Guanylate Binding Protein-1 Research Articles

Interferon signalling and non-canonical inflammasome activation promote host protection against multidrug-resistant Acinetobacter baumannii.

Multidrug-resistant (MDR) Acinetobacter baumannii are of major concern worldwide due to their resistance to last resort carbapenem and polymyxin antibiotics. To develop an effective treatment strategy, it is critical to better understand how an A. baumannii MDR bacterium interacts with its mammalian host. Pattern-recognition receptors sense microbes, and activate the inflammasome pathway, leading to pro-inflammatory cytokine production and programmed cell death. Here, we examined the effects of a systemic MDR A. baumannii infection and found that MDR A. baumannii activate the NLRP3 inflammasome complex predominantly via the non-canonical caspase-11-dependent pathway. We show that caspase-1 and caspase-11-deficient mice are protected from a virulent MDR A. baumannii strain by maintaining a balance between protective and deleterious inflammation. Caspase-11-deficient mice also compromise between effector cell recruitment, phagocytosis, and programmed cell death in the lung during infection. Importantly, we found that cytosolic immunity - mediated by guanylate-binding protein 1 (GBP1) and type I interferon signalling - orchestrates caspase-11-dependent inflammasome activation. Together, our results suggest that non-canonical inflammasome activation via the (Interferon) IFN pathway plays a critical role in the host response against MDR A. baumannii infection.

The Large GTPase Guanylate-Binding Protein-1 (GBP-1) Promotes Mitochondrial Fission in Glioblastoma.

Glioblastomas (aka Glioblastoma multiformes (GBMs)) are the most deadly of the adult brain tumors. Even with aggressive treatment, the prognosis is extremely poor. The large GTPase Guanylate-Binding Protein-1 (GBP-1) contributes to the poor prognosis of GBM by promoting migration and invasion. GBP-1 is substantially localized to the cytosolic side of the outer membrane of mitochondria in GBM cells. Because mitochondrial dynamics, particularly mitochondrial fission, can drive cell migration and invasion, the potential interactions between GBP-1 and mitochondrial dynamin-related protein 1 (Drp1) were explored. Drp1 is the major driver of mitochondrial fission. While GBP-1 and Drp1 both had punctate distributions within the cytoplasm and localized to regions of the cytoplasmic side of the plasma membrane of GBM cells, the proteins were only molecularly co-localized at the mitochondria. Subcellular fractionation showed that the presence of elevated GBP-1 promoted the movement of Drp1 from the cytosol to the mitochondria. The migration of U251 cells treated with the Drp1 inhibitor, Mdivi-1, was less inhibited in the cells with elevated GBP-1. Elevated GBP-1 in GBM cells resulted in shorter and wider mitochondria, most likely from mitochondrial fission. Mitochondrial fission can drive several important cellular processes, including cell migration, invasion, and metastasis.

Inhibition of GBP1 alleviates pyroptosis of human pulmonary microvascular endothelial cells through STAT1/NLRP3/GSDMD pathway

Restoring and maintaining the function of endothelial cells is critical for acute respiratory distress syndrome (ARDS). Guanylate binding protein 1(GBP1) is proved to elevated in ARDS patients, but its role and mechanism remains unclear. The objective of this study is to investigate the internal mechanism of GBP1 in lung injury. Our study showed that when the LPS and IFN-γ induced human Pulmonary Microvascular Endothelial Cells (HPMECs) injury model was established, cell viability was significantly reduced, and the levels of GBP1 levels and inflammatory factors were significantly increased. When transfection with si-GBP1, low expression of GBP1 promoted cell proliferation and migration, and decreased the expression of downstream inflammatory factors. Furthermore, the inhibition of GBP1 significantly reduced the occurrence of cell pyroptosis and the expression of NLRP3 and STAT1. Our study indicated that GBP1 alleviates endothelial pyroptosis and inflammation through STAT1 / NLRP3/GSDMD signaling pathway, and GBP1 may be a new target in the treatment of lung injury in the future.

Potential Mechanism and Therapeutic Targets of Polymyositis.

