In this application we propose to examine the role of the novel protein Chat-H in signaling pathways that regulate T lymphocyte migration. In preliminary studies, we used lentivirus-mediated RNA interference (RNAi) to silence expression of Chat-H in mouse primary T cells and study the effect of Chat-H deletion on T cell function. We found that whereas Chat-H downregulation had no effect on T cell receptor (TCR)-mediated signaling, in vitro and in vivo chemokine-induced migration of Chat-H deficient T cells was dramatically impaired. Defects in migration and adhesion correlated with impaired activation of the Rap-1 GTPase, which is a key regulator of integrin-mediated cellular adhesion and migration. Chat-H constitutively associated with the signaling protein CasL and formation of this complex was necessary for migration. These observations suggest that Chat-H is an important regulator of chemokine receptor signaling and T lymphocyte migration and it that it acts together with CasL to regulate these processes. To study the in vivo requirement for Chat-H we recently generated Chat-H knockout mice and consistent with previous results, preliminary studies show that T cells from these mice exhibit impaired in vitro migration. In the experiments described here, we propose to examine the mechanisms through which Chat-H regulates chemokine-induced T lymphocyte migration and the effect of Chat-H deficiency in this process. We will test the following hypothesis: Chat-H regulates chemokine-induced T lymphocyte migration by activating Rap1 and Rap1-mediated integrin activation, cell adhesion and migration. Deficiency in Chat-H expression results in defective integrin-mediated adhesion and as a result impaired homeostatic homing of T cells to secondary lymphoid organs, and compromised T-cell-mediated immune responses. To test this hypothesis we will use first use T cells in which Chat-H has been dowregulated by RNAi to define the biochemical mechanisms of how Chat-H regulates Rap1 activation and integrin-mediated adhesion. To study the in vivo requirement for Chat-H we will use Chat-H knockout mice to determine whether Chat-H deficiency affects in vivo migration and homeostatic trafficking of mature T cells to peripheral lymphoid organs, and T-cell-mediated immune responses. We anticipate that these experiments will lead to novel insight into the mechanisms that regulate lymphocyte chemotaxis and reveal important roles for both Chat-H and CasL in this process downstream of chemokine receptors. Through these studies we also aim towards gaining insight into the role of Chat-H in chronic inflammation and conditions associated with leukocyte adhesion deficiencies and identify therapeutic targets for treating human diseases.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Cellular and Molecular Immunology - A Study Section (CMIA)
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Miller, Lara R
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Icahn School of Medicine at Mount Sinai
Internal Medicine/Medicine
Schools of Medicine
New York
United States
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