Phosphatidylinositol 4-kinase III beta is the target of oxoglaucine and pachypodol (Ro 09-0179) for their anti-poliovirus activities, and is located at upstream of the target step of brefeldin A

CUR-N399, a PI4KB inhibitor, for the treatment of Enterovirus A71 infection

Over the years, the hand, foot and mouth disease (HFMD) has sparked epidemics across many countries which mainly affected young children. While symptoms are usually mild, severe complications may arise, and some even lead to death. Such concerns, coupled with the lack of approved vaccines and antivirals to date, create an urgency in the identification of safe therapeutics against HFMD. The disease is mainly transmitted by enteroviruses like enterovirus A71 (EV-A71). Essential for enterovirus replication is the host protein, PI4KB. In this study, we investigate the antiviral efficacy of a novel PI4KB inhibitor, CUR-N399. We found that CUR-N399 displayed broad-spectrum antiviral activity against picornaviruses in cell culture models. Using a suckling mouse model of lethal EV-A71 infection, CUR-N399 was found to be well-tolerated, promote survival and reduce viral titre in mice organs. Together, these support the discovery of CUR-N399 as an antiviral against EV-A71 and potentially other closely related viruses.

A Comprehensive Review on Pharmacological Activities of Pachypodol: A Bioactive Compound of an Aromatic Medicinal Plant Pogostemon Cablin Benth

As is well known, plant products have been increasingly utilized in the pharmaceutical industry in recent years. By combining conventional techniques and modern methodology, the future of phytomedicines appears promising. Pogostemon Cablin (patchouli) is an important herb used frequently in the fragrance industries and has various therapeutic benefits. Traditional medicine has long used the essential oil of patchouli (P. cablin) as a flavoring agent recognized by the FDA. This is a gold mine for battling pathogens in China and India. In recent years, this plant has seen a significant surge in use, and approximately 90% of the world's patchouli oil is produced by Indonesia. In traditional therapies, it is used for the treatment of colds, fever, vomiting, headaches, and stomachaches. Patchouli oil is used in curing many diseases and in aromatherapy to treat depression and stress, soothe nerves, regulate appetite, and enhance sexual attraction. More than 140 substances, including alcohols, terpenoids, flavonoids, organic acids, phytosterols, lignins, aldehydes, alkaloids, and glycosides, have been identified in P. cablin. Pachypodol (C18H16O7) is an important bioactive compound found in P. cablin. Pachypodol (C18H16O7) and many other biologically essential chemicals have been separated from the leaves of P. cablin and many other medicinally significant plants using repeated column chromatography on silica gel. Pachypodol's bioactive potential has been shown by a variety of assays and methodologies. It has been found to have a number of biological activities, including anti-inflammatory, antioxidant, anti-mutagenic, antimicrobial, antidepressant, anticancer, antiemetic, antiviral, and cytotoxic ones. The current study, which is based on the currently available scientific literature, intends to close the knowledge gap regarding the pharmacological effects of patchouli essential oil and pachypodol, a key bioactive molecule found in this plant.

Direct-Acting Antivirals and Host-Targeting Approaches against Enterovirus B Infections: Recent Advances

Enterovirus B (EV-B)-related diseases, which can be life threatening in high-risk populations, have been recognized as a serious health problem, but their clinical treatment is largely supportive, and no selective antivirals are available on the market. As their clinical relevance has become more serious, efforts in the field of anti-EV-B inhibitors have greatly increased and many potential antivirals with very high selectivity indexes and promising in vitro activities have been discovered. The scope of this review encompasses recent advances in the discovery of new compounds with anti-viral activity against EV-B, as well as further progress in repurposing drugs to treat these infections. Current progress and future perspectives in drug discovery against EV-Bs are briefly discussed and existing gaps are spotlighted.

