Biology subjects

Amorim, M. J.

Publications and source records attributed to Amorim, M. J..

12 recordsLinked to original sources

bioRxiv2026

Age-dependent disease tolerance to SARS-CoV-2 infection

Disease tolerance limits infectious disease severity through tissue damage control mechanisms that do not target pathogens directly. Here we demonstrate that age-dependent decline in adipose tissue lipolysis compromises disease tolerance to SARS-CoV-2 infection. Young adult mice exhibited robust adipocyte lipolysis and 80% survival, whereas old mice showed impaired adipocyte lipolysis and only 20% survival. Genetic repression of adipocyte lipolysis eliminated this age-dependent survival advantage without affecting viral titers, revealing that adipocyte lipolysis is essential for disease tolerance to SARS-CoV-2 in young adults. Impaired adipocyte lipolysis in aged mice was associated with a plasma lipidomic signature that predicts COVID-19 severity and mortality in three independent human cohorts. Mechanistically, adipocyte lipolysis provides free fatty acids (FFA) to support bone marrow emergency myelopoiesis, through CD36- and CPT1-dependent FFA cellular uptake and mitochondrial import, respectively. Bone marrow derived monocytes migrate to the lung via CCL2/CCR2-dependent mechanism where they enforce an immune-metabolic communication network with parenchymal cells to sustain lung structure and function. This circuit is not required to confer protection against influenza infection, revealing pathogen-specific disease tolerance mechanisms. These findings reveal adipose tissue catabolism as a central age-dependent factor responsible for exacerbated COVID-19 mortality in aged populations. One-Sentence SummarySARS-CoV-2 infection induces adipose tissue lipolysis to release fatty acids that drive myelopoiesis and monocyte production for lung protection and COVID-19 disease tolerance, but this protective circuit declines with age, increasing disease severity in the elderly.

immunology↗

bioRxiv2025

Functional redundancy in Oxa1-family insertases supports robust membrane insertion of influenza A virus M2 viroporin

The biogenesis of thousands of highly diverse membrane proteins in humans is facilitated by an array of ER-resident membrane protein translocases. While some membrane proteins have a strict requirement for a specific insertion machinery, membrane proteins with short translocated domains may be able to access multiple pathways. Here, we quantify the functional importance of redundancy in membrane protein translocation during influenza A virus (IAV) infection by examining the biogenesis of the viroporin M2. Given the wide host and cellular tropism of IAV, the virus likely evolved mechanisms to leverage host translocation pathways efficiently. We demonstrate that although M2 utilizes the ER membrane protein complex (EMC), driven by signals encoded in its transmembrane and C-terminal domains, M2 maintains an approximately 50% membrane insertion rate in the absence of the EMC. This influences viral cell-to-cell transmission across different IAV strains, with a greater impact on those expressing lower levels of M2. We identify alternative translocation of M2 via Oxa1-family translocons independent of canonical targeting chaperones. These findings reveal how the exploitation of multiple redundant pathways can ensure robust IAV infection. SIGNIFICANCE STATEMENTIAV must rapidly replicate in diverse mammalian hosts, which requires efficient integration of viral proteins into host cell membranes. This study uncovers how the viral proton channel M2 utilizes multiple redundant protein insertion pathways, accessing EMC and alternative Oxa1-family translocases. Revealing these redundant strategies clarifies how cells triage membrane proteins, offering insights into both viral adaptation and host cell robustness.

cell biology↗

bioRxiv2025

Membrane association prevents premature degradation and mitigates inefficient biogenesis of suboptimal membrane proteins

Accurate membrane protein biogenesis is essential for cellular function, yet many proteins contain suboptimal targeting or insertion signals. Influenza A virus (IAV) faces similar constraints during infection but may have evolved strategies to enhance the biogenesis of its own membrane proteins. One such protein, the viroporin M2, contains functionally essential hydrophilic residues within its transmembrane domain, which should hinder efficient membrane insertion. We hypothesize that IAV has adapted to overcome these sequence-based limitations and ensure robust M2 biogenesis. Using a biotin pulse-labelling system in intact cells, we uncover the dynamics of M2 targeting and ER insertion. Attenuating the insertion rate by ablating a key insertion factor, the ER membrane protein complex (EMC), leads to M2 accumulating in the cytosol, but remaining partially insertion competent. We find that cytosolic stability of non-inserted M2 is crucial for efficient biogenesis under these conditions and identify amphipathic helix- mediated membrane association as the molecular mechanism that counteracts proteasomal degradation. We propose membrane association as a novel buffering mechanism that regulates membrane protein biogenesis by stabilizing pre-insertion intermediates. SIGNIFICANCE STATEMENTMembrane proteins failing to insert into the endoplasmic reticulum (ER) may be rapidly degraded to avoid protein aggregation in the cytosol. Our findings challenge this prevailing view. We show that the influenza A viroporin M2, despite possessing unfavourable features for membrane insertion, can increase biogenesis efficiency by associating with the membrane prior to insertion. Membrane association buffers the protein against quality control pathways and promotes successful biogenesis--even in the absence of a key insertion factor. These results reveal an alternative fate for non-inserted membrane proteins and uncover a viral strategy that redefines how cells manage unstable insertion intermediates.

