ADAR1 utilizes independent mechanisms to suppress MDA5 and PKR activation by cellular double-stranded RNA
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ABSTRACT:
PROVIDER: PRJNA814746 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR18294835.fastq.gz | Fastqsanger.gz | |||
| SRR18294836.fastq.gz | Fastqsanger.gz | |||
| SRR18294837.fastq.gz | Fastqsanger.gz | |||
| SRR18294838.fastq.gz | Fastqsanger.gz | |||
| SRR18294839.fastq.gz | Fastqsanger.gz |
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Project description:The antiviral defense in vertebrates requires the innate immune system to sense foreign “non-self” nucleic acids while avoiding “self” nucleic acids, which is accomplished by an intricate system. Cellular double-stranded RNAs (dsRNAs) are edited by the RNA editing enzyme ADAR1 to prevent their dsRNA structure pattern from being recognized as viral dsRNA. Lack of RNA editing by ADAR1 enables activation of MDA5, a cytosolic dsRNA sensor, by cellular dsRNA. Additional RNA editing- independent functions of ADAR1 have been proposed, but the specific mechanism remains elusive. Here we demonstrate that RNA binding by ADAR1, independent of its editing activity, restricts the activation of PKR, another cytosolic dsRNA sensor, by cellular dsRNA. Mechanistically, the loss of ADAR1 editing caused MDA5 activation to induce interferon signaling, while a lack of ADAR1 protein or its dsRNA binding ability led to PKR activation, with subsequent stress granule formation and proliferation arrest. Based on these findings we rescued the Adar1−/− mice from embryonic lethality to adulthood by deleting both MDA5 and PKR, in contrast to the limited rescue of Adar1−/− mice by removing MDA5 or PKR alone. Our findings reveal a multifaceted contribution of ADAR1 in regulating the immunogenicity of “self” dsRNAs. Furthermore, ADAR1 is an immuno-oncology target for drug development, and the separation of ADAR1’s RNA editing and binding functions provides mechanistic insights for such developments.
2023-10-03 | GSE198386 | GEO
Project description:Endogenous double-stranded RNA (dsRNA) triggers pro-inflammatory signaling and has been shown to accumulate in Alzheimer’s disease (AD), but the origins of this dsRNA are incompletely understood. Transposable elements (TEs), which are non-coding DNA sequences capable of forming dsRNA, are a potential endogenous source of dsRNA in AD. We generated dsRNA immunoprecipitation (J2 dsRNA antibody) data on astrocytes treated with or without a siRNA to knock down the dsRNA editing enzyme ADAR1. We analyzed TE transcripts enriched in dsRNA pools when ADAR1 was knocked down, and we identified putative dsRNA-prone TEs, which were also present in secondary analyses of datasets profiling RNAs bound to PKR, MDA5, and the p110 isoform of ADAR1.
2025-07-25 | GSE303455 | GEO
Project description:Adenosine-to-Inosine (A-to-I) editing of double stranded RNA (dsRNA) is an essential modifier of dsRNA immunogenicity. Loss of Adenosine deaminase acting on RNA 1 (ADAR1), or its A-to-I editing activity, triggers a lethal MDA5-dependent autoinflammatory response to endogenous unedited dsRNA. We performed a genome-wide suppressor screen to map the genetic landscape regulating the response to a loss of ADAR1 mediated A-to-I editing. This identified that the interacting proteins GGNBP2, CNOT10 and CNOT11 regulate immunogenic sensing following loss of A-to-I editing. GGNBP2 acts between transcription and cytoplasmic MDA5 sensing. Loss of GGNBP2 modified the distribution of dsRNA within cells, reducing the cytoplasmic dsRNA load and preventing induction of type I IFN and lethal autoinflammation. GGNBP2, CNOT10 and CNOT11 are novel regulators of the cellular response to unedited dsRNA.
