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, it is shown 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). It is found 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 significantly alter its majority 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.
Highlights
Exosomes are small membrane-bound vesicles (40–200 nm in diameter) that are released to the extracellular space by most cell types under both physiological and pathological conditions.[1]
TSC2 normally functions in complex with TSC1 to elicit its negative activity on mechanistic target of rapamycin complex 1 (mTORC1).[8]. To determine whether TSC1 is involved in exosome release, we examined the effect of TSC1 downregulation on the process
We show that exosome release, like autophagic flux, is regulated by mTORC1
Summary
Exosomes are small membrane-bound vesicles (40–200 nm in diameter) that are released to the extracellular space by most cell types under both physiological and pathological conditions.[1]. Despite many years of study, our understanding on the basic biology of exosomes remains limited It is currently unclear whether formation and secretion of exosomes are regulated and whether exosomes alter their cargo content in response to changes in intracellular and extracellular conditions.[1c]. MVBs can either merge with lysosomes for cargo degradation or fuse with the plasma membrane to release ILVs into the extracellular space as exosomes. As part of endosomal trafficking, fusion of MVBs with the plasma membrane and release of exosomes are critical for delivery of extracellular messengers and for membrane homeostasis, lysosome function, and autophagy. We show that this secretion-dependent mechanism, like autophagy, is regulated by mTORC1 in response to changes in nutrient and growth factor conditions
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