To investigate the variability in the expression profile of genes associated with polymyositis (PM), explore the potential molecular mechanisms underlying PM, and predict novel targets for intervention. Descriptive study. Place and Duration of the Study: Department of Rheumatology, Taizhou Municipal Hospital, Taizhou, China, from August to November 2023. Three microarray datasets (GSE3112, GSE39454, and GSE128470) were extracted from the gene expression omnibus (GEO). The analysis of this research involved identifying the differentially expressed genes (DEGs) in PM compared to normal samples. Enrichment analysis, gene-microRNA, gene-transcription factor (TF), and protein-protein interaction (PPI) network studies were conducted to identify hub genes and relevant pathways. Additionally, the drug-gene interaction database (DGIdb) was used to predict therapeutic medications. Eighty-eight DEGs were identified. The enrichment analysis results highlighted the significant involvement of downregulated DEGs in antigen processing and presentation. Based on the PPI networks, seven hub genes with high connectivity degrees were selected including a cluster of differentiation 74 (CD74), human leukocyte antigen (HLA)-DPA1, HLA-B, guanylate-binding protein 1 (GBP1), recombinant 2', 5'-oligoadenylate synthetase 1 (OAS1), HLA-C, and HLA-E. This research screened-out core genes, projected prospective therapeutic medications, discovered DEGs between PM and normal samples, and offered fresh perspectives for additional research into the possible mechanism and therapeutic targets of PM. Polymyositis, DEGs, Hub genes, Bioinformatics, Potential therapeutic agents.

Guanylate-Binding Protein 1 (GBP1) Enhances IFN-α Mediated Antiviral Activity against Hepatitis B Virus Infection.

Interferon-alpha (IFN-α) is a first-line drug for treating chronic hepatitis B (CHB). Guanylate-binding protein 1 (GBP1) is one of the interferon-stimulating factors, which participates in the innate immunity of the host and plays an antiviral and antibacterial role. In this study, we explored how GBP1 is involved in IFN-α antiviral activity against HBV. Before being gathered, HepG2-NTCP and HepG2 2.15 cells were transfected with the wild-type hGBP1 plasmid or si-GBP1, respectively, and followed by stimulation with Peg-IFNα-2b. We systematically explored the role of GBP1 in regulating HBV infection in cell models. Additionally, we also examined GBP1 levels in CHB patients. GBP1 activity increased, and its half-life was prolonged after HBV infection. Overexpression of GBP1 inhibited the production of HBsAg and HBeAg, as well as HBs protein and HBV total RNA levels, whereas silencing of GBP1 inhibited its ability to block viral infections. Interestingly, overexpressing GBP1 co-treatment with Peg-IFNα-2b further increased the antiviral effect of IFN-α, while GBP1 silencing co-treatment with Peg-IFNα-2b partly restored its inhibitory effect on HBV. Mechanistically, GBP1 mediates the anti-HBV response of Peg-IFNα-2b by targeting HBs. Analysis of clinical samples revealed that GBP1 was elevated in CHB patients and increased with Peg-IFNα-2b treatment, while GBP1 showed good stability in the interferon response group. Our study demonstrates that GBP1 inhibits HBV replication and promotes HBsAg clearance. It is possible to achieve antiviral effects through the regulation of IFN-α induced immune responses in response to HBV.

Guanylate-binding protein 1 inhibits Hantaan virus infection by restricting virus entry.

Hantaan virus (HTNV) infection can cause hemorrhagic fever with renal syndrome (HFRS) in humans, and currently, there are no long-standing protective vaccines or specific antivirals available. Guanylate-binding protein 1 (GBP1) is an interferon-stimulated gene that defends against various pathogen infections. However, the function of GBP1 in HTNV infection remains unknown. Here, we describe how GBP1 prevents HTNV infection by obstructing virus entry. We found that HTNV infection induced GBP1 expression and that overexpression of GBP1 inhibited HTNV infection, while knockout of GBP1 had the opposite effect. Interestingly, GBP1 did not affect interferon (IFN) signaling during HTNV infection. Instead, GBP1 prevented HTNV from entering cells through clathrin-mediated endocytosis (CME). We also discovered that GBP1 specifically interacted with actin but not dynamin 2 (DNM2) and made it difficult for DNM2 to be recruited by actin, which may account for the suppression of CME during HTNV infection. These findings establish an antiviral role for GBP1 in inhibiting HTNV infection and help us better understand how GBP1 regulates HTNV entry and could potentially aid in developing treatments for this virus.

