: PI5P in T Cell Biology

International audiencePhosphoinositides are critical regulators in cell biology. Phosphatidylinositol 4,5-bisphosphate, also known as PI(4,5)P2 or PIP2, was the first variety of phosphoinositide to enter in the T cell signaling scene. Phosphatidylinositol bis-phosphates are the substrates for different types of enzymes such as phospholipases C (β and γ isoforms) and phosphoinositide 3-kinases (PI3K class IA and IB) that are largely involved in signal transduction. However until recently, only a few studies highlighted phosphatidylinositol monophosphates as signaling molecules. This was mostly due to the difficulty of detection of some of these phosphoinositides, such as phosphatidylinositol 5-phosphate, also known as PI5P. Some compelling evidence argues for a role of PI5P in cell signaling and/or cell trafficking. Recently, we reported the detection of a PI5P increase upon TCR triggering. Here, we describe the current knowledge of the role of PI5P in T cell signaling. The future challenges that will be important to achieve in order to fully characterize the role of PI5P in T cell biology, will be discussed

T lymphocyte singaling : indentification of e recently indentified lipid messenger, phosphatidylinositol 5-phosphate (Ptdlns5P)

Le PtdIns5P est un phosphoinositide très peu connu et émerge dernièrement en tant qu’important nouveau second messager. D’ailleurs, l’augmentation artificielle de PtdIns5Pdans les cellules épithéliales, favorise la voie pro-oncogénique Phosphoinositide 3-kinase/AKT. Plus récemment, il a été fait état d’un possible rôle du PtdIns5P dans le processus de lymphomagenèse.Notre laboratoire étudie depuis de nombreuses années les voies de signalisations importantes de l’activation lymphocytaire T et notamment la voie pro-oncogénique PI3K. Le laboratoire s’est tourné notamment vers l’étude des protéines adaptatrices de la famille Dok(Downstream of Kinase) lors de l’activation lymphocytaire T.Ainsi le but de ce travail a été dans un premier temps l’étude des protéines adaptatrices Dok-1 et Dok-2 durant l’activation lymphocytaire T. Plus précisément, nous nous sommes focalisés sur le rôle de leur domaine pleckstrin homology (PH) dans leur fonction inhibitrice durant l’activation lymphocytaire T. De manière intéressante nous avons pu caractériser lePtdIns5P comme un ligand convaincant des domaines PH de Dok-1 et Dok-2 et engendrant leur phosphorylation et donc leur activation. Des dosages de PtdIns5P effectués après une stimulation du récepteur des cellules T (TCR) nous ont permis d’observer une augmentation de PtdIns5P suite à cette activation lymphocytaire T.Dans un second temps nous nous sommes intéressés à caractériser les autres ligands des domaines PH de la famille Dok. De manière intéressante nous avons pu identifier le domaine PH de Dok-5 comme un interacteur fort avec le PtdIns5P. La caractérisation plus précise de l’impact du PtdIns5P, nous a permis de montrer la modulation positive de protéines clés des voies de signalisation intracellulaire telles que les Src kinases et AKT qui sont retrouvées phosphorylées suite à une augmentation de PtdIns5P.L’ensemble de ces résultats faisant du PtdIns5P un nouveau messager de l’activation lymphocytaire T, pouvant contribuer au maintien de l’homéostasie des lymphocytes TPtdIns5P is a rare phosphoinositide and is starting to emerge as a potential second messenger.Bacterial infection by Shigella flexnerii via the virulence factor IpgD, generates PtdIns5P in thehost cells and induces Akt activation. Recent evidences report that enhanced tyrosinephosphorylation increase cellular PtdIns5P levels and that PtdIns5P could have a role inoncogenesis. Altogether, these data argue for an important role of PtdIns5P in cell signalling.Recently, we demonstrated a PtdIns5P production in T cells upon TCR triggering.Interestingly we showed that Dok-1 and Dok-2 proteins (for Downstream of tyrosine kinase)tyrosine phosphorylation correlated with PtdIns5P increase. These structurally related adaptermolecules contain a pleckstrin homology (PH) domain generally acting as a lipid/proteininteractingmodule. We found that Dok-1/Dok-2 PH domains bind in vitro to PtdIns5P. Thepresence of this PH domain is necessary for the tyrosine phosphorylation of Dok-1 and Dok-2proteins and their negative functions in T cells. Together, our data identify a novel lipid mediatorin T cell signalling and suggest that PtdIns5P could be a new yet uncharacterized secondmessenger in T cell activation.We next focused on a new PtdIns5P binding module, the PH domain Dok-5. Our in vitrodata revealed a stronger interaction between Dok-5 PH and PtdIns5P. We used Dok-5 PHdomain and IpgD as tools to characterize PtdIns5P functional effects on T cells. Our results showthat IpgD expression induces Src-kinase and Akt activation, but not ERK activation andenhances IL-2 promoter activity in T cells. Expression of this PtdIns5P interacting domainblocks IpgD-induced T cell activation and selective signaling molecules downstream of TCRtriggering. Altogether, these data suggest that PtdIns5P may play a sensor function in setting thethreshold of T cell activation and contributing to maintain T cell homeostasi

