Biology subjects

Partlow, E. A.

Publications and source records attributed to Partlow, E. A..

4 recordsLinked to original sources

bioRxiv2026

Antibodies to influenza A virus hemagglutinin and neuraminidase limit egress and alter the physical properties of released virus particles

Influenza A virus (IAV)-specific antibodies neutralize mature virions by inhibiting functional sites or, in some cases, by promoting virion aggregation. Many antibodies also act on infected cells to reduce virion yields, but the underlying mechanisms and effects on the physical properties and function of released virus particles remain incompletely characterized. Here we use flow virometry to acquire high-sensitivity yield and size measurements of virus particles released in the presence of antibodies. Combined with digital-droplet PCR and electron microscopy, this approach enables comprehensive characterization of antibody-induced changes in particle genome-content and morphology. We show that antibodies rapidly and dynamically alter released particle distributions, reducing yields and inducing the production of larger particles. Both effects result in part from aggregation induced by crosslinking of viral antigen on the infected-cell surface and inhibition of viral NA. However, yield reduction is not fully explained by aggregation, and a subset of induced larger particles are elongated virions. Finally, particles formed in the presence of HA stem-binding antibody, which does not inhibit attachment of mature virions, show reduced attachment in subsequent rounds of infection. Altogether, we uncover an unappreciated mechanism by which antibodies interfere with viral infection that occurs only during budding and release. Our work highlights the necessity of studying how the immune response shapes virus populations in the context of active infection processes.

microbiology↗

bioRxiv2023

Influenza A Virus Infections Sense Host Membrane Tension to Dynamically Tune Assembly

Enveloped viruses often exhibit a pleomorphic morphology, ranging in size from 100nm spheres to tens-of-micron long filaments. For influenza A virus (IAV), spheres enable rapid replication and minimize metabolic cost, while filaments resist effects of antibodies or other cell-entry pressures. The current paradigm is that virion shape changes require genetic adaptation; however, a virus evolved to alter its shape phenotypically would outperform one that relies on genetic selection. Using a novel quantitative flow virometry assay to characterize virion shape dynamics we find that IAV rapidly tunes its shape distribution to favor spheres under optimal, and filaments under attenuating conditions including the presence of antibodies. We identify membrane tension as a key cue sensed by IAV determining shape distributions. This phenotypic shift outpaces genetic change and serves to enable additional life cycles under pressure. Our work expands knowledge of the complex host-virus interplay to include viral responses to the local environment by optimizing its structure to maximize replication and ultimately host-host transmission.

microbiology↗

bioRxiv2019

A structural mechanism for phosphorylation-dependent inactivation of the AP2 complex

Endocytosis of transmembrane proteins is orchestrated by the AP2 clathrin adaptor complex. AP2 dwells in a closed, inactive state in the cytosol, but adopts an open, active conformation on the plasma membrane. Membrane-activated complexes are also phosphorylated, but the significance of this mark is debated. We recently proposed that NECAP negatively regulates AP2 by binding open and phosphorylated complexes (Beacham et al., 2018). Here, we report high-resolution cryo-EM structures of NECAP bound to phosphorylated AP2. The site of AP2 phosphorylation is directly coordinated by residues of the NECAP PHear domain that are predicted from genetic screens in C. elegans. Using membrane mimetics to generate conformationally open AP2, we find that a second domain of NECAP binds these complexes and cryo-EM reveals both domains of NECAP engaging closed, inactive AP2. Assays in vitro and in vivo confirm these domains cooperate to inactivate AP2. We propose that phosphorylation marks adaptors for inactivation.

cell biology↗

bioRxiv2017

NECAPs are negative regulators of the AP2 clathrin adaptor complex

Eukaryotic cells internalize transmembrane receptors via clathrin-mediated endocytosis, but it remains unclear how the machinery underpinning this process is regulated. We recently discovered that membrane-associated muniscin proteins such as FCHo and SGIP initiate endocytosis by converting the AP2 clathrin adaptor complex to an open, active conformation that is then phosphorylated (Hollopeter et al., 2014). Here we report that loss of ncap-1, the sole C. elegans gene encoding an adaptiN Ear-binding Coat-Associated Protein (NECAP), bypasses the requirement for FCHO-1. Biochemical analyses reveal AP2 accumulates in an open, phosphorylated state in ncap-1 mutant worms, suggesting NECAPs promote the closed, inactive conformation of AP2. Consistent with this model, NECAPs preferentially bind open and phosphorylated forms of AP2 in vitro and localize with constitutively open AP2 mutants in vivo. NECAPs do not associate with phosphorylation-defective AP2 mutants, implying that phosphorylation precedes NECAP recruitment. We propose NECAPs function late in endocytosis to inactivate AP2.

cell biology↗