Toxoplasma gondii Type-I ROP18 Targeting Human E3 Ligase TRIM21 for Immune Escape

Friend or foe of tripartite motif-containing protein 21 in cardiovascular disease: A review

As an E3 ubiquitin ligase and an Fc receptor, tripartite motif-containing protein 21 (TRIM21) plays a crucial role in immune defense, signal transduction, and cellular regulation. TRIM21 is widely expressed in various tissues, but it is particularly abundant in cardiovascular tissues and is involved in the pathogenesis of various cardiovascular diseases (CVDs). However, although TRIM21 is involved in the regulation of several key molecular pathways in the immune system, its specific role in CVD remains unclear. In this review, we comprehensively summarize the regulatory role of TRIM21 in signaling pathways and discuss the function of TRIM21 in CVD, to provide a systematic understanding of this important protein in CVD and offer insights for further research into the pathogenesis of CVD and its potential applications.

TRIM21 interacts with IκBα and negatively regulates NF-κB activation in Corynebacterium pseudotuberculosis-infected macrophages

Corynebacterium pseudotuberculosis, a zoonotic intracellular bacteria, is responsible for abscesses and pyogranuloma formation of the infected host, which is essentially a chronic inflammatory response. Tripartite motif-containing protein 21 (TRIM21) negatively regulates pro-inflammatory cytokines production during C. pseudotuberculosis infection, the mechanism of which remains unclear. This study found that C. pseudotuberculosis infection in macrophages induced phosphorylation of IκB and p65. TRIM21 interacted with IκBα by PRY/SPRY domain, stabilizes IκBα and negatively regulates IκBα phosphorylation in macrophages during C. pseudotuberculosis infection. In addition, TRIM21 positively regulates the ubiquitination of IκBα via K48 linkage rather than K63 linkage in C. pseudotuberculosis-infected macrophages. In brief, our research confirmed that TRIM21 negatively regulates canonical NF-κB activation by interacting with IκBα and decreasing IκBα phosphorylation in macrophages during C. pseudotuberculosis infection. Preventing inflammation induced by C. pseudotuberculosis infection through regulation of the NF-κB pathway is a potential way to control this pathogen.

TRIM21 is critical in regulating hepatocellular carcinoma growth and response to therapy by altering the MST1/YAP pathway

Liver cancer is the sixth most common cancer and the third leading cause of cancer-related death globally. Despite efforts being made in last two decades in cancer diagnosis and treatment, the 5-year survival rate of liver cancer remains extremely low. TRIM21 participates in cancer metabolism, glycolysis, immunity, chemosensitivity and metastasis by targeting various substrates for ubiquitination. TRIM21 serves as a prognosis marker for human hepatocellular carcinoma (HCC), but the mechanism by which TRIM21 regulates HCC tumorigenesis and progression remains elusive. In this study, we demonstrated that TRIM21 protein levels were elevated in human HCC. Elevated TRIM21 expression was associated with HCC progression and poor survival. Knockdown of TRIM21 in HCC cell lines significantly impaired cell growth and metastasis and enhanced sorafenib-induced toxicity. Mechanistically, we found that knockdown of TRIM21 resulted in cytosolic translocation and inactivation of YAP. At the molecular level, we further identified that TRIM21 interacted and induced ubiquitination of MST1, which resulted in MST1 degradation and YAP activation. Knockdown of MST1 or overexpression of YAP reversed TRIM21 knockdown-induced impairment of HCC growth and chemosensitivity. Taken together, the current study demonstrates a novel mechanism that regulates the Hippo pathway and reveals TRM21 as a critical factor that promotes growth and chemoresistance in human HCC.

