Integrin β3, a RACK1 interacting protein, is critical for porcine reproductive and respiratory syndrome virus infection and NF-κB activation in Marc-145 cells

Molecular Cloning, Characterization, and Expression of a Receptor for Activated Protein Kinase C1 (RACK1) Gene in Exopalaemon carinicauda Zoea Larvae under Aroclor 1254 Stress

The receptor for activated protein kinase C1 (RACK1) belongs to the typical WD repeat family, which is extremely conservative and important in multiple signal transduction pathways related to growth and development that coordinate the intracellular role of various life activities. As a novel protein with versatile functions, it was found in a variety of organisms. In a previous study, we identified the RACK1 sequence of white shrimp from transcriptome data. In this study, we employed specialized bioinformatics software to conduct an in-depth analysis of EcRACK1 and compare its amino acid sequence homology with other crustaceans. Furthermore, we investigated the expression patterns of RACK1 at different developmental stages and tissues, as well as at various time points after exposure to Aroclor 1245, aiming to elucidate its function and potential response towards Aroclor 1245 exposure. The length of EcRACK1 is 957 nucleotides, which encodes 318 amino acids. Moreover, there were seven typical WD repeats in EcRACK1, which have more than a 96% sequence identity with the RACK1 proteins of Penaeus. The results of tissue expression and spatiotemporal expression showed that it was significantly increased in the II and IV stages, but had a significant tissue specificity in the hepatopancreas, spermary, and muscle tissues of E. carinicauda, adult stage. Compared to the control, EcRACK1 was significantly induced in E. carinicauda zoea larvae exposed to Aroclor 1254 for 6, 10, 20, and 30 d (p < 0.05). These results suggested that EcRACK1 may play an important role in the larval development and environmental defense of E. carinicauda.

Differences in Immune Characteristics and Related Gene Expression in Spleen among Ningxiang, Berkshire Breeds and Their Hybrid Pigs

To investigate the differential immunology in Ningxiang and Berkshire pigs and their F1 offspring (F1 offspring), physiological and biochemical indicators in the plasma and spleen were analyzed. Then, transcriptomic analysis of the spleen identified 1348, 408, and 207 differentially expressed genes (DEGs) in comparisons of Ningxiang vs. Berkshire, Berkshire vs. F1 offspring, and Ningxiang vs. F1 offspring, respectively. In Ningxiang vs. Berkshire pigs, the gene ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that the DEGs included CD163, MARCO, CXCL14, CCL19, and PPBP, which are associated with immunity. GO and KEGG analyses were also conducted comparing F1 offspring and their parents. The DEGs, including BPIFB1, HAVCR2, CD163, DDX3X, CCR5, and ITGB3, were enriched in immune-related pathways. Protein-protein interaction (PPI) analysis indicated that the EGFR and ITGA2 genes were key hub genes. In conclusion, this study identifies significant immune DEGs in different pig breeds, providing data to support the exploration of breeding strategies for disease resistance in local and crossbred pig populations.

RACK1 promotes porcine reproductive and respiratory syndrome virus infection in Marc-145 cells through ERK1/2 activation

Porcine reproductive and respiratory syndrome (PRRS) is an acute infectious disease that spreads rapidly among pigs and seriously threatens the pig industry. Activation of ERK1/2 is a hallmark of most viral infections. RACK1 interacts with a variety of kinases and membrane receptors that closely associated with viral infections and the development and progression of cancer. However, no studies have clearly defined whether RACK1 can regulate PRRSV infection through ERK1/2 activation. In our study, using RT-qPCR, immunoblotting, indirect fluorescent staining, siRNA knockdown and protein overexpression techniques, we found that downregulation of cellular RACK1 inhibited ERK1/2 activation and subsequently suppressed PRRSV infection, while overexpression of RACK1 enhanced ERK1/2 activation and PRRSV infection. Bioinformatic and Co-immunoprecipitation experimental analysis revealed that cellular RACK1 could interact with viral N protein to exert its function. We elaborated that RACK1 promoted PRRSV replication in Marc-145 cells through ERK1/2 activation. Our study provides new insights into regulating the innate antiviral immune responses during PRRSV infection and contributes to further understanding of the molecular mechanisms underlying PRRSV replication.

