RESUMO
Thymocyte development requires precise control of PI3K-Akt signaling to promote proliferation and prevent leukemia and autoimmune disorders. Here, we show that ablating individual clusters of the miR-17â¼92 family has a negligible effect on thymocyte development, while deleting the entire family severely impairs thymocyte proliferation and reduces thymic cellularity, phenocopying genetic deletion of Dicer. Mechanistically, miR-17â¼92 expression is induced by Myc-mediated pre-T cell receptor (TCR) signaling, and miR-17â¼92 promotes thymocyte proliferation by suppressing the translation of Pten. Retroviral expression of miR-17â¼92 restores the proliferation and differentiation of Myc-deficient thymocytes. Conversely, partial deletion of the miR-17â¼92 family significantly delays Myc-driven leukemogenesis. Intriguingly, thymocyte-specific transgenic miR-17â¼92 expression does not cause leukemia or lymphoma but instead aggravates skin inflammation, while ablation of the miR-17â¼92 family ameliorates skin inflammation. This study reveals intricate roles of the miR-17â¼92 family in balancing thymocyte development, leukemogenesis, and autoimmunity and identifies those microRNAs (miRNAs) as potential therapeutic targets for leukemia and autoimmune diseases.
Assuntos
Autoimunidade , Leucemia , MicroRNAs , Timócitos , MicroRNAs/metabolismo , MicroRNAs/genética , Animais , Timócitos/metabolismo , Timócitos/patologia , Autoimunidade/genética , Camundongos , Leucemia/patologia , Leucemia/genética , Proliferação de Células , PTEN Fosfo-Hidrolase/metabolismo , PTEN Fosfo-Hidrolase/genética , Diferenciação Celular/genética , Transdução de Sinais , Proteínas Proto-Oncogênicas c-myc/metabolismo , Proteínas Proto-Oncogênicas c-myc/genética , Camundongos Endogâmicos C57BL , Receptores de Antígenos de Linfócitos T/metabolismo , Carcinogênese/genética , Carcinogênese/patologia , Carcinogênese/metabolismoRESUMO
The T cell antigen receptor (TCR) contains ten immunoreceptor tyrosine-based activation motif (ITAM) signaling sequences distributed within six CD3 subunits; however, the reason for such structural complexity and multiplicity is unclear. Here we evaluated the effect of inactivating the three CD3ζ chain ITAMs on TCR signaling and T cell effector responses using a conditional 'switch' mouse model. Unexpectedly, we found that T cells expressing TCRs containing inactivated (non-signaling) CD3ζ ITAMs (6F-CD3ζ) exhibited reduced ability to discriminate between low- and high-affinity ligands, resulting in enhanced signaling and cytokine responses to low-affinity ligands because of a previously undetected inhibitory function of CD3ζ ITAMs. Also, 6F-CD3ζ TCRs were refractory to antagonism, as predicted by a new in silico adaptive kinetic proofreading model that revises the role of ITAM multiplicity in TCR signaling. Finally, T cells expressing 6F-CD3ζ displayed enhanced cytolytic activity against solid tumors expressing low-affinity ligands, identifying a new counterintuitive approach to TCR-mediated cancer immunotherapy.
