|Director : Lars Rogge (firstname.lastname@example.org)|
The Immunoregulation group studies the molecular mechanismes that control the differentiation of naive T helper cells into polarized Th1 and Th2 effector cells. This differentiation process is initiated by ligation of the T cell receptor and is directed by a variety of cytokines present at the time of T cell priming and co-stimulatory and adhesive interactions between antigen presenting dendritic cells and T cells. Our main goal is to understand how these signals are integrated into a specific genetic program which determines the outcome of the immune response. Our group is also interested in the study of the post-translational control of transcription factors. In particular, we are addressing the role of ubiquitin ligases of the RING finger subtype in regulating transcriptional activity.
The differentiation of naive CD4+ T lymphocytes to either T helper type 1 (Th1) or Th2 cells is a critical aspect of the adaptive immune response, with broad implications in host defense and disease pathogenesis. Th1 cells promote cell-mediated immunity and are necessary to clear the organism from intracellular pathogens but can cause chronic inflammatory diseases. On the other hand, Th2 responses are essential to combat extracellular pathogens but are associated with allergies and asthma. These findings indicate that the development of Th1 and Th2 cells must be tightly controlled and that therapeutic modulation of immune reponses may have an impact on human diseases.
Control of T cell recruitment into inflamed joints
Chronic inflammatory diseases such as rheumatoid arthritis (RA) and juvenile idiopathic arthritis (JIA) are associated with the presence of Th1 cells in the inflamed synovium, but the mechanisms controlling recruitment of Th1 cells to inflamed joints are not fully understood. We have analyzed the role of lpha(1,3)-fucosyltransferase-VII (FucT-VII), an enzyme responsible for the generation of functional P- and E-selectin ligands, in the recruitment of T cells to inflamed joints. Using kinetic RT-PCR analysis we showed that the mRNA levels of FucT-VII, IFN-g, and IL-12Rb2 are upregulated in T cells infiltrating the inflamed joints in children with JIA compared to paired samples of peripheral blood T cells. Higher expression of FucT-VII mRNA in synovial fluid T cells correlated with increased binding of T cells to P-selectin. Moreover, FucT-VII expression and increased P-selectin binding capacity of T cells were associated with a more severe course of the disease. Finally, we could demonstrate that expression of FucT-VII in T cells resulted in an increased accumulation of these cells into human RA synovial tissue grafted into SCID mice. Our data indicate a critical role of FucT-VII in the enhanced homing of T cells to the inflamed synovium and suggest that inhibitors of FucT-VII enzyme activity may be of significant therapeutic value for the treatment of chronic arthritis.
Transcriptional control of T helper cell differentiation
The goal of our present studies is to elucidate the genetic program that controls the development and functional properties of human helper T cell subsets. In particular, we focus on the role of the transcription factors T-bet and GATA-3 in the initiation of Th1 or Th2-specific transcriptional cascades. We have introduced T-bet into Th2 cells and GATA-3 into Th1 cells by retrovirus-mediated gene transfer. The expression signatures of the resulting T cell populations were analyzed using Affymetrix U95A arrays. Preliminary data from these experiments indicate that GATA-3, but not T-bet, can "switch" the developmental program of T helper cells. We are currently analyzing the functional properties of the retrovirus-transduced T cells and the transcriptional and post-transcriptional regulation of T-bet and GATA-3 in helper T cells.
Identification of a novel transcriptional regulator
RING-finger proteins have been implicated in many fundamental cellular processes, including the control of gene expression. In Arabidopsis Thaliana a key regulator of light-dependent development is Constitutive Photomorphogenesis Protein 1 (atCOP1), a RING-finger protein that translates light/dark signals into specific changes in gene transcription. atCOP1 binds the basic-leucine zipper (bZIP) factor HY5 and suppresses its transcriptional activity, through a yet undefined mechanism. Furthermore, the pleiotropic phenotype of atCOP1 mutants indicates that atCOP1 may be a central regulator of several transcriptional pathways. We have cloned and characterized the human orthologue of atCOP1. Human COP1 (huCOP1) distributes both to the cytoplasm and the nucleus of cells and showed a striking degree of sequence conservation with atCOP1, suggesting the possibility of a functional conservation as well. We found that huCOP1 specifically binds bZIP factors of the Jun family through a conserved aminoacid motif and that expression of huCOP1 in mammalian cells downregulates c-Jun dependent transcription. huCOP1 suppressive effect on transcription required the integrity of its RING domain. We could demonstrate that the RING domain of huCOP1 displayed ubiquitin ligase activity in an autoubiquitination assay in vitro, however suppression of AP-1-dependent transcription by huCOP1 occurred in the absence of changes in c-Jun protein levels, suggesting that this inhibitory effect is independent of c-Jun degradation. Our findings indicate that huCOP1 is a novel regulator of AP-1-dependent transcription.
Keywords: Human, Th1/Th2, Autoimmunity, Cellular Differentiation, Microarrays, Rheumatoid Arthritis
|Publications of the unit on Pasteur's references database|
|Office staff||Researchers||Scientific trainees||Other personnel|
|ROGGE, Lars, IP, (Chef de laboratoire,email@example.com)
BIANCHI, Elisabetta, Inserm, (Poste Orange,firstname.lastname@example.org)
|DENTI, Simona, post-doctoral fellow
MARTIN, Denise, post-doctoral fellow
GASPARIAN, Sona, Ph.D. student
LETIMIER, Fabrice, graduate student
|SECHET, Emmanuel, (technicien,email@example.com)|