Biology subjects

Baruah, V.

Publications and source records attributed to Baruah, V..

3 recordsLinked to original sources

bioRxiv2025

Human cytomegalovirus-encoded G protein-coupled receptor (GPCR), UL78, regulates viral reactivation

Human cytomegalovirus (CMV) is a ubiquitous pathogen that establishes life-long, latent infection in hematopoietic cells. Immune-competent individuals are usually asymptomatic for disease. However, immune dysregulation in latently-infected individuals can result in viral reactivation, often causing further complications. Viral gene transcription during latency is restricted, although the CMV-encoded G-protein coupled receptor homologs, US28 and UL78, are expressed. We and others find US28 is critical for establishing and maintaining viral latency, in part, through regulating host cell signaling. How US28 switches from pro-latent to pro-lytic during reactivation, however, is unknown, though our findings herein reveal a role for UL78. Myeloid cells infected with a UL78 ORF deletion mutant maintain viral latency yet fail to efficiently reactivate. However, the UL78 G protein-coupling domain is not required for reactivation, suggesting UL78-mediated signaling is not critical for reactivation. Prior work revealed UL78 and US28 interact, resulting in altered US28-mediated signaling. Additionally, we showed US28 attenuates ERK phosphorylation during latency, while ERK is phosphorylated upon reactivation; however, the mechanism underlying this switch is unknown. Thus, we hypothesized the UL78:US28 interaction is important for altering US28-mediating signaling upon viral reactivation. We find US28 and UL78 interact during lytic infection of fibroblasts and colocalize in myeloid cells upon their differentiation. Further, reactivation in myeloid cells latently-infected with wild-type virus results in upregulated ERK phosphorylation, while parallel cultures infected with the UL78-deficient virus fail to do so. Our data reveal the first function for UL78 in myeloid cells, where it influences cellular signaling to switch from pro-latent to pro-lytic. ImportanceCytomegalovirus (CMV) is a ubiquitous human herpesvirus, infecting the majority of the population worldwide. As with all herpesviruses, once an individual is infected with CMV, the virus remains in a persons blood cells for their life in a silenced state called latency, and this infection, for the most part, remains asymptomatic. When an infected individuals immune system fails to function properly, however, CMV can become active (termed viral reactivation), which allows the virus to replicate and cause downstream disease. Our understanding of the cellular and viral factors that dictate this switch from silenced to activated remains incomplete. Here, we show a viral protein, UL78, is required for this switch. We find UL78 helps to reshape cellular signaling, changing the cell environment from one that favors latency to one that instead supports reactivation. This highlights a new avenue for therapeutic intervention to prevent CMV reactivation and downstream disease.

microbiology↗

bioRxiv2025

Inhibition of MAPK signaling suppresses cytomegalovirus reactivation in CD34+ Kasumi-3 cells

Reactivation of latent human cytomegalovirus (CMV) can lead to severe complications in individuals with dysregulated immune systems. While antiviral therapies for CMV are approved, these compounds are limited by their toxicity and inability to specifically target the latent reservoir or prevent reactivation. Herein we show that CMV reactivation in Kasumi-3 cells, a CD34+ hematopoietic cell line, requires mitogen-activated protein kinase (MAPK) activation. Importantly, pharmacological inhibition of the MAPK signaling pathway, including MEK and ERK, restricts viral reactivation in Kasumi-3 cells. In sum, our findings show MAPK signaling is critical for CMV reactivation, revealing a potential avenue for therapeutic intervention to prevent viral reactivation and downstream pathogenesis that is often detrimental for immunosuppressed and immunocompromised patients.

microbiology↗

bioRxiv2024

Cytomegalovirus Restricts the Innate Immune Response by Nuclear Export of Host Restriction Factor DDX41

The innate immune response is the first line of defense against invading pathogens, including the betaherpesvirus, human cytomegalovirus (CMV). The hosts innate response acts as the first line of defense, and CMV, like other viruses, has consequently evolved multiple mechanisms to manipulate host interferon (IFN) responses. DEAD-box Helicase 41 (DDX41) is an intracellular dsDNA sensor that, upon activation by Brutons tyrosine kinase (BTK), triggers type I IFN production through the Stimulator of Interferon Genes (STING) signaling pathway. Here, we show the activation of this signaling pathway during lytic CMV infection, wherein BTK, DDX41, and STING are activated through tyrosine phosphorylation, and both DDX41 and BTK interact with STING. Further, CMV infection re-localizes DDX41 from the nucleus to the cytoplasm, where it localizes to the perinuclear virus assembly compartment (vAC). Here, DDX41 phosphorylation is attenuated, suggesting cytoplasmic redistribution leads to a less active or inactive form. Additionally, DDX41 co-localizes in the vAC with the CMV tegument proteins, pp65 and pp71, each of which interact with DDX41 in immunoprecipitation assays. We further demonstrate the protective role of this signaling pathway, as treatment with the BTK inhibitor, orelabrutinib, attenuates DDX41 phosphorylation/activation and supports increased expression of viral proteins and virus replication. In sum, our work highlights the important role of BTK-DDX41-STING signaling in the innate immune response against CMV, which the virus subverts by attenuating its cytoplasmic activity, thereby diverting it from its typically protective function. ImportanceHuman cytomegalovirus (CMV) is a ubiquitous pathogen that poses a significant threat to immunocompromised individuals, highlighting the critical role of innate immunity in controlling this viral infection. Despite extensive research, the complex mechanisms underlying innate immunity against CMV and the viruss strategies for evading immune detection remain only partially understood. This study identifies the activation of the cellular BTK-DDX41-STING innate signaling axis during lytic CMV infection, which ultimately results in protective interferon responses. Our findings show that CMV infection triggers the cytoplasmic redistribution of the cellular protein, DDX41, leading to reduced phosphorylation and activity, thereby undermining its protective function. Additionally, pharmacological inhibition of BTK enhances viral protein expression and replication, highlighting the importance of this pathway in immune defense. Our work identifies BTK- and DDX41-dependent STING signaling as important for innate immune responses against CMV and further advances our understanding of CMVs manipulation of these responses.

microbiology↗