Biology subjects

Pierce, L. R.

Publications and source records attributed to Pierce, L. R..

4 recordsLinked to original sources

bioRxiv2026

Plscr1 inhibits murine norovirus entry

Noroviruses are a leading cause of gastroenteritis worldwide, yet host factors that restrict norovirus replication are not well understood. By mining both CRISPR activation and CRISPR knockout genome-wide screens, we identified the interferon-stimulated gene Plscr1 as a restriction factor for murine norovirus (MNV). Plscr1 inhibits the fusion of enveloped viruses with endocytic membranes, making its antiviral activity against the nonenveloped MNV surprising. Here, we demonstrate that Plscr1 is both necessary and sufficient to restrict MNV infection in vitro and contributes to the control of colonic infection in mice. Mechanistically, we determined that Plscr1 inhibits MNV entry at a post-attachment step. A single amino acid substitution in the minor capsid protein VP2 confers resistance to Plscr1. Because VP2 delivers viral RNA by puncturing endocytic membranes during calicivirus entry, these findings implicate a late entry step targeted by Plscr1. Our results expand the antiviral activity of PLSCR1 to a nonenveloped virus and identify an unexpected point of convergence between enveloped- and non-enveloped-virus entry pathways.

microbiology↗

bioRxiv2025

Trim47 inhibits murine norovirus replication in a strain-dependent manner

Human norovirus is the leading cause of gastroenteritis worldwide. Norovirus exhibits remarkable genetic diversity. Understanding the impact of genetic diversity on infection and immunity has been challenging due to the difficulties of in vitro cultivation and the current lack of a small animal model. Murine norovirus (MNV) has emerged as a premier model system to investigate norovirus biology. Here, we identify Trim47 as a host restriction factor that potently inhibits MNV infection in a strain dependent manner. We determine that Trim47 expression inhibits an early stage of the viral life cycle for the MNV strain CR6, while the replication of the closely related strain CW3 is not restricted by Trim47. Using a forward genetic screen we determine that genetic variation within the nonstructural gene NS1 accounts for this differential sensitivity to Trim47. While most TRIM containing proteins promote the ubiquitination and degradation of its targets, Trim47 does neither. Instead, Trim47 promotes the deubiquitination of the NS1/2 precursor protein. Our data provide new insight into a potential antiviral gene and mechanistic insight into norovirus evolution that may impact viral tropism. ImportanceViruses exist as genetically heterogeneous populations. Understanding the contribution of viral genetic variation on infection outcomes is critical in predicting emerging viruses and their variants. Noroviruses are genetically diverse but human norovirus has been technically challenging to study. In this study we use the model system murine norovirus to identify a viral strain specific restriction mechanism where a host gene can specifically restrict one strain of the virus but has no impact on a closely related strain. Dissecting the mechanism of this specificity provides insight into viral diversity and possible host restriction pathways.

microbiology↗

bioRxiv2024

Membrane asymmetry facilitates murine norovirus entry and persistent enteric infection

Norovirus, the leading cause of gastroenteritis worldwide, is a non-enveloped virus whose tropism is determined in part by the expression patterns of entry receptors. However, the contribution of cellular lipids to viral entry is not well understood. Here, we determined that the asymmetrical distribution of lipids within membrane bilayers is required for murine norovirus (MNV) replication. Specifically, TMEM30a, an essential subunit of lipid flippases, is required for MNV replication in vitro. Disruption of TMEM30a in mouse intestinal epithelial cells prevents persistent, enteric infection by MNV in vivo. Mechanistically, TMEM30a facilitates MNV binding and entry. Surprisingly, exoplasmic phosphatidylserine (PS), a typical marker of dying cells, does not inhibit MNV infection. Rather, TMEM30a maintains a lipid ordered state that impacts membrane fluidity that is necessary for the low affinity, high avidity binding of MNV to cells. Our data provides a new role for lipid asymmetry in promoting non-enveloped virus infection in vitro and norovirus persistence in vivo.

microbiology↗

bioRxiv2024

Trim7 does not have a role in the restriction of murine norovirus infection in vivo

Trim7 is an E3 ubiquitin ligase that was recently identified as a central regulator of host- viral interactions with both pro-viral and anti-viral activity in cell culture. As an inhibitor, Trim7 overexpression ubiquitinates viral proteins by recognizing C-terminal glutamines that are hallmarks of 3C-like protease cleavage events. Here we sought to determine the physiological impact of Trim7 in resolving murine norovirus (MNV) infection of mice as MNV is potently inhibited by Trim7 in vitro. Utilizing two independently derived Trim7 deficient mouse lines we found no changes in the viral burden or tissue distribution of MNV in both an acute and persistent model of infection. Additionally, no changes in cytokine responses were observed after acute MNV infection of Trim7-deficient mice. Furthermore, removal of potentially confounding innate immune responses such as STING and STAT1 did not reveal any role for Trim7 in regulating MNV replication. Taken together, our data fails to find a physiological role for Trim7 in regulating MNV infection outcomes in mice and serves as a caution for defining Trim7 as a broad acting antiviral. ImportanceIntrinsic antiviral molecules that restrict viral replication are important drivers of viral evolution and viral tropism. Recently, Trim7 was shown to provide cell intrinsic protection against RNA viruses, including murine norovirus. Biochemically, Trim7 recognizes the cleavage product of viral proteases, suggesting a novel and broad mechanism to restrict viral replication. Here, we tested whether Trim7 had a physiological role in restricting murine norovirus replication in mice. Unexpectedly, we found no impact of viral replication or innate immune responses during murine norovirus infection. Our findings urge caution in defining Trim7 as a broad antiviral factor in the absence of in vivo evidence.

microbiology↗