Identification of Immune-Related Gene Signature in Schizophrenia.

Schizophrenia (SCZ) is a type of psychiatric disorder characterized by multiple symptoms. Our aim is to decipher the relevant mechanisms of immune-related gene signatures in SCZ. The SCZ dataset and its associated immunoregulatory genes were retrieved using Gene Expression Omnibus (GEO) and single-sample gene set enrichment analysis (ssGSEA). Co-expressed gene modules were determined through weighted gene correlation network analysis (WGCNA). To elucidate the functional characteristics of these clusters, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were used. Additionally, gene set enrichment analysis (GSEA) and Gene Set Variation Analysis (GSVA) were conducted to identify enriched pathways for the immune subgroups. A protein-protein interaction (PPI) network analysis was performed to identify core genes relevant to SCZ. A significantly higher immune score was observed in SCZ compared to control samples. Seven distinct gene modules were identified, with genes highlighted in green selected for further analysis. Using the Cell-type Identification By Estimating Relative Subsets Of RNA Transcripts (CIBERSORT) method, degrees of immune cell adhesion and accumulation related to 22 different immune cell types were calculated. Significantly enriched bioprocesses concerning the immunoregulatory genes with differential expressions included interferon-beta, IgG binding, and response to interferon-gamma, according to GO and KEGG analyses. Eleven hub genes related to immune infiltration emerged as key players among the three top-ranked GO terms. This study underscores the involvement of immunoregulatory reactions in SCZ development. Eleven immune-related genes (IFITM1 (interferon induced transmembrane protein 1), GBP1 (guanylate binding protein 1), BST2 (bone marrow stromal cell antigen 2), IFITM3 (interferon induced transmembrane protein 3), GBP2 (guanylate binding protein 2), CD44 (CD44 molecule), FCER1G (Fc epsilon receptor Ig), HLA-DRA (major histocompatibility complex, class II, DR alpha), FCGR2A (Fc gamma receptor IIa), IFI16 (interferon gamma inducible protein 16), and FCGR3B (Fc gamma receptor IIIb)) were identified as hub genes, representing potential biomarkers and therapeutic targets associated with the immune response in SCZ patients.

IFN-α/β/IFN-γ/IL-15 pathways identify GBP1-expressing tumors with an immune-responsive phenotype.

Immunotherapy is widely used in cancer treatment; however, only a subset of patients responds well to it. Significant efforts have been made to identify patients who will benefit from immunotherapy. Successful anti-tumor immunity depends on an intact cancer-immunity cycle, especially long-lasting CD8+ T-cell responses. Interferon (IFN)-α/β/IFN-γ/interleukin (IL)-15 pathways have been reported to be involved in the development of CD8+ T cells. And these pathways may predict responses to immunotherapy. Herein, we aimed to analyze multiple public databases to investigate whether IFN-α/β/IFN-γ/IL-15 pathways could be used to predict the response to immunotherapy. Results showed that IFN-α/β/IFN-γ/IL-15 pathways could efficiently predict immunotherapy response, and guanylate-binding protein 1 (GBP1) could represent the IFN-α/β/IFN-γ/IL-15 pathways. In public and private cohorts, we further demonstrated that GBP1 could efficiently predict the response to immunotherapy. Functionally, GBP1 was mainly expressed in macrophages and strongly correlated with chemokines involved in T-cell migration. Therefore, our study comprehensively investigated the potential role of GBP1 in immunotherapy, which could serve as a novel biomarker for immunotherapy and a target for drug development.

