Biology subjects

Anugraham, M.

Publications and source records attributed to Anugraham, M..

3 recordsLinked to original sources

bioRxiv2026

Influenza A virus infection perturbs host cell glycosylation

Glycosylation is critical for viral-host cell interactions in influenza A virus (IAV) infection, but we lack a comprehensive understanding of how IAV infection shapes the host glycoproteome and the implications of these changes. Here, we used a liquid chromatography-tandem mass spectrometry (LC-MS/MS) approach to perform proteomic, glycomic, and glycoproteomic characterisation of the dynamic subcellular responses to an in vitro time course infection of human A549 cells with two IAV strains (A/X-31, H3N2; and A/Puerto Rico/8/1934, H1N1). IAV infection resulted in only modest changes to the subcellular proteome, but robust and significant changes to the host secreted and organelle glycome and glycoproteome. Infection with either virus resulted in a widespread reduction in sialic acid across the N- and O-glyco(proteo)me; increased abundance of oligomannose, paucimannose, and phosphorylated glycans; and shorter hybrid/complex glycans. Reduced sialylation was consistent with desialylation of glycans by viral neuraminidase (NA), but with specific features of the glycan and protein controlling the extent of desialylation. Desialylation was greater when glycans were fucosylated; when the sialic acid was attached via an 2,3 linkage or positioned on the 3 arm; on larger, more complex glycans; and when present on proteins that are more accessible to IAV NA. Subtle but prolonged activation of the unfolded protein response in infection led to a doubling of oligomannose N-glycosylation. Glycans were shorter in infection, implicating IAV-induced disruption of Golgi glycoprotein flux as a mechanism that reduces host glycoprotein sialylation and promotes virion release, independent of NA activity. Our data provide important insights into the host glycoproteome during influenza virus infection, furthering our understanding of how influenza NA acts upon host glycans, and how cell stresses in infection perturb key mediators of protein stability and function, cell signalling and immunity.

biochemistry↗

bioRxiv2025

Sub-clinical exposure to Streptococcus pyogenes drives the development of immunity

Age-related decline in Streptococcus pyogenes infection rates suggests that immunity develops progressively through repeated exposure during early life. However, the intensity or duration of exposure required is unknown, as to why some individuals appear to develop immunity, despite having few or no previously detected infections. Here, drawing on samples from a human challenge model of pharyngeal S. pyogenes infection, we investigate whether symptomatic disease is required for induction of humoral and cellular immunity. Challenge with M75 S. pyogenes induced M75-specific serum IgG and IgA antibodies and memory B cell in both symptomatic and asymptomatic participants, with responses persisting for at least 6 months. Purified IgG from asymptomatic participants exhibited significantly enhanced binding to M75 S. pyogenes and were bactericidal when transferred into a murine model of pharyngeal infection. M75-specific IgG from these participants had an altered Fc glycosylation signature, indicative of enhanced effector function and ability to limit inflammation. However, S. pyogenes challenge had no impact on cellular or humoral immune responses to a conserved cryptic epitope, p*17. These findings show that asymptomatic (or sub-clinical) exposure to M75 S. pyogenes generates functional immune responses and contributes to the streptococcal immunity that emerges by adulthood.

microbiology↗

bioRxiv2024

ST6GAL1-mediated sialyl linkage switching in tumor-associated macrophages drives cancer-promoting nanotubes carrying α2,6-sialylation in anti-inflammatory cells

Tumor-associated macrophages (TAMs) form functionally diverse populations of innate immune cells in the tumor microenvironment (TME). Pro- and anti-inflammatory TAMs are central to cancer progression by shaping inflammation and immune (im)balance, but it remains unknown if polarization-induced remodeling of the TAM glycocalyx critical for cellular communication occurs within the TME. Taking a systems glycobiology approach, we here firstly used cell surface-focused glycomics and lectin flow cytometry of ex vivo polarized monocyte-derived macrophages to demonstrate profound sialyl linkage switching of the surface N-glycome in pro-inflammatory (2,3-sialo-favored) and anti-inflammatory (2,6-sialo-dominant) macrophages. In contrast, no polarization-induced alterations in sialylation were observed in the surface O-glycome. ST6GAL1 that modifies N-glycans with 2,6-sialylation was elevated in anti-inflammatory compared to levels in pro-inflammatory macrophages providing a mechanistic basis for the sialyl linkage switching, which was supported by ST6GAL1 silencing. Interestingly, SNA-focused lectin cytochemistry of anti-inflammatory macrophages revealed dense networks of dynamic 2,6-sialylated protein-based nanotubules forming inter-connecting cellular structures that were absent in pro-inflammatory macrophages. Temporal ST6GAL1 silencing in anti-inflammatory macrophages caused nanotubule disintegration as evidenced by SNA and biotin fluorescence microscopy. Moreover, live cell recordings of anti-inflammatory macrophages cultured with and without colorectal cancer (CRC) cells showed reduced macrophage motility, attenuated inter-macrophage and macrophage-CRC cell interactions and diminished CRC cell proliferation upon ST6GAL1 disruption indicating functional roles of the 2,6-sialylated nanotubules. Finally, sialyl linkage switching was recapitulated in pro- and anti-inflammatory TAMs from tumor tissues of patients with advanced CRC. We report on the mechanistic basis for and functional consequences of glycocalyx remodeling accompanying TAM polarization.

immunology↗