Project description:The interplay between effector and regulatory T (Treg) cells is crucial for adaptive immunity, but how Treg control effector cell flexibility is elusive. We found that the phosphatase PTEN links Treg stability to the repression of TH1 and TFH (follicular helper) responses. Depletion of PTEN in Treg resulted in excessive TFH and germinal center responses and spontaneous inflammatory disease. These defects are considerably blocked by deletion of Interferon-γ, indicating coordinated control of TH1 and TFH responses. Mechanistically, PTEN maintains Treg stability and proper metabolic balance between glycolysis and mitochondrial fitness. Moreover, PTEN deficiency markedly upregulates mTORC2-Akt activity, and loss of this activity restores PTEN-deficient Treg function. Our studies establish a PTEN-mTORC2 axis that actively maintains Treg stability and coordinates Treg-mediated control of effector cell flexibility. We used microarrays to explore the gene expression profiles differentially expressed in CD4+CD25+Foxp3-YFP+ Treg cells from wild-type (WT; C57BL/6 crossed with Foxp3-Cre) and Ptenfl/flFoxp3-Cre (Ptenfl/fl mice crossed with Foxp3-Cre) mice
Project description:The interplay between effector and regulatory T (Treg) cells is crucial for adaptive immunity, but how Treg control effector cell flexibility is elusive. We found that the phosphatase PTEN links Treg stability to the repression of TH1 and TFH (follicular helper) responses. Depletion of PTEN in Treg resulted in excessive TFH and germinal center responses and spontaneous inflammatory disease. These defects are considerably blocked by deletion of Interferon-γ, indicating coordinated control of TH1 and TFH responses. Mechanistically, PTEN maintains Treg stability and proper metabolic balance between glycolysis and mitochondrial fitness. Moreover, PTEN deficiency markedly upregulates mTORC2-Akt activity, and loss of this activity restores PTEN-deficient Treg function. Our studies establish a PTEN-mTORC2 axis that actively maintains Treg stability and coordinates Treg-mediated control of effector cell flexibility.
Project description:The PTEN tumor suppressor controls cell death and survival by regulating functions of various molecular targets. Whilst the role of PTEN lipid-phosphatase activity on PtdIns(3,4,5)P3 and inhibition of PI3K pathway is well characterized, the biological relevance of PTEN protein-phosphatase activity remains undefined. Using knock-in (KI) mice harbouring cancer-associated and functionally relevant missense mutations, we show that although loss of PTEN lipid-phosphatase function cooperates with oncogenic PI3K to promote rapid mammary tumorigenesis, the additional loss of PTEN protein-phosphatase activity triggered an extensive cell death response evident in early and advanced mammary tumors. Omics and drug-targeting studies revealed that PI3Ks act to reduce glucocorticoid receptor (GR) levels, which are rescued by loss of PTEN protein-phosphatase activity to restrain cell survival. The dual regulation of GR by PI3K and PTEN functions as a rheostat that can be exploited for the treatment of PTEN-loss driven cancers.
Project description:Beyond a function in hemostasis and thrombosis, platelets can regulate innate and adaptive immune responses. Hyperactive platelets are frequently associated with multiple human autoimmune diseases, yet their pathogenic functions in these diseases have not been fully established. Emerging studies show an essential function of the phosphatase and tensin homolog (PTEN) in maintenance of immune homeostasis. Here, we show that mice with platelet-specific deletion of Pten, develop age-related lymphoproliferative diseases and humoral autoimmunity not seen in wildtype animals. Platelet-specific Pten-deficient mice have aberrant T cell activation, excessive T follicular helper (Tfh) cell responses and accumulation of platelet aggregates in lymph nodes. Transferred Pten-deficient platelets are able to infiltrate into the peripheral lymphoid tissues and form more aggregates. Moreover, Pten-deficient platelets are hyperactive and overproduce multiple Tfh-promoting cytokines via activation of the PDK1/mTORC2-AKT-SNAP23 pathway. Pten-deficient platelets show enhanced interaction with CD4+ T cells and promote conversion of CD4+ T cells into Tfh cells. Our results implicate PTEN in platelet-mediated immune homeostasis, and provide evidence that hyperactive platelets function as an important mediator in autoimmune diseases using mouse models.