Insights into the effect of guanylate-binding protein 1 on the survival of Brucella intracellularly

Brucellosis is a zoonotic disease that affects wild and domestic animals. It is caused by members of the bacterial genus Brucella. Guanylate-binding protein 1 (GBP1) is associated with microbial infections. However, the role of GBP1 during Brucella infection remains unclear. This investigation aimed to identify the association of GBP1 with brucellosis. Results showed that Brucella infection induced GBP1 upregulation in RAW 264.7 murine macrophages. Small interfering GBP1 targeting RNAs were utilized to explore how GBP1 regulates the survival of Brucella intracellularly. Results revealed that GBP1 knockdown promoted Brucella’s survival ability, activated Nod-like receptor (NLR) containing a pyrin domain 3 (NLRP3) and absent in melanoma 2 (AIM2) inflammatory corpuscles, and induced pro-inflammatory cytokines IFN-γ and IL-1β. Furthermore, Brucella stimulated the expression of GBP1 in bone marrow-derived macrophages (BMDMs) and mice. During the inhibition of GBP1 in BMDMs, the intracellular growth of Brucella increased. In comparison, GBP1 downregulation enhanced the accumulation of Brucella-induced reactive oxygen species (ROS) in macrophages. Overall, the data indicate a significant role of GBP1 in regulating brucellosis and suggest the function underlying its suppressive effect on the survival and growth of Brucella intracellularly.

Interferon-γ-induced GBP1 is an inhibitor of human papillomavirus 18

BackgroundHuman papillomavirus (HPV) infection is an important factor leading to cervical cell abnormalities. 90% of cervical cancers are closely associated with persistent infection of high-risk HPV, with the highest correlation with HPV16 and 18. Currently available vaccines and antivirals have limited effectiveness and coverage. Guanylate binding protein 1 (GBP1) was induced by interferon gamma and involved in many important cellular processes such as clearance of various microbial pathogens. However, whether GBP1 can inhibit human papillomavirus infection is unclear.ResultsIn this study, we found that GBP1 can effectively degrade HPV18 E6, possibly through its GTPase activity or other pathways, and E6 protein degrades GBP1 through the ubiquitin-proteasome pathway to achieve immune escape.ConclusionTherefore, GBP1 is an effector of IFN-γ anti-HPV activity. Our findings provided new insights into the treatment of HPV 18 infections.

Guanylate-binding protein 1 acts as a pro-viral factor for the life cycle of hepatitis C virus.

Viral infections trigger the expression of interferons (IFNs) and interferon stimulated genes (ISGs), which are crucial to modulate an antiviral response. The human guanylate binding protein 1 (GBP1) is an ISG and exhibits antiviral activity against several viruses. In a previous study, GBP1 was described to impair replication of the hepatitis C virus (HCV). However, the impact of GBP1 on the HCV life cycle is still enigmatic. To monitor the expression and subcellular distribution of GBP1 and HCV we performed qPCR, Western blot, CLSM and STED microscopy, virus titration and reporter gene assays. In contrast to previous reports, we observed that HCV induces the expression of GBP1. Further, to induce GBP1 expression, the cells were stimulated with IFNγ. GBP1 modulation was achieved either by overexpression of GBP1-Wt or by siRNA-mediated knockdown. Silencing of GBP1 impaired the release of viral particles and resulted in intracellular HCV core accumulation, while overexpression of GBP1 favored viral replication and release. CLSM and STED analyses revealed a vesicular distribution of GBP1 in the perinuclear region. Here, it colocalizes with HCV core around lipid droplets, where it acts as assembly platform and thereby favors HCV morphogenesis and release. Collectively, our results identify an unprecedented function of GBP1 as a pro-viral factor. As such, it is essential for viral assembly and release acting through tethering factors involved in HCV morphogenesis onto the surface of lipid droplets.

Structural insights into the activation mechanism of antimicrobial GBP1

The dynamin-related human guanylate-binding protein 1 (GBP1) mediates host defenses against microbial pathogens. Upon GTP binding and hydrolysis, auto-inhibited GBP1 monomers dimerize and assemble into soluble and membrane-bound oligomers, which are crucial for innate immune responses. How higher-order GBP1 oligomers are built from dimers, and how assembly is coordinated with nucleotide-dependent conformational changes, has remained elusive. Here, we present cryo-electron microscopy-based structural data of soluble and membrane-bound GBP1 oligomers, which show that GBP1 assembles in an outstretched dimeric conformation. We identify a surface-exposed helix in the large GTPase domain that contributes to the oligomerization interface, and we probe its nucleotide- and dimerization-dependent movements that facilitate the formation of an antimicrobial protein coat on a gram-negative bacterial pathogen. Our results reveal a sophisticated activation mechanism for GBP1, in which nucleotide-dependent structural changes coordinate dimerization, oligomerization, and membrane binding to allow encapsulation of pathogens within an antimicrobial protein coat.