cell biology↗

bioRxiv2025

A critical role for the ER Membrane Complex (EMC) in lipid droplet homeostasis

The ER Membrane complex (EMC) facilitates insertion of multiple classes of integral membrane protein into the lipid bilayer of the endoplasmic reticulum (ER). Recent years have seen significant progress in understanding the structural aspects of EMC function, but the client protein/s enforcing its evolutionary conservation throughout eukaryotic kingdoms remain to be determined. Given reported role/s for the EMC in lipid homeostasis, we deleted the essential EMC3 subunit in the liver and adipose tissues of mice and examined the impact of EMC loss in a range of metabolic models. Intriguingly, absence of EMC3 in either the liver or adipose tissues results in defective storage of triglycerides and perturbations in lipid droplet (LD) homeostasis. EMC-deficient mouse adipose tissues were defective in their ability to mediate fat storage in response to a high fat diet and were unable to support non-shivering thermogenesis. Proteomic analyses of EMC3-deficient tissues found reduced levels of FITM2, a key regulator of LD biogenesis and ER homeostasis, identifying it as a novel EMC client. Strikingly, deletion of the EMC3 homolog dPob in the Drosophila fat body, which shares overlapping functions with mammalian liver/adipose tissues, revealed similar defects in LD homeostasis. Together, our results indicate that the EMC plays a key evolutionarily conserved role in biogenesis of machinery maintaining triglyceride storage in metazoans.

biochemistry↗

bioRxiv2025

A Metabolite-Based Resistance Mechanism Against Malaria

Whether jaundice, a common presentation of Plasmodium (P.) falciparum malaria (1-3) arising from the accumulation of circulating bilirubin, represents an adaptive or maladaptive response to Plasmodium spp. infection is not understood (1-3). We found that asymptomatic P. falciparum infection was associated with a >10-fold higher ratio of unconjugated bilirubin over parasite burden, compared to symptomatic malaria. Genetic suppression of bilirubin synthesis by biliverdin reductase A (BVRA) (4) increased parasite virulence and malaria mortality in mice. Accumulation of unconjugated bilirubin in plasma, via genetic inhibition of hepatic conjugation by UDP glucuronosyltransferase family 1 member A1 (UGT1A1) (5), was protective against malaria in mice. Unconjugated bilirubin inhibited P. falciparum proliferation in red blood cells (RBC) via a mechanism that suppressed mitochondrial pyrimidine synthesis. Moreover, unconjugated bilirubin inhibited hemozoin (Hz) crystallization and compromised the parasites food vacuole. In conclusion, jaundice represents a metabolic response to Plasmodium spp. infection that limits malaria severity.

immunology↗

bioRxiv2023

Influenza A virus activates the unfolded protein response and induces the accumulation of insoluble protein aggregates that are essential for efficient viral propagation

Influenza A virus (IAV) is one of the main causes of annual respiratory epidemics in humans. IAV employs multiple strategies to evade host immunity and hijack cellular mechanisms to support proper virion formation and propagation. Some of these strategies encompass the manipulation of pathways involved in protein homeostasis, leading to changes in the host proteome and protein distribution within the cell. In this study, we performed a detailed analysis of the interplay between IAV and the host cells proteostasis mechanisms throughout the entire infectious cycle. We reveal that IAV infection induces the activation of the inositol requiring enzyme 1 (IRE1) branch of the unfolded protein response (UPR), at an infection stage that coincides with high rates of viral protein translation. This activation is particularly important for infection, as attenuation of virus production was observed upon IRE1 inhibition. Concomitantly to UPR activation, we observed the accumulation of virus-induced insoluble protein aggregates, which contain both viral and host proteins and are associated with a dysregulation of the host cell RNA metabolism. We demonstrate that this accumulation is important for IAV propagation, as its prevention using a quinoline-steroid hybrid compound significantly reduces the number of produced infectious virus particles. Our data suggests that the formation of these insoluble protein aggregates favors the final steps of the infection cycle, more specifically the virion assembly. Our findings reveal additional mechanisms by which IAV disrupts the host cell proteostasis to favor infection and uncover new cellular targets that can be explored for the development of host-directed antiviral strategies.

