Integrative mapping of lymphocyte signaling and function
Coordinators : R. Lesourne / L. Dupré
A critical component of the immune defense against viruses and cancers is the activation of specific and well-calibrated T lymphocyte responses. T lymphocyte activation is governed by T-cell receptor (TCR) recognition of foreign peptides loaded on histocompatibility molecules (MHC). It is further modulated by a vast panel of activatory and inhibitory co-receptors. T lymphocytes integrate TCR and co-receptor triggering into a complex network of intracellular signaling pathways. The quality, strength and duration of these signals determine the outcome of T cell responses. Calibration of such signals is ultimately critical for the discrimination between self and non-self antigens, the generation and expansion of the appropriate functional T cell subsets (helper, cytotoxic, regulatory) and the control of pathological disorders.
Our research objective is to map the critical molecular hubs of the T cell signaling network and to investigate their contribution to the calibration of T cell activation in the context of physiological or pathophysiological settings such as malignancies, immunodeficiencies, autoimmune disorders and ageing. Our research strategy is to explore 3 layers of control of the T cell signaling map via the implementation of 3 complementary projects:
Axis 1 aims at identifying the primary molecular nodes integrating early signals from the TCR and co-receptors via a global proteomic-based approach and investigating the mechanisms by which they modulate T cell-mediated immunity in mouse models.
Axis 2 aims at characterizing the molecular gateways that connect early signals to the actin cytoskeleton, an essential orchestrator of lymphocyte activation and function.
Axis 3 aims at deciphering the signaling mechanisms controlling lymphocyte activation and differentiation via ubiquitin-mediated processes.
AXIS 1: Molecular dissection of lymphocyte signaling in health and diseases. Coordinator: Renaud Lesourne.
The TCR and the T-cell co-receptors operate together in a very organized and regulated fashion, triggering the assembly of signaling proteins into distinct molecular complexes that subsequently initiate and regulate the propagation of intracellular signals associated with specific functional outcomes. The composition, stoichiometry and activity of those early signaling complexes determine the effect by which each receptor modulate the T-cell signaling landscape and regulate ultimately the profile of lymphocyte responses. The specific goal of our project is to characterize mechanisms by which the TCR and the co-receptors modulate lymphocyte signaling and to investigate how those regulations shape the activity of T lymphocyte during immune responses. We integrate innovative proteomic approaches, to dissect signaling networks, with the use of genetically engineered murine models, to understand how genetic alteration of signaling processes may lead to the development of ineffective immune responses, in the context of cancer, ageing and auto-immunity. In the past years, we have focused our research on several actors of lymphocyte signaling such as the signaling regulator THEMIS and the co-receptor CD5.
Investigation on the signaling protein THEMIS
We previously identified THEMIS (also named THEMIS1) as a new actor of TCR signaling essential for the development of T cells. The mechanism by which THEMIS operates has long remained unclear. Using mass spectrometry, we characterized several new partners of THEMIS (VAV1, SHP-1, USP9X, LIS1) and investigated the role of those interactions on T cell development and peripheral T cell responses. We were engaged in collaborative studies, which identified THEMIS as an important player of regulatory T cell (Treg) suppressive function. We also contributed to the finding that THEMIS2 enables B cell selection through positive regulation of BCR signaling.
CD5 coordinates opposite TCR signals to regulate the inopportune emergence of Treg cells during viral infection
CD5 is characterized as an inhibitory co-receptor with important regulatory functions in thymic selection. The molecular mechanism by which CD5 operates and its precise function in mature T cells have been puzzling. By combining quantitative mass spectrometry and mouse genetics, we describe a novel and unexpected signaling process in which CD5, rather than exclusively acting as a broad repressor of TCR signals, engages a dedicated set of effector molecules that induce both stimulatory and inhibitory signaling events. Importantly, CD5 shapes TCR signals to control T cell responsiveness and repress the transactivation of Foxp3, thereby regulating the inopportune generation of extrathymic Treg during immune responses against pathogens.
AXIS 2: Control of human lymphocyte activation and function by the actin cytoskeleton. Coordinator: Loïc Dupré.