Function and mechanism of GBP1 in the development and progression of cervical cancer

Guanylate binding protein 1 (GBP1) is the most concerned member of the GBP family, which has a series of effects such as anti-infection and anti-angiogenesis. Its role in malignant tumors including cervical cancer is still controversial. We aim to explore the effects of GBP1 on cervical cancer through bioinformatics and related experiments. In this study, we first found that GBP1 was generally expressed in cervical cancer in various online databases and was closely related to immune invasion. Secondly, we used multicolor immunofluorescence technology to verify the expression of GBP1 in cervical cancer tissues and its relationship with immune invasion, and explored its relationship with the prognosis of patients with cervical cancer. Knockdown and overexpression assays of GBP1 in vitro were used to prove GBP1 as a potential oncogene of cervical cancer, and its carcinogenicity was verified by in vivo experiment. In order to explore the potential mechanism of GBP1 in promoting cancer, RNA-seq was performed on GBP1 overexpression and knockdown expression cell lines, and GBP1 knockdown and overexpression were found to be associated with many RNA alternative splicing events, suggesting that GBP1 maybe a RNA binding protein (RBP) which affect the biological characteristics of cervical cancer cells through the alternative splicing pathway. However, the later RNA binding protein immunoprecipitation (RIP) assay proved that GBP1 was not a direct alternative splicing factor, while the co-immunoprecipitation (CoIP)-mass spectroscopy (MS) assay combined with protein protein interaction (PPI) analysis proved that 8 alternative splicing factors including Heterogeneous Nuclear Ribonucleoprotein K (HNRNPK) were interacting proteins of GBP1. Combined with the existing reports and the results of RNA-seq alternative splicing analysis, it is speculated that GBP1 may regulate the alternative splicing of CD44 protein by binding to interacting protein-HNRNPK, and thus play a role in promoting cancer in cervical cancer.

Correlation between the risk of lymph node metastasis and the expression of GBP1 in breast cancer patients.

To explore the prognostic value and correlation between the risk of lymph node metastasis (LNM) and Guanylate-binding Protein 1 (GBP1) in breast cancer (BC) patients. In this retrospective study, the clinical data of 150 patients with BC who were surgically resected in The Affiliated Qingdao Central Hospital of Qingdao University from January 2019 to December 2021 were included. Patients were divided into metastasis group (n=110) or non-metastasis group (n=40) according to whether there was LNM post-surgery. Logistic regression was used to analyze the risk factors for LNM in BC, and Kaplan-Meier was used to assess the risk of disease progression 12 months post-operation in both groups. Patients were divided into a GBP1 low expression-group (n=75) or a GBP1 high expression-group (n=75). The risk of disease progression, one-year post-surgery was analyzed, and the predictive value of GBP1 in BC tissue was assessed by the receiver operating characteristics (ROC) curve. Independent risk factors for BC with LNM were GBP1, CEA and TNM stage (P<0.05). There is a linear relationship between GBP1 expression and LNM risk in BC (χ2=0.88, P<0.05). Patients with high expression of GBP1 had a higher risk of LNM (χ2=3.204, P<0.001) and early postoperative progression (χ2=7.412, P<0.05). The AUC of GBP1 in predicting the risk of LNM was 0.840. Patients with BC and a higher expression of GBP1 could be at an increased risk of LNM. Elevations in GBP1 expression can also suggest a poor prognosis for patients with BC.

Guanylate-binding protein 1 modulates proteasomal machinery in ovarian cancer

Guanylate-binding protein 1 (GBP1) is known as an interferon-γ-induced GTPase. Here, we used genetically modified ovarian cancer (OC) cells to study the role of GBP1. The data generated show that GBP1 inhibition constrains the clonogenic potential of cancer cells. Invivo studies revealed that GBP1 overexpression in tumors promotes tumor progression and reduces median survival, whereas GBP1 inhibition delayed tumor progression with longer median survival. We employed proteomics-based thermal stability assay (CETSA) on GBP1 knockdown and overexpressed OC cells to study its molecular functions. CETSA results show that GBP1 interacts with many members of the proteasome. Furthermore, GBP1 inhibition sensitizes OC cells to paclitaxel treatment via accumulated ubiquitinylated proteins where GBP1 inhibition decreases the overall proteasomal activity. In contrast, GBP1-overexpressing cells acquired paclitaxel resistance via boosted cellular proteasomal activity. Overall, these studies expand the role of GBP1 in the activation of proteasomal machinery to acquire chemoresistance.

