Biology subjects

Tavares, A. H.

Publications and source records attributed to Tavares, A. H..

6 recordsLinked to original sources

bioRxiv2026

The enteroviral protease target LSM14A operates outside of P-bodies to augment antiviral innate immunity

Antiviral innate immune networks in human cells comprise core components that serve as central signaling hubs and several context-dependent modulators whose role may be virus- or tissue-specific. One such modulator is LSM14A, which potentiates innate immune response but is not essential. We recently showed that enteroviruses deploy their protease activity to cleave LSM14A, thereby disabling its antiviral function. In this study, we probe the molecular mechanism by which LSM14A contributes to innate immunity. We show that although LSM14A predominantly localizes to processing bodies (P-bodies; PBs), this localization is not essential for its innate immune function. Likewise, association with peroxisomes does not contribute to its immune activity. Instead, an unbiased systems-level interactomic analysis reveals a distinct cohort of LSM14A-associated proteins that assemble outside canonical PBs and peroxisomes following infection with Sendai virus, a robust inducer of innate immunity. Functional interrogation of these interactors demonstrate that several are essential for LSM14A-dependent amplification of antiviral signaling. Together, these findings uncover a functional axis of LSM14A that operates independently of its canonical subcellular localizations and is mediated through a specialized interaction network, improving our understanding of how this protein reinforces the antiviral innate immune system.

microbiology↗

bioRxiv2022

Role of spike in the pathogenic and antigenic behavior of SARS-CoV-2 BA.1Omicron

The recently identified, globally predominant SARS-CoV-2 Omicron variant (BA.1) is highly transmissible, even in fully vaccinated individuals, and causes attenuated disease compared with other major viral variants recognized to date1-7. The Omicron spike (S) protein, with an unusually large number of mutations, is considered the major driver of these phenotypes3,8. We generated chimeric recombinant SARS-CoV-2 encoding the S gene of Omicron in the backbone of an ancestral SARS-CoV-2 isolate and compared this virus with the naturally circulating Omicron variant. The Omicron S-bearing virus robustly escapes vaccine-induced humoral immunity, mainly due to mutations in the receptor-binding motif (RBM), yet unlike naturally occurring Omicron, efficiently replicates in cell lines and primary-like distal lung cells. In K18-hACE2 mice, while Omicron causes mild, non-fatal infection, the Omicron S-carrying virus inflicts severe disease with a mortality rate of 80%. This indicates that while the vaccine escape of Omicron is defined by mutations in S, major determinants of viral pathogenicity reside outside of S.

microbiology↗

bioRxiv2022

High resolution photocatalytic mapping of SARS-CoV-2 Spike protein-host cell membrane interactions

Identifying protein environments at the virus-host cell interface can improve our understanding of viral entry and pathogenesis. SARS-CoV-2, the virus behind the ongoing COVID-19 pandemic, uses the cell surface ACE2 protein as a major receptor, but the contribution of other cellular proteins in the entry process is unknown. To probe the microenvironment of SARS-CoV-2 Spike-ACE2 protein interactomes on human cells, we developed a photocatalyst-based viral-host protein microenvironment mapping platform (ViraMap) employing iridium photocatalysts conjugated to Spike for visible-light driven proximity labelling on host cells. Application of ViraMap on ACE2-expressing cells captured ACE2, the established co-receptor NRP1, as well as other proteins implicated in host cell entry and immunomodulation. We further investigated these enriched proteins via loss-of-function and over-expression in pseudotype and authentic infection models and observed that the Ig receptor PTGFRN and tyrosine kinase ligand EFNB1 can serve as SARS-CoV-2 entry factors. Our results highlight additional host targets that participate infection and showcase ViraMap for interrogating virus-host cell surface interactomes.

biochemistry↗

bioRxiv2020

SARS-CoV-2 Requires Cholesterol for Viral Entry and Pathological Syncytia Formation

Many enveloped viruses induce multinucleated cells (syncytia), reflective of membrane fusion events caused by the same machinery that underlies viral entry. These syncytia are thought to facilitate replication and evasion of the host immune response. Here, we report that co-culture of human cells expressing the receptor ACE2 with cells expressing SARS-CoV-2 spike, results in synapse-like intercellular contacts that initiate cell-cell fusion, producing syncytia resembling those we identify in lungs of COVID-19 patients. To assess the mechanism of spike/ACE2-driven membrane fusion, we developed a microscopy-based, cell-cell fusion assay to screen [~]6000 drugs and >30 spike variants. Together with cell biological and biophysical approaches, the screen reveals an essential role for membrane cholesterol in spike-mediated fusion, which extends to replication-competent SARS-CoV-2 isolates. Our findings provide a molecular basis for positive outcomes reported in COVID-19 patients taking statins, and suggest new strategies for therapeutics targeting the membrane of SARS-CoV-2 and other fusogenic viruses. HighlightsO_LICell-cell fusion at ACE2-spike clusters cause pathological syncytia in COVID-19 C_LIO_LIDrug screen reveals critical role for membrane lipid composition in fusion C_LIO_LISpikes unusual membrane-proximal cysteines and aromatics are essential for fusion C_LIO_LICholesterol tunes relative infectivity of SARS-CoV-2 viral particles C_LI

