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 RasGRP1 and SOS1 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-MAPK activation via RasGRP1 or SOS1, downstream of LAT, and how these signaling events impact thymocyte selection.
In Aim 1, we will characterize RasGRP1 RasGEF function utilizing the three scientific disciplines in iterative approaches.
In Aim 2, we will define the requirement of allosteric regulation of the RasGEF SOS1.
In Aim 3. we will define the molecular basis of RasGRP1-SOS1 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 SOS-mediated 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 RasGRP1 and SOS1 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.

Public Health Relevance

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.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Program Projects (P01)
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Special Emphasis Panel (ZAI1-RRS-I)
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University of California San Francisco
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Courtney, Adam H; Lo, Wan-Lin; Weiss, Arthur (2018) TCR Signaling: Mechanisms of Initiation and Propagation. Trends Biochem Sci 43:108-123
Shah, Neel H; Löbel, Mark; Weiss, Arthur et al. (2018) Fine-tuning of substrate preferences of the Src-family kinase Lck revealed through a high-throughput specificity screen. Elife 7:
Cantor, Aaron J; Shah, Neel H; Kuriyan, John (2018) Deep mutational analysis reveals functional trade-offs in the sequences of EGFR autophosphorylation sites. Proc Natl Acad Sci U S A 115:E7303-E7312
Lo, Wan-Lin; Shah, Neel H; Ahsan, Nagib et al. (2018) Lck promotes Zap70-dependent LAT phosphorylation by bridging Zap70 to LAT. Nat Immunol 19:733-741
Pielak, Rafal M; O'Donoghue, Geoff P; Lin, Jenny J et al. (2017) Early T cell receptor signals globally modulate ligand:receptor affinities during antigen discrimination. Proc Natl Acad Sci U S A 114:12190-12195
Courtney, Adam H; Amacher, Jeanine F; Kadlecek, Theresa A et al. (2017) A Phosphosite within the SH2 Domain of Lck Regulates Its Activation by CD45. Mol Cell 67:498-511.e6
Ahsan, Nagib; Belmont, Judson; Chen, Zhuo et al. (2017) Highly reproducible improved label-free quantitative analysis of cellular phosphoproteome by optimization of LC-MS/MS gradient and analytical column construction. J Proteomics 165:69-74
Ahsan, Nagib; Salomon, Arthur R (2017) Quantitative Phosphoproteomic Analysis of T-Cell Receptor Signaling. Methods Mol Biol 1584:369-382
Ashouri, Judith F; Weiss, Arthur (2017) Endogenous Nur77 Is a Specific Indicator of Antigen Receptor Signaling in Human T and B Cells. J Immunol 198:657-668
Vercoulen, Yvonne; Kondo, Yasushi; Iwig, Jeffrey S et al. (2017) A Histidine pH sensor regulates activation of the Ras-specific guanine nucleotide exchange factor RasGRP1. Elife 6:

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