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Distinct interactomes of ADAR1 nuclear and cytoplasmic protein isoforms and their responses to Interferon induction

ABSTRACT: Adenosine deaminase acting on RNA 1 (ADAR1), is an enzyme that catalyzes the conversion of adenosine to inosine in double-stranded RNA, a process critical for regulation of innate immune response and distinguishing between ‘self and non-self RNA’. It is expressed as two isoforms: nucleolar p110 and cytoplasmic, interferon (IFN)-inducible, p150. The interactome of the p110 under steady-state conditions is well-studied; however, less is known about the interactions of the p150 isoform, particularly during IFN response. To elucidate ADAR1's protein interactions during IFN stimulation, alongside steady-state conditions, three distinct methods of enrichment were used followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). These included: immunoprecipitation (IP) of endogenous ADAR1, IP of Strep II-tagged ADAR1, and proximity labeling using BioID. Individual ADAR1 isoforms (p110 and p150) and their respective dsRNA binding-deficient mutants were created to discern isoform-specific and dsRNA-dependent interactions. Altogether, our results reveal a comprehensive ADAR1 interaction map, identifying both known and novel partners, and highlighting the isoform-specific and dsRNA-binding-dependent nature of ADAR1 interactions. Under IFN stimulation, ADAR1's interaction spectrum encompasses viral replication inhibitors and LINE-1 regulators. Mimicking viral infection with HMW poly(I:C) changed the proximal network of proteins for both isoforms. Our findings provide new insights into ADAR1's roles and its dynamic during IFN response.

INSTRUMENT(S): Orbitrap Fusion Lumos

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture

SUBMITTER: Katerina Hanakova

LAB HEAD: Zbynek Zdrahal

PROVIDER: PXD049681 | Pride | 2024-12-05

REPOSITORIES: Pride

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			Action	DRS
	3519_Lumik1_Vukic_90IS_IT50_HCD-OT-15k_s01_1.raw	Raw
	3519_Lumik1_Vukic_90IS_IT50_HCD-OT-15k_s02_1.raw	Raw
	3519_Lumik1_Vukic_90IS_IT50_HCD-OT-15k_s03_1.raw	Raw
	3519_Lumik1_Vukic_90IS_IT50_HCD-OT-15k_s04_1.raw	Raw
	3519_Lumik1_Vukic_90IS_IT50_HCD-OT-15k_s05_1.raw	Raw

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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.

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Distinct interactomes of ADAR1 nuclear and cytoplasmic protein isoforms and their responses to Interferon induction

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