T lymphocyte singaling (indentification of e recently indentified lipid messenger, phosphatidylinositol 5-phosphate (Ptdlns5P))

Le PtdIns5P est un phosphoinositide très peu connu et émerge dernièrement en tant qu important nouveau second messager. D ailleurs, l augmentation artificielle de PtdIns5Pdans les cellules épithéliales, favorise la voie pro-oncogénique Phosphoinositide 3-kinase/AKT. Plus récemment, il a été fait état d un possible rôle du PtdIns5P dans le processus de lymphomagenèse.Notre laboratoire étudie depuis de nombreuses années les voies de signalisations importantes de l activation lymphocytaire T et notamment la voie pro-oncogénique PI3K. Le laboratoire s est tourné notamment vers l étude des protéines adaptatrices de la famille Dok(Downstream of Kinase) lors de l activation lymphocytaire T.Ainsi le but de ce travail a été dans un premier temps l étude des protéines adaptatrices Dok-1 et Dok-2 durant l activation lymphocytaire T. Plus précisément, nous nous sommes focalisés sur le rôle de leur domaine pleckstrin homology (PH) dans leur fonction inhibitrice durant l activation lymphocytaire T. De manière intéressante nous avons pu caractériser lePtdIns5P comme un ligand convaincant des domaines PH de Dok-1 et Dok-2 et engendrant leur phosphorylation et donc leur activation. Des dosages de PtdIns5P effectués après une stimulation du récepteur des cellules T (TCR) nous ont permis d observer une augmentation de PtdIns5P suite à cette activation lymphocytaire T.Dans un second temps nous nous sommes intéressés à caractériser les autres ligands des domaines PH de la famille Dok. De manière intéressante nous avons pu identifier le domaine PH de Dok-5 comme un interacteur fort avec le PtdIns5P. La caractérisation plus précise de l impact du PtdIns5P, nous a permis de montrer la modulation positive de protéines clés des voies de signalisation intracellulaire telles que les Src kinases et AKT qui sont retrouvées phosphorylées suite à une augmentation de PtdIns5P.L ensemble de ces résultats faisant du PtdIns5P un nouveau messager de l activation lymphocytaire T, pouvant contribuer au maintien de l homéostasie des lymphocytes TPtdIns5P is a rare phosphoinositide and is starting to emerge as a potential second messenger.Bacterial infection by Shigella flexnerii via the virulence factor IpgD, generates PtdIns5P in thehost cells and induces Akt activation. Recent evidences report that enhanced tyrosinephosphorylation increase cellular PtdIns5P levels and that PtdIns5P could have a role inoncogenesis. Altogether, these data argue for an important role of PtdIns5P in cell signalling.Recently, we demonstrated a PtdIns5P production in T cells upon TCR triggering.Interestingly we showed that Dok-1 and Dok-2 proteins (for Downstream of tyrosine kinase)tyrosine phosphorylation correlated with PtdIns5P increase. These structurally related adaptermolecules contain a pleckstrin homology (PH) domain generally acting as a lipid/proteininteractingmodule. We found that Dok-1/Dok-2 PH domains bind in vitro to PtdIns5P. Thepresence of this PH domain is necessary for the tyrosine phosphorylation of Dok-1 and Dok-2proteins and their negative functions in T cells. Together, our data identify a novel lipid mediatorin T cell signalling and suggest that PtdIns5P could be a new yet uncharacterized secondmessenger in T cell activation.We next focused on a new PtdIns5P binding module, the PH domain Dok-5. Our in vitrodata revealed a stronger interaction between Dok-5 PH and PtdIns5P. We used Dok-5 PHdomain and IpgD as tools to characterize PtdIns5P functional effects on T cells. Our results showthat IpgD expression induces Src-kinase and Akt activation, but not ERK activation andenhances IL-2 promoter activity in T cells. Expression of this PtdIns5P interacting domainblocks IpgD-induced T cell activation and selective signaling molecules downstream of TCRtriggering. Altogether, these data suggest that PtdIns5P may play a sensor function in setting thethreshold of T cell activation and contributing to maintain T cell homeostasisAIX-MARSEILLE2-Bib.electronique (130559901) / SudocSudocFranceF

Une piste en immunothérapie du cancer

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Evolutionary and expression analyses reveal a pattern of ancient duplications and functional specializations in the diversification of the Downstream of Kinase (DOK) genes

International audienceDownstream of Kinase (DOK) proteins represent a multigenic family of adaptors that includes negative regulators of immune cell signaling. Using phylogenetics and intron/exon structure data, we show here that the seven human DOK genes (DOK1 to DOK7) form three highly divergent groups that emerged before the protostome-deuterostome split: DOK1/2/3, DOK4/5/6, and DOK7. For two of these three groups (DOK1/2/3 and DOK4/5/6), further gene duplications occurred in vertebrates and so while chordates only have three DOK genes, vertebrates have seven DOK genes over the three groups. From our expression analysis in humans, we show that each group of DOK genes has a distinct pattern of expression. The DOK1/2/3 group is immune specific, yet each of the three genes in the group has a distinct pattern of expression in immune cells. This immune specificity could thus be ancestral, with the DOK1/2/3 gene also being immune -related in protostomes. The DOK4/5/6 and DOK7 groups represent genes that are much less expressed in immune system than the DOK1/2/3 group. Interestingly, we identify a novel tyrosine based motif that is specific to the vertebrate DOK41516 sequences. The evolution of the DOK genes is thus marked by a pattern of ancient duplications and functional specializations