The signaling processes activated upon stimulation of lymphocytes with various receptors are intimately connected to the actin cytoskeleton. Indeed, the precise localization and topology of receptors and their associated signaling networks rely on the local organization of actin filaments beneath the plasma membrane. In turn, signaling cascades promote actin cytoskeleton remodeling via the activation of numerous actin regulators. Such reciprocal relationship positions the actin cytoskeleton as a pivotal scaffold for the integration and organization of signals within lymphocytes.
We initially approached the study of the T cell actin cytoskeleton via the characterization of primary immunodeficiencies caused by defects in actin cytoskeleton regulators. We have a long-standing interest in the study of the Wiskott-Aldrich syndrome (WAS), which is the first described actin-related primary immunodeficiency (PID). We have characterized multiple defects in various T lymphocyte subsets from WAS patients. Beyond WAS, we recently contributed to the description of multiple novel rare deficiencies in actin regulators causing PID. Through these natural models, we are studying how different actin regulators control specific steps and compartments of actin remodeling and thereby play non-redundant roles in the tuning of lymphocyte responses.
The study of actin-related pathologies brings us to interrogate at a fundamental level the contribution of actin remodeling to the control of lymphocyte shape and receptor topology in the context of antigen scanning. We are also particularly interested at elucidating how actin remodeling conditions lymphocyte decisions when it comes to migrate, kill or secrete cytokines. Addressing such fundamental questions is key to further characterize disease mechanisms.
Our studies on the actin cytoskeleton benefit from a close partnership with the campus of the University of Medicine of Vienna and in particular the Ludwig Boltzmann Institute for Rare and Undiagnosed Diseases (LBI-RUD). This partnership was recently formalized in the form of a cooperation agreement set up as part of the CNRS IRP (International Research Project “SysTact”) program. In addition, Loïc Dupré, coordinator of this partnership, benefits from a double affiliation CPTP / LBI-RUD (https://rud.lbg.ac.at/de/immune-cell-imaging).
AXIS 3: Ubiquitin Enzymes in Immunity and Disease. Coordinators: Isabelle Lamsoul & Pierre G. Lutz.
A tight regulation of lymphocyte differentiation and activation is of uttermost importance to set calibrated adaptive immune responses. This is largely achieved through transcriptional and epigenetic regulations. While powerful, these mechanisms do not allow cells to acutely adapt or fine‐tune cellular processes. For this purpose, post-translational modifications such as ubiquitylation – the conjugation of ubiquitin to a protein substrate – are used. Ubiquitylation is rapid, reversible and versatile, directing proteins to proteasomal degradation and additional fates. The reversibility of this post-translational modification is driven by deubiquitinating enzymes responsible for removing ubiquitin conjugates from substrates. Importantly, alteration of the ubiquitin pathway results in human disease pathogenesis including cancer and leukemia, neurological disorders or inflammatory and infectious diseases. In this context, we focus on ubiquitin enzymes regulating the precise dosage or activity of signaling hubs and actin cytoskeletal proteins that play key roles in immune cells. The overall goal of our project is to better understand ubiquitylation/deubiquitylation events in immunity and disease in order to identify novel biomarkers and therapeutic targets for precision medicine.
A key regulatory step of the ubiquitylation cascade is governed by the E3 ubiquitin ligase, which dictates substrate selectivity. Several E3 ubiquitin ligases regulate T cell differentiation and functions. We have recently gathered solid molecular, cellular and in vivo evidence that the ASB2α E3 ubiquitin ligase controls T helper 2 lymphocyte functions in a mouse model of colon cancer. ASB2α triggers ubiquitylation (K48-linked polyubiquitin chains) and proteasomal degradation of the actin-binding proteins filamin A and filamin B, thereby regulating actin cytoskeleton organization and remodeling, as well as different aspects of cell motility. One of our specific goals is therefore to elucidate the roles of the ASB2α E3 ubiquitin ligase in the regulation of lymphocyte function in physiological and pathological settings.
Much evidence suggests a link between imbalances in protein homeostasis and the development of specific subtypes of leukemia and lymphoma. P.G. Lutz is the CNRS partner of a French-Spanish cooperative network involving researchers from universities, research centers and companies, PROTEOblood*, thanks to the cofunding of Interreg-POCTEFA. PROTEOblood investigates proteinopathies for the development of individualized therapies in hematological cancers. Indeed, we bring our expertise to generate innovative tools and technologies to identify the ubiquitylome of leukemia and lymphoma cells for the development of efficient and safe therapies.
