Biology subjects

Saftics, A.

Publications and source records attributed to Saftics, A..

3 recordsLinked to original sources

bioRxiv2025

State-dependent release of extracellular particles with distinct α2,6-sialylation patterns and small RNA cargo related to neuroinflammation

Neuroinflammation is a significant contributor to neurodegenerative diseases, including Alzheimers disease, Parkinsons disease, and related dementias; yet peripheral biomarkers for neuroinflammation remain an unmet medical need. Microglia, the resident immune cells of the central nervous system, play a dual role in maintaining homeostasis under physiological conditions and driving neuronal damage when chronically dysregulated. One mechanism by which microglia influence their environment is through the release of extracellular vesicles (EVs) and non-vesicular extracellular particles (NVEPs), which can serve as biomarkers the reflect cellular states. Here, we systematically isolated and characterized microglia-derived EVs and NVEPs under pro- and anti-inflammatory conditions and profiled their small RNA cargo by small RNA sequencing. We validated these findings in human iPSC-derived microglia and further recapitulated them in EVs and NVEPs from mouse brain and plasma. Using an engineered mouse model, we were able to isolate plasma microglia-specific EVs in vivo and demonstrated that their RNA cargo reflects their inflammatory state. Importantly, microglial EVs and NVEPs display distinct 2,6-sialylation patterns and small RNA signatures implicated in neurological diseases. These findings demonstrate that microglia-derived EVs and NVEPs cargo reflect microglial cellular state and establish them as putative minimally non-invasive biomarkers of early-stage neurodegenerative diseases.

neuroscience↗

bioRxiv2023

Exomap1 mouse: a transgenic model for in vivo studies of exosome biology

Exosomes are small extracellular vesicles (sEVs) of [~]30-150 nm in diameter that have the same topology as the cell, are enriched in selected exosome cargo proteins, and play important roles in health and disease. To address large unanswered questions regarding exosome biology in vivo, we created the exomap1 transgenic mouse model. In response to Cre recombinase, exomap1 mice express HsCD81mNG, a fusion protein between human CD81, the most highly enriched exosome protein yet described, and the bright green fluorescent protein mNeonGreen. As expected, cell type-specific expression of Cre induced the cell type-specific expression of HsCD81mNG in diverse cell types, correctly localized HsCD81mNG to the plasma membrane, and selectively loaded HsCD81mNG into secreted vesicles that have the size ([~]80 nm), topology (outside out), and content (presence of mouse exosome markers) of exosomes. Furthermore, mouse cells expressing HsCD81mNG released HsCD81mNG-marked exosomes into blood and other biofluids. Using high-resolution, single-exosome analysis by quantitative single molecule localization microscopy, we show here that that hepatocytes contribute [~]15% of the blood exosome population whereas neurons contribute <1% of blood exosomes. These estimates of cell type-specific contributions to blood EV population are consistent with the porosity of liver sinusoidal endothelial cells to particles of [~]50-300 nm in diameter, as well as with the impermeability of blood-brain and blood-neuron barriers to particles >5 nm in size. Taken together, these results establish the exomap1 mouse as a useful tool for in vivo studies of exosome biology, and for mapping cell type-specific contributions to biofluid exosome populations. In addition, our data confirm that CD81 is a highly-specific marker for exosomes and is not enriched in the larger microvesicle class of EVs.

cell biology↗

bioRxiv2023

Syntenin and CD63 Promote Exosome Biogenesis from the Plasma Membrane by Blocking Cargo Endocytosis

Exosomes are small extracellular vesicles important in health and disease. Syntenin is thought to drive the biogenesis of CD63 exosomes by recruiting Alix and the ESCRT machinery to endosomes, initiating an endosome-mediated pathway of exosome biogenesis. Contrary to this model, we show here that syntenin drives the biogenesis of CD63 exosomes by blocking CD63 endocytosis, thereby allowing CD63 to accumulate at the plasma membrane, the primary site of exosome biogenesis. Consistent with these results, we find that inhibitors of endocytosis induce the exosomal secretion of CD63, that endocytosis inhibits the vesicular secretion of exosome cargo proteins, and that high-level expression of CD63 itself also inhibits endocytosis. These and other results indicate that exosomes bud primarily from the plasma membrane, that endocytosis inhibits their loading into exosomes, that syntenin and CD63 are expression-dependent regulators of exosome biogenesis, and that syntenin drives the biogenesis of CD63 exosomes even in Alix knockout cells.

cell biology↗