The GTPase activity and isoprenylation of Swine GBP1 are critical for inhibiting the production of Japanese Encephalitis Virus

Japanese encephalitis virus (JEV) is a flavivirus that cause severe neurological deficits. The guanylate-binding protein 1 (GBP1) gene is an interferon-stimulated gene and exerts antiviral functions on many RNA and DNA viruses via diverse mechanisms, however, the roles and the action modes of GBP1 in the antiviral effect on the production of JEV RNA and infectious virions remain to be clarified. In this study, we found that the RNA levels of swine GBP1 (sGBP1) in PK15 cells were up-regulated at the late stage of JEV infection. The overexpression of sGBP1 significantly inhibited the production of JEV while the knockdown of sGBP1 promoted the production of JEV. The GTPase activity and isoprenylation of sGBP1 both are critical for anti-JEV activity. The GTPase activity of sGBP1 is responsible for inhibiting the production of JEV genomic RNA. The isoprenylation of sGBP1 inhibited the expression and cleavage of JEV prM to decrease the yields of infectious virions, which may be associated with the interaction between sGBP1 and cellular proprotein convertase furin. Taken together, the study dissected the action modes of sGBP1with potent anti-JEV activity in more details.

Dietary Supplementation with Puerarin Improves Intestinal Function in Piglets Challenged with Escherichia coli K88

The objective of this study was to investigate the effect of puerarin supplementation on the growth performance and intestinal function of piglets challenged with enterotoxigenic Escherichia coli (ETEC) K88. Twenty-four ternary crossbred piglets were randomly assigned to three treatment groups: control group, ETEC group (challenged with ETEC K88 on day 8), and ETEC + Puerarin group (supplemented with 5 mg/kg puerarin and challenged with ETEC K88 on day 8). All piglets were orally administered D-xylose (0.1 g/kg body weight) on day 10, and blood samples were collected after 1 h. Subsequently, piglets were killed and intestinal samples were collected for further analysis. The results showed that puerarin supplementation significantly decreased the adverse effects of ETEC K88-challenged piglets; significantly improved growth performance; increased the number of Bifidobacterium in the colon and Lactobacillus in the jejunum, cecum and colon; decreased the number of Escherichia coli in the jejunum and cecum; reduced the hydrogen peroxide content in the jejunum and myeloperoxidase activity in the jejunum and ileum; and increased the activities of catalase and superoxide dismutase in the jejunum and ileum. In addition, puerarin supplementation alleviated ETEC K88-induced intestinal injury in piglets, significantly downregulated the mRNA level of Interleukin-1β and upregulated the mRNA levels of intercellular cell adhesion molecule-1, myxovirus resistance protein 1, myxovirus resistance protein 2, and guanylate-binding protein-1 in the small intestine of piglets. In conclusion, dietary supplementation with puerarin could attenuate ETEC K88-induced intestinal injury by increasing the antioxidant and anti-inflammatory capacity and the number of beneficial intestinal bacteria in piglets.

Oncolytic herpes simplex virus armed with a bacterial GBP1 degrader improves antitumor activity

Oncolytic viruses (OVs) encoding various transgenes are being evaluated for cancer immunotherapy. Diverse factors such as cytokines,immune checkpoint inhibitors, tumor-associated antigens, and Tcell engagers have been exploited as transgenes. These modifications are primarily aimed to reverse the immunosuppressive tumor microenvironment. By contrast, antiviral restriction factors that inhibit the replication of OVs and result in suboptimal oncolytic activity have received far less attention. Here, we report that guanylate-binding protein 1 (GBP1) is potently induced duringHSV-1 infection and restricts HSV-1 replication. Mechanistically, GBP1 remodels cytoskeletal organization to impede nuclear entry of HSV-1 genome. Previous studies have established that IpaH9.8, a bacterial E3 ubiquitin ligase, targets GBPs for proteasomal degradation. We therefore engineered an oncolytic HSV-1 to express IpaH9.8 and found that the modified OV effectively antagonized GBP1, replicated to a higher titer invitro and showed superior antitumor activity invivo. Our study features a strategy for improving the replication of OVs via targeting a restriction factor and achieving promising therapeutic efficacy.

