Davey, G. P. | Search bioRxiv

bioRxiv2022

Mitochondrial complex I controls blood brain barrier permeability

Mitochondrial electron transport chain (ETC) complexes are key mediators of energy metabolism in astrocytes and neurons, with subsequent effects on memory, behaviour and neurodegeneration. Mitochondrial dysfunction and increased blood brain barrier (BBB) permeability are known pathologies in Parkinsons and Alzheimers diseases. However, knowledge of how ETC activities regulate metabolic flux and influence permeability in the BBB is lacking. Using metabolic flux control analysis we show that complex I is a critical control point for oxidative flux and permeability in brain microvascular endothelial cells derived from human induced pluripotent stem cells. Inhibition of complex I activity immediately reduced the transendothelial electrical resistance (TEER) by 60%, leading to an increase in protein transport across the BBB. These events were accompanied by a transient reduction in ATP that was recovered, along with TEER values, over an extended time period. Furthermore, while inhibition of downstream complexes III or IV decreased oxygen respiration rates, no effects on BBB permeability were identified, due to compensatory glycolytic flux and maintenance of ATP synthesis. These data show that mitochondrial complex I is critical for maintaining energy production in endothelial cells and transiently controls BBB permeability, which may contribute to brain disorders where complex I dysfunction is a hallmark.

neuroscience↗

bioRxiv2022

In silico analysis of the human milk oligosaccharide glycome reveals key enzymes of their biosynthesis

Human milk oligosaccharides (HMOs) form the third most abundant component of human milk and are known to convey several benefits to the neonate, including protection from viral and bacterial pathogens, training of the immune system, and influencing the gut microbiome. As HMO production during lactation is driven by enzymes that are common to other glycosylation processes, we adapted a model of mucin-type GalNAc-linked glycosylation enzymes to act on free lactose. We identified a subset of 11 enzyme activities that can account for 206 of 226 distinct HMOs isolated from human milk, and constructed a biosynthetic reaction network that identifies 5 new core HMO structures. A comparison of monosaccharide compositions demonstrated that the model was able to discriminate between two possible groups of intermediates between major subnetworks, and to assign possible structures to several previously uncharacterised HMOs. The effect of enzyme knockouts is presented, identifying {beta}-1,4-galactosyltransferase and {beta}-1,3-N-acetylglucosaminyltransferase as key enzyme activities involved in the generation of the observed HMO glycosylation patterns. The model also provides a synthesis chassis for the most common HMOs found in lactating mothers.

biochemistry↗