PD-L1 degradation is regulated by electrostatic membrane association of its cytoplasmic domain.
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ABSTRACT:
SUBMITTER: Wen M
PROVIDER: S-EPMC8384847 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:How PD-L1 expression is regulated in cancer is poorly understood. Here, we report that the ATP-binding activity of ERBB3 pseudokinase regulates PD-L1 gene expression in colorectal cancers (CRCs). ERBB3 is one of the four members of the EGF receptor family, all with protein tyrosine kinase domains. ERBB3 is a pseudokinase with a high binding affinity to ATP. We showed that ERBB3 ATP-binding inactivation mutant reduces tumorigenicity in genetically engineered mouse models and impairs xenograft tumor growth of CRC cell lines. The ERBB3 ATP-binding mutant cells dramatically reduce IFN-γ-induced PD-L1 expression. Mechanistically, ERBB3 regulates IFN-γ-induced PD-L1 expression through the IRS1-PI3K-PDK1-RSK-CREB signaling axis. CREB is the transcription factor that regulates PD-L1 gene expression in CRC cells. Knockin of a tumor-derived ERBB3 mutation located in the kinase domain sensitizes mouse colon cancers to anti-PD1 antibody therapy, suggesting that ERBB3 mutations could be predictive biomarkers for tumors amenable to immune checkpoint therapy.
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Project description:Blocking the programmed death-1 (PD-1) pathway has clinical benefit in metastatic cancer and has led to the approval of the mAbs pembrolizumab and nivolumab to treat melanoma and nivolumab for non-small cell lung cancer. Expression of PD-L1 on the cell surface of either tumor cells or infiltrating immune cells is associated with a higher likelihood of response to PD-1 blockade in multiple studies. Most mAbs to PD-L1 in use are directed to its extracellular domain and immunohistochemically stain tumor tissue with a mixture of cytoplasmic and membrane staining. Cytoplasmic staining obscures the interpretation of a positive reaction on the tumor cell membrane, and thus affects the accuracy of PD-L1 scoring systems. We developed a mAb to the cytoplasmic domain of PD-L1, 405.9A11 (9A11), which is both more selective for membranous PD-L1 and more sensitive in IHC and Western blotting, compared with previous mAbs specific for the PD-L1 extracellular domain. Here, we compare immunohistochemical staining patterns of PD-L1 expression in five types of tumors, using five PD-L1 mAbs: 9A11, 7G11, and three commercially available mAbs. We demonstrate that 9A11, as well as two other cytoplasmic domain-specific mAbs, E1L3N and SP142, can clearly delineate the membrane of PD-L1-positive cells in formalin-fixed paraffin-embedded tissue and facilitate interpretation of staining results.
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Project description:Lymphatic endothelial cells (LEC) comprise lymphatic vessels that guide immune cells to lymph nodes (LN) and form the subcapsular sinus and cortical and medullary lymphatic structures of the LN. During an active immune response the lymphatics remodel to accommodate the influx of immune cells from the tissue. In this study we determined that a TSS motif within the cytoplasmic domain of programmed death ligand 1 (PD-L1), expressed by LECs in the LN, participates in lymphatic remodeling during inflammation. Mutation of the TSS motif to AAA in the cytoplasmic domain of PD-L1 does not affect surface expression of PD-L1 but instead causes defects in LN cortical and medullary lymphatic organization following Poly I:C in vivo. Supporting this observation, in vitro treatment of the LEC cell line, SVEC4-10, with the cytokines TNF alpha and IFN alpha significantly impeded SVEC4-10 movement in the presence of the TSS-AAA cytoplasmic mutation. The cellular movement defects coincided with reduced F-actin polymerization, consistent with differences previously found in dendritic cells. Here, in addition to loss of actin polymerization we define STAT3 and Paxillin as important binding partners to PD-L1. STAT3 and Paxillin were previously demonstrated to be important at focal adhesions for cellular motility. We further demonstrate the TSS-AAA motif mutation of PD-L1 reduced the amount of pSTAT3 and Paxillin bound to PD-L1 both before and after exposure to TNF alpha and IFN alpha. Together, these findings highlight PD-L1 as an important component of a membrane complex that is involved in cellular motility which leads to defects in lymphatic organization.