Partners: Gaël Roué (coordinator; Josep Carreras Leukaemia Research Institute, Barcelona, Spain), Pablo Menéndez Bujan (Josep Carreras Leukaemia Research Institute, Barcelona, Spain), David Valcárcel (Experimental Haematology Unit of the Vall d’Hebron Institute of Oncology – VHIO), Jean-Emmanuel Sarry (UMR1037 from the French Institute of Health and Medical Research – INSERM, Toulouse, France), María Rosa Barrio Olano (Association Centre for Cooperative Research in Biosciences – CIC bioGUNE, Derio, Spain), Pierre G. Lutz (UMR5282 from the French National Center for Scientific Research – CNRS, Toulouse, France), Judith Farrés (ANAXOMICS Biotech, Barcelona, Spain) and José Ignacio Borrell Bilbao (Pharmaceutical Chemistry Group of the Sarrià Institute of Chemistry – IQS, Barcelona, Spain).
Isabelle Lamsoul, PhD, Isabelle.Lamsoul@inserm.fr, ORCID: 0000-0002-7769-5627
Pierre G. Lutz, PhD, Pierre.Lutz@inserm.fr, ORCID: 0000-0003-0590-9101
LinkedIn : Pierre-Lutz
Numerous primary immunodeficiencies results from mutations on genes encoding for signalling molecules that control T cell development and function. The molecular mechanism by which many of these molecules and mutations operate remains unknown. Beyond these rare pathologies, the susceptibility to many and more frequent diseases results from the combined association of genetic variants affecting the expression and function of signalling molecules involved in T cell activation.
These defects can trigger uncontrolled reactions of T lymphocytes against healthy cells (diabetes, multiple sclerosis) or against generally harmless environmental factors (allergy). On the contrary, in some pathology they can prevent efficient T cell-dependent immune reaction (cancers). Some virus (like the HIV) or pathogenic bacteria also divert T cell signaling pathways to inhibit or control immune responses in their advantages. Understanding T cell signaling is therefore a major challenge to determine the etiology of several human pathologies and to facilitate the development of specific therapy.
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Laurène PFAJFER (Master & PhD student jan. 2016 – dec. 2020)
Yolla GERMAN (PhD student jan 2017 – feb 2020)
Jérémy ARGENTY (PhD student oct 2015 – oct 2018; postdoctoral researcher mar. 2020 – Aug 2021)
Gaëtan BLAIZE (PhD student sept 2015 – jun 2018).
Delphine GUIPOUY (PhD student dec 2014 – dec 2017).
Anne GARREAU (PhD student sept 2013 – apr 2017).
– Nicolas Destainville (Institut de Physique Théorique)
– Audrey Ferrand (IRSD)
– Anne Gonzalez de Peredo (IPBS)
– Anne Quillet-Mary (CRCT)
– Loïc Ysebaert (IUCT-Oncopole)
– Victor Appay (ImmunoConcEpT, University of Bordeaux)
– Marina Cavazzana/Emmanuelle Six/Alessandra Magnani (Imagine Institute, Paris)
– Emmanuel Donnadieu (Institut Cochin, Paris)
– Olivier Théodoly (Adhesion and Inflammation lab, Marseille)
Partnership with Vienna, Austria
Our laboratory coordinates a bilateral reasearch axis in between Toulouse and Vienna, conducted under the auspice of the International Research Project Program of CNRS. Our Austrian partners are:
– Kaan Boztug (Ludwig Boltzmann Institute Rare and Undiagnosed Diseases, LBI-RUD)
– Johannes Huppa (Immunology Department, Medical University of Vienna)
– Jörg Menche (Max Perutz labs, University of Vienna)
– Georg Stary (Dermatology Department, Medical University of Vienna)
In addition, we have established a research branch in Vienna (https://rud.lbg.ac.at/de/immune-cell-imaging), lead by L. Dupré and affiliated to the Ludwig Boltzmann Institute Rare and Undiagnosed Diseases and to the Medical University of Vienna.
International (other than Austria)
– Alessandro Aiuti (San Raffaele Telethon Institute for Gene Therapy, Milan, Italy)
– Vinicius Cotta-de-Almeida (Oswaldo Cruz Foundation, FIOCRUZ, Rio de Janeiro, Brazil)
– Roeland Merks (Mathematical Institute, Leiden University, The Netherlands)