cell biology↗

bioRxiv2020

SARS-CoV-2 desensitizes host cells to interferon through inhibition of the JAK-STAT pathway

SARS-CoV-2 can infect multiple organs, including lung, intestine, kidney, heart, liver, and brain. The molecular details of how the virus navigates through diverse cellular environments and establishes replication are poorly defined. Here, we performed global proteomic analysis of the virus-host interface in a newly established panel of phenotypically diverse, SARS-CoV-2-infectable human cell lines representing different body organs. This revealed universal inhibition of interferon signaling across cell types following SARS-CoV-2 infection. We performed systematic analyses of the JAK-STAT pathway in a broad range of cellular systems, including immortalized cell lines and primary-like cardiomyocytes, and found that several pathway components were targeted by SARS-CoV-2 leading to cellular desensitization to interferon. These findings indicate that the suppression of interferon signaling is a mechanism widely used by SARS-CoV-2 in diverse tissues to evade antiviral innate immunity, and that targeting the viral mediators of immune evasion may help block virus replication in patients with COVID-19.

microbiology↗

bioRxiv2019

Cryptococcus neoformans secretes small molecules that inhibit IL-1β inflammasome-dependent secretion

Cryptococcus neoformans is an encapsulated yeast that causes disease mainly in immunosuppressed hosts. It is considered a facultative intracellular pathogen because of its capacity to survive and replicate inside phagocytes, especially macrophages. This capacity is heavily dependent on various virulence factors, particularly the glucuronoxylomannan (GXM) component of the polysaccharide capsule, that render the non- or poorly-activated macrophage ineffective against phagocytosed yeast. Strategies utilized by macrophages to prevent this scenario include pyroptosis (a rapid highly inflammatory cell death) and vomocytosis (the expulsion of the pathogen from the intracellular environment without lysis). Inflammasome activation in phagocytes is usually protective against fungal infections, including cryptococcosis. Nevertheless, recognition of C. neoformans by inflammasome receptors requires specific changes in morphology or the opsonization of the yeast, impairing a proper inflammasome function. In this context, we analyzed the impact of molecules secreted by C. neoformans B3501 strain and its acapsular mutant{Delta} cap67 in an inflammasome activation in vitro model. Our results showed that conditioned media derived from B3501 was capable of inhibiting inflammasome dependent events (i. e. IL-1{beta} secretion and LDH release via pyroptosis) more strongly than conditioned media from{Delta} cap67, regardless of GXM presence. We also demonstrated that macrophages treated with conditioned media were less responsive against infection with the virulent strain H99, exhibiting lower rates of phagocytosis, increased fungal burdens and enhanced vomocytosis. Moreover, we showed that the aromatic metabolite DL-Indole-3-lactic acid (ILA) was present in B3501s conditioned media and that this fungal metabolite is involved in the regulation of inflammasome activation by C. neoformans. Overall, the results presented show that conditioned media from a wild-type strain can inhibit an important recognition pathway and subsequent fungicidal functions of macrophages, contributing to fungal survival in vitro and suggesting that this serves as an important role for secreted molecules during cryptococcal infections. Authors SummaryCryptococcus neoformans is the agent of cryptococcal meningitis, a disease that can be life-threatening in immunocompromised hosts such as those infected with HIV. The infection thrives in hosts that poorly activate their immune system, mainly because of the yeasts ability to survive inside macrophages and migrate towards the central nervous system. Emerging data indicate that cryptococci modulate the host immune response, but the underlying mechanisms remain largely uncharacterized. Here we show that secreted molecules from a wild-type strain of C. neoformans impair inflammatory responses driven by inflammasome activation, which in turn impact the macrophage antifungal activity. We further show that this inhibition does not involve GXM, the main constituent of the fungal capsule, but rather is partially dependent on DL-Indole-3-lactic acid (ILA), a metabolite not previously implicated in fungal virulence.

immunology↗