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Project description:The assembly of most retroviruses occurs at the plasma membrane. Membrane association is directed by MA, the N-terminal domain of the Gag structural protein. For human immunodeficiency virus type 1 (HIV-1), this association is mediated in part by a myristate fatty acid modification. Conflicting evidence has been presented on the relative importance of myristoylation, of ionic interactions between protein and membrane, and of Gag multimerization in membrane association in vivo. We addressed these questions biochemically by determining the affinity of purified myristoylated HIV-1 MA for liposomes of defined composition, both for monomeric and for dimeric forms of the protein. Myristoylation increases the barely detectable intrinsic affinity of the apo-protein for liposomes by only 10-fold, and the resulting affinity is still weak, similar to that of the naturally nonmyristoylated MA of Rous sarcoma virus. Membrane binding of HIV-1 MA is absolutely dependent on the presence of negatively charged lipid and is abrogated at high ionic strength. Forced dimerization of MA increases its membrane affinity by several orders of magnitude. When green fluorescent protein fusions of monomeric or dimeric MA are expressed in cells, the dimeric but not the monomeric protein becomes strongly membrane associated. Computational modeling supports these results and suggests a molecular mechanism for the modest effect of myristoylation on binding, wherein the membrane provides a hydrophobic environment for the myristate that is energetically similar to that provided by the protein. Overall, the results imply that the driving force for membrane association stems largely from ionic interactions between multimerized Gag and negatively charged phospholipids.
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Project description:The T-cell receptor (TCR) consists of a TCR?? heterodimer, a TCR? homodimer, and CD3?? and CD3?? heterodimers. The precise mechanism of T-cell triggering following TCR ligand engagement remains elusive. Previous studies reported that the cytoplasmic tail of CD3? binds to the plasma membrane through a basic residue-rich stretch (BRS) and proposed that dissociation from the membrane is required for phosphorylation thereof. In this report we show that BRS motifs within the cytoplasmic tail of TCR? mediate association with the plasma membrane and that TCR engagement results in TCR? dissociation from the membrane. This dissociation requires phosphorylation of the TCR? immunoreceptor tyrosine-based activation motifs by lymphocyte cell-specificprotein tyrosine kinase (Lck) but not ?-chain-associated protein kinase 70 binding. Mutations of the TCR? BRS motifs that disrupt this membrane association attenuate proximal and distal responses induced by TCR engagement. These mutations appear to alter the localization of TCR? with respect to Lck as well as the mobility of the TCR complex. This study reveals that tyrosine phosphorylation of the TCR? cytoplasmic domain regulates its association with the plasma membrane and highlights the functional importance of TCR? BRS motifs.
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Project description:We have seen a notable increase in the application of PD-1/PD-L1 inhibitors for the treatment of several solid and hematogenous malignancies including metastatic melanoma, non-small-cell lung cancer and lymphoma to name a few. The need for biomarkers for identification of a suitable patient population for this type of therapy is now pressing. While specific biomarker assays have been developed for these checkpoint inhibitors based on their respective epitopes, the available studies suggested the clinical utility of these biomarker assays is for response stratification and not patient selection. Further improvement in assay development is needed to utilize this type of assay in identification of ideal patient population for this therapy.
