Wojciech Swat - US grants

DESCRIPTION (provided by applicant): The Vav family proteins are thought to function as molecular adaptors and guanine-nucleotide exchange factors orchestrating signaling downstream of antigen receptors in lymphocytes. Previous efforts to elucidate Vav function in lymphocyte development and activation in vivo have been hampered by the redundancy among individual members of the Vav family, which comprises 3 highly homologous proteins. As a part of our preliminary studies for this proposal we generated and characterized for the first time mice lacking all 3 Vav proteins which allowed us to demonstrate the essential function of the entire Vav family as well as to conclusively define the limits of functional redundancy among the individual isoforms in the lymphoid lineage. However, the exact mechanism of Vav function remains elusive. To facilitate biochemical analyses of Vav function, in Aim 1 we propose to use Vav-deficient antigen-specific Jurkat T cells engineered to express a murine alpha/beta TCR, the 3.L2, and a murine CD4. Since 3.L2 TCR-ligands are soluble I-Ek MHC molecules covalently linked to antigenic peptides of graded potency, this system allows both the subtlety of antigen activation (by altered peptide ligands) but also the convenience of biochemical analysis possible when using a transformed tissue culture cell line. Using J.3.L2 system we will determine the effects of a large panel of Vav mutants in multiple signaling pathways emanating from the TCR. These Vav mutants were motivated by structural features which implicitly incorporate several distinct hypotheses about Vav mechanism. In Aim 2, we propose to use a novel Vav null-hematopoietic stem cell complementation (Vav nulI-HSCC)assay developed for rapid analyses of the effects of mutant Vav proteins in T cell development and activation. Using this assay, we will determine the structural basis for Vav protein function in T lymphocytes in vivo. Based on results of these experiments, selected Vav mutants will be introduced into murine germ line using Vav exon-replacement (knock-in). In Aim 3 we will examine the major unanswered questions surrounding the regulation of Vav function in vivo by carrying out complex analyses, which will build on the strength of a large panel of Vav mutants examined by approaches established in Aims 1 and 2.

DESCRIPTION (provided by applicant): Vav proteins are guanine nucleotide exchange factors and molecular adaptors that play a key role in signal transduction of lymphocyte antigen receptors. Several recent studies have also implicated Vav1 in natural killer (NK) cell-mediated cytotoxicity of tumor cells. However, whether Vav1 effects all NK cell activating pathways is not known, and it is possible that other Vav family molecules are involved in NK cell triggering. NK cells recognize tumor or virally-infected cells through multiple activating receptors with diverse structures, specificities and signaling adaptors. The activating NK cell receptor NKG2D recognizes endogenous major histocompatibility complex (MHC) class I-related molecules expressed at high levels primarily in virally infected and tumor cells while Ly49H mediates selective recognition of m157, a murine cytomegalovirus (MCMV)-encoded class I-like molecule that is expressed on infected cells. Both NKG2D and Ly49H deliver stimulatory signals which trigger secretion of IFN-? and release of cytotoxic granules that contain perforin and granzymes. However, it is not know exactly how such stimulatory signals are transduced inside the NK cells. NKG2D and Ly49D/H lack cytoplasmic signaling elements and can deliver stimulatory signals only by associating with transmembrane adaptor proteins. Ly49D and Ly49H signal through DAP12 (also called KARAP) which contains immunoreceptor tyrosine-based activation motifs (ITAM) that are phosphorylated and function as docking sites for Syk and ZAP70 protein tyrosine kinases. In contrast, NKG2D signals through DAP10, a unique adapter that contains a YxNM motif which recruits phosphatidyl inositol 3-kinase (PI3-K) and Grb-2. As part of our preliminary studies for this proposal we generated mice lacking the individual, or all, Vavfamily proteins and began to examine the potential contribution of these proteins to NK cell cytotoxicity. Intriguingly, these data indicate that Vav is essential for DAP10- but not for DAP12-mediated natural cytotoxicity. Thus, these data suggest a new paradigm regarding the utilization of Vav in activation of natural cytotoxicity downstream of NK cell surface receptors associated with non-ITAM- vs. ITAM-containing adaptors. Here, we propose to use several in vitro and in vivo approaches to determine Vav mechanism in NK cell function and development of natural cytotoxicity against virally-infected and tumor cells.

DESCRIPTION (provided by applicant): The Vav family proteins are thought to function as molecular adaptors and guanine-nucleotide exchange factors orchestrating signaling downstream of antigen receptors in lymphocytes. Previous efforts to elucidate Vav function in lymphocyte development and activation in vivo have been hampered by the redundancy among individual members of the Vav family, which comprises 3 highly homologous proteins. As a part of our preliminary studies for this proposal we generated and characterized for the first time mice lacking all 3 Vav proteins which allowed us to demonstrate the essential function of the entire Vav family as well as to conclusively define the limits of functional redundancy among the individual isoforms in the lymphoid lineage. However, the exact mechanism of Vav function remains elusive. To facilitate biochemical analyses of Vav function, in Aim 1 we propose to use Vav-deficient antigen-specific Jurkat T cells engineered to express a murine alpha/beta TCR, the 3.L2, and a murine CD4. Since 3.L2 TCR-ligands are soluble I-Ek MHC molecules covalently linked to antigenic peptides of graded potency, this system allows both the subtlety of antigen activation (by altered peptide ligands) but also the convenience of biochemical analysis possible when using a transformed tissue culture cell line. Using J.3.L2 system we will determine the effects of a large panel of Vav mutants in multiple signaling pathways emanating from the TCR. These Vav mutants were motivated by structural features which implicitly incorporate several distinct hypotheses about Vav mechanism. In Aim 2, we propose to use a novel Vav null-hematopoietic stem cell complementation (Vav nulI-HSCC)assay developed for rapid analyses of the effects of mutant Vav proteins in T cell development and activation. Using this assay, we will determine the structural basis for Vav protein function in T lymphocytes in vivo. Based on results of these experiments, selected Vav mutants will be introduced into murine germ line using Vav exon-replacement (knock-in). In Aim 3 we will examine the major unanswered questions surrounding the regulation of Vav function in vivo by carrying out complex analyses, which will build on the strength of a large panel of Vav mutants examined by approaches established in Aims 1 and 2.