microbiology↗

bioRxiv2022

ATG9A facilitates the biogenesis of influenza A virus liquid condensates near the ER by dissociating recycling vesicles from microtubules

It is now established that many viruses that threaten public health establish condensates via phase transitions to complete their lifecycles, and knowledge on such processes may offer new strategies for antiviral therapy. In the case of influenza A virus (IAV), liquid condensates known as viral inclusions, concentrate the 8 distinct viral ribonucleoproteins (vRNPs) that form IAV genome and are viewed as sites dedicated to the assembly of the 8-partite genomic complex. Despite not being delimited by host membranes, IAV liquid inclusions accumulate host membranes inside as a result of vRNP binding to the recycling endocytic marker Rab11a, a driver of the biogenesis of these structures. We lack molecular understanding on how Rab11a-recycling endosomes condensate specifically near the endoplasmic reticulum (ER) exit sites upon IAV infection. We show here that liquid viral inclusions interact with the ER to fuse, divide and slide. We uncover that, contrary to previous indications, the reported reduction in recycling endocytic activity is a regulated process rather than a competition for cellular resources involving a novel role for the host factor ATG9A. In infection, ATG9A mediates the removal of Rab11a-recycling endosomes carrying vRNPs from microtubules. We observe that the recycling endocytic usage of microtubules is rescued when ATG9A is depleted, which prevents condensation of Rab11a endosomes near the ER. The failure to produce viral inclusions accumulates vRNPs in the cytosol, reduces genome assembly and the release of infectious virions. We propose that the ER supports the dynamics of liquid IAV inclusions, with ATG9A facilitating their formation. This work advances our understanding on how epidemic and pandemic influenza genomes are formed. It also reveals the plasticity of recycling pathway endosomes to undergo condensation in response to infection, disclosing new roles for ATG9A beyond its classical involvement in autophagy.

cell biology↗

bioRxiv2022

Influenza A virus liquid condensates can undergo pharmacological hardening

Multiple viral infections form biomolecular condensates in the host cell to compartmentalize viral reactions. Accumulating evidence indicates that these viral condensates may be hardened, a strategy with potential for exploitation as novel antiviral therapy, given that viral reactions rely on specific material properties for function. However, there is no molecular understanding on how to specifically and efficiently modify the material properties of viral condensates, a pre-requisite for overcoming off-target effects by rational drug design. In vitro, the material properties of biological condensates are modified by different thermodynamic parameters, including free energy, concentration, and type/strength of interactions. Here, we used influenza A virus liquid cytosolic condensates, A.K.A viral inclusions, to provide a proof of concept that modulating the type/strength of transient interactions among the interactome in IAV inclusions is more efficient at hardening these structures than varying the temperature or concentration, both in in vitro and in in vivo models. This stabilization can be achieved by a known pharmacological sticker that can specifically change the material properties of viral inclusions without affecting host proteome abundance nor solubility. Our work supports the development of antivirals targeting the material properties of biomolecular condensates in viral infections. It also provides a framework for the selection of compounds with this activity for general application and thus provides an advance in disease therapy.

cell biology↗

bioRxiv2021

PI4P and BLOC-1 remodel endosomal membranes into tubules

Intracellular trafficking is mediated by transport carriers that originate by membrane remodeling from donor organelles. Tubular carriers play major roles in the flux of membrane lipids and proteins to acceptor organelles. However, how lipids and proteins impose a tubular geometry on the carriers is incompletely understood. By exploiting imaging approaches at different scales on cells and in vitro membrane systems, we show that phosphatidylinositol-4-phosphate (PI4P) and biogenesis of lysosome-related organelles complex 1 (BLOC-1) govern the formation, stability and functions of recycling endosomal tubules. Endosomal PI4P production by type II PI4-kinases is needed to form nascent curved tubules through binding of BLOC-1 that stabilize and elongate them. Membrane remodeling by the PI4P/ BLOC-1 module functions not only in the recycling of endosomal cargoes, but also in the lifecycles of intracellular pathogens such as Chlamydia bacteria and influenza virus. This study demonstrates how a phospholipid and a protein complex coordinate as a minimal machinery to remodel cellular membranes into functional tubes.

cell biology↗

bioRxiv2021

Amino acids 484 and 494 of SARS-CoV-2 spike are hotspots of immune evasion affecting antibody but not ACE2 binding

