5-Oxo-1-[(2,3,6,7-tetramethoxy-9-phenanthrenyl)methyl]-L-proline Inhibits Hepatitis C Virus Entry

Network pharmacology and molecular docking technology for exploring the effect and mechanism of Radix Bupleuri and Radix Paeoniae Alba herb-pair on anti-hepatitis: A review

The Radix Bupleuri and Radix Paeoniae Alba herb-pair (RRH) are the most classic compatible drug pair for the treatment of hepatitis. However, the underlying mechanism remains unclear. Therefore, network pharmacology and molecular docking were conducted to investigate the prospective therapeutic constituents, targets, and pharmacological mechanisms of RRH in the treatment of hepatitis. The active components of RRH from the TCMSP database and disease-related targets from the OMIM, PharmGkb, GeneCards, TTD, and DrugBank databases were identified. The "drug-target-disease" network diagram and protein-protein interaction (PPI) network were constructed using Cytoscape (v3.8.0) and Online STRING 11.0. GO and KEGG pathway enrichment analyses were performed using R version 4.1.2, and molecular docking was performed to verify the results. We placed 176 overlapping cross genes into Online STRING 11.0 and obtained 14 core targets. A "Component-Target-GO-KEGG" network diagram was constructed, which was composed of 7 components, 14 targets, 10 biological processes, and 10 signal pathways. A total of 2413 GO biological processes and 174 KEGG pathways were explored for hepatitis treatment. Quercetin, kaempferol, isorhamnetin, and beta-sitosterol, which are the main bioactive components, were employed to bind the disease's hub targets, ensuring fulfillment of spatial and energy matching. The anti-hepatitis mechanism of RRH may be associated with several targets including RELA, AKT1, JUN, MAPK1, TP53, CCND1, MYC, NFKBIA, CDKN1A, and their respective signaling pathways. The main bioactive components in RRH, including quercetin, kaempferol, isorhamnetin, and beta-sitosterol, were used to bind the hub targets of the disease, which may provide insights into drug development for hepatitis.

Targeting of Tetraspanin CD81 with Monoclonal Antibodies and Small Molecules to Combat Cancers and Viral Diseases

Tetraspanin CD81 plays major roles in cell-cell interactions and the regulation of cellular trafficking. This cholesterol-embarking transmembrane protein is a co-receptor for several viruses, including HCV, HIV-1 and Chikungunya virus, which exploits the large extracellular loop EC2 for cell entry. CD81 is also an anticancer target implicated in cancer cell proliferation and mobility, and in tumor metastasis. CD81 signaling contributes to the development of solid tumors (notably colorectal, liver and gastric cancers) and has been implicated in the aggressivity of B-cell lymphomas. A variety of protein partners can interact with CD81, either to regulate attachment and uptake of viruses (HCV E2, claudin-1, IFIM1) or to contribute to tumor growth and dissemination (CD19, CD44, EWI-2). CD81-protein interactions can be modulated with molecules targeting the extracellular domain of CD81, investigated as antiviral and/or anticancer agents. Several monoclonal antibodies anti-CD81 have been developed, notably mAb 5A6 active against invasion and metastasis of triple-negative breast cancer cells. CD81-EC2 can also be targeted with natural products (trachelogenin and harzianoic acids A-B) and synthetic compounds (such as benzothiazole-quinoline derivatives). They are weak CD81 binders but offer templates for the design of new compounds targeting the open EC2 loop. There is no anti-CD81 compound in clinical development at present, but this structurally well-characterized tetraspanin warrants more substantial considerations as a drug target.

Cortactin Interacts with Hepatitis C Virus Core and NS5A Proteins: Implications for Virion Assembly

