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Mertk negatively regulates adaptive immunity

ABSTRACT: Tolerogenic dendritic cells (tol-DCs) offer a promising therapeutic potential for autoimmune diseases. Tol-DCs have been reported to inhibit immunogenic responses, yet little is known about the mechanisms controlling their tolerogenic status, as well as associated specific markers. Here we show that the anti-inflammatory TAM receptor tyrosine kinase MERTK, is highly expressed on clinical grade dexamethasone-induced human tol-DCs and mediates their tolerogenic effect. Neutralization of MERTK in allogenic mixed lymphocyte reactions as well as autologous DC-T cell cultures leads to increased T cell proliferation and IFN-g production. Additionally, we identify a previously unrecognized non-cell autonomous regulatory function of MERTK expressed on DCs. Recombinant Mer-Fc protein, used to mimic MERTK on DCs, suppresses naïve and antigen-specific memory T cell activation. This mechanism is mediated by the neutralization of the MERTK agonist Protein S (PROS1) expressed by T cells. We find that MERTK and PROS1 are expressed in human T cells upon TCR activation and drive an autocrine pro-proliferative mechanism. Collectively, these results suggest that MERTK on tol-DCs directly inhibits T cell activation through the competition for PROS1 interaction with MERTK in the T cells. Targeting MERTK may provide an interesting approach to effectively increase or suppress tolerance for the purpose of immunotherapy.

ORGANISM(S): Homo sapiens

PROVIDER: GSE56017 | GEO | 2015/01/29

SECONDARY ACCESSION(S): PRJNA242228

REPOSITORIES: GEO

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Mertk negatively regulates adaptive immunity

Project description:Tolerogenic dendritic cells (tol-DCs) offer a promising therapeutic potential for autoimmune diseases. Tol-DCs have been reported to inhibit immunogenic responses, yet little is known about the mechanisms controlling their tolerogenic status, as well as associated specific markers. Here we show that the anti-inflammatory TAM receptor tyrosine kinase MERTK, is highly expressed on clinical grade dexamethasone-induced human tol-DCs and mediates their tolerogenic effect. Neutralization of MERTK in allogenic mixed lymphocyte reactions as well as autologous DC-T cell cultures leads to increased T cell proliferation and IFN-g production. Additionally, we identify a previously unrecognized non-cell autonomous regulatory function of MERTK expressed on DCs. Recombinant Mer-Fc protein, used to mimic MERTK on DCs, suppresses naïve and antigen-specific memory T cell activation. This mechanism is mediated by the neutralization of the MERTK agonist Protein S (PROS1) expressed by T cells. We find that MERTK and PROS1 are expressed in human T cells upon TCR activation and drive an autocrine pro-proliferative mechanism. Collectively, these results suggest that MERTK on tol-DCs directly inhibits T cell activation through the competition for PROS1 interaction with MERTK in the T cells. Targeting MERTK may provide an interesting approach to effectively increase or suppress tolerance for the purpose of immunotherapy. The complete database comprised the expression measurements of 54,675 genes for: immature (n=9), mature (n=7) and tolerogenic (n=8). Influence of treatment with dexamethasone (n=3) and LPS (n=2) are included.

2015-01-29 | E-GEOD-56017 | biostudies-arrayexpress

Transcription profiling of human alveolar macrophages reveals overexpression of apoptotic cell removal receptor, MERTK,

Project description:Mononuclear phagocytes play an important role in the removal of apoptotic cells by expressing cell surface receptors that recognize and remove apoptotic cells. Based on the knowledge that cigarette smoking is associated with increased lung cell turnover, we hypothesized that alveolar macrophages (AM) of normal cigarette smokers may exhibit enhanced expression of apoptotic cell removal receptor genes. AM obtained by bronchoalveolar lavage of normal non-smokers (n=11) and phenotypic normal smokers (n=13, 36 +/- 6 pack per year) were screened for mRNA expression of all known apoptotic cell removal receptors using Affymetrix HG-U133 Plus 2.0 chips with TaqMan RT-PCR confirmation. Of the 14 known apoptotic receptors expressed, only MER Tyrosine Kinase (MERTK), a transmembrane tyrosine kinase receptor, was significantly up-regulated in smokers. MERTK expression was then assessed in AM of smokers vs nonsmokers by TaqMan RT-PCR, immunohistochemistry, Western and flow analysis. Smoker AM had up-regulation of MERTK mRNA levels (smoker vs non-smoker, 3.6-fold by microarray, p<0.003; 9.5-fold by TaqMan RT-PCR, p<0.02). Immunohistochemistry demonstrated a qualitative increase in MERTK protein expression on AM of smokers. Increased protein expression of MERTK on AM of smokers was confirmed by Western and flow analyses (p< 0.007 and p< 0.0002, respectively). MERTK, a cell surface receptor that recognizes apoptotic cells, is expressed on human AM, and its expression is up-regulated in AM of cigarette smokers. This may reflect an increased demand for removal of apoptotic cells in smokers, an observation with implications for the development of chronic obstructive pulmonary disease (COPD), a disorder associated with dysregulated apoptosis of lung parenchymal cells. Experiment Overall Design: Alveolar macrophages were obtained from bronchoalveolar lavage.