Assuntos
Motivo de Ativação do Imunorreceptor Baseado em Tirosina , Receptores de Antígenos de Linfócitos T , Animais , Camundongos , Complexo CD3 , Ligantes , Peptídeos , Linfócitos TRESUMO
The T cell lineage-restricted protein THEMIS plays a critical role in T cell development at the positive selection stage. In the SHP1 activation model, THEMIS is proposed to enhance the activity of the tyrosine phosphatase SHP1 (encoded by Ptpn6), thereby dampening T cell antigen receptor (TCR) signaling and preventing the inappropriate negative selection of CD4+CD8+ thymocytes by positively selecting ligands. In contrast, in the SHP1 inhibition model, THEMIS is proposed to suppress SHP1 activity, rendering CD4+CD8+ thymocytes more sensitive to TCR signaling initiated by low-affinity ligands to promote positive selection. We sought to resolve the controversy regarding the molecular function of THEMIS. We found that the defect in positive selection in Themis-/- thymocytes was ameliorated by pharmacologic inhibition of SHP1 or by deletion of Ptpn6 and was exacerbated by SHP1 overexpression. Moreover, overexpression of SHP1 phenocopied the Themis-/- developmental defect, whereas deletion of Ptpn6, Ptpn11 (encoding SHP2), or both did not result in a phenotype resembling that of Themis deficiency. Last, we found that thymocyte negative selection was not enhanced but was instead impaired in the absence of THEMIS. Together, these results provide evidence favoring the SHP1 inhibition model, supporting a mechanism whereby THEMIS functions to enhance the sensitivity of CD4+CD8+ thymocytes to TCR signaling, enabling positive selection by low-affinity, self-ligand-TCR interactions.
Assuntos
Peptídeos e Proteínas de Sinalização Intercelular , Proteína Tirosina Fosfatase não Receptora Tipo 6 , Timócitos , Linfócitos T CD8-Positivos , Proteína Tirosina Fosfatase não Receptora Tipo 6/genética , Animais , Peptídeos e Proteínas de Sinalização Intercelular/genéticaRESUMO
The T-lineage restricted protein THEMIS has been shown to play a critical role in T cell development. THEMIS, via its distinctive CABIT domains, inhibits the catalytic activity of the tyrosine phosphatase SHP1 (PTPN6). SHP1 and THEMIS bind to the ubiquitous cytosolic adapter GRB2, and the purported formation of a tri-molecular THEMIS-GRB2-SHP1 complex facilitates inactivation of SHP1 by THEMIS. The importance of this function of GRB2 among its numerous documented activities is unclear as GRB2 binds to multiple proteins and participates in several signaling responses in thymocytes. Here, we show that similar to Themis-/- thymocytes, the primary molecular defect in GRB2-deficient thymocytes is increased catalytically active SHP1 and the developmental block in GRB2-deficient thymocytes is alleviated by deletion or inhibition of SHP1 and is exacerbated by SHP1 overexpression. Thus, the principal role of GRB2 during T cell development is to promote THEMIS-mediated inactivation of SHP1 thereby enhancing the sensitivity of TCR signaling in CD4+CD8+ thymocytes to low affinity positively selecting self-ligands.
Assuntos
Proteína Adaptadora GRB2 , Proteína Tirosina Fosfatase não Receptora Tipo 6 , Receptores de Antígenos de Linfócitos T , Timócitos , Diferenciação Celular , Proteína Tirosina Fosfatase não Receptora Tipo 6/metabolismo , Receptores de Antígenos de Linfócitos T/metabolismo , Transdução de Sinais , Timócitos/metabolismo , Proteína Adaptadora GRB2/metabolismoRESUMO
CD5 is constitutively expressed on all T cells and is a negative regulator of lymphocyte function. However, the full extent of CD5 function in immunity remains unclear. CD5 deficiency impacts thymic selection and extra-thymic regulatory T cell generation, yet CD5 knockout was reported to cause no immune pathology. Here we show that CD5 is a key modulator of gut immunity. We generated mice with inducible CD5 knockdown (KD) in the autoimmune-prone nonobese diabetic (NOD) background. CD5 deficiency caused T cell-dependent wasting disease driven by chronic gut immune dysregulation. CD5 inhibition also exacerbated acute experimental colitis. Mechanistically, loss of CD5 increased phospho-Stat3 levels, leading to elevated IL-17A secretion. Our data reveal a new facet of CD5 function in shaping the T cell cytokine profile.
