The LC3 conjugation machinery specifies the loading of RNA-binding proteins into extracellular vesicles (lrgRNA-seq dataset)
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ABSTRACT: We employed RNA sequecing to profile large RNAs (mRNAs and lincRNAs) packaged into extracellular vesicles (EVs) from WT cells and cells deficient for the LC3 conjugation machinery
Project description:We employed small non-coding RNA sequecing to profile the small RNAs in extracellular vesicles (EVs) from WT cells and cells deficient for the LC3 conjugation machinery
Project description:Traditionally viewed as an autodigestive pathway, autophagy also facilitates cellular secretion; however, the mechanisms underlying these processes remain unclear. Here, we demonstrate that components of the autophagy machinery specify secretion within extracellular vesicles (EVs). Using a proximity-dependent biotinylation proteomics strategy, we identify 200 putative targets of LC3-dependent secretion. This secretome consists of a highly interconnected network enriched in RNA-binding proteins (RBPs) and EV cargoes. Proteomic and RNA profiling of EVs identifies diverse RBPs and small non-coding RNAs requiring the LC3-conjugation machinery for packaging and secretion. Focusing on two RBPs, heterogeneous nuclear ribonucleoprotein K (HNRNPK) and scaffold-attachment factor B (SAFB), we demonstrate that these proteins interact with LC3 and are secreted within EVs enriched with lipidated LC3. Furthermore, their secretion requires the LC3-conjugation machinery, neutral sphingomyelinase 2 (nSMase2) and LC3-dependent recruitment of factor associated with nSMase2 activity (FAN). Hence, the LC3-conjugation pathway controls EV cargo loading and secretion.
Project description:PINK1-Parkin mediated mitophagy, a selective form of autophagy, represents an important mechanism in mitochondrial quality control (MQC) via clearance of damaged mitochondria. Although it is well known that the conjugation of mammalian ATG8s to phosphatidylethanolamine (PE) is a key step in autophagy, its role in mitophagy remains controversial. In this study, we attempted to clarify the role of the mATG8-conjugation system in mitophagy by generating knockouts of the mATG8-conjugation machinery. Unexpectedly, we show that mitochondria could still be cleared in the absence of mATG8 lipidation, in a process that was found to be independent of lysosomal degradation. Instead, mitochondria were found to be cleared via a secretory autophagy pathway, resulting in the extracellular release of mitochondria, in a process we defined as autophagic secretion of mitochondria (ASM). Functionally, increased ASM promoted the activation of the innate immune cGAS-STING pathway in recipient cells. Overall, data from this study reveal ASM as a novel mechanism in MQC, especially when the cellular mATG8-conjugation machinery is dysfunctional.
Project description:Transcription factor EB (TFEB), well characterized as a master regulator of autophagy and lysosomal biogenesis, is translocated to the nucleus and activated by varieties of cellular stresses including starvation and lysosomal damage. However, compared to the starvation condition, the molecular mechanism of TFEB activation by other stress conditions is poorly understood. Previously, we have shown that TFEB activation during lysosomal damage but not starvation condition depends on a subset of autophagy regulators, collectively called ATG conjugation system, whose function is essential for the lipidation of ATG8 proteins. In this study, by time-lapse imaging, we newly identified the presence of ATG conjugation system -independent TFEB regulation which precedes the ATG conjugation system-dependent regulation, designated mode I and mode II, respectively. Consistent with the presence of different modes, our time course transcriptome analysis revealed two different sets of TFEB downstream. Comprehensive interactome analysis of TFEB and subsequent functional screening identified unique regulars of TFEB in each mode: APEX1 for Mode I and CCT7 and/or TRIP6 for Mode II, respectively. APEX1 interacted with TFEB and was required for its protein stability in a manner independent of ATG conjugation system. On the other hand, both CCT7 and TRIP6 were accumulated on lysosomes during lysosomal damage and interacted with TFEB mainly in ATG conjugation system deficient cells, presumably blocking TFEB nuclear translocation. Moreover, we further revealed that TFEB regulatory mechanisms by other cellular stresses such as oxidative stress, proteasome inhibition, mitochondria depolarization, and DNA damage can be classified into either APEX1-mediated Mode I or TRIP6-mediated Mode II. Our results pave the way for a unified understanding TFEB regulatory mechanisms from the perspective of ATG conjugation system under varieties of cellular stresses.
Project description:Although innate immunity is critical for antifungal host defense against the human opportunistic fungal pathogen Aspergillus fumigatus, potentially damaging inflammation must be controlled. Adiponectin (APN) is an anti-inflammatory adipokine, and we observed 100% mortality and increased fungal burden and inflammation in neutropenic mice with invasive aspergillosis (IA) that lack APN or the APN receptors AdipoR1 or AdipoR2. Alveolar macrophages (AMs), early immune sentinels that detect and respond to lung infection, express both receptors, and APN-/- AMs exhibited an inflammatory/M1 phenotype that was associated with decreased fungal killing and decreased activation of LC3-associated phagocytosis (LAP). Furthermore, AM treatment with the AdipoR agonist AdipoRon partially rescued deficient killing in APN-/- AMs that was dependent on both receptors. Our study identifies a novel role for APN in LC3-mediated killing of A.fumigatus.