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Project description:BackgroundMany cancers evade immune surveillance by overexpressing PD-L1. PD-L1 interacted with its receptor PD-1, resulting in reduction of T cell proliferation and activation and thereafter cancer cell death mediated by T-lymphocyte. Understanding the mechanisms that regulate PD-L1 was of vital importance for immune checkpoint blockade therapy (ICBT).MethodsHuman non-small cell lung cancer cells and 293FT cells were used to investigate the function of USP22 upon PD-L1 and CSN5 by WB, Immunoprecipitation, Immunofluorescence and Flow cytometry analysis. B16-F10 cells were used to explore the role of USP22 on tumorigenesis and T cell cytotoxicity. The relationship between USP22 and PD-L1 expression was investigated by Immunohistochemistry analysis in human non-small cell lung cancer samples.ResultsOur data showed that USP22 interacted with PD-L1 and promoted its stability. USP22 deubiquitinated PD-L1 and inhibited its proteasome degradation. Moreover, USP22 also interacted with CSN5 and stabilized CSN5 through deubiquitination. Either USP22 or CSN5 could facilitate the interaction of PD-L1 with the other one. Furthermore, USP22 removed K6, K11, K27, K29, K33 and K63-linked ubiquitin chain of both CSN5 and PD-L1. In addition, USP22 depletion inhibited tumorigenesis and promoted T cell cytotoxicity. Besides, USP22 expression positively correlated with PD-L1 expression in human non-small cell lung cancer samples.ConclusionsHere, we suggested that USP22 is a new regulator for PD-L1. On the one hand, USP22 could directly regulate PD-L1 stability through deubiquitination. On the other hand, USP22 regulated PD-L1 protein level through USP22-CSN5-PD-L1 axis. In addition, USP22 depletion inhibited tumorigenesis and promoted T cell cytotoxicity. Besides, USP22 expression positively correlated with PD-L1 expression in human non-small cell lung cancer samples. Together, we identified a new regulator of PD-L1 and characterized the important role of USP22 in PD-L1 mediated immune evasion. Targeting USP22 might be a new solution to ICBT. Video abstract.
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Project description:Blockade of the programmed death 1 (PD-1)/ programmed death ligand 1 (PD-L1) immune checkpoint could increase antitumor immunotherapy for multiple types of cancer, but the response rate of patients is about 10%-40%. Peroxisome proliferator activated receptor γ (PPARγ) plays an important role in regulating cell metabolism, inflammation, immunity, and cancer progression, while the mechanism of PPARγ on cancer cell immune escape is still unclear. Here we found that PPARγ expression exhibits a positive correlation with activation of T cells in non-small-cell lung cancer (NSCLC) by clinical analysis. Deficiency of PPARγ promoted immune escape of NSCLC by inhibiting T-cell activity, which was associated with increased PD-L1 protein level. Further analysis showed that PPARγ reduced PD-L1 expression independent of its transcriptional activity. PPARγ contains the microtubule-associated protein 1A/1B-light chain 3 (LC3) interacting region motif, which acts as an autophagy receptor for PPARγ binding to LC3, leading to degradation of PD-L1 in lysosomes, which in turn suppresses NSCLC tumor growth by increasing T-cell activity. These findings suggest that PPARγ inhibits the tumor immune escape of NSCLC by inducing PD-L1 autophagic degradation.
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Project description:We have previously reported that tumor antigen-specific DNA vaccination in mice led to an increase in IFNγ-secreting T cells and an increase in tumor expression of PD-L1. Further, we demonstrated that increasing the encoded antigen's MHC-binding affinity led to increased PD-1 expression on antigen-specific CD8(+) T cells. Together these phenomena provided resistance to antitumor immunization that was abrogated with PD-1/PD-L1 blockade. We consequently sought to determine whether similar regulation occurred in human patients following antitumor immunization. Using clinical samples from prostate cancer patients who were previously immunized with a DNA vaccine, we analyzed changes in checkpoint receptor expression on antigen-specific CD8(+) T cells, the effect of PD-1 blockade on elicited immune responses, and for changes in checkpoint ligand expression on patients' circulating tumor cells (CTCs). We observed no significant changes in T-cell expression of PD-1 or other checkpoint receptors, but antigen-specific immune responses were detected and/or augmented with PD-1 blockade as detected by IFNγ and granzyme B secretion or trans vivo DTH testing. Moreover, PD-L1 expression was increased on CTCs following vaccination, and this PD-L1 upregulation was associated with the development of sustained T-cell immunity and longer progression-free survival. Finally, similar results were observed with patients treated with sipuleucel-T, another vaccine targeting the same prostate antigen. These findings provide in-human rationale for combining anticancer vaccines with PD-1 blocking antibodies, particularly for the treatment of prostate cancer, a disease for which vaccines have demonstrated benefit and yet PD-1 inhibitors have shown little clinical benefit to date as monotherapies.
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