2024-11-21 | GSE234570 | GEO
Project description:Sensing of double-stranded RNA (dsRNA) is an important component of innate immunity. Proteins like PKR and MDA5 recognize dsRNA and activate various pathways to fight viral infection. In addition to viral dsRNA, many endogenous RNAs containing double-stranded regions can be misrecognized as immunogenic. The RNA editing enzyme ADAR1, specifically its p150 isoform, has been shown to suppress activation of PKR and MDA5 through its A-to-I editing activity. While the cytoplasmic ADAR1-p150 isoform has been well established within this role, the functions of the nuclear ADAR1-p110 isoform are less understood. To address this knowledge gap, we utilized proximity labeling by APEX2 to identify putative ADAR1-p110 interacting proteins. We identified 110 proteins across three breast cancer cell lines that either interact with p110 or are within close proximity. Many of these proteins have known roles in RNA metabolism. Nine of the identified proteins belong to the DEAD or DEAH box families of RNA helicases, including DHX9. DHX9 is overexpressed in breast cancer, with expression closely correlated with that of p110. By co-immunoprecipitation we confirmed that p110 interacts with DHX9. Knockdown of DHX9 in several triple-negative breast cancer cell lines caused cell death and activation of the dsRNA sensor PKR. In two cell lines that are refractory to knockdown of ADAR1, the combined knockdown of DHX9 and ADAR1 caused a substantial increase in PKR activity, where knockdown of either alone had no effect. Knockdown of DHX9 and ADAR1 caused activation of the type I IFN pathway, RNase L and NF-KB signaling. Activation of these proteins and pathways was not seen with individual knockdown of ADAR1 or DHX9. Activation of PKR following combined knockdown of ADAR1 and DHX9 could be rescued by expression of p110, p150, DHX9, and catalytically inactive DHX9. Additionally PKR activation could be rescued by the dsRBM of DHX9, revealing an important role for dsRBMs in suppressing PKR activation. Together these results reveal an important role for DHX9 in suppressing dsRNA sensing by multiple pathways.
2023-08-07 | GSE224677 | GEO
Project description:Eukaryotic translation initiation factor 2 alpha kinase 2 (EIF2AK2), better known as PKR plays a key role in the response to viral infections and cellular homeostasis by regulating mRNA translation. Upon binding dsRNA, PKR is activated through homodimerization and subsequent autophosphorylation on Thr446 and Thr451 residues. In this study, we identified a novel PKR phosphorylation site, Ser6, located 3 aminoacids upstream the first double-stranded RNA binding domain (DRBM1). Another Ser residue occurs in PKR at position 97, the very same position relative to the DRBM2. Ser or Thr residues also occur 3 amino acids upstream DRBMs of other proteins such as ADAR1 or DICER. Phosphoinhibiting mutations (Ser-to-Ala) introduced at Ser6 and Ser97 spontaneously activated PKR. In contrast, phosphomimetic mutations (Ser-to-Asp) inhibited PKR activation following either poly (I:C) transfection or virus infection. These mutations moderately affected dsRNA binding, suggesting a model where negative charges occuring at position 6 and 97 tighten the interaction of DRBMs with the kinase domain, thus keeping PKR in an inactive, closed conformation even in the presence of dsRNA. This study provides new insights on PKR regulation mechanisms and identifies Ser6 and Ser97 as potential targets to modulate PKR activity for therapeutic purposes
2021-05-10 | PXD022564 | Pride
Project description:GGNBP2 regulates MDA5 sensing triggered by self double stranded RNA following loss of ADAR1 editing
| PRJNA982066 | ENA
Project description:Adenosine deaminase acting on RNA 1 (ADAR1) catalyzes the conversion of adenosine (A) to inosine (I) in double-stranded RNA (dsRNA), which is critical to prevent auto-inflammatory responses mediated by activation of the type I interferon (IFN) signaling. Here, we define the role of ADAR1-dependent RNA editing in interferon-β(IFNβ) activation and pulmonary artery smooth muscle cell (PASMC) remodeling in pulmonary arterial hypertension (PAH), a devastating disease leading to right heart failure and premature death. Methods: RNA editing levels were analyzed in human pulmonary artery smooth muscle cells (PASMCs) from idiopathic PAH (IPAH) patients versus healthy controls. A conditional transgenic line ADAR1SMC-KO was generated by knocking out ADAR1 selectively in α-smooth muscle actin-positive cells, followed by hypoxic exposure to induce PH. Results: PASMCs from IPAH patients displayed decreased levels of ADAR1 mRNA and protein, accompanied by reduced A-to-I editing compared to healthy PASMCs. ADAR1 knockdown in PASMCs upregulated MDA5, PKR, IFN-β and IFN-Stimulated Genes (ISGs). Compared with controls in vivo, hypoxic ADAR1SMC-KO mice developed severe PH, as evidenced by excessive vascular remodeling in distal arterioles and increased vascular leakage resulting in elevated right ventricular systolic pressure and right ventricular hypertrophy. Mechanistically, IFNβ signaling in ADAR1SMC-KO lungs induced the recruitment of inflammatory cells, including macrophages, which in turn enhanced PASMC proliferation and muscularization. Correspondingly, pharmacological treatment with PKR kinase inhibitor Imoxin decreased IFNβ thus attenuating the hypoxia-induced PH phenotype of ADAR1SMC-KO mice. Conclusions: ADAR1-dependent A-to-I RNA editing tempers IFN signaling in PASMCs. Pathologic reduction of ADAR1 in SMCs increased IFNβ activity, macrophage recruitment, and worsened PH, thus demonstrating a direct detrimental role of vascular innate immune responses in PH. Targeting PKR could be the new therapeutic strategy aimed at treating PAH.