Long non-coding RNA LOC103222771 promotes infection of porcine reproductive and respiratory syndrome virus in Marc-145 cells by downregulating Claudin-4

Porcine reproductive and respiratory syndrome (PRRS) is an important swine disease caused by infection of porcine reproductive and respiratory syndrome virus (PRRSV), which leads to huge loss in swine industry. How to effectively control PRRS is challenging. Long non-coding RNA (lncRNA) are key regulator of viral infections and anti-virus immunological responses, therefore, further understanding of lncRNAs will aid to identification of novel regulators of viral infections and better design of prevention and control strategies to viral infection related diseases and immune disorders. We demonstrated that PRRSV infection upregulated the expression of lncRNA LOC103222771 in Marc-145 cells and porcine alveolar macrophage cells (PAMs) and that LOC103222771 is mainly located in cytoplasm. Knockdown of LOC103222771 could inhibit the PRRSV infection in Marc-145 cells. RNA-seq analysis and subsequent validation revealed increased expression of Claudin-4 (CLDN4) in Marc-145 when LOC103222771 was specifically downregulated，suggesting that LOC103222771 might be an upstream regulator of CLDN4, an important component of tight junctions for establishment of the paracellular barrier that controls the flow of molecules in the intercellular space between epithelial cells. We and others showed that Downregulation of CLDN4 could boost the infection of PRRSV. Collectively, LOC103222771/CLDN4 signal axis might be a novel mechanism of PRRSV pathogenesis, implying a potential therapeutic target against PRRSV infection.

Role of the receptor for activated C kinase 1 during viral infection

Viruses can survive only in living cells, where they depend on the host's enzymatic system for survival and reproduction. Virus-host interactions are complex. On the one hand, hosts express host-restricted factors to protect the host cells from viral infections. On the other hand, viruses recruit certain host factors to facilitate their survival and transmission. The identification of host factors critical to viral infection is essential for comprehending the pathogenesis of contagion and developing novel antiviral therapies that specifically target the host. Receptor for activated C kinase 1 (RACK1), an evolutionarily conserved host factor that exists in various eukaryotic organisms, is a promising target for antiviral therapy. This review primarily summarizes the roles of RACK1 in regulating different viral life stages, particularly entry, replication, translation, and release.

Integrated miRNA and mRNA Expression Profiles Reveal Differentially Expressed miR-222a as an Antiviral Factor Against Duck Hepatitis A Virus Type 1 Infection

Duck hepatitis A virus 1 (DHAV-1) is a highly contagious etiological agent that causes acute hepatitis in young ducklings. MicroRNAs (miRNAs) play important regulatory roles in response to pathogens. However, the interplay between DHAV-1 infection and miRNAs remains ambiguous. We characterized and compared miRNA and mRNA expression profiles in duck embryo fibroblasts cells (DEFs) infected with DHAV-1. In total, 36 and 96 differentially expressed (DE) miRNAs, and 4110 and 2595 DE mRNAs, were identified at 12 and 24 h after infection. In particular, 126 and 275 miRNA-mRNA pairs with a negative correlation were chosen to construct an interaction network. Subsequently, we identified the functional annotation of DE mRNAs and target genes of DE miRNAs enriched in diverse Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, which may be important for virus resistance, cell proliferation, and metabolism. Moreover, upregulated miR-222a could negatively regulate DHAV-1 replication in DEFs and downregulate integrin subunit beta 3 (ITGB3) expression by targeting the 3' untranslated region (3'UTR), indicating that miR-222a may modulate DHAV-1 replication via interaction with ITGB3. In conclusion, the results reveal changes of mRNAs and miRNAs during DHAV-1 infection and suggest miR-222a as an antiviral factor against DHAV-1.

Classical swine fever virus infection suppresses claudin-1 expression to facilitate its replication in PK-15 cells

Classical swine fever (CSF) is one of the most epidemic viral diseases in swine industry. The causative pathogen is CSF virus (CSFV), a small enveloped RNA virus of Flaviviridae family. Claudin-1 was reported to be involved in the infections of a number of viruses, including many from Flaviviridae family, but no studies have investigated the role of porcine claudin-1 during CSFV infection in PK-15 cells. In this study, on the one hand, we demonstrated that CSFV infection reduced the claudin-1 expression at both mRNA and protein levels; on the other hand, CSFV infection was enhanced after claudin-1 knockdown, but inhibited by claudin-1 overexpression in a dose-dependent manner. Furthermore, negative correlation was demonstrated between the claudin-1 expression and CSFV titer. In conclusion, claudin-1 might be a barrier for CSFV infection in PK-15 cells, while CSFV bypasses the barrier through lysosome mediated degradation of claudin-1, which could be repressed by bafilomycin A1. Although the elaborate mechanisms how claudin-1 plays its roles in CSFV infection require further investigations, this study may advance our understanding of the molecular host-pathogen interaction mechanisms underlying CSFV infection and suggests enhancement of porcine claudin-1 as a potential preventive or therapeutic strategy for CSF control.

