VAP-A and its binding partner CERT drive biogenesis of RNA-containing extracellular vesicles at ER membrane contact sites
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ABSTRACT: RNA transfer via extracellular vesicles (EVs) influences cell phenotypes; however, lack of information regarding biogenesis of RNA-containing EVs has limited progress in the field. Here, we identify endoplasmic reticulum membrane contact sites (ER MCS) as platforms for generation of RNA-containing EVs. We identify a subpopulation of small EVs that is highly enriched in RNA and regulated by the ER MCS linker protein VAP-A. Functionally, VAP-A-regulated EVs are critical for miR-100 transfer between cells and in vivo tumor formation. Lipid analysis of VAP-A-knockdown EVs revealed reductions in the EV biogenesis lipid ceramide. Knockdown of the VAP-A-binding ceramide transfer protein CERT led to similar defects in EV RNA content. Imaging experiments revealed that VAP-A promotes lumenal filling of multivesicular bodies (MVBs). CERT localizes to MVBs, and the ceramide-generating enzyme neutral sphingomyelinase 2 colocalizes with VAP-A-positive ER. We propose that ceramide transfer via VAP-A-CERT linkages drives biogenesis of a select RNA-containing population.
Project description:The biogenesis of extracellular vesicles (EVs) is a regulated process, driven by mechanisms at specific subcellular milieus. Sphingomyelinases (SMases), which metabolize sphingomyelin in membranes, play a role in EV biogenesis. Their metabolic product, ceramide, induces invaginations at the endosome or blebbing from the plasma membrane, both important in EV generation. Here, we sought to evaluate the impact of SMase inhibition on EV protein and RNA cargoes. For this, we treated human MCF7 cells with the neutral SMase (NSM) inhibitor GW4869 or the acid SMase (ASM) inhibitor FTY720. EVs were then purified from the conditioned media of control or inhibitor-treated cells and characterized by a variety of approaches, including LC-MS/MS and RNA-sequencing. SMase inhibition resulted in morphological and phenotypic changes in the heterogeneous EV population. Strikingly, NSM inhibition resulted in a depletion of nanoparticles, as well as a decrease in the RNA and protein content of EVs, with a marked reduction in endosomal, spliceosomal, and translation-related proteins. Furthermore, we observed a reduction in the overall RNA-binding proteins (RBPs) in EVs released by cells treated with the NSM-inhibitor. In contrast, the ASM-inhibitor treatment, which appears to reduce plasma membrane-derived vesicles, elicited an inverse response, leading to an increase of RBP and associated machineries within the released EV population. RNA sequencing of these EV revealed changes in the RNA biotypes composition, with an increase in protein coding transcripts. Interestingly, ASM-inhibitor resulting EVs induced increased cell migration and protein translation in recipient MCF10A cells. These results suggest that SMase-dependent vesiculation represents a major route of RBP and RNA trafficking outside the cell, via endosomal pathways.
Project description:Exosome-like extracellular vesicles (EVs) are very important vesicles for intercellular signal transmission. Although host factors involving exosome-like EV production and release has been reported, the cellular signaling pathway regulating EV production is largely unknown. Here we performed a kinase inhibitor library screening to identify pathways controlling EV’s production. We found a kinase inhibitor, APY0201, which significantly increased EV secretion through upregulation of intracellular sterol synthesis and the volume of intracellular multivesicular bodies (MVBs). APY0201 specifically caused the decrease of AMP-activated protein kinase (AMPK) phosphorylation and activation of sterol regulatory element-binding protein (SREBP1), a pivotal transcription factor of sterol synthesis gene expression. In addition, both AMPK agonist and SREBP inhibitor deteriorate augmented EV production induced by APY0201. Ectopic expression of AMPK and SREBP1 corroborated that AMPK and SREBP1 are two major host factors governing the production of exosome-like EVs. Taken together, we identified that APY0201 is a novel kinase inhibitor targeting AMPK-SREBP1 pathway which is important for EV biogenesis and release. Our findings might pave the way to achievable finely upregulated EV production.
