Browsing by Author "Vale-Costa, Sílvia"
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- ATG9A facilitates the biogenesis of influenza A virus liquid condensates near the ER by dissociating recycling vesicles from microtubulesPublication . Vale-Costa, Sílvia; Etibor, Temitope Akghibe; Brás, Daniela; Sousa, Ana Laura; Amorim, Maria JoãoMany viruses that threaten public health establish condensates via phase transitions to complete their lifecycles, and knowledge on such processes is key for the design of new antivirals. In the case of influenza A virus, liquid condensates known as viral inclusions are sites dedicated to the assembly of its 8-partite RNA genome. Liquid viral inclusions emerge near the endoplasmic reticulum (ER) exit sites, but we lack the molecular understanding on how the ER contributes to their biogenesis. We show here that viral inclusions develop at remodeled ER sites and display dynamic interactions using the ER, including fusion and fission events and sliding movements. We also uncover a novel role for the host factor, ATG9A, in mediating the exchange of viral inclusions between the ER and microtubules. Depletion of ATG9A arrests viral inclusions at microtubules and prevents their accumulation at the ER, leading to a significantly reduced production of viral genome complexes and infectious virions. In light of our recent findings, we propose that a remodeled ER supports the dynamics of liquid IAV inclusions, with ATG9A acting locally to facilitate their formation. This work advances our current knowledge regarding influenza genome assembly, but also reveals new roles for ATG9A beyond its classical involvement in autophagy.
- ATG9A regulates the dissociation of recycling endosomes from microtubules to form liquid influenza A virus inclusionsPublication . Vale-Costa, Sílvia; Etibor, Temitope Akhigbe; Brás, Daniela; Sousa, Ana Laura; Ferreira, Mariana; Martins, Gabriel G.; Mello, Victor Hugo; Amorim, Maria JoãoAU It is:now Pleaseconfirmthatallheadinglevelsarerepresentedcorrectly 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 andAU reduces: Pleasecheckandconfirmthattheeditst 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.
- Challenges in imaging analyses of biomolecular condensates in cells infected with influenza A virusPublication . Etibor, Temitope Akhigbe; O’Riain, Aidan; Alenquer, Marta; Diwo, Christian; Vale-Costa, Sílvia; Amorim, Maria JoãoBiomolecular condensates are crucial compartments within cells, relying on their material properties for function. They form and persist through weak, transient interactions, often undetectable by classical biochemical approaches. Hence, microscopy-based techniques have been the most reliable methods to detail the molecular mechanisms controlling their formation, material properties, and alterations, including dissolution or phase transitions due to cellular manipulation and disease, and to search for novel therapeutic strategies targeting biomolecular condensates. However, technical challenges in microscopy-based analysis persist. This paper discusses imaging, data acquisition, and analytical methodologies’ advantages, challenges, and limitations in determining biophysical parameters explaining biomolecular condensate formation, dissolution, and phase transitions. In addition, we mention how machine learning is increasingly important for efficient image analysis, teaching programs what a condensate should resemble, aiding in the correlation and interpretation of information from diverse data sources. Influenza A virus forms liquid viral inclusions in the infected cell cytosol that serve as model biomolecular condensates for this study. Our previous work showcased the possibility of hardening these liquid inclusions, potentially leading to novel antiviral strategies. This was established using a framework involving live cell imaging to measure dynamics, internal rearrangement capacity, coalescence, and relaxation time. Additionally, we integrated thermodynamic characteristics by analysing fixed images through Z-projections. The aforementioned paper laid the foundation for this subsequent technical paper, which explores how different modalities in data acquisition and processing impact the robustness of results to detect bona fide phase transitions by measuring thermodynamic traits in fixed cells. Using solely this approach would greatly simplify screening pipelines. For this, we tested how single focal plane images, Z-projections, or volumetric analyses of images stained with antibodies or live tagged proteins altered the quantification of thermodynamic measurements. Customizing methodologies for different biomolecular condensates through advanced bioimaging significantly contributes to biological research and potential therapeutic advancements.