Negative intracellular regulators of T-cell receptor (TCR) signaling as potential antitumor immunotherapy targets

Immunotherapy strategies aim to mobilize immune defenses against tumor cells by targeting mainly T cells. Co‐inhibitory receptors or immune checkpoints (ICPs) (such as PD-1 and CTLA4) can limit T cell receptor (TCR) signal propagation in T cells. Antibody-based blocking of immune checkpoints (immune checkpoint inhibitors, ICIs) enable escape from ICP inhibition of TCR signaling. ICI therapies have significantly impacted the prognosis and survival of patients with cancer. However, many patients remain refractory to these treatments. Thus, alternative approaches for cancer immunotherapy are needed. In addition to membrane‐associated inhibitory molecules, a growing number of intracellular molecules may also serve to downregulate signaling cascades triggered by TCR engagement. These molecules are known as intracellular immune checkpoints (iICPs). Blocking the expression or the activity of these intracellular negative signaling molecules is a novel field of action to boost T cell-mediated antitumor responses. This area is rapidly expanding. Indeed, more than 30 different potential iICPs have been identified. Over the past 5 years, several phase I/II clinical trials targeting iICPs in T cells have been registered. In this study, we summarize recent preclinical and clinical data demonstrating that immunotherapies targeting T cell iICPs can mediate regression of solid tumors including (membrane associated) immune‐checkpoint inhibitor refractory cancers. Finally, we discuss how these iICPs are targeted and controlled. Thereby, iICP inhibition is a promising strategy opening new avenues for future cancer immunotherapy treatments

Production of CRISPRi-engineered primary human mammary epithelial cells with baboon envelope pseudotyped lentiviral vectors

Summary: Primary human mammary epithelial cells (pHMECs) are known to be remarkably difficult to engineer genetically. Here, we present a protocol for efficient transduction of pHMECs using a baboon retroviral envelope glycoprotein for pseudotyping of lentiviral vectors (BaEV-LVs). We describe the preparation of the BaEV-LVs, the isolation of pHMECs from breast samples, and the subsequent transduction of pHMECs. We also detail the use of CRISPRi technology to efficiently silence gene expression in pHMECs, which can then be used for functional assays.For complete details on the use and execution of this protocol, please refer to Richart et al. (2022).1 : Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics

Evidence for a positive role of PtdIns5P in T-cell signal transduction pathways.: PtdIns5P and T cell signaling

International audiencePhosphatidylinositol 5-phosphate (PtdIns5P) is emerging as a potential lipid messenger involved in several cell types, from plants to mammals. Expression of IpgD, a PtdIns(4,5)P(2) 4-phosphatase induces Src kinase and Akt, but not ERK activation and enhances interleukin II promoter activity in T-cells. Expression of a new PtdIns5P interacting domain blocks IpgD-induced T-cell activation and selective signaling molecules downstream of TCR triggering. Altogether, these data suggest that PtdIns5P may play a sensor function in setting the threshold of T-cell activation and contributing to maintain T-cell homeostasis

CISH Expression Is Associated with Metastasis-Free Interval in Triple-Negative Breast Cancer and Refines the Prognostic Value of PDL1 Expression

International audienceStrategies are being explored to increase the efficiency of immune checkpoint inhibitors (ICIs) targeting PD1/PDL1 in triple-negative breast cancer (TNBC), including combination with therapies inhibiting intracellular immune checkpoints such as CISH (Cytokine-induced SH2 protein). Correlation between CISH expression and TNBC features is unknown. We retrospectively analyzed CISH expression in 1936 clinical TNBC samples and searched for correlations with clinical variables, including metastasis-free interval (MFI). Among TNBCs, 44% were identified as “CISH-up” and 56% “CISH-down”. High expression was associated with pathological axillary lymph node involvement, more adjuvant chemotherapy, and Lehmann’s immunomodulatory and luminal AR subtypes. The “CISH-up” class showed longer 5-year MFI (72%) than the “CISH-down” class (60%; p = 2.8 × 10−2). CISH upregulation was associated with activation of IFNα and IFNγ pathways, antitumor cytotoxic immune response, and signatures predictive for ICI response. When CISH and PDL1 were upregulated together, the 5-year MFI was 81% versus 52% when not upregulated (p = 6.21 × 10−6). The two-gene model provided more prognostic information than each gene alone and maintained its prognostic value in multivariate analysis. CISH expression is associated with longer MFI in TNBC and refines the prognostic value of PDL1 expression. Such observation might reinforce the therapeutic relevance of combining CISH inhibition with an anti-PD1/PDL1 ICI