2025-09-03 | GSE228134 | GEO
Project description:Adenosine deaminase acting on RNA 1 (ADAR1) catalyzes the conversion of adenosine (A) to inosine (I) in double-stranded RNA (dsRNA), which is critical to prevent auto-inflammatory responses mediated by activation of the type I interferon (IFN) signaling. Here, we define the role of ADAR1-dependent RNA editing in interferon-β(IFNβ) activation and pulmonary artery smooth muscle cell (PASMC) remodeling in pulmonary arterial hypertension (PAH), a devastating disease leading to right heart failure and premature death. Methods: RNA editing levels were analyzed in human pulmonary artery smooth muscle cells (PASMCs) from idiopathic PAH (IPAH) patients versus healthy controls. A conditional transgenic line ADAR1SMC-KO was generated by knocking out ADAR1 selectively in α-smooth muscle actin-positive cells, followed by hypoxic exposure to induce PH. Results: PASMCs from IPAH patients displayed decreased levels of ADAR1 mRNA and protein, accompanied by reduced A-to-I editing compared to healthy PASMCs. ADAR1 knockdown in PASMCs upregulated MDA5, PKR, IFN-β and IFN-Stimulated Genes (ISGs). Compared with controls in vivo, hypoxic ADAR1SMC-KO mice developed severe PH, as evidenced by excessive vascular remodeling in distal arterioles and increased vascular leakage resulting in elevated right ventricular systolic pressure and right ventricular hypertrophy. Mechanistically, IFNβ signaling in ADAR1SMC-KO lungs induced the recruitment of inflammatory cells, including macrophages, which in turn enhanced PASMC proliferation and muscularization. Correspondingly, pharmacological treatment with PKR kinase inhibitor Imoxin decreased IFNβ thus attenuating the hypoxia-induced PH phenotype of ADAR1SMC-KO mice. Conclusions: ADAR1-dependent A-to-I RNA editing tempers IFN signaling in PASMCs. Pathologic reduction of ADAR1 in SMCs increased IFNβ activity, macrophage recruitment, and worsened PH, thus demonstrating a direct detrimental role of vascular innate immune responses in PH. Targeting PKR could be the new therapeutic strategy aimed at treating PAH.
2025-09-03 | GSE228133 | GEO
Project description:Protein kinase RNA-activated (PKR) induces immune response by sensing viral double-stranded RNAs (dsRNAs). However, growing evidence suggests that PKR can also be activated by endogenously expressed dsRNAs. Here, we capture these dsRNAs by formaldehyde-mediated crosslinking and immunoprecipitation-sequencing and find that various noncoding RNAs interact with PKR. Surprisingly, the majority of the PKR-interacting RNA repertoire is occupied by mitochondrial RNAs (mtRNAs). MtRNAs can form intermolecular dsRNAs owing to bidirectional transcription of mitochondrial genome and regulate PKR and eIF2α phosphorylation to control cell signaling and translation. Moreover, PKR activation by mtRNAs is counteracted by PKR phosphatases, disruption of which causes apoptosis from PKR overactivation even in uninfected cells. Our work unveils dynamic regulation of PKR even without infection and establishes PKR as a sensor for nuclear and mitochondrial signaling cues in regulating cellular metabolism.
2018-07-18 | GSE108986 | GEO
Project description:Adenosine deaminases acting on RNA (Adar1 and Adar2) catalyze I-to-A RNA editing, a post-transcriptional mechanism involved in multiple cellular functions. The role of Adar1-dependent RNA editing in cardiomyocytes (CMs) remains unclear. Here we show that conditional deletion of Adar1 in CMs results in myocarditis progressively evolving into dilated cardiomyopathy and heart failure at only 6 months of age. Adar1 depletion drives activation of interferon signaling genes (ISGs) in the absence of apoptosis and cytokine activation, and reduces the hypertrophic response of CMs upon pressure overload. Interestingly, ablation of the cytosolic sensor MDA5 prevents cardiac ISG activation and delays disease onset, but does not rescue the long-term lethal phenotype elicited by conditional deletion of Adar1. Retention of a single catalytically inactive Adar1 allele in CMs, in combination with MDA5 depletion, however, completely restores the cardiac function and prevents heart failure. Finally, ablation of interferon regulatory factor 7 (Irf7) attenuates the phenotype of Adar1-deficient CMs to a similar extent as MDA5 depletion, highlighting Irf7 as the main regulator of the immune response triggered by lack of Adar1 in CMs.
2022-08-24 | PXD024974 | Pride