Small molecule screening identified cepharanthine as an inhibitor of porcine reproductive and respiratory syndrome virus infection in vitro by suppressing integrins/ILK/RACK1/PKCα/NF-κB signalling axis

Porcine Reproductive and Respiratory Syndrome (PRRS) is a devastating disease among the most notorious threats to the swine industry worldwide and is characterized by respiratory distress and reproductive failure. Highly evolving porcine reproductive and respiratory syndrome virus (PRRSV) strains with complicated genetic diversity make the current vaccination strategy far from cost-effective and thus urge identification of potent lead candidates to provide prevention and treatment approaches. From an in vitro small molecule screening with the TargetMol Natural Compound Library comprising 623 small molecules, cytopathic effect (CPE) observations and RT-qPCR analysis of viral ORF7 gene expression identified cepharanthine (CEP) to be one of the most protent inhibitors of PRRSV infection in Marc-145 cells. When compared with tilmicosin, which is one of the most commonly used antibiotics in swine industry to inhibit infections, CEP more prominently inhibited PRRSV infection represented by both RNA and protein levels, further reduced the TCID₅₀ by 5.6 times, and thus more remarkably protected Marc-145 cells against PRRSV infection. Mechanistically, western blot analyses of the Marc-145 cells and the porcine alveolar macrophages (PAMs) with or without CEP treatment and PRRSV infection at various time points revealed that CEP can inhibit the expression of integrins β1 and β3, integrin-linked kinase (ILK), RACK1 and PKCα, leading to NF-κB suppression and consequent alleviation of PRRSV infection. Collectively, our small molecule screening identified cepharanthine as an inhibitor of PRRSV infection in vitro by suppressing Integrins/ILK/RACK1/PKCα/NF-κB signalling axis, which may enlighten the deeper understanding of the molecular pathogenesis of PRRSV infection and more importantly, suggested CEP as a potential promising drug for PRRS control in veterinary clinics.

Inhibition of porcine reproductive and respiratory syndrome virus by PKC inhibitor dequalinium chloride in vitro

As a severe disease characterized by reproductive failure and respiratory distress, porcine reproductive and respiratory syndrome (PRRS) is one of the most leading threats to the swine industry worldwide. Highly evolving porcine reproductive and respiratory syndrome virus (PRRSV) strains with distinct genetic diversity make the current vaccination strategy much less cost-effective and thus urge alternative protective host directed therapeutic approaches. RACK1-PKC-NF-κB signalling axis was suggested as a potential therapeutic target for PRRS control, therefore we tested the inhibitory effect of PKC inhibitor dequalinium chloride (DECA) on the PRRSV infection in vitro. RT-qPCR, western blot, Co-IP and cytopathic effect (CPE) observations revealed that DECA suppressed PRRSV infection and protected Marc-145 cells and porcine alveolar macrophages (PAMs) from severe cytopathic effects, by repressing the PKCα expression, the interaction between RACK1 and PKCα, and subsequently the NF-κB activation. In conclusion, the data presented in this study shed more light on deeper understanding of the molecular pathogenesis upon PRRSV infection and more importantly suggested DECA as a potential promising drug candidate for PRRS control.

Porcine RACK1 negatively regulates the infection of classical swine fever virus and the NF-κB activation in PK-15 cells

Classical swine fever (CSF) is one of the main viral diseases of swine worldwide. The causative pathogen is CSF virus (CSFV), a small enveloped RNA virus of the genus Pestivirus. Activation of NF-κB is a hallmark of most viral infections and the viral pathogens frequently kidnap NF-κB pathway for their own advantages, however, it is unclear or even controversial about whether CSFV infection can activate NF-κB signal pathway. RACK1 was shown as an interacting host protein with CSFV NS5A protein, but no studies so far have clearly defined the role of RACK1 during CSFV infection and NF-κB activation. In this study, to properly address these open questions, using RT-qPCR, western blot, indirect fluorescence staining, siRNA knockdown and protein overexpression techniques, we demonstrated that CSFV infection reduced the RACK1 expression at both mRNA and protein levels in PK-15 cells. Downregulation of cellular RACK1 enhanced CSFV infection and subsequent NF-κB activation, while RACK1 overexpression inhibited CSFV infection and the NF-κB activation. In conclusion, RACK1 is a negative cellular regulator for CSFV infection and NF-κB activation in PK-15 cells. Our work addressed a novel aspect concerning the regulation of innate antiviral immune response during CSFV infection. This study may provide some insights into the molecular mechanisms of CSFV infection in swine. However, the elaborate mechanism by which CSFV regulates NF-κB activation and how RACK1 plays its roles in CSFV infection and NF-κB induction require further in-depth studies.