Essential Domains of Oxysterol-Binding Protein Required for Poliovirus Replication

Oxysterol-binding protein (OSBP) is a host factor required for enterovirus (EV) replication. OSBP locates at membrane contact site and acts as a lipid exchanger of cholesterol and phosphatidylinositol 4-phosphate (PI4P) between cellular organelles; however, the essential domains required for the viral replication remain unknown. In this study, we define essential domains of OSBP for poliovirus (PV) replication by a functional dominance assay with a series of deletion variants of OSBP. We show that the pleckstrin homology domain (PHD) and the ligand-binding domain, but not the N-terminal intrinsically disordered domain, coiled-coil region, or the FFAT motif, are essential for PV replication. The PHD serves as the primary determinant of OSBP targeting to the replication organelle in the infected cells. These results suggest that not all the domains that support important biological functions of OSBP are essential for the viral replication.

Therapeutics for fulminant hepatitis caused by enteroviruses in neonates

Neonatal infection with nonpolio enteroviruses (EVs) causes nonspecific febrile illnesses and even life-threatening multiorgan failure. Hepatitis, which often results in hepatic necrosis followed by disseminated intravascular coagulopathy, is one of the most severe and frequent fatal neonatal EV infection complications. Coxsackievirus B (CVB) 1–5 and many echoviruses have been most commonly identified. Neonatal EV infection treatment has usually involved initial supportive care. Studies for CVB and echovirus infection treatments were developed for more than thirty years. Intravenous immunoglobulin and pleconaril therapy was performed in some clinical trials. Additionally, other studies demonstrated antiviral and/or anti-inflammatory pathogenesis mechanisms of neonatal EV hepatitis in in vitro or in vivo models. These treatments represented promising options for the clinical practice of neonatal EV hepatitis. However, further investigation is needed to elucidate the whole therapeutic potential and safety problems.

Ligand Recognition by the Lipid Transfer Domain of Human OSBP Is Important for Enterovirus Replication

Oxysterol-binding protein (OSBP), which transports cholesterol and phosphatidylinositol 4-monophosphate (PtdIns[4]P) between different organelles, serves as a conserved host factor for the replication of various viruses, and OSBP inhibitors exhibit antiviral effects. Here, we determined the crystal structure of the lipid transfer domain of human OSBP in complex with endogenous cholesterol. The hydrocarbon tail and tetracyclic ring of cholesterol interact with the hydrophobic tunnel of OSBP, and the hydroxyl group of cholesterol forms a hydrogen bond network at the bottom of the tunnel. Systematic mutagenesis of the ligand-binding region revealed that M446W and L590W substitutions confer functional tolerance to an OSBP inhibitor, T-00127-HEV2. Employing the M446W variant as a functional replacement for the endogenous OSBP in the presence of T-00127-HEV2, we have identified previously unappreciated amino acid residues required for viral replication. The combined use of the inhibitor and the OSBP variant will be useful in elucidating the enigmatic in vivo functions of OSBP.

Bithiazole Inhibitors of Phosphatidylinositol 4-Kinase (PI4KIIIβ) as Broad-Spectrum Antivirals Blocking the Replication of SARS-CoV-2, Zika Virus, and Human Rhinoviruses

Over half a century since the description of the first antiviral drug, "old" re-emerging viruses and "new" emerging viruses still represent a serious threat to global health. Their high mutation rate and rapid selection of resistance toward common antiviral drugs, together with the increasing number of co-infections, make the war against viruses quite challenging. Herein we report a host-targeted approach, based on the inhibition of the lipid kinase PI4KIIIβ, as a promising strategy for inhibiting the replication of multiple viruses hijacking this protein. We show that bithiazole inhibitors of PI4KIIIβ block the replication of human rhinoviruses (hRV), Zika virus (ZIKV) and SARS-CoV-2 at low micromolar and sub-micromolar concentrations. However, while the anti-hRV/ZIKV activity can be directly linked to PI4KIIIβ inhibition, the role of PI4KIIIβ in SARS-CoV-2 entry/replication is debated.

