Systematic identification of regulatory proteins critical for T-cell activation
- Equal contributors
1 Rigel Pharmaceuticals Inc., 1180 Veterans Blvd., South San Francisco, CA 94080, USA
2 Novartis Pharma AG, S-386.6.25, CH-4002 Basel, Switzerland
3 Novartis Forschungsinstitut GmbH, Brunner Strasse 59, A-1235 Vienna, Austria
4 Current address: Exelixis Inc., 170 Harbor Way, South San Francisco, CA 94083, USA
5 Current address: Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
Journal of Biology 2003, 2:21 doi:10.1186/1475-4924-2-21Published: 15 September 2003
The activation of T cells, mediated by the T-cell receptor (TCR), activates a battery of specific membrane-associated, cytosolic and nuclear proteins. Identifying the signaling proteins downstream of TCR activation will help us to understand the regulation of immune responses and will contribute to developing therapeutic agents that target immune regulation.
In an effort to identify novel signaling molecules specific for T-cell activation we undertook a large-scale dominant effector genetic screen using retroviral technology. We cloned and characterized 33 distinct genes from over 2,800 clones obtained in a screen of 7 × 108 Jurkat T cells on the basis of a reduction in TCR-activation-induced CD69 expression after expressing retrovirally derived cDNA libraries. We identified known signaling molecules such as Lck, ZAP70, Syk, PLCγ1 and SHP-1 (PTP1C) as truncation mutants with dominant-negative or constitutively active functions. We also discovered molecules not previously known to have functions in this pathway, including a novel protein with a RING domain (found in a class of ubiquitin ligases; we call this protein TRAC-1), transmembrane molecules (EDG1, IL-10Rα and integrin α2), cytoplasmic enzymes and adaptors (PAK2, A-Raf-1, TCPTP, Grb7, SH2-B and GG2-1), and cytoskeletal molecules (moesin and vimentin). Furthermore, using truncated Lck, PLCγ1, EDG1 and PAK2 mutants as examples, we showed that these dominant immune-regulatory molecules interfere with IL-2 production in human primary lymphocytes.
This study identified important signal regulators in T-cell activation. It also demonstrated a highly efficient strategy for discovering many components of signal transduction pathways and validating them in physiological settings.