Biology subjects

Jacquemyn, M.

Publications and source records attributed to Jacquemyn, M..

4 recordsLinked to original sources

bioRxiv2025

Random mutagenesis of influenza hemagglutinin identifies new sites which modulate its acid-stability and cleavability

The structural instability of influenza hemagglutinin (HA) is related to its function in low pH-mediated membrane fusion, which requires prior cleavage of the premature HA0 by a host protease. The precise determinants underlying the stability and cleavability of HA remain to be fully understood and have implications for risk assessment of zoonotic influenza A viruses (IAV), viral transmissibility and vaccine production. To address this, we conducted random mutagenesis on early 2009 pandemic H1 HA, followed by selection of acid-stable viruses and detailed profiling of the mutant HAs. This resulted in identification of four mutations, which increase the acid-stability and decrease the fusion-promoting activity of H1 HA, without compromising viral entry and replication in cells. The newly recognized mutations are situated in the globular head, vestigial esterase and membrane-proximal part of H1 HA, in regions involved in the refolding of HA at low pH. A fifth mutation, D346N, is located in the cleavage loop and renders H1 HA0 12-fold resistant to trypsin activation, whereas its cleavage by transmembrane serine protease 2 (TMPRSS2) is not affected. Along this line, we found that the poor cleavage of H16 HA0, which is unusual in carrying an N346 residue, only applies when it is performed by extracellular proteases. Since H16 HA also exhibits a very low fusion pH, we propose that gull H16N3 virus may carry a much more stable HA than other avian IAVs. Collectively, our mutagenesis approach revealed new determinants of HA stability and cleavability, with relevance for viral surveillance and vaccine production. IMPORTANCEThe presence of influenza A viruses (IAV) throughout the animal world, particularly avian species, represents a constant threat for zoonotic infections or a new influenza pandemic. To be transmissible among humans, a zoonotic IAV requires mutations in the viral hemagglutinin (HA) that increase the acid-stability of this mediator of viral entry. Understanding the determinants of HA stability is also important to produce vaccines with high shelf-stability. By combining random mutagenesis with selection of acid-stable viruses, we identified new stabilizing mutations located in different parts of HA. Besides, we discovered a mutation that renders HA resistant to cleavage by extracellular proteases. Since this residue is naturally occurring in H16 HA, we propose that the gull H16N3 virus may differ from other avian IAVs in carrying an environmentally stable HA. Hence, our study delivers new insight in factors that modulate HA acid-stability and cleavability, with relevance for viral surveillance and vaccine production.

microbiology↗

bioRxiv2023

Aberrant N-glycosylation in pathogenic variants of adenosine deaminase 2 underlying human ADA2 deficiency

Human deficiency of adenosine deaminase 2 (DADA2) is an autoinflammatory disease caused by pathogenic variants in ADA2 that lead to impaired deaminase activity. Recently, a lysosomal function of ADA2 has been proposed but an intracellular form of the protein has not yet been characterized. Here, we analyze protein expression of mutant ADA2 in human monocyte-derived macrophages from 10 DADA2 patients. We identify an intracellular low-molecular-weight (LMW) form of ADA2 that undergoes glycan trimming by -mannosidases and is absent in DADA2 macrophages. Subcellular fractionation and immunofluorescence microscopy demonstrate that LMW-ADA2 is localized in the lysosomes. By overexpression of 34 ADA2 variants in HEK293T and U-937 cells, we show that absence of LMW-ADA2 strongly correlates with reduced deaminase activity and predicts variant pathogenicity. In conclusion, we describe a previously unreported intracellular hypoglycosylated form of ADA2 and establish the absence of this LMW-ADA2 as a cellular characteristic of DADA2. Thereby, we introduce a protein correlate of the recently described lysosomal form of ADA2. SummaryEhlers et al. demonstrate that mutant ADA2 fails to undergo glycan processing beyond the ER leading to the absence of intracellular low-molecular-weight (LMW) ADA2 in DADA2 patients macrophages. LMW-ADA2 localizes to the lysosomes and can be generated from extracellular wild-type ADA2.

immunology↗

bioRxiv2021

A modular platform for engineering function ofnatural and synthetic biomolecular condensates

Phase separation is emerging as a universal principle for how cells use dynamic subcompartmentalization to organize biochemical reactions in time and space1,2. Yet, whether the emergent physical properties of these biomolecular condensates are important for their biological function remains unclear. The intrinsically disordered protein PopZ forms membraneless condensates at the poles of the bacterium Caulobacter crescentus and selectively sequesters kinase-signaling cascades to regulate asymmetric cell division3-5. By dissecting the molecular grammar underlying PopZ phase separation, we find that unlike many eukaryotic examples, where unstructured regions drive condensation6,7, a structured domain of PopZ drives condensation, while conserved repulsive features of the disordered region modulate material properties. By generating rationally designed PopZ mutants, we find that the exact material properties of PopZ condensates directly determine cellular fitness, providing direct evidence for the physiological importance of the emergent properties of biomolecular condensates. Our work codifies a clear set of design principles illuminating how sequence variation in a disordered domain alters the function of a widely conserved bacterial condensate. We used these insights to repurpose PopZ as a modular platform for generating synthetic condensates of tunable function in human cells.

cell biology↗

bioRxiv2020

Identification of TMEM106B as proviral host factor for SARS-CoV-2

The ongoing COVID-19 pandemic is responsible for worldwide economic damage and nearly one million deaths. Potent drugs for the treatment of severe SARS-CoV-2 infections are not yet available. To identify host factors that support coronavirus infection, we performed genome-wide functional genetic screens with SARS-CoV-2 and the common cold virus HCoV-229E in non-transgenic human cells. These screens identified PI3K type 3 as a potential drug target against multiple coronaviruses. We discovered that the lysosomal protein TMEM106B is an important host factor for SARS-CoV-2 infection. Furthermore, we show that TMEM106B is required for replication in multiple human cell lines derived from liver and lung and is expressed in relevant cell types in the human airways. Our results identify new coronavirus host factors that may potentially serve as drug targets against SARS-CoV-2 or to quickly combat future zoonotic coronavirus outbreaks.

microbiology↗