A Interacting Model: How TRIM21 Orchestrates with Proteins in Intracellular Immunity

Tripartite motif-containing protein 21 (TRIM21), identified as both a cytosolic E3 ubiquitin ligase and FcR (Fragment crystallizable receptor), primarily interacts with proteins via its PRY/SPRY domains and promotes their proteasomal degradation to regulate intracellular immunity. But how TRIM21 involves in intracellular immunity still lacks systematical understanding. Herein, it is probed into the TRIM21-related literature and raises an interacting model about how TRIM21 orchestrates proteins in cytosol. In this novel model, TRIM21 generally interacts with miscellaneous protein in intracellular immunity in two ways: For one, TRIM21 solely plays as an E3, ubiquitylating a glut of proteins that contain specific interferon-regulatory factor, nuclear transcription factor kappaB, virus sensors and others, and involving inflammatory responses. For another, TRIM21 serves as both E3 and specific FcR that detects antibody-complexes and facilitates antibody destroying target proteins. Correspondingly delineated as Fc-independent signaling and Fc-dependent signaling in this review, how TRIM21's interactions contribute to intracellular immunity, expecting to provide a systematical understanding of this important protein and invest enlightenment for further research on the pathogenesis of related diseases and its prospective application is elaborated.

Improved understanding of biorisk for research involving microbial modification using annotated sequences of concern

Regulation of research on microbes that cause disease in humans has historically been focused on taxonomic lists of 'bad bugs'. However, given our increased knowledge of these pathogens through inexpensive genome sequencing, 5 decades of research in microbial pathogenesis, and the burgeoning capacity of synthetic biologists, the limitations of this approach are apparent. With heightened scientific and public attention focused on biosafety and biosecurity, and an ongoing review by US authorities of dual-use research oversight, this article proposes the incorporation of sequences of concern (SoCs) into the biorisk management regime governing genetic engineering of pathogens. SoCs enable pathogenesis in all microbes infecting hosts that are 'of concern' to human civilization. Here we review the functions of SoCs (FunSoCs) and discuss how they might bring clarity to potentially problematic research outcomes involving infectious agents. We believe that annotation of SoCs with FunSoCs has the potential to improve the likelihood that dual use research of concern is recognized by both scientists and regulators before it occurs.

Transcriptomic analysis of LMH cells in response to the overexpression of a protein of Eimeria tenella encoded by the locus ETH_00028350

A protein of Eimeria tenella (encoded by the locus ETH_00028350) homologous to Toxoplasma gondii dense granule protein 9, designated as EtHGRA9 hereafter, was reported to be expressed in all life cycle stages of E. tenella. However, no data are currently available regarding its functional properties. In the present study, a recombinant vector harboring a 741 bp gene segment encoding the mature form of EtHGRA9 was constructed and transfected into leghorn male hepatoma (LMH) cells. Then, transcriptomic analysis of the transfected LMH cells was carried out by using a high-throughput RNA-seq technology. The LMH cells overexpressing EtHGRA9 was validated by means of Western blotting as well as indirect immunofluorescence staining. The results demonstrated that the expression of 547 genes (275 upregulated genes and 272 downregulated genes) was altered by EtHGRA9. The quantitative real-time polymerase chain reaction (qRT-PCR) validation of the ten genes with differential expression between the two groups was consistent with the transcriptome analysis. According to pathway enrichment analysis for the obtained differentially expressed genes, seven pathways were significantly affected by EtHGRA9, such as cytokine-cytokine receptor interaction, MAPK signaling pathway, and protein processing in endoplasmic reticulum. Our data reveal several possible roles of EtHGRA9 in immune or inflammatory responses, which paves the way for a better understanding of the molecular interplay between E. tenella and its host.

Toxoplasmosis vaccines: what we have and where to go?

Despite recent major advances in developing effective vaccines against toxoplasmosis, finding new protective vaccination strategies remains a challenging and elusive goal as it is critical to prevent the disease. Over the past few years, various experimental approaches have shown that developing an effective vaccine against T. gondii is achievable. However, more remains unknown due to its complicated life cycle, difficulties in clinical translation, and lack of a standardized platform. This minireview summarizes the recent advances in the development of T. gondii vaccines and the main obstacles to developing a safe, effective and durable T. gondii vaccine. The successes and failures in developing and testing vaccine candidates for the T. gondii vaccine are also discussed, which may facilitate the future development of T. gondii vaccines.

