of MIF on the surface of the B cell. Abundant surface molecules, such as B220 or TfnR, did not cocluster with the BCR. Some membrane raft-associated molecules, such as peptide-loaded MHC II, coclustered with the BCR, whereas others, such as GM1, did not. The formation of a BCR- and Ii-MHC II-containing membrane domain by antibody-mediated clustering was independent of F-actin and led to the coendocytosis of its constituents. With a rapid Brij 98 extraction method, it was possible to capture this membrane domain biochemically as a DRM. Ii and clustered BCR were present on the same DRM, as shown by immunoisolation. The coalescence of BCR and Ii-MHC II increased tyrosine phosphorylation, indicative of enhanced BCR signaling. Our work suggests a novel role for MIF and Ii-MHC II in BCR-mediated antigen processing.
Collapse
Affiliation(s)
- Julian T Hauser
- Hannover Medical School, Department of Cell Biology, Center for Anatomy, Hannover, Germany
| | - Robert Lindner
- Hannover Medical School, Department of Cell Biology, Center for Anatomy, Hannover, Germany
| |
Collapse
|
16
|
Slupsky JR. Does B cell receptor signaling in chronic lymphocytic leukaemia cells differ from that in other B cell types? SCIENTIFICA 2014; 2014:208928. [PMID: 25101192 PMCID: PMC4102070 DOI: 10.1155/2014/208928] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Accepted: 06/02/2014] [Indexed: 06/03/2023]
Abstract
Chronic lymphocytic leukaemia (CLL) is an incurable malignancy of mature B cells. CLL is important clinically in Western countries because of its commonality and because of the significant morbidity and mortality associated with the progressive form of this incurable disease. The B cell receptor (BCR) expressed on the malignant cells in CLL contributes to disease pathogenesis by providing signals for survival and proliferation, and the signal transduction pathway initiated by engagement of this receptor is now the target of several therapeutic strategies. The purpose of this review is to outline current understanding of the BCR signal cascade in normal B cells and then question whether this understanding applies to CLL cells. In particular, this review studies the phenomenon of anergy in CLL cells, and whether certain adaptations allow the cells to overcome anergy and allow full BCR signaling to take place. Finally, this review analyzes how BCR signals can be therapeutically targeted for the treatment of CLL.
Collapse
Affiliation(s)
- Joseph R. Slupsky
- Department of Molecular and Clinical Cancer Medicine, University of Liverpool, 6th Floor, Duncan Building, Daulby Street, Liverpool L69 3GA, UK
| |
Collapse
|
17
|
Zhong Y, Byrd JC, Dubovsky JA. The B-cell receptor pathway: a critical component of healthy and malignant immune biology. Semin Hematol 2014; 51:206-18. [PMID: 25048784 DOI: 10.1053/j.seminhematol.2014.05.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The pathogenesis and progression of normal B-cell development to malignant transformation of chronic lymphocytic leukemia (CLL) is still poorly understood and has hampered attempts to develop targeted therapeutics for this disease. The dependence of CLL cells on B-cell receptor signaling has fostered a new area of basic and therapeutic research interest. In particular, identification of the dependence of CLL cells on both phosphatidylinositol 3-kinase delta and Bruton's tyrosine kinase signaling for survival and proliferation has come forth through well-performed preclinical studies and subsequent trials demonstrating dramatic efficacy. This review outlines essential components of B-cell receptor signaling and briefly addresses therapeutics that are emerging to target these in patients with CLL and related lymphoid malignancies.
Collapse
Affiliation(s)
- Yiming Zhong
- Division of Hematology, Department of Internal Medicine, The Ohio State University, Columbus, OH
| | - John C Byrd
- Division of Hematology, Department of Internal Medicine, The Ohio State University, Columbus, OH; Division of Medicinal Chemistry, College of Pharmacy, The Ohio State University, Columbus, OH
| | - Jason A Dubovsky
- Division of Hematology, Department of Internal Medicine, The Ohio State University, Columbus, OH.