Consecutive alternating administration as an effective anti-coxsackievirus B3 in vivo treatment scheme

Although chemotherapy is generally indicated for treatment of enterovirus infections, antivirals are currently not used in clinical practice. The use of monotherapy is the main reason for this unfavourable state. This is related to the fact that enterovirus progeny consist of innumerable quasispecies, allowing the virus to develop drug resistance quickly. Here, we present a consecutive alternating administration (CAA) treatment scheme for combining enterovirus inhibitors. Applying the CAA approach with a combination of pleconaril (capsid binder), guanidine HCl (viral 2C inhibitor), and oxoglaucine (PI4KB inhibitor) (PGO) was found to be effective in the treatment of newborn mice infected with a massive inoculum (20 MLD₅₀) of the coxsackievirus B3 cardiotropic Woodruff or neurotropic Nancy strain. In addition to preventing drug resistance, the CAA approach resulted in the parallel development of increased susceptibility to the compounds in the PGO combination. These observations demonstrate the therapeutic potential of the CAA approach for treatment of enterovirus infections.

Effect of Consecutive Alternating Administration of a Triple Combination of Anti-Enteroviral Compounds in Mice Infected with Coxsackievirus B3

A novel approach for treatment of enterovirus infections was characterized. Application of treatment course of consecutive alternating administration (CAA) of triple combination of enterovirus replication inhibitors in experimental infections (20 MLD50) with coxsackievirus B3 (CVB3) strains in newborn mice is presented. It was established that in infection with cardiotropic Woodruff strain the combination of pleconaril, МDL-860 and oxoglaucine (PMO) subjected to the CAA scheme, a significant protective effect was observed. Monotherapeutic courses as well as simultaneously daily applied PMO were without effect. Analogous data were observed at experimental infection with the neurotriopic Nancy strain of CVB3. Following IC50 values of virus samples taken every day from target organs of infected animals during the whole period of study, a drug-resistance was established in monotherapy with compounds-partners in the PMO combination. At courses by the treatment scheme CAA of PMO development of drug-resistance was not established, but an increased susceptibility to the effect of the inhibitor-components in the combination was proven. Toxicity of PMO applied via the CAA scheme and in the monotherapeutic courses in both healthy and CVB3 infected animals was recorded. All data obtained prove the potential of the CAA treatment scheme for development of effective chemotherapy of enterovirus infections.

Sphingomyelin Is Essential for the Structure and Function of the Double-Membrane Vesicles in Hepatitis C Virus RNA Replication Factories

Some plus-stranded RNA viruses generate double-membrane vesicles (DMVs), one type of the membrane replication factories, as replication sites. Little is known about the lipid components involved in the biogenesis of these vesicles. Sphingomyelin (SM) is required for hepatitis C virus (HCV) replication, but the mechanism of SM involvement remains poorly understood. SM biosynthesis starts in the endoplasmic reticulum (ER) and gives rise to ceramide, which is transported from the ER to the Golgi by the action of ceramide transfer protein (CERT), where it can be converted to SM. In this study, inhibition of SM biosynthesis, either by using small-molecule inhibitors or by knockout (KO) of CERT, suppressed HCV replication in a genotype-independent manner. This reduction in HCV replication was rescued by exogenous SM or ectopic expression of the CERT protein, but not by ectopic expression of nonfunctional CERT mutants. Observing low numbers of DMVs in stable replicon cells treated with a SM biosynthesis inhibitor or in CERT-KO cells transfected with either HCV replicon or with constructs that drive HCV protein production in a replication-independent system indicated the significant importance of SM to DMVs. The degradation of SM of the in vitro-isolated DMVs affected their morphology and increased the vulnerability of HCV RNA and proteins to RNase and protease treatment, respectively. Poliovirus, known to induce DMVs, showed decreased replication in CERT-KO cells, while dengue virus, known to induce invaginated vesicles, did not. In conclusion, these findings indicated that SM is an essential constituent of DMVs generated by some plus-stranded RNA viruses.IMPORTANCE Previous reports assumed that sphingomyelin (SM) is essential for HCV replication, but the mechanism was unclear. In this study, we showed for the first time that SM and ceramide transfer protein (CERT), which is in the SM biosynthesis pathway, are essential for the biosynthesis of double-membrane vesicles (DMVs), the sites of viral replication. Low numbers of DMVs were observed in CERT-KO cells transfected with replicon RNA or with constructs that drive HCV protein production in a replication-independent system. HCV replication was rescued by ectopic expression of the CERT protein, but not by CERT mutants, that abolishes the binding of CERT to vesicle-associated membrane protein-associated protein (VAP) or phosphatidylinositol 4-phosphate (PI4P), indicating new roles for VAP and PI4P in HCV replication. The biosynthesis of DMVs has great importance to replication by a variety of plus-stranded RNA viruses. Understanding of this process is expected to facilitate the development of diagnosis and antivirus.

