Synaptotagmin 5 regulates Ca2+-dependent Weibel-Palade body exocytosis in human endothelial cells.

Elevations of intracellular free Ca2+ concentration ([Ca2+]i) are a potent trigger for Weibel-Palade body (WPB) exocytosis and secretion of von Willebrand factor (VWF) from endothelial cells; however, the identity of WPB-associated Ca2+-sensors involved in transducing acute increases in [Ca2+]i into granule exocytosis remains unknown. Here, we show that synaptotagmin 5 (SYT5) is expressed in human umbilical vein endothelial cells (HUVECs) and is recruited to WPBs to regulate Ca2+-driven WPB exocytosis. Western blot analysis of HUVECs identified SYT5 protein, and exogenously expressed SYT5-mEGFP localised almost exclusively to WPBs. shRNA-mediated knockdown of endogenous SYT5 (shSYT5) reduced the rate and extent of histamine-evoked WPB exocytosis and reduced secretion of the WPB cargo VWF-propeptide (VWFpp). The shSYT5-mediated reduction in histamine-evoked WPB exocytosis was prevented by expression of shRNA-resistant SYT5-mCherry. Overexpression of SYT5-EGFP increased the rate and extent of histamine-evoked WPB exocytosis, and increased secretion of VWFpp. Expression of a Ca2+-binding defective SYT5 mutant (SYT5-Asp197Ser-EGFP) mimicked depletion of endogenous SYT5. We identify SYT5 as a WPB-associated Ca2+ sensor regulating Ca2+-dependent secretion of stored mediators from vascular endothelial cells.

Parental age effect on the longevity and healthspan in Drosophila melanogaster and Caenorhabditis elegans.

Several studies have investigated the effect of parental age on biological parameters such as reproduction, lifespan, and health; however, the results have been inconclusive, largely due to inter-species variation and/or modest effect sizes. Here, we examined the effect of parental age on the lifespan, reproductive capacity, and locomotor activity of genetic isogenic lines of the nematode Caenorhabditis elegans and the fruit fly Drosophila melanogaster. We found that the progeny of successive generations of old parents had significantly shorter lifespans than the progeny of young parents in both species. Moreover, we investigated the fertility, fecundity, and locomotor activity of C. elegans. Interestingly, both the shorter lifespan and deteriorated healthspan of the progeny were significantly improved by switching to only one generation of younger parents. Collectively, these data demonstrate that the detrimental effect of older parental age on the longevity of the progeny can be reversed, suggesting the existence of a beneficial non-genetic mechanism.

Cellular sensing of extracellular purine nucleosides triggers an innate IFN-ß response.

Mechanisms linking immune sensing of DNA danger signals in the extracellular environment to innate pathways in the cytosol are poorly understood. Here, we identify a previously unidentified immune-metabolic axis by which cells respond to purine nucleosides and trigger a type I interferon-ß (IFN-ß) response. We find that depletion of ADA2, an ectoenzyme that catabolizes extracellular dAdo to dIno, or supplementation of dAdo or dIno stimulates IFN-ß. Under conditions of reduced ADA2 enzyme activity, dAdo is transported into cells and undergoes catabolysis by the cytosolic isoenzyme ADA1, driving intracellular accumulation of dIno. dIno is a functional immunometabolite that interferes with the cellular methionine cycle by inhibiting SAM synthetase activity. Inhibition of SAM-dependent transmethylation drives epigenomic hypomethylation and overexpression of immune-stimulatory endogenous retroviral elements that engage cytosolic dsRNA sensors and induce IFN-ß. We uncovered a previously unknown cellular signaling pathway that responds to extracellular DNA-derived metabolites, coupling nucleoside catabolism by adenosine deaminases to cellular IFN-ß production.