| |
Collapse
|
18
|
Courtney AH, Bennett NR, Zwick DB, Hudon J, Kiessling LL. Synthetic antigens reveal dynamics of BCR endocytosis during inhibitory signaling. ACS Chem Biol 2014; 9:202-10. [PMID: 24131142 DOI: 10.1021/cb400532y] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
B cells detect foreign antigens through their B cell antigen receptor (BCR). The BCR, when engaged by antigen, initiates a signaling cascade. Concurrent with signaling is endocytosis of the BCR complex, which acts to downregulate signaling and facilitate uptake of antigen for processing and display on the cell surface. The relationship between signaling and BCR endocytosis is poorly defined. Here, we explore the interplay between BCR endocytosis and antigens that either promote or inhibit B cell activation. Specifically, synthetic antigens were generated that engage the BCR alone or both the BCR and the inhibitory co-receptor CD22. The lectin CD22, a member of the Siglec family, binds sialic acid-containing glycoconjugates found on host tissues, inhibiting BCR signaling to prevent erroneous B cell activation. At low concentrations, antigens that can cocluster the BCR and CD22 promote rapid BCR endocytosis; whereas, slower endocytosis occurs with antigens that bind only the BCR. At higher antigen concentrations, rapid BCR endocytosis occurs upon treatment with either stimulatory or inhibitory antigens. Endocytosis of the BCR, in response to synthetic antigens, results in its entry into early endocytic compartments. Although the CD22-binding antigens fail to activate key regulators of antigen presentation (e.g., Syk), they also promote BCR endocytosis, indicating that inhibitory antigens can be internalized. Together, our observations support a functional role for BCR endocytosis in downregulating BCR signaling. The reduction of cell surface BCR levels in the absence of B cell activation should raise the threshold for BCR subsequent activation. The ability of the activating synthetic antigens to trigger both signaling and entry of the BCR into early endosomes suggests strategies for targeted antigen delivery.
Collapse
Affiliation(s)
- Adam H. Courtney
- Department
of Biochemistry, University of Wisconsin—Madison, 433 Babcock Drive, Madison, Wisconsin 53706, United States
| | - Nitasha R. Bennett
- Department
of Chemistry, University of Wisconsin—Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Daniel B. Zwick
- Department
of Biochemistry, University of Wisconsin—Madison, 433 Babcock Drive, Madison, Wisconsin 53706, United States
| | - Jonathan Hudon
- Department
of Chemistry, University of Wisconsin—Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Laura L. Kiessling
- Department
of Biochemistry, University of Wisconsin—Madison, 433 Babcock Drive, Madison, Wisconsin 53706, United States
- Department
of Chemistry, University of Wisconsin—Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
| |
Collapse
|
19
|
Palmitoylated transmembrane adaptor proteins in leukocyte signaling. Cell Signal 2014; 26:895-902. [PMID: 24440308 DOI: 10.1016/j.cellsig.2014.01.007] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 01/07/2014] [Accepted: 01/09/2014] [Indexed: 12/14/2022]
Abstract
Transmembrane adaptor proteins (TRAPs) are structurally related proteins that have no enzymatic function, but enable inducible recruitment of effector molecules to the plasma membrane, usually in a phosphorylation dependent manner. Numerous surface receptors employ TRAPs for either propagation or negative regulation of the signal transduction. Several TRAPs (LAT, NTAL, PAG, LIME, PRR7, SCIMP, LST1/A, and putatively GAPT) are known to be palmitoylated that could facilitate their localization in lipid rafts or tetraspanin enriched microdomains. This review summarizes expression patterns, binding partners, signaling pathways, and biological functions of particular palmitoylated TRAPs with an emphasis on the three most recently discovered members, PRR7, SCIMP, and LST1/A. Moreover, we discuss in silico methodology used for discovery of new family members, nature of their binding partners, and microdomain localization.
Collapse
|
20
|
|
21
|
Abstract
The Rac inhibitor EHop-016 was developed as a compound with the potential to inhibit cancer metastasis. Inhibition of the first step of metastasis, migration, is an important strategy for metastasis prevention. The small GTPase Rac acts as a pivotal binary switch that is turned "on" by guanine nucleotide exchange factors (GEFs) via a myriad of cell surface receptors, to regulate cancer cell migration, survival, and proliferation. Unlike the related GTPase Ras, Racs are not usually mutated, but overexpressed or overactivated in cancer. Therefore, a rational Rac inhibitor should block the activation of Rac by its upstream effectors, GEFs, and the Rac inhibitor NSC23766 was developed using this rationale. However, this compound is ineffective at inhibiting the elevated Rac activity of metastatic breast cancer cells. Therefore, a panel of small molecule compounds were derived from NSC23766 and screened for Rac activity inhibition in metastatic cancer cells. EHop-016 was identified as a compound that blocks the interaction of Rac with the GEF Vav in metastatic human breast cancer cells with an IC50 of ~1μM. At higher concentrations (10μM), EHop-016 inhibits the related Rho GTPase Cdc42, but not Rho, and also reduces cell viability. Moreover, EHop-016 inhibits the activation of the Rac downstream effector p21-activated kinase, extension of motile actin-based structures, and cell migration. Future goals are to develop EHop-016 as a therapeutic to inhibit cancer metastasis, either individually or in combination with current anticancer compounds. The next generation of EHop-016-based Rac inhibitors is also being developed.
