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Principal Investigator: RICHARD J. HODES
Organization: DIVISION OF BASIC SCIENCES - NCI
Fiscal Year: 2020
Award: $361,631
Funding agency: National Cancer Institute
The src family kinase lck plays a critical role in T lymphocyte development and activation. Expression of lck is regulated by two promoters, termed distal and proximal promoters, in both mice and humans. Although the existence of these promoters was described 20 years ago, their function in developing and mature T cells has not been analyzed. To address this question, we have generated mutant BAC transgenes by deletion of either proximal or distal lck promoter. Studies of these mice have demonstrated selective expression of lck at preferential and different stages of development when driven by one or the other of its two promoters. Corresponding selective stages of T cell development and differentiation have been shown to be dependent upon promoter-specific lck expression. The proximal lck promoter is critical for early stages of thymic T cell development, but insufficient to support later stages of development or mature T cell responses to TCR stimulation. The distal promoter does not support early development, but does support differentiation from DP to mature SP thymocytes, as well as the TCR-mediated response of mature peripheral T cells. Mice expressing proximal and distal promoters on distinct BAC transgenes support wild-type levels of T cell development. The proximal and distal promoters thus function at distinct stages of T cell development and have non-redundant roles in the developmental process. Stimulated by the observation that alternative promoters can have distinct functional roles during development, we have initiated studies in collaboration with the lab of Keji Zhao to analyze genome-wide patterns of differential promoter expression during T cell development. In initial experiments, we have identified multiple genes that are regulated by differential use of alternative promoters during stages of T cell development. Further studies in progress will analyze chromatin structure and epigenetic correlates of gene expression. The developmental stage-specific function of alternative promoters will next be analyzed using CRISPR-Cas methodology already established in our lab. We investigated the function of tumor suppressor p53 in regulating proliferation and function of T lymphocytes. We have made the unexpected observation that antigen-specific proliferative responses of naive and memory CD4 T cells require the down-modulation of tumor suppressor p53. In the absence of TCR signal, IL-2 induces a sustained increase in p53 protein, which prevents proliferative responses despite strong signaling through the IL-2 receptor. In contrast, TCR signaling results in early termination of p53 protein expression by decreasing p53 mRNA as well as by strong transcriptional induction of the p53-regulating protein Mdm2. Down-modulation of p53 in response to antigen stimulation is in fact critical for antigen-specific T cell proliferation; and preventing p53 degradation by inhibiting Mdm2 results in sustained p53 protein levels and prevents antigen-specific T cell proliferation. These studies elucidate a critical role of p53 as a negative regulator of T cell proliferation. It is the termination of p53 elevation by TCR signaling that allows proliferative responses to occur, enforcing antigen specificity. Preliminary studies of p53 effect on antigen-inexperienced and memory T cell repertoire have strongly suggested that p53 affects the threshold of TCR signaling required for activation of unprimed T cells by specific antigen, and their subsequent differentiation into memory T cells. p53 thus appears to be an important regulator of antigen-specific T cell activation and in vivo response, proliferation, and differentiation. T cell-dependent germinal center (GC) responses require coordinated interactions of T cells with two distinct antigen-presenting cell populations (APCs), B cells and dendritic cells (DCs), in the presence of B7- and CD40-dependent costimulatory pathways. Conventional models describe the expression of both of these costimulatory molecules on the same APC, both for