Project description:Membrane contact sites (MCS) are intracellular regions where two organelles come closer to exchange information and material. The majority of the endoplasmic reticulum (ER) MCS are attributed to the ER-localized tether proteins VAPA, VAPB, and MOSPD2. These recruit other proteins to the ER by interacting with their FFAT motifs. Here, we describe MOSPD1 and MOSPD3 as ER-localized tethers interacting with FFAT motif-containing proteins. Using BioID, we identify proteins interacting with VAP and MOSPD proteins and find that MOSPD1 and MOSPD3 prefer unconventional FFAT-related FFNT (two phenylalanines [FF] in a neutral tract) motifs. Moreover, VAPA/VAPB/MOSPD2 and MOSPD1/MOSPD3 assemble into two separate ER-resident complexes to interact with FFAT and FFNT motifs, respectively. Because of their ability to interact with FFNT motifs, MOSPD1 and MOSPD3 could form MCS between the ER and other organelles. Collectively, these findings expand the VAP family of proteins and highlight two separate complexes in control of interactions between intracellular compartments.
Project description:The biogenesis of extracellular vesicles (EVs) is a regulated process, driven by mechanisms at specific subcellular milieus. Sphingomyelinases (SMases), which metabolize sphingomyelin in membranes, play a role in EV biogenesis. Their metabolic product, ceramide, induces invaginations at the endosome or blebbing from the plasma membrane, both important in EV generation. Here, we sought to evaluate the impact of SMase inhibition on EV protein and RNA cargoes. For this, we treated human MCF7 cells with the neutral SMase (NSM) inhibitor GW4869 or the acid SMase (ASM) inhibitor FTY720. EVs were then purified from the conditioned media of control or inhibitor-treated cells and characterized by a variety of approaches, including LC-MS/MS and RNA-sequencing. SMase inhibition resulted in morphological and phenotypic changes in the heterogeneous EV population. Strikingly, NSM inhibition resulted in a depletion of nanoparticles, as well as a decrease in the RNA and protein content of EVs, with a marked reduction in endosomal, spliceosomal, and translation-related proteins. Furthermore, we observed a reduction in the overall RNA-binding proteins (RBPs) in EVs released by cells treated with the NSM-inhibitor. In contrast, the ASM-inhibitor treatment, which appears to reduce plasma membrane-derived vesicles, elicited an inverse response, leading to an increase in RBP and associated machineries within the released EV population. RNA sequencing of these EV revealed changes in the RNA biotypes composition, with an increase in protein coding transcripts. Interestingly, ASM-inhibitor resulting EVs induced increased cell migration and protein translation in recipient MCF10A cells. These results suggest that SMase-dependent vesiculation represents a major route of RBP and RNA trafficking outside the cell, via endosomal pathways.
Project description:Astrocytes are essential cells of the central nervous system, characterized by dynamic relationships with neurons that range from functional metabolic interactions and regulation of neuronal firing activities, to the release of neurotrophic and neuroprotective factors. In Parkinson’s disease (PD), dopaminergic neurons are a vulnerable population progressively lost during the course of the disease, but the effects of PD on astrocytes and astrocyte-to-neuron communication remains mostly unknown. This study focuses on the effects of the PD-related mutation LRRK2 G2019S in astrocytes, using patient-derived induced pluripotent stem cells. We report the alteration of extracellular vesicle (EV) biogenesis in astrocytes, and we identify the abnormal accumulation of key PD-related proteins within multi vesicular bodies (MVBs). We found that dopaminergic neurons internalize astrocyte-secreted EVs but LRRK2 G2019S EVs are abnormally enriched in the neurites and provide only marginal neurotrophic support to dopaminergic neurons. Thus, dysfunctional astrocyte-to-neuron communication via altered EV biological properties could participate in the progression of PD.