Collapse
Affiliation(s)
- Suranganie Dharmawardhane
- Department of Biochemistry, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico, USA.
| | - Eliud Hernandez
- Department of Biochemistry, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico, USA
| | - Cornelis Vlaar
- Department of Biochemistry, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico, USA
| |
Collapse
|
22
|
The actin cytoskeleton coordinates the signal transduction and antigen processing functions of the B cell antigen receptor. ACTA ACUST UNITED AC 2013; 8:475-485. [PMID: 24999354 DOI: 10.1007/s11515-013-1272-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The B cell antigen receptor (BCR) is the sensor on the B cell surface that surveys foreign molecules (antigen) in our bodies and activates B cells to generate antibody responses upon encountering cognate antigen. The binding of antigen to the BCR induces signaling cascades in the cytoplasm, which provides the first signal for B cell activation. Subsequently, BCRs internalize and target bound antigen to endosomes, where antigen is processed into T cell recognizable forms. T helper cells generate the second activation signal upon binding to antigen presented by B cells. The optimal activation of B cells requires both signals, thereby depending on the coordination of BCR signaling and antigen transport functions. Antigen binding to the BCR also induces rapid remodeling of the cortical actin network of B cells. While being initiated and controlled by BCR signaling, recent studies reveal that this actin remodeling is critical for both the signaling and antigen processing functions of the BCR, indicating a role for actin in coordinating these two pathways. Here we will review previous and recent studies on actin reorganization during BCR activation and BCR-mediated antigen processing, and discuss how actin remodeling translates BCR signaling into rapid antigen uptake and processing while providing positive and negative feedback to BCR signaling.
Collapse
|
23
|
Song W, Liu C, Upadhyaya A. The pivotal position of the actin cytoskeleton in the initiation and regulation of B cell receptor activation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:569-78. [PMID: 23886914 DOI: 10.1016/j.bbamem.2013.07.016] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2013] [Revised: 07/08/2013] [Accepted: 07/15/2013] [Indexed: 01/14/2023]
Abstract
The actin cytoskeleton is a dynamic cellular network known for its function in cell morphology and motility. Recent studies using high resolution and real time imaging techniques have revealed that actin plays a critical role in signal transduction, primarily by modulating the dynamics and organization of membrane-associated receptors and signaling molecules. This review summarizes what we have learned so far about a regulatory niche of the actin cytoskeleton in the signal transduction of the B cell receptor (BCR). The activation of the BCR is initiated and regulated by a close coordination between the dynamics of surface BCRs and the cortical actin network. The actin cytoskeleton is involved in regulating the signaling threshold of the BCR to antigenic stimulation, the kinetics and amplification of BCR signaling activities, and the timing and kinetics of signaling downregulation. Actin exerts its regulatory function by controlling the kinetics, magnitude, subcellular location, and nature of BCR clustering and BCR signaling complex formation at every stage of signaling. The cortical actin network is remodeled by initial detachment from the plasma membrane, disassembly and subsequent reassembly into new actin structures in response to antigenic stimulation. Signaling responsive actin regulators translate BCR stimulatory and inhibitory signals into a series of actin remodeling events, which enhance signaling activation and down-regulation by modulating the lateral mobility and spatial organization of surface BCR. The mechanistic understanding of actin-mediated signaling regulation in B cells will help us explore B cell-specific manipulations of the actin cytoskeleton as treatments for B cell-mediated autoimmunity and B cell cancer. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters. Guest Editor: Jean Claude Hervé.
