Biology subjects

Galitska, G.

Publications and source records attributed to Galitska, G..

3 recordsLinked to original sources

bioRxiv2023

Enterovirus D68 capsid formation and stability requires acidic compartments

Enterovirus D68 (EV-D68), a picornavirus traditionally associated with respiratory infections, has recently been linked to a polio-like paralytic condition known as acute flaccid myelitis (AFM). EV-D68 is understudied, and much of the fields understanding of this virus is based on studies of poliovirus. For poliovirus, we previously showed that low pH promotes virus capsid maturation, but here we show that, for EV-D68, inhibition of compartment acidification during a specific window of infection causes a defect in capsid formation and maintenance. These phenotypes are accompanied by radical changes in the infected cell, with viral replication organelles clustering in a tight juxtanuclear grouping. Organelle acidification is critical during a narrow window from 3-4hpi, which we have termed the "transition point," separating translation and peak RNA replication from capsid formation, maturation and egress. Our findings highlight that acidification is crucial only when vesicles convert from RNA factories to virion crucibles. ImportanceThe respiratory picornavirus enterovirus D68 is a causative agent of Acute Flaccid Myelitis, a childhood paralysis disease identified in the last decade. Poliovirus, another picornavirus associated with paralytic disease, is a fecal-oral virus which survives acidic environments when passing from host-to-host. Here we follow up on our previous work showing a requirement for acidic intracellular compartments for maturation cleavage of poliovirus particles. Enterovirus D68 requires acidic vesicles for an earlier step, assembly and maintenance of viral particles themselves. These data have strong implications for the use of acidification blocking treatments to combat enterovirus diseases.

microbiology↗

bioRxiv2022

SIRT-1 connects autophagy and release of virus-containing vesicles during picornavirus infection

Enterovirus D68 is a re-emerging enterovirus that causes acute respiratory illness in infants and has recently been linked to Acute Flaccid Myelitis. Here, we show that the histone deacetylase, SIRT-1, is essential for autophagy and EV-D68 infection. Knockdown of SIRT-1 inhibits autophagy and reduces EV-D68 extracellular titers. The proviral activity of SIRT-1 does not require its deacetylase activity or functional autophagy. SIRT-1s proviral activity is, we demonstrate, mediated through the repression of ER stress. Inducing ER stress through thapsigargin treatment or SERCA2A knockdown in SIRT-1 knockdown cells had no additional effect on EV-D68 extracellular titers. Knockdown of SIRT-1 also decreases poliovirus and SARS-CoV-2 titers but not coxsackievirus B3. In non-lytic conditions, EV-D68 is primarily released in an enveloped form, and SIRT-1 is required for this process. Our data show that SIRT-1, through its translocation to the cytosol, is critical to promote the release of enveloped EV-D68 viral particles.

microbiology↗

bioRxiv2019

A Conserved Mechanism of APOBEC3 Relocalization by Herpesviral Ribonucleotide Reductase Large Subunits

An integral part of the antiviral innate immune response is the APOBEC3 family of single-stranded DNA cytosine deaminases, which inhibits virus replication through deamination-dependent and -independent activities. Viruses have evolved mechanisms to counteract these enzymes such as HIV-1 Vif-mediated formation of a ubiquitin ligase to degrade virus-restrictive APOBEC3 enzymes. A new example is Epstein-Barr virus (EBV) ribonucleotide reductase (RNR)-mediated inhibition of cellular APOBEC3B (A3B). The large subunit of the viral RNR, BORF2, causes A3B relocalization from the nucleus to cytoplasmic bodies and thereby protects viral DNA during lytic replication. Here, we use co-immunoprecipitation and immunofluorescent microscopy approaches to ask whether this mechanism is shared with the closely related {gamma}-herpesvirus Kaposis sarcoma-associated herpesvirus (KSHV) and the more distantly related -herpesvirus, herpes simplex virus-1 (HSV-1). The large RNR subunit of KSHV, ORF61, co-precipitated multiple APOBEC3s including A3B and APOBEC3A (A3A). KSHV ORF61 also caused relocalization of these two enzymes to perinuclear bodies (A3B) and to oblong cytoplasmic structures (A3A). The large RNR subunit of HSV-1, ICP6, also co-precipitated A3B and A3A and was sufficient to promote the relocalization of these enzymes from nuclear to cytoplasmic compartments. HSV-1 infection caused similar relocalization phenotypes that required ICP6. However, unlike the infectivity defects previously reported for BORF2-null EBV, ICP6 mutant HSV-1 showed normal growth rates and plaque phenotypes. These results combine to indicate that both {gamma}- and -herpesviruses use a conserved RNR-dependent mechanism to relocalize A3B and A3A and, further, suggest that HSV-1 possesses at least one additional mechanism to neutralize these antiviral enzymes.\n\nImportanceThe APOBEC3 family of DNA cytosine deaminases constitutes a vital innate immune defense against a range of different viruses. A novel counter-restriction mechanism has recently been uncovered for the {gamma}-herpesvirus EBV, in which a subunit of the viral protein known to produce DNA building blocks (ribonucleotide reductase) causes A3B to relocalize from the nucleus to the cytosol. Here, we extend these observations with A3B to include a closely related {gamma}-herpesvirus, KSHV, and to a more distantly related -herpesvirus, HSV-1. These different viral ribonucleotide reductases also caused relocalization of A3A, which is 92% identical to A3B. These studies are important because they suggest a conserved mechanism of APOBEC3 evasion by large double-stranded DNA herpesviruses. Strategies to block this host-pathogen interaction may be effective for treating infections caused by these herpesviruses.

microbiology↗