Hepatitis C virus (HCV) exploits cellular proteins to facilitate viral propagation. To identify the cellular factors involved in the HCV life cycle, we previously performed protein microarray assays using either HCV nonstructural 5A (NS5A) protein or core protein as a probe. Interestingly, cellular cortactin strongly interacted with both NS5A and core. Cortactin is an actin-binding protein critically involved in tumor progression by regulating the migration and invasion of cancerous cells. Protein interaction between cortactin and NS5A or core was confirmed by coimmunoprecipitation and immunofluorescence assays. We showed that cortactin interacted with NS5A and core via the N-terminal acidic domain of cortactin. Cortactin expression levels were not altered by HCV infection. Small interfering RNA (siRNA)-mediated knockdown of cortactin dramatically decreased HCV protein expression and infectivity levels, whereas overexpression of cortactin increased viral propagation. Ectopic expression of the siRNA-resistant cortactin recovered the viral infectivity, suggesting that cortactin was specifically required for HCV propagation. We further showed that cortactin was involved in the assembly step without affecting viral entry, HCV internal ribosome entry site (IRES)-mediated translation, and the replication steps of the HCV life cycle. Of note, silencing of cortactin markedly reduced both NS5A and core protein levels on the lipid droplets (LDs), and this effect was reversed by the overexpression of cortactin. Importantly, NS5A and core promoted cell migration by activating the phosphorylation of cortactin at tyrosine residues 421 and 466. Taken together, these data suggest that cortactin is not only involved in HCV assembly but also plays an important role in the cell migration.IMPORTANCE Cortactin is a cytoskeletal protein that regulates cell migration in response to a number of extracellular stimuli. The functional involvement of cortactin in the virus life cycle is not yet fully understood. The most significant finding is that cortactin strongly interacted with both hepatitis C virus (HCV) core and NS5A. Cortactin is involved in HCV assembly by tethering core and NS5A on the lipid droplets (LDs) with no effect on LD biogenesis. It was noteworthy that HCV NS5A and core activated cortactin by phosphorylation at tyrosines 421 and 466 to regulate cell migration. Collectively, our study shows that cortactin is a novel host factor involved in viral production and HCV-associated pathogenesis.

PACSIN2 Interacts with Nonstructural Protein 5A and Regulates Hepatitis C Virus Assembly

Hepatitis C virus (HCV) is a major etiologic agent of chronic liver diseases. HCV is highly dependent on cellular machinery for viral propagation. Using protein microarray analysis, we previously identified 90 cellular proteins as nonstructural 5A (NS5A) interacting partners. Of these, protein kinase C and casein kinase substrate in neurons protein 2 (PACSIN2) was selected for further study. PACSIN2 belongs to the PACSIN family, which is involved in the formation of caveolae. Protein interaction between NS5A and PACSIN2 was confirmed by pulldown assay and further verified by both coimmunoprecipitation and immunofluorescence assays. We showed that PACSIN2 interacted with domain I of NS5A and the Fer-CIP4 homology (FCH)-Bin/amphiphysin/Rvs (F-BAR) region of PACSIN2. Interestingly, NS5A specifically attenuated protein kinase C alpha (PKCα)-mediated phosphorylation of PACSIN2 at serine 313 by interrupting PACSIN2 and PKCα interaction. In fact, mutation of the serine 313 to alanine (S313A) of PACSIN2 increased protein interaction with NS5A. Silencing of PACSIN2 decreased both viral RNA and protein expression levels of HCV. Ectopic expression of the small interfering RNA (siRNA)-resistant PACSIN2 recovered the viral infectivity, suggesting that PACSIN2 was specifically required for HCV propagation. PACSIN2 was involved in viral assembly without affecting other steps of the HCV life cycle. Indeed, overexpression of PACSIN2 promoted NS5A and core protein (core) interaction. We further showed that inhibition of PKCα increased NS5A and core interaction, suggesting that phosphorylation of PACSIN2 might influence HCV assembly. Moreover, PACSIN2 was required for lipid droplet formation via modulating extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation. Taken together, these data indicate that HCV modulates PACSIN2 via NS5A to promote virion assembly.IMPORTANCE PACSIN2 is a lipid-binding protein that triggers the tubulation of the phosphatidic acid-containing membranes. The functional involvement of PACSIN2 in the virus life cycle has not yet been demonstrated. We showed that phosphorylation of PACSIN2 displayed a negative effect on NS5A and core interaction. The most significant finding is that NS5A prevents PKCα from binding to PACSIN2. Therefore, the phosphorylation level of PACSIN2 is decreased in HCV-infected cells. We showed that HCV NS5A interrupted PKCα-mediated PACSIN2 phosphorylation at serine 313, thereby promoting NS5A-PACSIN2 interaction. We further demonstrated that PACSIN2 modulated lipid droplet formation through ERK1/2 phosphorylation. These data provide evidence that PACSIN2 is a proviral cellular factor required for viral propagation.