Collapse
Affiliation(s)
- Wenxia Song
- Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, MD 20742, USA; Department of Physics, University of Maryland, College Park, MD 20742, USA.
| | - Chaohong Liu
- Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, MD 20742, USA; Department of Physics, University of Maryland, College Park, MD 20742, USA
| | - Arpita Upadhyaya
- Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, MD 20742, USA; Department of Physics, University of Maryland, College Park, MD 20742, USA
| |
Collapse
|
24
|
Abstract
Ras guanyl nucleotide releasing proteins (RasGRPs) are guanyl nucleotide exchange factors that activate Ras and related GTPases such as Rap. Like Sos proteins, RasGRPs have a catalytic region composed of a Ras exchange motif (REM) and a CDC25 domain. RasGRPs also possess a pair of atypical EF hands that may bind calcium in vivo and a C1 domain resembling the diacylglycerol (DAG)-binding domain of protein kinase C. DAG directly activates RasGRPs by a membrane recruitment mechanism as well as indirectly by PKC-mediated phosphorylation. RasGRPs are prominently expressed in blood cells. RasGRP1 acts downstream of TCR, while RasGRP1 and RasGRP3 both act downstream of BCR. Together, they regulate Ras in adaptive immune cells. RasGRP2, through Rap, plays a role in controlling platelet adhesion, while RasGRP4 controls Ras activation in mast cells. RasGRP malfunction likely contributes to autoimmunity and may contribute to blood malignancies. RasGRPs might prove to be viable drug targets. The intracellular site of RasGRP action and the relationship between RasGRPs and other Ras regulatory mechanisms are subjects of lively debate.
Collapse
Affiliation(s)
- James C Stone
- Department of Biochemistry, University of Alberta, Edmonton, AB, Canada
| |
Collapse
|
25
|
Gray PEA, Sillence D, Kakakios A. Is Roifman syndrome an X-linked ciliopathy with humoral immunodeficiency? Evidence from 2 new cases. Int J Immunogenet 2011; 38:501-5. [PMID: 21977988 DOI: 10.1111/j.1744-313x.2011.01041.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Roifman syndrome is a rare syndrome of bone dysplasia, growth retardation, retinal dystrophy and humeral immunodeficiency. Six cases have been reported to date, all of whom are male. We report a boy with clinical features of Roifman syndrome, whose older sister has skewed X-inactivation and a milder phenotype of the same disorder, supporting the hypothesis that this is an X-linked recessive condition. Both children had previously had a provisional diagnosis of Jeune dysplasia, and the boy had neonatal hip X-rays which demonstrated 'acetabular spurs' which are seen in a number of diseases thought to be caused by dysfunction of nonmotile cilia, including Jeune asphyxiating thoracic dystrophy. This finding in combination with other features such as retinal dystrophy, hepatic and renal disease suggests that the gene which is affected in Roifman syndrome may be involved with the function of nonmotile cilia and that Roifman syndrome may be the first example of a ciliopathy with associated immunodeficiency.
Collapse
Affiliation(s)
- P E A Gray
- Department of Immunology and Infectious Diseases, Sydney Children's Hospital, Sydney, Australia.
| | | | | |
Collapse
|
26
|
Chaturvedi A, Martz R, Dorward D, Waisberg M, Pierce SK. Endocytosed BCRs sequentially regulate MAPK and Akt signaling pathways from intracellular compartments. Nat Immunol 2011; 12:1119-26. [PMID: 21964606 DOI: 10.1038/ni.2116] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2011] [Accepted: 08/23/2011] [Indexed: 01/15/2023]
Abstract
Binding of antigen to the B cell antigen receptor (BCR) triggers both BCR signaling and endocytosis. How endocytosis regulates BCR signaling remains unknown. Here we report that BCR signaling was not extinguished by endocytosis of BCRs; instead, BCR signaling initiated at the plasma membrane continued as the BCR trafficked intracellularly with the sequential phosphorylation of kinases. Blocking the endocytosis of BCRs resulted in the recruitment of both proximal and downstream kinases to the plasma membrane, where mitogen-activated protein kinases (MAPKs) were hyperphosphorylated and the kinase Akt and its downstream target Foxo were hypophosphorylated, which led to the dysregulation of gene transcription controlled by these pathways. Thus, the cellular location of the BCR serves to compartmentalize kinase activation to regulate the outcome of signaling.
