Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0392674 (exhaustion)
 13,658 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Molecular cloning of the prolactin (PRL) receptor cDNA has revealed different forms of the receptor: among them, the longest form encodes a transmembrane protein of 592-598 amino acids and was originally found in rabbit mammary gland as well as in human and rat tissues. It contains a cytoplasmic domain of 358 amino acids. In CHO cells transfected with the PRL receptor cDNA, PRL is able to induce the specific expression of a reporter gene provided with the promoter of the milk protein gene beta-lactoglobulin. The cDNA encoding this long receptor form has been expressed permanently after stable transfection of Chinese hamster ovary (CHO) cells. In these cells, we have determined the fate of the bound hormone and of the receptor. At 37 degrees C, transfected cells were able to endocytose 125I-labeled human growth hormone (hGH) or ovine prolactin (oPRL) at an initial rate of about 1 fmol/h at 100 pM labeled hormone and 10(6) cells/well. Lowering the temperature to 15 degrees C slowed the endocytosis of [125I]hGH by a factor of 5. These results were confirmed by electron microscopy with oPRL labeled with colloidal gold. At 37 degrees C, the receptor underwent rapid insertion to the cell surface and constitutive endocytosis (half-life 80 min). This rate of endocytosis was enhanced in the presence of 10 nM oPRL (half-life 8 min), leading to down-regulation of the receptor by exhaustion of the intracellular receptor pool. After down-regulation, the cell surface was replenished with newly synthesized PRL receptor with a half-time of 8-10 min. If cycloheximide was added, almost no receptors could be found on the cell surface. These results indicate that in transfected cells the PRL receptor behaved largely as in classical target cells. A "conveyor belt" endocytosis behavior was found, with degradation of the endocytosed receptors, and occupation by the hormone enhancing this process. Moreover, since the PRL receptor belongs to a family of receptors in which companion protein(s) seem to play important roles, transfected CHO cells appear to provide the expressed receptors with the necessary element(s) to function as in normal PRL target cells.
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PMID:Endocytosis and degradation of prolactin and its receptor in Chinese hamster ovary cells stably transfected with prolactin receptor cDNA. 820 30

PD-1 is a transmembrane protein involved in the regulation of immunological tolerance. Multiple studies have reported an association between high levels of PD-1 expressed on T cell surfaces and exhaustion in lymphocyte populations when challenged by chronic viral infections, such as HIV. By using model systems consisting of murine EL4 cells, which constitutively express PD-1, and primary murine CD8 T cells that express PD-1 upon T cell stimulation, we have identified two tissue-specific hypersensitive sites at the 5' CR of the PD-1 locus. Gene reporter assays in CD8 T cells have shown that one of these sites has robust transcriptional activity in response to cell stimulation. Cell treatment with the calcineurin inhibitor cyclosporine A or a NFAT-specific inhibitor led to a sharp reduction in PD-1 expression in the constitutive and inducible systems. Furthermore, analysis of this region by chromatin immunoprecipitation assay revealed NFATc1 binding associated with gene activation in EL4 and primary CD8 T cells. Mutation of the NFATc1 binding site in PD-1 reporter constructs resulted in a complete loss of promoter activity. Together, these results demonstrate that PD-1 gene regulation occurs in part via the recruitment of NFATc1 to a novel regulatory element at the pdcd1 locus and provides the molecular mechanism responsible for the induction of PD-1 in response to T cell stimulation.
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PMID:NFATc1 regulates PD-1 expression upon T cell activation. 1880 87

The outcome of viral infections is dependent on the function of CD8+ T cells which are tightly regulated by costimulatory molecules. The NK cell receptor 2B4 (CD244) is a transmembrane protein belonging to the Ig superfamily which can also be expressed by CD8+ T cells. The aim of this study was to analyze the role of 2B4 as an additional costimulatory receptor regulating CD8+ T cell function and in particular to investigate its implication for exhaustion of hepatitis C virus (HCV)-specific CD8+ T cells during persistent infection. We demonstrate that (i) 2B4 is expressed on virus-specific CD8+ T cells during acute and chronic hepatitis C, (ii) that 2B4 cross-linking can lead to both inhibition and activation of HCV-specific CD8+ T cell function, depending on expression levels of 2B4 and the intracellular adaptor molecule SAP and (iii) that 2B4 stimulation may counteract enhanced proliferation of HCV-specific CD8+ T cells induced by PD1 blockade. We suggest that 2B4 is another important molecule within the network of costimulatory/inhibitory receptors regulating CD8+ T cell function in acute and chronic hepatitis C and that 2B4 expression levels could also be a marker of CD8+ T cell dysfunction. Understanding in more detail how 2B4 exerts its differential effects could have implications for the development of novel immunotherapies of HCV infection aiming to achieve immune control.
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PMID:Dual function of the NK cell receptor 2B4 (CD244) in the regulation of HCV-specific CD8+ T cells. 2162 89

