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Exosome release is regulated by mTORC1 via a Rab27A-dependent mechanism

ABSTRACT: Exosomes are small membrane-bound vesicles released into extracellular spaces by many types of cells. These nanovesicles carry proteins, mRNA and miRNA and are involved in cell waste management and intercellular communication. In the present study we show that exosome release, which leads to net loss of cellular membrane and protein content, is negatively regulated by mechanistic target of rapamycin complex 1 (mTORC1). We find that in cells and animal models exosome release is inhibited by sustained activation of mTORC1, leading to intracellular accumulation of CD63-positive exosome precursors. Inhibition of mTORC1 by rapamycin or nutrient and growth factor deprivation stimulates exosome release, which occurs concomitantly with autophagy. The drug-stimulated release is blocked by siRNA-mediated downregulation of small GTPase Rab27A. Analysis of the cargo content in exosomes released from rapamycin treated cells reveals that inhibition of mTORC1 does not alter its protein and miRNA profiles. These observations demonstrate that exosome release, like autophagy, is negatively regulated by mTORC1 in response to changes in nutrient and growth factor conditions

ORGANISM(S): Homo sapiens

PROVIDER: GSE114235 | GEO | 2019/03/05

REPOSITORIES: GEO

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Project description:Background: Cellular communication among different types of vascular cells is indispensable for maintenance of vascular homeostasis and prevention of atherosclerosis (AS). However, the biological mechanism involved in cellular communication among these cells and whether this biological mechanism can be used to treat AS remain unknown. This study hypothesizes that endothelial autophagy mediates the cellular communication of vascular tissue through exosome-mediated delivery of AS-related genes.Methods: ApoE-/- mice fed with high-fat diet (HFD) were received rapamycin to activate autophagy, or were intravenously injected with adeno-associated virus (AAV) vectors carrying shRNA against Atg7 mRNA under the Tie (tyrosine kinase) promoter to specifically inhibit endothelial autophagy. miRNA microarray, in vivo and in vitro experiments and human vascular tissues/blood vessels were used to explore the molecular mechanisms of atheroprotective effect of endothelial autophagy. Exosomes were isolated and characterized. Immunofluorescence and exosomes coculture experiments were conducted to examine the role of endothelial autophagy in regulating communication between endothelial cells (ECs) and smooth muscle cells (SMCs) via exosome.Results: Endothelial autophagy was inhibited in ECs of thoracic aortas in HFD fed ApoE-/- mice. Furthermore, rapamycin alleviated HFD-triggered atherosclerotic burden and endothelial dysfunction, while endothelial-specific depletion of Atg7 aggravated atherosclerotic burden. miRNA microarray, in vivo and in vitro experiments and human vascular tissues analysis revealed that endothelial autophagy alleviated endothelial dysfunction by downregulating miR-204-5p expression by directly targeting BCL2 to regulate apoptosis in ECs. Moreover, endothelial autophagy decreased miR-204-5p expression by loading this molecule into multivesicular bodies and secreting them out of cells via exosomes, and ECs-derived exosomal miR-204-5p could be transferred to SMCs, antagonized SMCs calcification.Conclusions: Our study first revealed that endothelial autophagy was a critical regulator of atherogenesis by transferring miR-204-5p from ECs to SMCs by exosomes, and endothelial autophagy activation by rapamycin, could alleviate AS in a “one stone hit two birds” manner.

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Exosome release is regulated by mTORC1 via a Rab27A-dependent mechanism

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