Interferon-Inducible E3 Ligase RNF213 Facilitates Host-Protective Linear and K63-Linked Ubiquitylation of Toxoplasma gondii Parasitophorous Vacuoles

The obligate intracellular protozoan pathogen Toxoplasma gondii infects a wide range of vertebrate hosts and frequently causes zoonotic infections in humans. Whereas infected immunocompetent individuals typically remain asymptomatic, toxoplasmosis in immunocompromised individuals can manifest as a severe, potentially lethal disease, and congenital Toxoplasma infections are associated with adverse pregnancy outcomes. The protective immune response of healthy individuals involves the production of lymphocyte-derived cytokines such as interferon gamma (IFN-γ), which elicits cell-autonomous immunity in host cells. IFN-γ-inducible antiparasitic defense programs comprise nutritional immunity, the production of noxious gases, and the ubiquitylation of the Toxoplasma-containing parasitophorous vacuole (PV). PV ubiquitylation prompts the recruitment of host defense proteins to the PV and the consequential execution of antimicrobial effector programs, which reduce parasitic burden. However, the ubiquitin E3 ligase orchestrating these events has remained unknown. Here, we demonstrate that the IFN-γ-inducible E3 ligase RNF213 translocates to Toxoplasma PVs and facilitates PV ubiquitylation in human cells. Toxoplasma PVs become decorated with linear and K63-linked ubiquitin and recruit ubiquitin adaptor proteins in a process that is RNF213 dependent but independent of the linear ubiquitin chain assembly complex (LUBAC). IFN-γ priming fails to restrict Toxoplasma growth in cells lacking RNF213 expression, thus identifying RNF213 as a potent executioner of ubiquitylation-driven antiparasitic host defense. IMPORTANCE Globally, approximately one out of three people become infected with the obligate intracellular parasite Toxoplasma. These infections are typically asymptomatic but can cause severe disease and mortality in immunocompromised individuals. Infections can also be passed on from mother to fetus during pregnancy, potentially causing miscarriage or stillbirth. Therefore, toxoplasmosis constitutes a substantial public health burden. A better understanding of mechanisms by which healthy individuals control Toxoplasma infections could provide roadmaps toward novel therapies for vulnerable groups. Our work reveals a fundamental mechanism controlling intracellular Toxoplasma infections. Cytokines produced during Toxoplasma infections instruct human cells to produce the enzyme RNF213. We find that RNF213 labels intracellular vacuoles containing Toxoplasma with the small protein ubiquitin, which functions as an "eat-me" signal, attracting antimicrobial defense programs to fight off infection. Our work therefore identified a novel antiparasitic protein orchestrating a central aspect of the human immune response to Toxoplasma.

Host cell proteins modulated upon Toxoplasma infection identified using proteomic approaches: a molecular rationale

Toxoplasma gondii is a pathogenic protozoan parasite belonging to the apicomplexan phylum that infects the nucleated cells of warm-blooded hosts leading to an infectious disease known as toxoplasmosis. Apicomplexan parasites such as T. gondii can display different mechanisms to control or manipulate host cells signaling at different levels altering the host subcellular genome and proteome. Indeed, Toxoplasma is able to modulate host cell responses (especially immune responses) during infection to its advantage through both structural and functional changes in the proteome of different infected cells. Consequently, parasites can transform the invaded cells into a suitable environment for its own replication and the induction of infection. Proteomics as an applicable tool can identify such critical proteins involved in pathogen (Toxoplasma)-host cell interactions and consequently clarify the cellular mechanisms that facilitate the entry of pathogens into host cells, and their replication and transmission, as well as the central mechanisms of host defense against pathogens. Accordingly, the current paper reviews several proteins (identified using proteomic approaches) differentially expressed in the proteome of Toxoplasma-infected host cells (macrophages and human foreskin fibroblasts) and tissues (brain and liver) and highlights their plausible functions in the cellular biology of the infected cells. The identification of such modulated proteins and their related cell impact (cell responses/signaling) can provide further information regarding parasite pathogenesis and biology that might lead to a better understanding of therapeutic strategies and novel drug targets.