T cell presentation and for cross-regulation of B7 and CD40 expression. Here, we report that, contrary to the conventional paradigm, cellular requirements for B7 and CD40 expression were distinct for GC TFH , GC B cell, and high affinity antibody responses. B7 expression was required on DCs but not on B cells, while CD40 was required on B cells but not DCs; and there was in fact no requirement for co-expression of B7 and CD40 on the same cell for GC responses. Our findings thus identify a much revised model for costimulatory function in the GC response, with crucial and distinct contributions of B7- and CD40-dependent pathways expressed by distinct APC populations. T cell-dependent germinal center (GC) responses require coordinated interactions of T cells with two distinct antigen-presenting cell populations (APCs)-B cells and dendritic cells (DCs)-in the presence of B7- and CD40-dependent costimulatory pathways. T-APC interactions with both populations are generally considered to depend on similar molecular mechanisms, including the involvement of these two costimulatory receptor-ligand pairs, but direct assessment of the role of each pathway in germinal center-dependent adaptive responses has not been conducted. Here we have utilized models that enable the selective elimination of CD28-B7 and CD40-CD40L signaling during T-DC vs. T-B antigen-driven interactions to probe this issue. In contrast to prevailing views that both pathways are critical for productive T-dependent humoral immunity at both the early (T-DC) and late (T-B) phases of the response, we found that the cellular requirements for B7 and CD40 expression were distinct. B7 expression was required on DCs but not on B cells, while CD40 was required on B cells but not DCs. These data emphasize the emerging evidence that distinct molecular rules apply to CD4+ T cell-myeloid cell and CD4+ T cell-lymphoid cell interactions, with important implications for understanding how to optimize or inhibit these events to promote vaccine responses or limit autoimmunity To further elucidate the role of CD40-CD40L interactions in multiple T cell-developmental and functional events, we have generated unique mouse genetic models. To analyze the role of signaling through CD40 on diverse cell populations, we have produced by CRISPR-Cas9 a set of CD40 cytoplasmic domain mutants that disrupt putative binding sites for TRAFs 2,3, and 6, and have generated initial data indicating differential dependence of these cytoplasmic domains for diverse functions, including B cell germinal center responses, Ig class switching, and affinity maturation; susceptibility to experimental autoimmune encephalomyelitis (EAE); in vivo T cell cytokine responses; and iNKT cell selection. Our studies of EAE have identified requirements for CD40 expression by B cells and DC for distinct functions in disease induction. They have further identified requirements for distinct cytoplasmic domains of CD40 in EAE. To determine CD40L function, we are in the process of generating mutants that express only cell surface or only secreted forms of CD40L.
Terms: <Address><Affect><Affinity><Antibody Affinity><Antibody Response><Antigen-Presenting Cells><Antigens><Antioncogene Protein p53><Autoimmune Status><Autoimmunity><B blood cells><B cell><B cells><B-Cell Activation><B-Cells><B-Lymphocytes><B-cell><BAC clone><BACs><Bacterial Artificial Chromosomes><Binding Sites><Bp50><CD154><CD28><CD28 gene><CD4 Cells><CD4 Positive T Lymphocytes><CD4 T cells><CD4 helper T cell><CD4 lymphocyte><CD4+ T-Lymphocyte><CD4-Positive Lymphocytes><CD40><CD40L><CD40LG><CDW40><CRISPR><CRISPR method><CRISPR methodology><CRISPR technique><CRISPR technology><CRISPR-CAS-9><CRISPR-based method><CRISPR-based technique><CRISPR-based technology><CRISPR-based tool><CRISPR/Cas method><CRISPR/Cas system><CRISPR/Cas technology><CRISPR/Cas9><CRISPR/Cas9 technology><Cas nuclease technology><Cell Body><Cell Communication><Cell Communication and Signaling><Cell Cycle><Cell Death><Cell Division Cycle><Cell Interaction><Cell Signaling><Cell surface><Cell-to-Cell Interaction><Cells><Cellular Tumor Antigen P53><Chromatin Structure><Class Switching><Class Switchings><Clustered Regularly Interspaced Short Palindromic Repeats><Clustered