Biology subjects

Lehoux, S. D.

Publications and source records attributed to Lehoux, S. D..

6 recordsLinked to original sources

bioRxiv2022

Plasma ST6Gal1 is Dispensable for IgG Sialylation

The glycosylation of IgG has attracted increased attention due to the impact of N-glycan modifications at N297 on IgG function, acting primarily through modulation of Fc domain conformation and Fc{gamma} receptor binding affinities and signaling. However, the mechanisms regulating IgG glycosylation and especially 2,6-sialylation of its N-glycan remain poorly understood. We observed previously that IgG is normally sialylated in mice with B cells lacking the sialyltransferase ST6Gal1. This supported the hypothesis that IgG may be sialylated outside of B cells, perhaps through the action of hepatocyte-released plasma ST6Gal1. Here we demonstrate that this model is incorrect. Animals lacking hepatocyte expressed ST6Gal1 retain normal IgG 2,6-sialylation, despite the lack of detectable ST6Gal1 in plasma. Moreover, we confirmed that B cells were not a redundant source of IgG sialylation. Thus, while 2,6-sialylation is lacking in IgG from mice with germline ablation of ST6Gal1, IgG 2,6-sialylation is normal in mice lacking ST6Gal1 in either hepatocytes or B cells. These results indicate that IgG 2,6-sialylation arises after release from a B cell, but is not dependent on plasma-localized ST6Gal1 activity.

immunology↗

bioRxiv2020

The restricted nature of protein glycosylation in the mammalian brain

Glycosylation is essential to brain development and function, though prior studies have often been limited to a single analytical technique. Using several methodologies, we analyzed Asn-linked (N-glycans) and Ser/Thr/Tyr-linked (O-glycans) protein glycosylation between brain regions and sexes in mice. Brain N-glycans were surprisingly less complex in sequence and variety compared to other tissues, consisting predominantly of high-mannose precursors and fucosylated/bisected structures. Most brain O-glycans were unbranched, sialylated O-GalNAc and O-mannose structures. A consistent pattern was observed between regions, and sex differences were minimal compared to those observed in plasma. Brain glycans correlate with RNA expression of their synthetic enzymes, and analysis of all glycosylation genes in humans showed a global downregulation in the brain compared to other tissues. We hypothesize that the restricted repertoire of protein glycans arises from their tight regulation in the brain. These results provide a roadmap for future studies of glycosylation in neurodevelopment and disease.

neuroscience↗

bioRxiv2020

Mucin glycans signal through the sensor kinase RetS to inhibit virulence-associated traits in Pseudomonas aeruginosa

Mucus is a densely populated ecological niche that coats all epithelia, and plays a critical role in protecting the human body from infections. Although traditionally viewed as a physical barrier, emerging evidence suggests that mucus can directly suppress virulence traits in opportunistic pathogens like Pseudomonas aeruginosa. However, the molecular mechanisms by which mucus affords this protection are unclear. Here, we show that mucins, and particularly their associated glycans, activate the sensor kinase RetS via its Dismed2 domain in P. aeruginosa. We find that this RetS-dependent signaling leads to the direct inhibition of the GacS-GacA two-component system, the activity of which is associated with a chronic infection state. This signaling includes the downregulation of the type VI secretion system (T6SS), and prevents T6SS-dependent bacterial killing by P. aeruginosa. Overall, these results shed light on how mucus impacts P. aeruginosa behavior in the human host, and may inspire novel approaches for controlling P. aeruginosa infections.

microbiology↗

bioRxiv2020

Differential glycosylation of alpha-1-acid glycoprotein (AGP-1) contributes to its functional diversity.