Collapse
Affiliation(s)
- Akanksha Chaturvedi
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, USA.
| | | | | | | | | |
Collapse
|
27
|
Fuller DM, Zhu M, Ou-Yang CW, Sullivan SA, Zhang W. A tale of two TRAPs: LAT and LAB in the regulation of lymphocyte development, activation, and autoimmunity. Immunol Res 2011; 49:97-108. [PMID: 21136199 DOI: 10.1007/s12026-010-8197-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Transmembrane adaptor proteins (TRAPs) link antigen receptor engagement to downstream cellular processes. Although these proteins typically lack intrinsic enzymatic activity, they are phosphorylated on multiple tyrosine residues following lymphocyte activation, allowing them to function as scaffolds for the assembly of multi-molecular signaling complexes. Among the many TRAPs that have been discovered in recent years, the LAT (linker for activation of T cells) family of adaptor proteins plays an important role in the positive and negative regulation of lymphocyte maturation, activation, and differentiation. Of the two members in this family, LAT is an indispensable component controlling T cell and mast cell activation and function; LAB (linker for activation of B cells), also called NTAL, is necessary to fine-tune lymphocyte activation and may be a key regulator of innate immune responses. Here, we review recent advances on the function of LAT and LAB in the regulation of development and activation of immune cells.
Collapse
Affiliation(s)
- Deirdre M Fuller
- Department of Immunology, Duke University Medical Center, Durham, NC 27710, USA
| | | | | | | | | |
Collapse
|
28
|
Clark MR, Tanaka A, Powers SE, Veselits M. Receptors, subcellular compartments and the regulation of peripheral B cell responses: the illuminating state of anergy. Mol Immunol 2010; 48:1281-6. [PMID: 21144589 DOI: 10.1016/j.molimm.2010.10.024] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Revised: 10/13/2010] [Accepted: 10/26/2010] [Indexed: 12/22/2022]
Abstract
Signals through the B cell antigen receptor (BCR) are necessary but not sufficient for cellular activation. Co-stimulatory signals must be provided through other immune recognition receptor systems, such as MHC class II/CD40 and the toll-like receptor (TLR) 9 that can only productively acquire their ligands in the processive environment of specialized late endosomes (MHC class II containing compartment or MIIC). It has long been appreciated that the BCR, by effectively capturing complex antigens and delivering them to late endosomes, is the link between activation events on the cell surface and those dependent on late endosomes. However, it has become increasingly apparent that the BCR also directs the translocation of MHC class II and TLR9 into the MIIC and that the endocytic flow of these receptors coincides with that of the BCR. This likely ensures close apposition of receptor complexes within the MIIC and the efficient transfer of ligands from the BCR to MHC class II and TLR9. This complex orchestration of receptor endocytic movement is dependent upon the quality of signals elicited through the BCR. Failure to activate specific signaling pathways, such as occurs in anergic B cells, prevents the entry of the BCR and TLR9 into the MIIC and abrogates TLR9 activation. Like anergy, this block in endocytic trafficking is rapidly reversible. These findings indicate that cellular responsiveness can be determined by mechanisms that control the subcellular location of important immune recognition receptors.
Collapse
Affiliation(s)
- Marcus R Clark
- Section of Rheumatology, Department of Medicine and Knapp Center for Lupus and Immunological Research, University of Chicago, 5841 S. Maryland Ave, Chicago, IL 60637, USA.
| | | | | | | |
Collapse
|
29
|
Tůmová M, Koffer A, Simíček M, Dráberová L, Dráber P. The transmembrane adaptor protein NTAL signals to mast cell cytoskeleton via the small GTPase Rho. Eur J Immunol 2010; 40:3235-45. [PMID: 21061444 DOI: 10.1002/eji.201040403] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2010] [Revised: 07/14/2010] [Accepted: 08/06/2010] [Indexed: 01/08/2023]
Abstract
The transmembrane adaptor protein NTAL (non-T-cell activation linker) participates in signalosome assembly in hematopoietic cells, but its exact role in cell physiology remains enigmatic. We report here that BM-derived mast cells from NTAL-deficient mice, responding to Ag alone or in combination with SCF, exhibit reduced spreading on fibronectin, enhanced filamentous actin depolymerization and enhanced migration towards Ag relative to WT cells. No such differences between WT and NTAL(-/-) BM-derived mast cells were observed when SCF alone was used as activator. We have examined the activities of two small GTPases, Rac and Rho, which are important regulators of actin polymerization. Stimulation with Ag and/or SCF enhanced activity of Rac(1,2,3) in both NTAL(-/-) and WT cells. In contrast, RhoA activity decreased and this trend was much faster and more extensive in NTAL(-/-) cells, indicating a positive regulatory role of NTAL in the recovery of RhoA activity. After restoring NTAL into NTAL(-/-) cells, both spreading and actin responses were rescued. This is the first report of a crucial role of NTAL in signaling, via RhoA, to mast cell cytoskeleton.
