Project description:Heterogeneous nuclear ribonucleoprotein A2B1 (HNRNPA2B1) is a well known RNA binding protein but the mechanisms by which it contributes to innate immune gene regulation is poorly understood. Here we report that HNRNPA2B1 functions in macrophages to regulate IFNG signaling through alternative splicing of the IFNG receptor. Specific deletion of HNRNPA2B1 in macrophages using our newly developed conditional mice crossed to LysMCre resulted in altered cytokine responses in both an endotoxic shock model and following Salmonella infection. Interestingly, while HNRNPA2B1 can function as a viability gene, we observed increased macrophage and neutrophil numbers in the KO mice following LPS induced endotoxic shock. HNRNPA2B1 KO mice were more susceptible to Salmonella and Mycobacterium Tuberculosis infections and failed to effectively clear the pathogens. Mechanistically, loss of HNRNPA2B1 resulted in an increase in No-GO transcripts of the IFNG receptor (Ifngr) leading to lower expression of the receptor at the cell surface impacting the downstream IFNG signaling cascade. Collectively, our data highlights an important role for HNRNPA2B1 in regulating IFNG signaling in macrophages.
Project description:RNA molecules are localized to subcellular regions through interactions between localization-regulatory cis-elements and trans-acting RNA binding proteins (RBPs). However, the identities of RNAs whose localization is regulated by a specific RBP as well as the impacts of that RNA localization on cell function have generally remained unknown. Here, we demonstrate that the RBP HNRNPA2B1 acts to keep specific RNAs out of neuronal projections. Using subcellular fractionation, high-throughput sequencing, and single molecule RNA FISH, we find that hundreds of RNAs demonstrate markedly increased abundance in neurites in HNRNPA2B1 knockout cells. These RNAs often encode motor proteins and are enriched for known HNRNPA2B1 binding sites and motifs in their 3′ UTRs. The speed and processivity of microtubule-based transport is impaired in these cells, specifically in their neurites. HNRNPA2B1 point mutations that increase its cytoplasmic abundance relative to wildtype lead to stronger suppression of both RNA mislocalization and transport defects than seen with wildtype HNRNPA2B1. We further find that the subcellular localizations of HNRNPA2B1 target RNAs are sensitive to perturbations of RNA decay machinery, suggesting that it is HNRNPA2B1’s known role in regulating RNA stability that may explain these observations. These findings establish HNRNPA2B1 as a negative regulator of neurite RNA abundance and link the subcellular activities of motor proteins with the subcellular abundance of the RNAs that encode them.
Project description:To identify HNRNPA2B1 binding sites on endogenous nuclear RNAs, we performed HITS-CLIP for endogenous HNRNPA2B1 and RNA-seq to analyze the nuclear RNA under either METTL3 or HNRNPA2B1 depletion. Wild type MDA-MB-231 cells were subjected to the HITS-CLIP procedure on immunoprecipitated HNRNPA2B1 associated RNA obtained from the nuclear fraction (Licatalosi D, et al. 2008, Nature 456:464-U22). For RNA-seq, nuclear RNA was extracted from MDA-MB-231 or Hela cells knocked down for METTL3 or HNRNPA2B1.
Project description:IFNg is an essential and pleiotropic activator of monocytes, but little is known about the changes in cellular metabolism required for IFNg-induced activation. We sought to characterize and elucidate the mechanisms by which IFNg reprograms monocyte metabolism to support its immunologic activities. Monocytes from healthy controls and patients with gain-of-function mutations in STAT1 (STAT1 GOF), or loss-of-function mutations in mitochondrial complex I (Leigh syndrome) and NADPH oxidase (chronic granulomatous disease, CGD) were metabolically phenotyped. We found that IFNg increased oxygen consumption rates (OCR), indicative of reactive oxygen species generation by both mitochondria and NADPH oxidase. Transcriptional profiling of human monocyte derived macrophages revealed that this oxidative phenotype was driven by an IFNg-induced reprogramming of NAD+ metabolism, which is dependent on nicotinamide phosphoribosyltransferase (NAMPT)-mediated NAD+ salvage to generate NADH and NADPH for oxidation by mitochondrial complex I and NADPH oxidase, respectively. Monocytes from patients with STAT1 GOF demonstrated higher than normal OCR, while monocytes from Leigh syndrome and CGD patients demonstrated reduced OCR. Chemical inhibition of NAMPT completely abrogated the IFNg-induced oxygen consumption, comparable to levels observed in CGD patients. These data identify an IFNg-induced, NAMPT-dependent, NAD+ salvage pathway that is critical for IFNg activation of human monocytes.
Project description:Macrophages play a crucial role in eliminating respiratory pathogens. Both pulmonary resident alveolar macrophages (AMs) and recruited macrophages contribute to detecting, responding to, and resolving infections in the lungs. Despite their distinct functions, it remains unclear how these macrophage subsets regulate their responses to infection, including how activation by the cytokine IFNg is regulated. This shortcoming prevents the development of therapeutics that effectively target distinct lung macrophage populations without exacerbating inflammation. We aimed to better understand the transcriptional regulation of resting and IFNg-activated cells using a new ex vivo model of AMs from mice, fetal liver-derived alveolar-like macrophages (FLAMs), and immortalized bone marrow-derived macrophages (iBMDMs). Our findings reveal that IFNg robustly activates both macrophage types; however, the profile of activated IFNg-stimulated genes varies greatly between these cell types. Notably, FLAMs show limited expression of costimulatory markers essential for T cell activation upon stimulation with only IFNg. To understand cell type-specific differences, we examined how the inhibition of the regulatory kinases GSK3a/b alters the IFNg response. GSK3a/b controlled distinct IFNg responses, and in AM-like cells, we found GSK3a/b restrained the induction of type I IFN and TNF, thus preventing the robust expression of costimulatory molecules and limiting CD4+ T cell activation. Together, these data suggest that the capacity of AMs to respond to IFNg is restricted in a GSK3a/b-dependent manner and that IFNg responses differ across distinct macrophage populations. These findings lay the groundwork to identify new therapeutic targets that activate protective pulmonary responses during infection without driving deleterious inflammation.
Project description:Exosomes are released by most cells to the extracellular environment, and are involved in cell-to-cell-communication. Exosomes contain specific repertoires of mRNAs, miRNAs and other non-coding RNAs that can be functionally transferred to recipient cells. However, the mechanisms that control the specific loading of RNA species into exosomes remain unknown. Here we describe short sequence motifs present in miRNAs that control their localization into exosomes. The protein hnRNPA2B1 specifically binds exosomal miRNAs through the recognition of these motifs and controls their loading into exosomes. Moreover, hnRNPA2B1 in exosomes is sumoylated, and sumoylation controls the binding of hnRNPA2B1 to miRNAs. The loading of miRNAs into exosomes can be modulated by mutagenesis of the identified motifs or changes in hnRNPA2B1 expression levels. These findings identify hnRNPA2B1 as a key player in miRNA sorting into exosomes and provide potential tools for the packaging of selected regulatory RNAs into exosomes and their use in biomedical applications.
Project description:To identify HNRNPA2B1 binding sites on endogenous nuclear RNAs, we performed HITS-CLIP for endogenous HNRNPA2B1 and RNA-seq to analyze the nuclear RNA under either METTL3 or HNRNPA2B1 depletion.