Efficient thymocyte selection is critical to generate T lymphocytes with a very broad spectrum of specific T cell receptors (TCR) that recognize foreign antigens, while avoiding development of autoimmunity. The exact molecular mechanisms underlying thymocyte positive versus negative selection are not know, but different patterns of Ras-MAP kinase (MAPK) activation have long been postulated to be involved. MAPK are tunable signaling molecules that lie downstream of active Ras and that regulate gene expression. We hypothesize that the choice of Ras Guanine nucleotide Exchange Factors usage, namely RasGRP or SOS + RasGRP, governs distinct Ras activation characteristics and thymocyte selection. This project will focus on understanding the characteristics of Ras-MAPK signaling by RasGRPI and S0S1 and how this affects thymocyte fate decisions by combining the biophysical, computational, and cellular-biochemical expertise of the Kuriyan (UCB), Groves (UCB), Chakraborty (MIT), and Roose (UCSF) labs. Combination of: 1) purified recombinant proteins;2) a model two dimensional lipid bilayer system containing defined quantities of recombinant proteins;3) computational modeling;and 4) model systems of the Jurkat T cell, DT40 B cell, and mutant cell lines and mouse model studies provide an unique approach that has not been taken previously. The overall goal of project #2 is to understand the distinct characteristics of Ras- IVIAPK activation via RasGRPI or S0S1, downstream of LAT, and how these signaling events impact thymocyte selection.
In Aim 1, we will characterize RasGRPI RasGEF function utilizing the three scientific disciplines in iterative approaches.
In Aim 2, we will define the requirement of allosteric regulation of the RasGEF S0S1.
In Aim 3. we will define the molecular basis of RasGRPI-S0S1 synergy.
In Aim 4, we will Characterize the role of LAT in digital Ras-MAPK signaling.
In Aim 5. we will define the role of SOSmediated Ras activation in thymocyte selection. Understanding the specific nature of Ras activation and the downstream activation of the ERK, P38, and JNK MAPK will be the endpoint goals for this project; specifically we will focus on the role of the RasGEF characteristics of RasGRPI and S0S1 as well as on phospho-LAT, which could serve as a point of bifurcation between analog and digital Ras signaling. We expect that we will gain insights from both concurrence and contradiction between the three disciplines. By building step-wise to increasingly complex models we aim to understand the molecular mechanism of selective Ras-MAPK activation patterns and how these impact thymocyte selection.
Despite many years of excellent research, the molecular details that discriminate positive and negative selection of thymocyte are still unknown. Our collaborative approach provides unique opportunities to understand how reliable selection exactly occurs and will help understand how development of autoreactive T cells can occur, which can cause development of autoimmune diseases in humans.
|Christensen, Sune M; Tu, Hsiung-Lin; Jun, Jesse E et al. (2016) One-way membrane trafficking of SOS in receptor-triggered Ras activation. Nat Struct Mol Biol 23:838-46|
|Thill, Peter A; Weiss, Arthur; Chakraborty, Arup K (2016) Phosphorylation of a Tyrosine Residue on Zap70 by Lck and Its Subsequent Binding via an SH2 Domain May Be a Key Gatekeeper of T Cell Receptor Signaling In Vivo. Mol Cell Biol 36:2396-402|
|Chen, Hang; Thill, Peter; Cao, Jianshu (2016) Transitions in genetic toggle switches driven by dynamic disorder in rate coefficients. J Chem Phys 144:175104|
|Rooney, Gemma E; Goodwin, Alice F; Depeille, Philippe et al. (2016) Human iPS Cell-Derived Neurons Uncover the Impact of Increased Ras Signaling in Costello Syndrome. J Neurosci 36:142-52|
|Chan, Alice Y; Punwani, Divya; Kadlecek, Theresa A et al. (2016) A novel human autoimmune syndrome caused by combined hypomorphic and activating mutations in ZAP-70. J Exp Med 213:155-65|
|Huang, William Y C; Yan, Qingrong; Lin, Wan-Chen et al. (2016) Phosphotyrosine-mediated LAT assembly on membranes drives kinetic bifurcation in recruitment dynamics of the Ras activator SOS. Proc Natl Acad Sci U S A 113:8218-23|
|Chung, Jean K; Lee, Young Kwang; Lam, Hiu Yue Monatrice et al. (2016) Covalent Ras Dimerization on Membrane Surfaces through Photosensitized Oxidation. J Am Chem Soc 138:1800-3|
|Ashouri, Judith F; Weiss, Arthur (2016) Endogenous Nur77 Is a Specific Indicator of Antigen Receptor Signaling in Human T and B Cells. J Immunol :|
|Christensen, Sune M; Triplet, Meredith G; Rhodes, Christopher et al. (2016) Monitoring the Waiting Time Sequence of Single Ras GTPase Activation Events Using Liposome Functionalized Zero-Mode Waveguides. Nano Lett 16:2890-5|
|Shah, Neel H; Wang, Qi; Yan, Qingrong et al. (2016) An electrostatic selection mechanism controls sequential kinase signaling downstream of the T cell receptor. Elife 5:|
Showing the most recent 10 out of 50 publications