Enterovirus Replication Organelles and Inhibitors of Their Formation

Enteroviral replication reorganizes the cellular membrane. Upon infection, viral proteins and hijacked host factors generate unique structures called replication organelles (ROs) to replicate their viral genomes. ROs promote efficient viral genome replication, coordinate the steps of the viral replication cycle, and protect viral RNA from host immune responses. More recent researches have focused on the ultrastructure structures, formation mechanism, and functions in the virus life cycle of ROs. Dynamic model of enterovirus ROs structure is proposed, and the secretory pathway, the autophagy pathway, and lipid metabolism are found to be associated in the formation of ROs. With deeper understanding of ROs, some compounds have been found to show inhibitory effects on viral replication by targeting key proteins in the process of ROs formation. Here, we review the recent findings concerning the role, morphology, biogenesis, formation mechanism, and inhibitors of enterovirus ROs.

The Great Escape: how phosphatidylinositol 4-kinases and PI4P promote vesicle exit from the Golgi (and drive cancer)

Phosphatidylinositol 4-phosphate (PI4P) is a membrane glycerophospholipid and a major regulator of the characteristic appearance of the Golgi complex as well as its vesicular trafficking, signalling and metabolic functions. Phosphatidylinositol 4-kinases, and in particular the PI4KIIIβ isoform, act in concert with PI4P to recruit macromolecular complexes to initiate the biogenesis of trafficking vesicles for several Golgi exit routes. Dysregulation of Golgi PI4P metabolism and the PI4P protein interactome features in many cancers and is often associated with tumour progression and a poor prognosis. Increased expression of PI4P-binding proteins, such as GOLPH3 or PITPNC1, induces a malignant secretory phenotype and the release of proteins that can remodel the extracellular matrix, promote angiogenesis and enhance cell motility. Aberrant Golgi PI4P metabolism can also result in the impaired post-translational modification of proteins required for focal adhesion formation and cell–matrix interactions, thereby potentiating the development of aggressive metastatic and invasive tumours. Altered expression of the Golgi-targeted PI 4-kinases, PI4KIIIβ, PI4KIIα and PI4KIIβ, or the PI4P phosphate Sac1, can also modulate oncogenic signalling through effects on TGN-endosomal trafficking. A Golgi trafficking role for a PIP 5-kinase has been recently described, which indicates that PI4P is not the only functionally important phosphoinositide at this subcellular location. This review charts new developments in our understanding of phosphatidylinositol 4-kinase function at the Golgi and how PI4P-dependent trafficking can be deregulated in malignant disease.

Pachypodol, a Methoxyflavonoid Isolated from Pogostemon cablin Bentham Exerts Antioxidant and Cytoprotective Effects in HepG2 Cells: Possible Role of ERK-Dependent Nrf2 Activation

Oxidative stress has been implicated in the pathogenesis of many diseases including chronic liver diseases. Nrf2 is a master transcriptional factor regulating the induction of cellular antioxidant defense systems. Here, the Nrf2-activating effect of the crude methanol extract of dried leaves of Pogostemon cablin Bentham was demonstrated by measuring the antioxidant response element (ARE)-driven luciferase activity and pachypodol, 4′,5-dihydroxy-3,3′,7-trimethoxyflavone, was isolated by bioactivity-guided fractionation and further separation using chromatographic techniques. To our knowledge, this is the first study to evaluate the antioxidant and cytoprotective effects of pachypodol in HepG2 cells as well as the underlying molecular mechanisms. Indeed, pachypodol protected HepG2 cells from cell death caused by tert-butylhydroperoxide-induced oxidative stress and also attenuated ROS production. The ability of pachypodol to activate Nrf2/ARE pathway was further confirmed by observing Nrf2 expression in nuclear fraction, mRNA levels of Nrf2 target antioxidants, and cellular glutathione content in HepG2 cells. Extracellular signal-regulated kinase (ERK) is one of the important kinases involved in Nrf2 activation. Pachypodol increased ERK phosphorylation and ERK inhibition by PD98059 totally abrogated the increase in ARE luciferase activity, nuclear Nrf2 accumulation and mRNA levels of antioxidant enzymes by pachypodol. In conclusion, pachypodol isolated from P. cablin can protect hepatocytes from oxidative injury, possibly mediated by enhancing endogenous antioxidant defense system through ERK-dependent Nrf2 activation.