Alpha-1-acid glycoprotein (AGP-1) is a positive acute phase glycoprotein with uncertain functions. Serum AGP-1 (sAGP-1) is primarily derived from hepatocytes and circulates as 12 to 20 different glycoforms. We isolated a glycoform secreted from stimulated human neutrophils (nAGP-1). Its peptide sequence was identical to hepatocyte-derived sAGP-1, but nAGP-1 differed from sAGP-1 in its chromatographic behaviour, electrophoretic mobility, and glycosylation. The function of these two glycoforms also differed. sAGP-1 activated neutrophil adhesion, migration and NETosis in a dose-dependent fashion, while nAGP-1 was ineffective as an agonist for these events. Furthermore, sAGP-1, but not nAGP-1, inhibited LPS-stimulated NETosis. However, nAGP-1 inhibited sAGP-1-stimulated neutrophil NETosis. The discordant effect of the differentially glycosylated AGP-1 glycoforms was also observed in platelets where neither of the AGP-1 glycoforms alone stimulated aggregation of washed human platelets, but sAGP-1, and not nAGP-1, inhibited aggregation induced by Platelet-activating Factor (PAF) or ADP, but not by thrombin. These functional effects of sAGP-1 correlated with intracellular cAMP accumulation and were accompanied by phosphorylation of the PKA substrate Vasodialator stimulated phosphoprotein (VASP) and reduction of Akt, ERK, and p38 phosphorylation. Thus, the sAGP-1 glycoform limits platelet reactivity while nAGP-1 glycoform also limits pro-inflammatory actions of sAGP-1. These studies identify new functions for this acute phase glycoprotein and demonstrate that the glycosylation of AGP-1 controls its effects on two critical cells of acute inflammation.

biochemistry↗

bioRxiv2019

A schizophrenia risk locus alters brain metal transport and plasma glycosylation

A common missense variant in SLC39A8 is convincingly associated with schizophrenia and several additional phenotypes. Homozygous loss-of-function mutations in SLC39A8 result in undetectable serum manganese (Mn) and a Congenital Disorder of Glycosylation (CDG) due to the exquisite sensitivity of glycosyltransferases to Mn concentration. Here, we identified several Mn-related changes in human carriers of the common SLC39A8 missense allele. Analysis of structural brain MRI scans showed a dose-dependent change in the ratio of T2w to T1w signal in several regions. Comprehensive trace element analysis confirmed a specific reduction of only serum Mn, and plasma protein N-glycome profiling revealed reduced complexity and branching. N-glycome profiling from two individuals with SLC39A8-CDG showed similar but more severe alterations in branching that improved with Mn supplementation, suggesting that the common variant exists on a spectrum of hypofunction with potential for reversibility. Characterizing the functional impact of this variant will enhance our understanding of schizophrenia pathogenesis and identify novel therapeutic targets and biomarkers of disease. SummaryA common variant in the manganese transporter SLC39A8 is associated with numerous phenotypes including schizophrenia. Mealer et. al. presents an in-depth analysis of brain MRI and plasma glycomics in human carriers of the common variant, identifying several manganese-related changes with potential for diagnostic and therapeutic biomarker development.

biochemistry↗

bioRxiv2019

Glycosylation of Zika Virus Is Important in Host-Virus Interaction and Pathogenesis

Zika virus (ZIKV) is a global public health issue due to its association with severe developmental disorders in infants and neurological disorders in adults. Because ZIKV uses glycosylation of its envelope (E) protein to interact with host cell receptors to facilitate entry, these interactions could also be important for designing therapeutics and vaccines. Due to a lack of information about Asn-linked (N-glycans) on ZIKV E, we analyzed ZIKV E of various strains derived from different cells. ZIKV E proteins are extensively modified with oligomannose-, hybrid- and complex-N-glycans of a highly heterogeneous nature. Host cell-surface glycans correlated strongly with the glycomic features of ZIKV E. Mechanistically, we discovered that ZIKV N-glycans are important in viral pathogenesis, as mannose-specific C-type lectins DC-SIGN and L-SIGN mediate cell entry of ZIKV. Our findings represent the first detailed mapping of N-glycans on ZIKV E of various strains and their functional significance.

biochemistry↗