Selective packaging of mitochondrial proteins into extracellular vesicles prevents the release of mitochondrial DAMPs

Abstract

Most cells constitutively secrete mitochondrial DNA and proteins in extracellular vesicles (EVs), small vesicles that allow the transfer of material between cells. While under pro-inflammatory conditions, this mitochondrial content can further enhance inflammation, its role in the absence of inflammation remains elusive. Here, we demonstrate that mitochondrial components found in normal EVs are not pro-inflammatory and that cells actively prevent the packaging of proinflammatory, damaged mitochondrial proteins into EVs. Importantly, the distinction between material to be included into EVs and damaged mitochondrial content to be excluded was dependent on their selective targeting to one of two distinct Mitochondria-Derived Vesicles (MDVs) pathways, MDVs being small vesicles carrying material between mitochondria and other organelles. Sorting nexin 9 (Snx9)-dependent MDVs were required to target mitochondrial proteins into EVs, while the Parkinson's disease related protein Parkin blocked this process by targeting damaged mitochondrial content to lysosomes. Our results thus provide important insight into the interplay between mitochondrial quality control mechanisms and mitochondria driven immune responses.

Mitochondria-containing Extracellular Vesicles (EV) Reduce Mouse Brain Infarct Sizes and EV/HSP27 Protect Ischemic Brain Endothelial Cultures

“…7e). It can be inferred from our western blot results and published reports (38,39) that the MV-mediated increase in recipient endothelial cell ATP levels is associated with the presence of functional mitochondria and mitochondrial proteins and their transfer into the recipient cells. High throughput proteomic analysis revealed 89 types of mitochondrial proteins in MVs vs. a single type in EXOs isolated from hCMEC/D3 cells (32).…”

“…We have used EVs: a natural nanocarrier, for this one, two-punch delivery strategy. EVs are known to incorporate mitochondrial components such as mitochondria, mitochondrial DNA, and proteins along with their inherent nucleic acid, lipids, and protein cargoes during their biogenesis (39,(46)(47)(48). On the other hand, endothelial overexpression of HSP27 in a transgenic mouse model of focal cerebral ischemia decreased mice brain infarct volume compared to neuronallyoverexpressed HSP27 and placebo mice (9,10,49).…”

“…Mitochondria, the central metabolic hub of cells, are essential organelles especially in high metabolic rate organs such as the brain (68). Mitochondria regulate and are involved in critical cellular events such as the production of cellular energy by ATP synthesis, induction of apoptosis, cell reproduction, growth, and differentiation, calcium homeostasis, immune activation, and mitophagy (39,68,69). Therefore, it is essential to maintain the quantity and quality of mitochondria for cell survival and tissue homeostasis.…”

Metabolism and Innate Immunity Meet at the Mitochondria

“…It will be fascinating to address whether metabolic signalling programmes control the selective packaging and extracellular extrusion of mtDNA via exosomes. Recently, Todkar et al (2021) reported that mitochondrial derived vesicles ( Sugiura et al, 2014 ) control the incorporation of mitochondrial proteins and mtDNA into exosomes in cultured cells. Finally, what is the physiological role of regulated mtDNA release and can it be manipulated, for example in order to improve chemotherapy or treat autoimmune diseases?…”

Defective mitochondrial-lysosomal axis promotes extracellular vesicles release of mitochondrial components in Huntington’s Disease

“…Recent work has revealed an intimate interconnection between classical autophagy machinery and autophagy-dependent EVs pathways that facilitates the disposal of unwanted genetic material and proteins (Leidal et al, 2020). Additionally, recent evidence suggests that EVs transfer mitochondrial DNA (mtDNA) and mitochondrial proteins intercellularly (Pasquale Sansone et al, 2017; Kiran Todkar et al, 2021; Xiaowan Wang et al, 2020); however, the biological relevance, the mechanisms underlying this process and the contribution in pathophysiological contexts are not clear. Neuronal-derived EVs (NDE) are a subpopulation of the central nervous system (CNS)-derived EVs that can be isolated from human fluids, including blood plasma and cerebrospinal fluid, to investigate their neuron-specific contents (Yousif et al, 2021).…”