Understanding SARS-CoV-2 evolution and host immunity is critical to control COVID-19 pandemics. At the core is an arms-race between SARS-CoV-2 antibody and angiotensin-converting enzyme 2 (ACE2) recognition, a function of the viral protein spike. Mutations in spike impacting antibody and/or ACE2 binding are appearing worldwide, with the effect of mutation synergy still incompletely understood. We engineered 25 spike-pseudotyped lentiviruses containing individual and combined mutations, and confirmed that E484K evades antibody neutralization elicited by infection or vaccination, a capacity augmented when complemented by K417N and N501Y mutations. In silico analysis provided an explanation for E484K immune evasion. E484 frequently engages in interactions with antibodies but not with ACE2. Importantly, we identified a novel amino acid of concern, S494, which shares a similar pattern. Using the already circulating mutation S494P, we found that it reduces antibody neutralization of convalescent and post-immunization sera, particularly when combined with E484K and N501Y. Our analysis of synergic mutations provides a landscape for hotspots for immune evasion and for targets for therapies, vaccines and diagnostics. One-Sentence SummaryAmino acids in SARS-CoV-2 spike protein implicated in immune evasion are biased for binding to neutralizing antibodies but dispensable for binding the host receptor angiotensin-converting enzyme

immunology↗

bioRxiv2021

Complement Decay-Accelerating Factor is a modulator of influenza A virus lung immunopathology

Clearance of viral infections, such as SARS-CoV-2 and influenza A virus (IAV), must be fine-tuned to eliminate the pathogen without causing immunopathology. As such, an aggressive initial innate immune response favors the host in contrast to a detrimental prolonged inflammation. The complement pathway bridges innate and adaptive immune system and contributes to the response by directly clearing pathogens or infected cells, as well as recruiting proinflammatory immune cells and regulating inflammation. However, the impact of modulating complement activation in viral infections is still unclear. In this work, we targeted the complement decay-accelerating factor (DAF/CD55), a surface protein that protects cells from non-specific complement attack, and analyzed its role in IAV infections. We found that DAF modulates IAV infection in vivo, via an interplay with the antigenic viral proteins hemagglutinin (HA) and neuraminidase (NA), in a strain specific manner. Our results reveal that, contrary to what could be expected, DAF potentiates complement activation, increasing the recruitment of neutrophils, monocytes and T cells. We also show that viral NA acts on the heavily sialylated DAF and propose that it exacerbates complement activation, leading to lung immunopathology. Remarkably, this mechanism has no impact on viral loads but rather on the host resilience to infection and may have direct implications in zoonotic influenza transmissions. Author summaryExacerbated complement activation and immune deregulation are at the basis of several pathologies induced by respiratory viruses. Here, we report that complement decay-accelerating factor (DAF), which inhibits complement activation in healthy cells, increases disease severity upon Influenza A virus (IAV) infection. Remarkably, DAF interaction with IAV proteins, hemagglutinin (HA) and neuraminidase (NA), resulted in excessive complement activation and recruitment of innate and adaptive immune cells, without affecting viral loads. Furthermore, we observed that viral NA directly cleaves DAF and promotes complement activation, providing a possible link between IAV-DAF interaction and pathology. Therefore, our results unveil a novel pathway that could modulate disease severity, which may help to understand the increased pathogenicity of zoonotic and pandemic IAV infections.

microbiology↗

bioRxiv2018

Pleotropic effects of mutations in the effector domain of influenza A virus NS1 protein

ObjectiveThe multifunctional NS1 protein of influenza A virus has roles in antagonising cellular innate immune responses and promoting viral gene expression. To better understand the interplay between these functions, we tested the effects of NS1 effector domain mutations known to affect homo-dimerisation or interactions with cellular PI3 kinase or Trim25 on NS1 ability to promote nuclear export of viral mRNAs.\n\nResultsThe NS1 dimerisation mutant W187R retained the functions of binding cellular NXF1 as well as stabilising NXF1 interaction with viral segment 7 mRNAs and promoting their nuclear export. Two PI3K-binding mutants, NS1 Y89F and Y89A still bound NXF1 but no longer promoted NXF1 interactions with segment 7 mRNA or its nuclear export. The Trim25-binding mutant NS1 E96A/E97A bound NXF1 and supported NXF1 interactions with segment 7 mRNA but no longer supported mRNA nuclear export. Analysis of WT and mutant NS1 interaction partners identified hsp70 as specifically binding to NS1 E96A/E97A. Whilst these data suggest the possibility of functional links between NS1s effects on intracellular signalling and its role in viral mRNA nuclear export, they also indicate potential pleiotropic effects of the NS1 mutations; in the case of E96A/E97A possibly via disrupted protein folding leading to chaperone recruitment.

microbiology↗