[unreadable] DESCRIPTION (provided by applicant): The long term objective of this research involves determining the mechanism whereby the mouse discs- large homolog 1 gene, Dlgh1, regulates urogenital development. DLGH1 is a scaffolding protein with multiple protein-protein interaction domains, including three PDZ domains and one SH3 domain. Dlgh1 is a homolog of the Drosophila discs-large gene, dlg, which is a founding member of the eponymous PDZ family of proteins and also of the MAGUK (membrane-associated guanylate kinase) family. Studies in Drosophila suggest that dlg is a tumor suppressor, because mutation of dlg causes overgrowth of imaginal discs. Studies in both fly and mammalian cells suggest that dlg and its homologs are also involved in establishing and/or maintaining epithelial cell polarity. We have studied mice lacking DLGH1 and found several urogenital defects, including sporadic renal agenesis, congenital hydronephrosis, and reproductive tract abnormalities. We have shown that hydronephrosis is associated with dramatic smooth muscle alignment defects; the normally circular muscle aberrantly aligns in the longitudinal direction. This greatly impairs the squeezing motion of peristalsis, such that urine is retained in the kidney. In addition, ureteric stromal cells, which normally lie between the urothelium and the smooth muscle layers and express Raldh2, are absent from Dlgh1 mutant ureters. The absence of these cells could also affect ureteric function, either directly or indirectly. Immunofluorescence studies show that DLGH1 is expressed strongly in the urothelium and weakly in other cells of the ureter. We will determine which cellular compartment must express Dlgh1 for normal smooth muscle cell alignment and for differentiation and/or migration of ureteric stromal cells using a new floxed Dlgh1 allele and appropriate Cre transgenic mice. In addition, we will generate chimeric mice to investigate whether DLGH1 acts in a non-cell autonomous fashion. Morphological and functional assessments will be performed to determine the cellular requirements for Dlgh1 expression. Next we will use genetic methods to investigate the hypothesis that the interaction of other DLGH family members with known or suspected DLGH1 binding proteins are compensating in part for the absence of DLGH1. Finally, we will use in vitro methods to define the role of DLGH1 in cell migration, polarization, and signaling. PUBLIC HEALTH RELEVANCE: Congenital urinary tract abnormalities are a relatively common health problem in the human population and are responsible for a significant number of cases of progressive renal disease. We have generated a novel mouse model of hydronephrosis (Dlgh1-/- mice) involving the misalignment of ureteric smooth muscle, which is commonly found in human cases of urinary tract obstruction. A better understanding of the biology of DLGH1 could have important implications for understanding and perhaps for treatment or prevention of urinary tract abnormalities in humans. [unreadable] [unreadable] [unreadable]

This proposal is in response to Notice Number NOT-OD-09-088 of the American Recovery and Reinvestment Act of 2009. We request funding for the first two years of the revised grant application 1R01AI73718-01A2, with changes in scope approved by the NIAID Program Officer. Specifically, we propose to elucidate the molecular mechanism of signaling by DAP10/DAP12/FcR[unreadable]-associated activating receptors (DAP- AARs), such as NKG2D in NK cells and integrins in myeloid cells, and to establish the role for several genes encoding proteins essential for mediating signals emanating from DAP-AARs as susceptibility loci in microbial pathogenesis. In this context, we have recently identified critical new functions of Vav and DAP10/DAP12/FcR[unreadable] proteins in transducing signals emanating from innate immune receptors including activating receptors in NK cells and myeloid cells. Based on these preliminary data, we propose a model in which Vav and Phosphoinositide 3-kinase (PI3K) engage in crosstalk to amplify signals leading to NK cytotoxicity. The concept that Vav proteins control innate immune responses by activating both ITAM- and non-ITAM-dependent signaling represents a novel paradigm in signal transduction and cellular activation. In this context, striking new findings from several labs including ours reveal a previously unanticipated mechanism in which integrins and other adhesion receptors utilize DAP12 and FcR[unreadable] to promote both adhesion and effector responses. While the augmentation of neutrophil effector responses including cytokine production, degranulation, and phagocytosis by adherence to integrin ligands has been appreciated for over 30 years, these new results reveal shared signaling modules activated by both proinflammatory stimuli and adhesion receptors. In this modified proposal, we aim to establish the mechanism of NKG2D- DAP10-proximal signaling and Vav1-PI3K crosstalk (Aim 1), and to delineate signaling pathways emanating from the DAP10/DAP12/FcR[unreadable]-associated activating receptors (DAP-AARs) and establish the role for several genes encoding proteins essential for mediating signals emanating from DAP-AARs as susceptibility loci in microbial pathogenesis in vivo (Aim 2).