The transmembrane protein Tim-3 has been shown to negatively regulate T-cell-dependent immune responses and was recently demonstrated to be associated with the phenomenon of immune exhaustion, which can occur as a consequence of chronic viral infection. Unlike other negative regulators of T-cell function (e.g., PD-1), Tim-3 does not contain any obvious inhibitory signaling motifs. We have found that ectopic expression of Tim-3 in T cells leads to enhancement of T-cell receptor (TCR)-dependent signaling pathways, which was observed at the level of transcriptional reporters and endogenous cytokine production. We have exploited this observation to dissect what elements within the cytoplasmic tail of Tim-3 are required for coupling to downstream signaling pathways. Here we have demonstrated that two of the more membrane-proximal cytoplasmic tail tyrosines are required for Tim-3 signaling to T-cell activation pathways in a redundant fashion. Furthermore, we show that Tim-3 can directly bind to the Src family tyrosine kinase Fyn and the p85 phosphatidylinositol 3-kinase (PI3K) adaptor. Thus, at least under conditions of short-term stimulation, Tim-3 can augment T-cell activation, although this effect can be blocked by the inclusion of an agonistic antibody to Tim-3. These findings should help further the study of Tim-3 function in other physiological settings, such as those that lead to immune exhaustion.
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PMID:Phosphotyrosine-dependent coupling of Tim-3 to T-cell receptor signaling pathways. 2180 95

Programmed death-1 (PD-1) is a transmembrane protein that shares homology with the B7/CD28 family of T cell signaling molecules. PD-1 interacts with its ligands PD-L1 and/or PD-L2 and provides a negative regulatory signal to CD4 and CD8 T cells that results ultimately in a phenotype termed T cell exhaustion. Here we expressed and purified mouse PD-1 protein and developed a monoclonal antibody (MAb) against mouse PD-1 by immunizing BALB/c mice with a specific region of the extracellular domains of PD-1 as antigen, which was expressed in Escherichia coli. A stable hybridoma cell line was established by animal immunization, cell fusion, and hybridoma screening. The MAb was then prepared from mouse ascites after inoculating the hybridoma cells. Different methods were used to analyze the characterization of the MAb, including ELISA, Western blotting, flow cytometry, and RT-PCR techniques. The results showed that the PD-1 MAb can bind to the PD-1 protein and promote lymphocyte proliferation. This PD-1 MAb will be a valuable tool for further investigation of programmed death-1 functions.
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PMID:Generation of a monoclonal antibody recognizing mouse PD-1. 2535 6

Insulin is a major regulator of cell metabolism but, in addition, is also a growth factor. Insulin effects in target cells are mediated by the insulin receptor (IR), a transmembrane protein with enzymatic (tyrosine kinase) activity. The insulin receptor, however, is represented by a heterogeneous family of proteins, including two different IR isoforms and also hybrid receptors resulting from the IR hemireceptor combination with a hemireceptor of the cognate IGF-1 receptor. These different receptors may bind insulin and its analogs with different affinity and produce different biologic effects. Since many years, it is known that many cancer cells require insulin for optimal in vitro growth. Recent data indicate that: (1) insulin stimulates growth mainly via its own receptor and not the IGF-1 receptor; (2) in many cancer cells, the IR is overexpressed and the A isoform, which has a predominant mitogenic effect, is more represented than the B isoform. These characteristics provide a selective growth advantage to malignant cells when exposed to insulin. For this reason, all conditions of hyperinsulinemia, both endogenous (prediabetes, metabolic syndrome, obesity, type 2 diabetes before pancreas exhaustion and polycystic ovary syndrome) and exogenous (type 1 diabetes) will increase the risk of cancer. Cancer-related mortality is also increased in patients exposed to hyperinsulinemia but other factors, related to the different diseases, may also contribute. The complexity of the diseases associated with hyperinsulinemia and their therapies does not allow a precise evaluation of the cancer-promoting effect of hyperinsulinemia, but its detrimental effect on cancer incidence and mortality is well documented.
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PMID:Insulin, insulin receptors, and cancer. 2736 23

An effective antitumor immune response requires interaction between cells of the adaptive and innate immune system. Three key elements are required: generation of activated tumor-directed T cells, infiltration of activated T cells into the tumor microenvironment, and killing of tumor cells by activated T cells. Tumor immune evasion can occur as a result of the disruption of each of these three key T cell activities, resulting in three distinct cancer-immune phenotypes. The immune inflamed phenotype, characterized by the presence of a robust tumor immune infiltrate, suggests impaired activated T cell killing of tumor cells related to the presence of inhibitory factors. Programmed death receptor-1 (PD-1) is an inhibitory transmembrane protein expressed on T cells, B cells, and NK cells. The interaction between PD-1 and its ligands (PD-L1/L2) functions as an immune checkpoint against unrestrained cytotoxic T effector cell activity-it promotes peripheral T effector cell exhaustion and conversion of T effector cells to immunosuppressive T regulatory (Treg) cells. Immune checkpoint inhibitors, which block the PD-1/PD-L1 axis and reactivate cytotoxic T effector cell function, are actively being investigated for the treatment of breast cancer.
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PMID:Immune Checkpoint Blockade for Breast Cancer. 2934 63