Project description:The PTEN tumor suppressor controls cell death and survival by regulating functions of various molecular targets. Whilst the role of PTEN lipid-phosphatase activity on PtdIns(3,4,5)P3 and inhibition of PI3K pathway is well characterized, the biological relevance of PTEN protein-phosphatase activity remains undefined. Using knock-in (KI) mice harbouring cancer-associated and functionally relevant missense mutations, we show that although loss of PTEN lipid-phosphatase function cooperates with oncogenic PI3K to promote rapid mammary tumorigenesis, the additional loss of PTEN protein-phosphatase activity triggered an extensive cell death response evident in early and advanced mammary tumors. Omics and drug-targeting studies revealed that PI3Ks act to reduce glucocorticoid receptor (GR) levels, which are rescued by loss of PTEN protein-phosphatase activity to restrain cell survival. The dual regulation of GR by PI3K and PTEN functions as a rheostat that can be exploited for the treatment of PTEN-loss driven cancers.
Project description:Roquin proteins are required to preclude spontaneous T cell activation and aberrant T follicular helper (Tfh) or T helper 17 (Th17) differentiation. Here, we show that deletion of Roquin encoding alleles in regulatory T cells (Tregs) also caused the activation of conventional T cells. These Tregs exhibited a follicular Treg phenotype, CD25 downregulation and could not protect from colitis. Mechanistically, Roquin was required for full expression and activity of Pten and Foxo1, two essential signaling molecules in Tregs and effector T cells. Roquin upregulated Pten by interfering with miR-17~92 binding to an overlapping cis-element in the Pten 3' UTR and downregulated the Foxo1-specific E3 ubiquitin ligase Itch. Loss of Roquin enhanced mTOR signaling and global protein synthesis, while inhibition of PI3K or mTOR in Roquin-deficient CD4+ T cells corrected increased Tfh and Th17 differentiation. Thereby, the control of PI3K-mTOR signaling by Roquin prevents autoimmunity through T cell-intrinsic and Treg-mediated regulation.
Project description:Pathogenic antibodies produced by alloreactive B cells mediate antibody-mediated rejection (ABMR) after kidney transplantation, but the mechanisms controlling these antibodies remain poorly understood. Follicular Regulatory T (Tfr) cells modulate follicular helper T (Tfh) cell-mediated B cell responses but their roles in controlling alloreactive antibody are unknown. Here, we studied the developmental signals and functions of Tfr cells in allogeneic kidney transplantation. We show that costimulatory blockade alters the development of Tfr cells disproportionately by decreasing germinal center (GC)-like Tfr cells and increasing follicular-like Tfr cells. Functionally, Tfr cell deletion resulted in accelerated rejection and increases in donor-specific B cells in both draining lymph nodes and kidney allografts. Mechanistically, Tfr cell deletion increased GC B cell expression of pro-inflammatory cytokines such as IL-15. Neutralization of IL-15 compensated for the loss of Tfr cells and prolonged kidney transplant recipient survival. Together these data demonstrate the signals for Tfr cell development and how these cells restrain rejection by limiting alloreactive B cell responses.
Project description:Regulatory B cells (Breg) express high levels of CD1d that presents lipid antigens to invariant natural killer T (iNKT) cells. The function of CD1d in Breg biology and iNKT cell activity during inflammation remains unclear. Here we show, using chimeric mice, cell depletion and adoptive cell transfer, that CD1d-lipid presentation by Bregs induces iNKT cells to secret IFN-γ to contribute, partially, to the down-regulation of T helper (Th)1 and Th17 adaptive immune responses for ameliorating experimental arthritis. Mice lacking CD1d-expressing B cells develop exacerbated diseases compared to wild-type mice, and fail to respond to α-galactosylceramide treatment. Absence of lipid presentation by B cells causes altered activation of iNKT cells, with disruption of regulatory pathways including those involved in metabolism and cytokine responses. Thus, we identify an IL-10-independent mechanism by which Bregs restrain excessive inflammation via lipid presentation.