Regularly Interspaced Short Palindromic Repeats method><Clustered Regularly Interspaced Short Palindromic Repeats methodology><Clustered Regularly Interspaced Short Palindromic Repeats technique><Clustered Regularly Interspaced Short Palindromic Repeats technology><Co-Stimulator><Collaborations><Combining Site><Complex><Costimulator><Critical Paths><Critical Pathways><Cytoplasmic Domain><Cytoplasmic Tail><DNA Alteration><DNA Sequence Alteration><DNA mutation><Data><Dendritic Cells><Dependence><Development><Developmental Process><Disease><Disorder><Distal><EAE><Epidermal Thymocyte Activating Factor><Epigenetic><Epigenetic Change><Epigenetic Mechanism><Epigenetic Process><Event><Experimental Allergic Encephalitis><Experimental Allergic Encephalomyelitis><Experimental Autoimmune Encephalitis><Experimental Autoimmune Encephalomyelitis><Gene Expression><Gene Transcription><General Population><General Public><Generations><Genes><Genetic Models><Genetic Transcription><Genetic mutation><Germinal Center><HDM2><High Affinity Interleukin-2 Receptor><Human><Humoral Immunities><IL-2><IL-2 Receptors><IL2 Protein><IL2 Receptors><Immunoglobulin Class Switching><Immunoglobulin Class Switchings><Interleukin 2><Interleukin 2 Precursor><Interleukin 2 Receptor><Interleukin II><Interleukin-2><Interleukine 2><Interleukine 2 Precursor><Interleukine II><Intracellular Communication and Signaling><Isotype Switching><Isotype Switchings><Ligands><Lymphocyte Mitogenic Factor><Lymphocyte-Specific Protein-Tyrosine Kinase><Lymphocyte-Specific p56LCK Tyrosine Protein Kinase><Lymphoid Cell><MDM2><MDM2 gene><MDMX protein><MGC9013><Mature T-Cell><Mature T-Lymphocyte><Mdm-2 protein><Mediating><Messenger RNA><Methodology><Mice><Mice Mammals><Mitogenic Factor><Modeling><Modern Man><Molecular><Mouse Strains><Murine><Mus><Myeloid Cells><Oncoprotein MDM2><Oncoprotein p53><P53><Pathway interactions><Pattern><Peripheral><Phase><Phosphoprotein P53><Phosphoprotein pp53><Play><Population><Predisposition><Process><Protein TP53><Protein Tyrosine Kinase p56(lck)><Protein p53><Proto-Oncogene Protein c-lck><Proto-Oncogene Protein lck><Proto-Oncogene Tyrosine-Protein Kinase LCK><RNA Expression><Reactive Site><Receptor Protein><Regulation><Reporting><Role><Sequence Alteration><Signal Transduction><Signal Transduction Systems><Signaling><Specificity><Structure of germinal center of lymph node><Susceptibility><T cell growth factor><T cell response><T memory cell><T-Cell Activation><T-Cell Development><T-Cell Growth Factor><T-Cell Growth Factor Receptors><T-Cell Ontogeny><T-Cell Proliferation><T-Cell Specific Protein Tyrosine Kinase><T-Cell Stimulating Factor><T-Cells><T-Lymphocyte><T-Lymphocyte Development><T-Stage><T4 Cells><T4 Lymphocytes><T44><TCGF Receptors><TNFRSF5><TNFRSF5 gene><TNFSF5><TNFSF5 gene><TP53><TP53 gene><TRAP Gene><TRP53><Testing><Thymocyte Stimulating Factor><Thymus><Thymus Gland><Thymus Proper><Thymus Reticuloendothelial System><Transcription><Transgenes><Tumor Necrosis Factor Receptor Superfamily Member 5 Gene><Tumor Protein p53><Tumor Protein p53 Gene><Tumor stage><Veiled Cells><accessory cell><activated B cells><antibody-based immunity><antigen antibody affinity><antigen-specific T cells><autoimmune encephalomyelitis><base><biological signal transduction><class development><course development><course material development><cytokine><developmental><experiment><experimental research><experimental study><gene product><genome scale><genome wide analysis><genome wide studies><genome-wide><genome-wide analysis><genome-wide identification><genomewide><genomic alteration><immunogen><in vivo><insight><lck Kinase><mRNA><mdm-2 oncogene protein><mdm2 protein><memory CD4 T cell><memory CD4 T lymphocyte><memory T lymphocyte><mouse genetics><mutant><necrocytosis><new approaches><novel><novel approaches><novel strategies><novel strategy><p50><p53 Antigen><p53 Genes><p53 Tumor Suppressor><p53-Binding Protein MDM2><p56 lck><pathway><prevent><preventing><promoter><promotor><protein expression><receptor><response><selective expression><selectively expressed><social role><src Kinases><src Protein-Tyrosine Kinases><src Tyrosine Kinases><src-Family Kinases><src-Family Tyrosine Kinases><thymocyte><thymus derived lymphocyte><vaccine response>