Biology subjects

Liem, J.

Publications and source records attributed to Liem, J..

3 recordsLinked to original sources

bioRxiv2024

Antagonizing the SAMD9 pathway is key to myxoma virus host shut-off and immune evasion.

Poxviruses have life cycles exclusively in the cytoplasm. However, these viruses can have profound impact to host transcription. One possible mechanism is through viral manipulation of host protein synthesis and such ability is critical for viral immune evasion. Many mammalian poxviruses encode more than one viral protein to interact with the host SAMD9 protein. In myxoma virus (MYXV), a rabbit specific poxvirus and non-pathogenic for other species, viral M062 protein is the lone inhibitor to SAMD9 with broad species specificity and loss of M062R in viral genome ({Delta}M062R mutant) leads to profound infection defect. We previously found {Delta}M062R remodeled transcriptomic landscape in monocytes/macrophages that is associated with the crosstalk between the SAMD9 pathway and cGAS/STING/IRF3 DNA sensing pathway. In this study we completed the characterization of {Delta}M062R infection. We observed that although this replication-defective virus preserved intact early protein synthesis, it failed to conduct host shutoff. Despite a defect in viral DNA replication, {Delta}M062R infection retained intact intermediate protein synthesis comparable to the wildtype virus. Using time course dual RNAseq analyses we found that the overall viral gene transcription profile was mostly indistinguishable from that of the wildtype MYXV. However, the slightly attenuated late RNA synthesis along with the block at viral protein synthesis led to its infection defect. Infection by {Delta}M062R in macrophages potentiated the antiviral responses to new danger signals. We provided an initial characterization of such a state in which host antiviral protein synthesis may be promoted leading to the immunological consequence. ImportancePoxviruses utilize multi-faceted strategies to evade and manipulate host immunity. Through targeted gene deletion, we generated useful tools of mutant poxviruses to investigate specific crosstalk between host defense mechanisms. Through studying MYXV M062 protein function, we previously identified SAMD9 as one host target of poxvirus C7L superfamily, in which family M062R is one member. However, what kind of cellular outcome caused by {Delta}M062R infection remained unknown. The infection defect of {Delta}M062R caused the induction of host inflammation program is likely due to the activation of the host pathway governed by SAMD9. Because little is known about SAMD9 cellular function and the pathways it regulates, which are important for cellular homeostasis and immune regulation, this study on {Delta}M062R induced effect in host cells will provide new insight on how SAMD9 affects cellular protein synthesis and immunological responses.

microbiology↗

bioRxiv2022

Myxoma virus lacking the host range determinant M062 stimulates cGAS-dependent type 1 interferon response and unique transcriptomic changes in human macrophages

The evolutionarily successful poxviruses possess effective and diverse strategies to circumvent or overcome host defense mechanisms. Poxviruses encode many immunoregulatory proteins to evade host immunity to establish a productive infection and have unique means of inhibiting DNA sensing-dependent type 1 interferon (IFN-I) responses, a necessity given their dsDNA genome and exclusively cytoplasmic life cycle. We found that the key DNA sensing inhibition by poxvirus infection was dominant during the early stage of poxvirus infection before DNA replication. In an effort to identify the poxvirus gene products which subdue the antiviral proinflammatory responses (e.g., IFN-I response), we investigated the function of one early gene that is the known host range determinant from the highly conserved poxvirus host range C7L superfamily, myxoma virus (MYXV) M062. Host range factors are unique features of poxviruses that determine the species and cell type tropism. Almost all sequenced mammalian poxviruses retain at least one homologue of the poxvirus host range C7L superfamily. In MYXV, a rabbit-specific poxvirus, the dominant and broad-spectrum host range determinant of the C7L superfamily is the M062R gene. The M062R gene product is essential for MYXV infection in almost all cells tested from different mammalian species and specifically inhibits the function of host Sterile Motif Domain-containing 9 (SAMD9), as M062R-null ({Delta}M062R) MYXV causes abortive infection in a SAMD9-dependent manner. In this study we investigated the immunostimulatory property of the {Delta}M062R. We found that the replication-defective {Delta}M062R activated host DNA sensing pathway during infection in a cGAS-dependent fashion and that knocking down SAMD9 expression attenuated proinflammatory responses. Moreover, transcriptomic analyses showed a unique feature of the host gene expression landscape that is different from the dsDNA-stimulated inflammatory state. This study establishes a link between the anti-neoplastic function of SAMD9 and the regulation of innate immune responses. Author SummaryPoxviruses encode a group of genes called host range determinants to maintain or expand their host tropism. The mechanism by which many viral host range factors function remains elusive. Some host range factors possess immunoregulatory functions responsible for evading or subduing host immune defense mechanisms. Most known immunoregulatory proteins encoded by poxviruses are dispensable for viral replication in vitro. The uniqueness of MYXV M062R is that it is essential for viral infection in vitro and belongs to one of the most conserved poxvirus host range families, the C7L superfamily. There is one known host target of the MYXV M062 protein, SAMD9. SAMD9 is constitutively expressed in mammalian cells and exclusively present in the cytoplasm and has an anti-neoplastic function. Humans with deleterious mutations in SAMD9 present disease that ranges from lethality at a young age to a predisposition to myelodysplastic syndromes (MDS) that often require bone marrow transplantation. More importantly, SAMD9 serves as an important antiviral intrinsic molecule to many viruses. The cellular function of SAMD9 remains unclear mostly due to the difficulty of studying this protein, i.e., its large size, long half-life, and its constitutive expression in most cells. In this study we used M062R-null MYXV as a tool to study SAMD9 function and report a functional link between SAMD9 and the regulation of the proinflammatory responses triggered by cGAS-dependent DNA sensing.

immunology↗

bioRxiv2020

Computational design of two new soluble epoxide hydrolase (sEH) inhibitors

Inhibitors of soluble epoxide hydrolase (sEH) enzymes have shown great potential for the treatment of neuropathic pain. However, current sEH inhibitors have poor physicochemical properties and has not been proven to be safe for human treatments yet. New inhibitor designs could have the potential to improve current drugs efficacy, and so in this work, chemical intuition and bioisosteric replacement were used to computationally design two novel sEH inhibitors. These new candidates showed good pharmacokinetic properties and presented better docking scores compared to a known sEH inhibitor, t-TUCB, used in the treatment of pain in horses. Homology analysis revealed that Mus musculus may not be suitable organism for preclinical trials studies of these novel inhibitors.

pharmacology and toxicology↗