Project description:Extracellular vesicles (EVs) enable cell-to-cell communication in the nervous system essential for development and adult function. Endosomal Sorting Complex Required for Transport (ESCRT) complex proteins regulate EV formation and release. Recent work shows loss of function (LOF) mutations in, CHMP1A, which encodes one ESCRT-III member, cause autosomal recessive microcephaly with pontocerebellar hypoplasia in humans (Mochida et al., 2012). Here we show CHMP1A is required for maintenance of progenitors in human cerebral organoids and that mouse Chmp1a is required for progenitor proliferation in cortex and cerebellum and specifically for sonic hedgehog (SHH) mediated proliferation through SHH secretion. CHMP1A mutation reduces intraluminal vesicle (ILV) formation in multivesicular bodies (MVBs), and EV release. SHH protein is present on a subset of EVs marked by a unique set of proteins we call ART-EVs. CHMP1A’s requirement in formation of ART-EVs and other EVs provides a model to elucidate EV functions in multiple brain processes.
Project description:Mice were intravenously injected with extracellular vesicles (EVs) isolated from B16V wt (n=3) or BAG6KO (n=3) cells or with PBS (n=3) as a control for 4 weeks on a weekly basis. Since B-16V melanoma cells colonise the lung upon intravenous injection and referring to current literature, we hypothesise that melanoma EVs alter the (immune-) microenvironment of the lung to prepare a pre-metastatic niche. Based on current literature and own previous experiments identifying BAG6 as an immunoregulatory protein that is also involved in the biogenesis of EVs, we are particularly interested in differences between the immune signature upon wt EV treatment compared to BAG6KO EV treatment.
Project description:Osteolineage cells represent one of the critical bone marrow niche components that support maintenance of hematopoietic stem and progenitor cells (HSPCs). Recent studies demonstrate that extracellular vesicles (EVs) regulate stem cell development via horizontal transfer of bioactive cargo, including microRNAs (miRNAs). Here, we characterize the miRNA profile of EVs secreted by human osteoblasts and study their biological effect of on human umbilical cord blood-derived CD34+ HSPCs by sequencing, gene expression and biochemical analyses. Using next-generation sequencing we show that osteoblast-derived EVs contain highly abundant miRNAs specifically enriched in EVs, including critical regulators of hematopoietic proliferation (e.g., miR-29a). EV treatment of CD34+ HSPCs alters the expression of candidate miRNA targets, such as HBP1, BCL2 and PTEN. Furthermore, EVs enhance proliferation of CD34+ cells and their immature subsets in growth factor-driven ex vivo expansion cultures. Importantly, EV-expanded cells retain their differentiation capacity in vitro and show successful engraftment in NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice in vivo. These discoveries reveal a novel osteoblast-derived EV-mediated mechanism for regulation of HSPC proliferation and warrant consideration of EV-miRNAs for the development of expansion strategies to treat hematological disorders.
Project description:Hematopoietic stem and progenitor cells (HSPCs) rely upon cellular crosstalk, including extracellular vesicles (EVs) for lifelong niche occupancy and cellular function. Vesicle secretion is tightly linked to intracellular homeostasis; however, these mechanisms are poorly understood in HSPCs, particularly at the single-cell level. In this study, we target ceramide-dependent EV secretion by pharmacologic blockade in ex vivo expanded HSPCs. We use these cells to investigate single-cell resolution of short-term and delayed transcriptional changes induced by ceramide-EV inhibition.
Project description:Cellular crosstalk within the bone marrow niche maintains hematopoietic stem and progenitor cell (HSPC) integrity and safeguards lifelong blood and immune cell production. Deeper understanding of reciprocal niche signals governing crucial properties of HSPCs is relevant to the pathophysiology of blood disorders and improving HSPC transplantation. Extracellular vesicles (EVs) are key factors of the HSPC secretome, providing signals that regulate homeostasis and stemness. Here we demonstrate ex vivo blockade of ceramide-dependent vesicle secretion from HSPCs activates an integrated stress response (ISR), promoting downstream mTOR inhibition and metabolic quiescence. Crucially, ceramide-EV depletion leads to striking improvements in long-term transplantation. The aggregate findings link ceramide-dependent EV secretion and the ISR as a regulatory dyad guarding HSPC homeostasis and long-term fitness. Translationally, these data support exploration of ceramide inhibition during ex vivo maintenance of HSPCs for adoptive transfer.