CAPRIN1 Is Required for Control of Viral Replication Complexes by Interferon Gamma.

Replication complexes (RCs), formed by positive-strand (+) RNA viruses through rearrangements of host endomembranes, protect their replicating RNA from host innate immune defenses. We have shown that two evolutionarily conserved defense systems, autophagy and interferon (IFN), target viral RCs and inhibit viral replication collaboratively. However, the mechanism by which autophagy proteins target viral RCs and the role of IFN-inducible GTPases in the disruption of RCs remains poorly understood. Here, using murine norovirus (MNV) as a model (+) RNA virus, we show that the guanylate binding protein 1 (GBP1) is the human GTPase responsible for inhibiting RCs. Furthermore, we found that ATG16L1 mediates the LC3 targeting of MNV RC by binding to WIPI2B and CAPRIN1, and that IFN gamma-mediated control of MNV replication was dependent on CAPRIN1. Collectively, this study identifies a novel mechanism for the autophagy machinery-mediated recognition and inhibition of viral RCs, a hallmark of (+) RNA virus replication. IMPORTANCE Replication complexes provide a microenvironment important for (+) RNA virus replication and shield it from host immune response. Previously we have shown that interferon gamma (IFNG) disrupts the RC of MNV via evolutionarily conserved autophagy proteins and IFN-inducible GTPases. Elucidating the mechanism of targeting of viral RC by ATG16L1 and IFN-induced GTPase will pave the way for development of therapeutics targeting the viral replication complexes. Here, we have identified GBP1 as the sole GBP targeting viral RC and uncovered the novel role of CAPRIN1 in recruiting ATG16L1 to the viral RC.

Abstract 1695: Guanylate binding protein 1 modulate the proteasomal machinery and causes the cytochrome C degradation

Abstract Guanylate Binding Protein 1 (GBP1) is known as an interferon γ induced GTPase. It plays a crucial role in innate immunity against pathogenic infections but its role in cancer and therapeutic response is not well understood. Therefore, to study the role of GBP1, we investigated genetically manipulated ovarian cancer cells. We have employed in vitro and in vivo studies along with a proteomics approach to uncover the protein-protein interactions and their crosstalk with GBP1. The data suggest that GBP1 knockdown (KD) inhibits the clonogenic potential of cancer cells. In vivo studies including subcutaneous xenograft and intraperitoneal models revealed that GBP1 overexpressing (OV) tumor cells growing faster and reduce the median survival of animals compared to vehicle control (VC). Whereas GBP1 KD tumors were progressing slowly with longer median survival compared to scrambled control (SC). To study the molecular interactions of GBP1, we performed a proteomics-based Cellular thermal shift assay (CETSA) on GBP1 OV and KD ovarian cancer cells. We found that GBP1 interacts with members of proteasome including PSMB1, PSMB6, PSMA3, and Cytochrome C (CYCS). Protein analysis showed that GBP1 over-expressing cells had less ubiquitinylated proteins compared to VC, whereas GBP1 KD cells accumulate the ubiquitinylated proteins compared to SC. We also found that the GBP1 KD cells are sensitive to paclitaxel treatment and accumulated ubiquitinylated proteins compared to SC. Moreover, GBP1 KD inhibits the overall proteasomal activity. Paclitaxel-treated GBP1 OV cells accumulated the ubiquitination of CYCS, followed by clearance of cytosolic CYCS. Furthermore, global proteome profiling also suggests that GBP1 KD induces apoptotic pathways whereas GBP1 OV induces pathways associated with the stress response. Overall, the results from our studies elucidate the role of GBP1 in chemotherapeutic stress response via the activation of proteasomal machinery. Citation Format: Dhanir Tailor, Fernando Jose Garcia-Marques, Abel Bermudez, Sharon J. Pitteri, Sanjay V. Malhotra. Guanylate binding protein 1 modulate the proteasomal machinery and causes the cytochrome C degradation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1695.