2008-10-18 | E-GEOD-8823 | biostudies-arrayexpress

Expression of MERTK based on Multiple Sclerosis (MS) risk haplotype

Project description:Whole transcriptome RNA-seq analysis to measure group-wise RNA expression level of the MERTK gene in 3 healthy controls (known to be homozygous non-risk haplotype at MERTK gene locus) and to compare this to the group-wise RNA expression level of the MERTK gene in 5 Multiple Sclerosis-affected (MS-affected) individuals (known to be homozygous for the MS risk haplotype at the MERTK gene locus). We sequenced the whole transcriptome of 3 healthy control samples which were all homozygous for the MS non-risk haplotype at the MERTK gene. We also did the same RNA-seq protocol on 5 MS-affected subjects that were all homozygous for the Risk haplotype at the MERTK gene. All 8 samples were sequenced evenly across 3 lanes of an Illumina HiSeq NGS machine to remove any batch-type effects that could be caused by sequencing e.g. all cases in one lane and all controls in another lane.

2016-02-06 | E-GEOD-77598 | biostudies-arrayexpress

Gene expression profile at single cell level of dendritic cells (DC) from the lung of neonatal (NEO) or adult (AD) mice

Project description:Multiple mechanisms restrain inflammation in neonates. Here we identify a population of pulmonary dendritic cells (DCs) that appear in the lungs and lung−draining lymph nodes between birth and two weeks of age and express intermediate levels of CD103 (CD103int). CD103int DCs express XCR1, CD205, and require the transcription factor, Batf3, suggesting that they belong to the cDC1 lineage. They also constitutively express CCR7 and spontaneously migrate to the lung−draining lymph node, where they promote stromal cell maturation and lymph node expansion, independently of microbial exposure and Trif− or MyD88−dependent signaling. CD103int DCs are transcriptionally related to efferocytic and tolerogenic DCs as well as mature, regulatory DCs. CD103int DCs efficiently acquire apoptotic cells and become activated through Mertk signaling, which also impairs CD8+ T cell activation. The appearance of CD103int DCs coincides with a temporal wave of apoptosis in developing lungs and explains, in part, impaired pulmonary immunity in neonatal mice.

2023-04-13 | GSE224178 | GEO

scRNAseq of Mertk-WT and Mertk-KO corpus callosum

Project description:Purpose: The goal of this study is to characterize the the different CNS cell types in the mouse corpus callosum over three different cuprizone treatment timepoints - (Baseline, 4 weeks, 4 weeks + 3 weeks of recovery) and compare the Mertk-WT vs Mertk-KO response to demyelination. Methods: 3-4 biological replicates (mice) were used for each timepoint/genotype. Tissues were dissociated into single cells for preparation of 10X libraries and sequenced with HiSeq 2500 (Illumina). Results: scRNA-Seq data were analyzed with an in-house analysis pipeline. Briefly, reads were demultiplexed based on perfect matches to expected cell barcodes. Transcript reads were aligned to the mouse reference genome (GRCm38) using GSNAP (Wu and Nacu, 2010). Only uniquely mapping reads were considered for downstream analysis. Transcript counts for a given gene were based on the number of unique molecular identifiers (UMIs) for reads overlapping exons in sense orientation. To account for sequencing or PCR errors, one mismatch was allowed when collapsing UMI sequences. Cell barcodes from empty droplets were filtered by requiring a minimum number of detected transcripts. Cells with less than 1000 total UMIs were discarded. Conclusions: We show differences between Mertk-WT and Mertk-KO cellular profiles, particularly at the 4 week Cuprizone timepoint. In addition, our data show a distinct, yet heterogenous, population of oligodendrocytes that arise in the cuprizone model where remyelination is spontaneous and robust. Our results provide new insights into the cellular response to demyelination, that includes a resource for comparing and interpreting neurodegenerative disease models.

2021-04-13 | GSE148676 | GEO

MERTK inhibition for the treatment of tissue fibrosis [scMultiome]

Project description:Fibrosis is a core pathway that drives the progression of multiple chronic diseases for which there is a paucity of safe and effective treatments. In these diseases, transforming growth factor–β (TGF-β)–driven scarring propels disease progression. However, targeting this ubiquitously expressed cytokine is unlikely to yield a viable and safe antifibrotic therapy; thus, identification of alternative mechanisms to inhibit TGF-β signalling is required. We identified Mer tyrosine kinase (MERTK) as a TGF-β–inducible nodal effector of fibrosis that is up-regulated with fibrosis in multiple organs in both mice and humans. MERTK also induces TGF-β expression and promotes it’s signalling resulting in a positive feedback loop that promotes fibrosis. Mechanistically, MERTK regulates both canonical and non-canonical TGFβ signalling. Further downstream, MERTK modulates the fibrotic regulatory gene transcription network by regulating chromatin accessibility, RNA polymerase II (pol II) pausing and reprograming the enhancer landscape. Using mouse models of kidney, lung, and liver fibrosis, we demonstrate that this fibrosis-promoting signalling loop can be interrupted by loss of MERTK expression, leading to marked attenuation of fibrosis. Pharmacologic MERTK inhibition reduced fibrosis either when initiated immediately after injury or when initiated after fibrosis is established. Together, this data suggests that MERTK plays a critical role in modulating organ fibrosis, while small-molecule MERTK inhibitors are an attractive target for the treatment of diseases characterized by fibrosis.

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