Collapse
Affiliation(s)
- Magda Tůmová
- Laboratory of Signal Transduction, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | | | | | | | | |
Collapse
|
30
|
Orr SJ, McVicar DW. LAB/NTAL/Lat2: a force to be reckoned with in all leukocytes? J Leukoc Biol 2010; 89:11-9. [PMID: 20643813 DOI: 10.1189/jlb.0410221] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
LAB/NTAL/Lat2 is a transmembrane adaptor protein closely related to LAT. It is expressed in various myeloid and lymphoid cells, many of which also express LAT. Phosphorylation of LAB occurs following engagement of various ITAM- and non-ITAM-linked receptors and can play positive and negative roles following receptor engagement. LAT binds PLCγ directly, resulting in efficient Ca²+ flux and degranulation. However, LAB does not contain a PLCγ-binding motif and only binds PLCγ indirectly, possibly via Grb2, thereby resulting in suboptimal signaling. As LAT can signal more efficiently than LAB, competition between the 2 for space/substrates in the lipid rafts can attenuate signaling. This competition model requires coexpression of LAT; however, LAB is repressive, even in cells lacking substantial LAT expression such as macrophages and mature B cells. The reported interaction between LAB and the ubiquitin E3-ligase c-Cbl suggests 1 possible mechanism for LAT-independent inhibition by LAB, but such a model requires further investigation. Given the wide-reaching expression pattern of LAB, LAB has the ability to modulate signaling in virtually every type of leukocyte. Regardless of its ultimate mode of action, the potent regulatory capability of LAB proves this protein to be a complex adaptor that warrants continued, substantial scrutiny by biochemists and immunologists alike.
Collapse
Affiliation(s)
- Selinda J Orr
- Cancer and Inflammation Program, National Cancer Institute-Frederick, Frederick, MD 21702, USA
| | | |
Collapse
|
31
|
Samson T, Welch C, Monaghan-Benson E, Hahn KM, Burridge K. Endogenous RhoG is rapidly activated after epidermal growth factor stimulation through multiple guanine-nucleotide exchange factors. Mol Biol Cell 2010; 21:1629-42. [PMID: 20237158 PMCID: PMC2861620 DOI: 10.1091/mbc.e09-09-0809] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
In this article it is shown that EGF stimulation leads to rapid activation of RhoG through Vav GEFs and the GEF PLEKHG6. Importantly, different cellular responses induced by EGF are determined by the available GEFs. Furthermore, this article presents results showing that EGF-stimulated cell migration and EGFR internalization are regulated by RhoG. RhoG is a member of the Rac-like subgroup of Rho GTPases and has been linked to a variety of different cellular functions. Nevertheless, many aspects of RhoG upstream and downstream signaling remain unclear; in particular, few extracellular stimuli that modulate RhoG activity have been identified. Here, we describe that stimulation of epithelial cells with epidermal growth factor leads to strong and rapid activation of RhoG. Importantly, this rapid activation was not observed with other growth factors tested. The kinetics of RhoG activation after epidermal growth factor (EGF) stimulation parallel the previously described Rac1 activation. However, we show that both GTPases are activated independently of one another. Kinase inhibition studies indicate that the rapid activation of RhoG and Rac1 after EGF treatment requires the activity of the EGF receptor kinase, but neither phosphatidylinositol 3-kinase nor Src kinases. By using nucleotide-free RhoG pull-down assays and small interfering RNA-mediated knockdown studies, we further show that guanine-nucleotide exchange factors (GEFs) of the Vav family mediate EGF-induced rapid activation of RhoG. In addition, we found that in certain cell types the recently described RhoG GEF PLEKHG6 can also contribute to the rapid activation of RhoG after EGF stimulation. Finally, we present results that show that RhoG has functions in EGF-stimulated cell migration and in regulating EGF receptor internalization.
Collapse
Affiliation(s)
- Thomas Samson
- Department of Cell and Developmental Biology, Lineberger Comprehensive Cancer Center, Chapel Hill, NC 27599, USA
| | | | | | | | | |
Collapse
|