Assuntos
Antígenos CD5 , Animais , Contagem de Linfócitos , CamundongosRESUMO
The human Phosphatase of Regenerative Liver (PRL) family comprises three members (PRL-1, -2, -3; gene name PTP4A1, PTP4A2, PTP4A3) that are highly expressed in a majority of cancers. This review summarizes our current understanding of PRL biology, including an overview of their evolutionary relationships and the regulatory mechanisms controlling their expression. We provide an updated view on our current knowledge on the PRL functions in solid tumors, hematological cancer, and normal physiology, particularly emphasizing on the use of in vivo mouse models. We also highlight a novel relationship positioning PRL as a central node controlling magnesium homeostasis through an association with the CNNM proteins, which are involved in magnesium transport.
Assuntos
Homeostase , Regeneração Hepática , Neoplasias/enzimologia , Neoplasias/patologia , Oncogenes , Proteínas Tirosina Fosfatases/metabolismo , Proteínas de Ciclo Celular/metabolismo , Humanos , Proteínas de Membrana/metabolismo , Proteínas de Neoplasias/metabolismoRESUMO
The family of protein tyrosine phosphatases (PTPs) includes 107 genes in humans that are diverse in their structures and expression profiles. The majority are present in immune cells and play various roles in either inhibiting or promoting the duration and amplitude of signaling cascades. Several PTPs, including TC-PTP (PTPN2) and SHP-1 (PTPN6), have been recognized as being crucial for maintaining proper immune response and self-tolerance, and have gained recognition as true immune system checkpoint modulators. This chapter details the most recent literature on PTPs and immunity by examining their known functions in regulating signaling from either established checkpoint inhibitors or by their intrinsic properties, as modulators of the immune response. Notably, we review PTP regulatory properties in macrophages, antigen-presenting dendritic cells, and T cells. Overall, we present the PTP gene family as a remarkable source of novel checkpoint inhibitors wherein lies a great number of new targets for immunotherapies.
Assuntos
Imunidade , Proteínas Tirosina Fosfatases , Transdução de Sinais , Humanos , Macrófagos , Proteínas Tirosina Fosfatases/metabolismoRESUMO
Most of our knowledge on protein tyrosine phosphatases (PTPs) is derived from human pathologies and mouse knockout models. These models largely correlate well with human disease phenotypes, but can be ambiguous due to compensatory mechanisms introduced by paralogous genes. Here we present the analysis of the PTP complement of the fruit fly and the complementary view that PTP studies in Drosophila will accelerate our understanding of PTPs in physiological and pathological conditions. With only 44 PTP genes, Drosophila represents a streamlined version of the human complement. Our integrated analysis places the Drosophila PTPs into evolutionary and functional contexts, thereby providing a platform for the exploitation of the fly for PTP research and the transfer of knowledge onto other model systems.
Assuntos
Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Família Multigênica , Proteínas Tirosina Fosfatases/genética , Animais , Proteínas de Drosophila/classificação , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/enzimologia , Evolução Molecular , Humanos , Camundongos , Mutação , Filogenia , Proteínas Tirosina Fosfatases/classificação , Proteínas Tirosina Fosfatases/metabolismoRESUMO
Reversible tyrosine phosphorylation is a fundamental signaling mechanism controlling a diversity of cellular processes. Whereas protein tyrosine kinases have long been implicated in many diseases, aberrant protein tyrosine phosphatase (PTP) activity is also increasingly being associated with a wide spectrum of conditions. PTPs are now regarded as key regulators of biochemical processes instead of simple "off" switches operating in tyrosine kinase signaling pathways. Despite the central importance that PTPs play in the cell's biochemistry, the tyrosine phosphatomes of most species remain uncharted. Here we present a highly sensitive and specific sequence-based method for the automatic classification of PTPs. As proof of principle we re-annotated the human tyrosine phosphatome, and discovered four new PTP genes that had not been reported before. Our method and the predicted tyrosine phosphatomes of 65 eukaryotic genomes are accessible online through the user-friendly PTP-central resource (http://www.PTP-central.org/), where users can also submit their own sequences for prediction. PTP-central is a comprehensive and continually developing resource that currently integrates the predicted tyrosine phosphatomes with structural data and genetic association disease studies, as well as homology relationships. PTP-central thus fills an important void for the systematic study of PTPs, both in model organisms and from an evolutionary perspective.