Biology subjects

Khafaji, R.

Publications and source records attributed to Khafaji, R..

4 recordsLinked to original sources

bioRxiv2026

Sirtuin 1 Is Required for Optimal Mammarenavirus Multiplication

Mammarenaviruses (MaAv) cause persistent infections in diverse rodent reservoirs worldwide and several are zoonotic pathogens with an important public-health burden in their endemic regions. Moreover, the globally distributed MaAv lymphocytic choriomeningitis virus (LCMV) is an underrecognized pathogen of clinical significance in congenital infections and immunocompromised individuals. The lack of FDA-approved vaccines or antivirals for MaAv infections underscores the urgent need for novel anti-MaAv therapeutic strategies. Neutral sphingomyelinase 2 (nSMase2) was recently identified as a host factor contributing to LCMV multiplication, and its inhibitor cambinol exhibits dose-dependent antiviral activity against LCMV but the underlying mechanisms remain undefined. Here, we show that cambinol disrupts multiple stages of the LCMV life cycle. Cambinol inhibits the pH-dependent fusion event mediated by MaAv glycoprotein, a step required for completion of virus cell entry. It also reduces viral ribonucleoprotein (vRNP)-directed genome replication and transcription and impairs the budding activity of the virus matrix Z protein. Cambinol also inhibits sirtuins 1 and 2 (Sirt-1 and Sirt-2), two NAD+-dependent protein deacetylases with pleiotropic roles in cellular metabolism and stress responses, raising the question of whether cambinol anti-LCMV activity reflects nSMase2 inhibition alone or also involves sirtuin-dependent pathways. LCMV multiplication was significantly reduced in SIRT1, but not SIRT2, knockout (KO) cells, uncovering a pro-viral role for Sirt-1 in the LCMV life cycle. Consistent with this finding, LCMV vRNP activity and production of infectious progeny were reduced in SIRT1 KO cells. These findings identify Sirt-1 as a host factor required for optimal LCMV multiplication. Sirt-1 inhibitors are in clinical development for oncological and neurological indications, raising the possibility of repurposing Sirt-1 inhibitors as host-directed antivirals (HDAs) against human pathogenic MaAv. Abstract figure O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/740332v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@d53c5forg.highwire.dtl.DTLVardef@16ea861org.highwire.dtl.DTLVardef@1f09addorg.highwire.dtl.DTLVardef@1472e6b_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2026

Prolyl tRNA Synthetase Is Required for Mammarenavirus Multiplication

Several mammarenaviruses (MaAv), chiefly Lassa virus (LASV) in Western Africa and Junin virus (JUNV) in the Argentinean Pampas, cause severe disease in humans and pose important public health problems in their endemic regions. In addition, the globally distributed MaAv lymphocytic choriomeningitis virus (LCMV) is an underrecognized human pathogen of clinical significance especially in congenital infections and LCMV poses a serious risk for immunocompromised individuals. There are no FDA-approved MaAv vaccines or antivirals and current anti-MaAv therapy is limited to an off-label use of ribavirin whose efficacy remains controversial. This highlights an urgent unmet need for developing antivirals against human pathogenic MaAv. Halofuginone (HF), a derivative of the natural alkaloid febrifugine, has been shown to exhibit antiviral activity against several RNA viruses. Here, we present evidence that HF exhibits a potent dose-dependent antiviral activity against LCMV, and the hemorrhagic fever causing MaAv LASV and JUNV. HF binds to the bifunctional enzyme glutamyl-prolyl-tRNA synthetase 1 (EPRS1) and specifically inhibits its prolyl-tRNA synthetase (PRS) activity, resulting in translation inhibition via the amino acid starvation (AAS) response with preferential impact on proline-rich proteins. HF anti-LCMV activity was prevented by the addition of exogenous proline supporting that inhibition of PRS activity plays a critical role on the anti-MaAv activity of HF. We found that HF did not affect LCMV cell entry, modestly (twofold) reduced the activity of the virus ribonucleoprotein (vRNP) but strongly inhibited (>90%) Z budding activity, a process involving the Z proline-rich late domain motifs.

microbiology↗

bioRxiv2024

Cellular N-myristoyl transferases Are Required for Mammarenavirus Multiplication

The mammarenavirus matrix Z protein plays critical roles in virus assembly and cell egress, whereas heterotrimer complexes of a stable signal peptide (SSP) together with glycoprotein subunits GP1 and GP2, generated via co-and post-translational processing of the surface glycoprotein precursor GPC, form the spikes that decorate the virion surface and mediate virus cell entry via receptor-mediated endocytosis. The Z protein and SSP undergo N-terminal myristoylation by host cell N-myristoyltransferases (NMT1 and NMT2), and G2A mutations that prevent myristoylation of Z or SSP have been shown to affect Z mediated virus budding and GP2 mediated fusion activity required to complete the virus cell entry process. In the present work, we present evidence that the validated on-target specific pan NMT inhibitor DDD85464 exerts a potent antiviral activity against the prototypic mammarenavirus lymphocytic choriomeningitis virus (LCMV) that correlated with reduced Z budding activity and GP2 mediated fusion activity, as well as proteasome mediated degradation of the Z protein. The potent anti-mammarenaviral activity of DDD85646 was also observed with the hemorrhagic fever causing mammarenaviruses Junin (JUNV) and Lassa (LASV) viruses. Our results support exploration of NMT inhibition as a broad-spectrum antiviral against human pathogenic mammarenaviruses.

microbiology↗

bioRxiv2023

Activation of Protein Kinase R (PKR) Plays a Pro-Viral Role in Mammarenavirus Infected Cells

Many viruses, including mammarenaviruses, have evolved mechanisms to counteract different components of the host cell innate immunity, which is required to facilitate robust virus multiplication. The double strand (ds)RNA sensor protein kinase receptor (PKR) pathway plays a critical role in the cell antiviral response. Whether PKR can restrict the multiplication of the Old World mammarenavirus lymphocytic choriomeningitis virus (LCMV) and the mechanisms by which LCMV may counteract the antiviral functions of PKR have not yet been investigated. Here we present evidence that LCMV infection results in very limited levels of PKR activation, but LCMV multiplication is enhanced in the absence of PKR. In contrast, infection with a recombinant LCMV with a mutation affecting the 3-5 exonuclease (ExoN) activity of the viral nucleoprotein (NP) resulted in robust PKR activation in the absence of detectable levels of dsRNA, which was associated with severely restricted virus multiplication that was alleviated in the absence of PKR. However, pharmacological inhibition of PKR activation resulted in reduced levels of LCMV multiplication. These findings uncovered a complex role of the PKR pathway in LCMV-infected cells involving both pro-and anti- viral activities. IMPORTANCEAs with many other viruses, the prototypic Old World mammarenavirus lymphocytic choriomeningitis virus (LCMV) can interfere with the host cell innate immune response to infection, which includes the double strand (ds)RNA sensor protein kinase receptor (PKR) pathway. A detailed understanding of LCMV-PKR interactions can provide novel insights about mammarenavirus-host cell interactions and facilitate the development of effective antiviral strategies against human pathogenic mammarenaviruses. In the present work, we present evidence that LCMV multiplication is enhanced in PKR- deficient cells, but pharmacological inhibition of PKR activation unexpectedly resulted in severely restricted propagation of LCMV. Likewise, we document a robust PKR activation in LCMV-infected cells in the absence of detectable levels of dsRNA. Our findings have revealed a complex role of the PKR pathway during LCMV infection and uncovered the activation of PKR as a druggable target for the development of antiviral drugs against human pathogenic mammarenaviruses.

microbiology↗