Novel total syntheses of oxoaporphine alkaloids enabled by mild Cu-catalyzed tandem oxidation/aromatization of 1-Bn-DHIQs

Novel total syntheses of oxoaporphine alkaloids such as liriodenine, dicentrinone, cassameridine, lysicamine, oxoglaucine and O-methylmoschatoline were developed. The key step of these total syntheses is Cu-catalyzed conversion of 1-benzyl-3,4-dihydro-isoquinolines (1-Bn-DHIQs) to 1-benzoyl-isoquinolines (1-Bz-IQs) via tandem oxidation/aromatization. This novel Cu-catalyzed conversion has been studied in detail, and was successfully used for constructing the 1-Bz-IQ core.

Novel total syntheses of several oxoaporphine alkaloids were developed. The Cu-catalyzed conversion of 1-benzyl-3,4-dihydro-isoquinolines (1-Bn-DHIQs) to 1-benzoyl-isoquinolines (1-Bz-IQs) as the key step of these total syntheses has also been investigated in detail.

Posaconazole inhibits dengue virus replication by targeting oxysterol-binding protein

Dengue virus (DENV) is associated with an estimated 390 million infections per year, occurring across approximately 100 countries in tropical and sub-tropical regions. To date, there are no antiviral drugs or specific therapies to treat DENV infection. Posaconazole and itraconazole are potent antifungal drugs that inhibit ergosterol biosynthesis in fungal cells, but also target a number of human proteins. Here, we show that itraconazole and posaconazole have antiviral activity against DENV. Posaconazole inhibited replication of multiple serotypes of DENV and the related flavivirus Zika virus, and reduced viral RNA replication, but not translation of the viral genome. We used a combination of knockdown and drug sensitization assays to define the molecular target of posaconazole that mediates its antiviral activity. We found that knockdown of oxysterol-binding protein (OSBP) inhibited DENV replication. Moreover, knockdown of OSBP, but not other known targets of posaconazole, enhanced the inhibitory effect of posaconazole. Our findings imply OSBP as a potential target for the development of antiviral compounds against DENV.

The Golgi complex in disease and therapy

The Golgi complex occupies a strategic position in the endomembrane system and acts not only as a key trafficking and sorting station and a vital biosynthetic center for glycoproteins and lipids, but also as an active signaling hub. As such, the Golgi complex participates in the establishment and maintenance of cell compartmentalization and in general, cell processes such as cell growth and apoptosis. The different functions of the Golgi complex are executed by composite molecular machineries that have been exhaustively dissected over the last three decades. These machineries can become dysfunctional as a result of mutations in the respective encoding genes or may be hijacked by infectious agents or misregulated in the course of multifactorial diseases such as neurodegeneration and cancer. Small molecules targeting components of these machineries have been instrumental in dissecting their functions in in vitro studies and some of them have been developed or are currently under development for clinical use.

Allosteric Regulation of Phosphatidylinositol 4-Kinase III Beta by an Antipicornavirus Compound MDL-860

MDL-860 is a broad-spectrum antipicornavirus compound discovered in 1982 and one of the few promising candidates effective in in vivo virus infection. Despite the effectiveness, the target and the mechanism of action of MDL-860 remain unknown. Here, we have characterized antipoliovirus activity of MDL-860 and identified host phosphatidylinositol-4 kinase III beta (PI4KB) as the target. MDL-860 treatment caused covalent modification and irreversible inactivation of PI4KB. A cysteine residue at amino acid 646 of PI4KB, which locates at the bottom of a surface pocket apart from the active site, was identified as the target site of MDL-860. This work reveals the mechanism of action of this class of PI4KB inhibitors and offers insights into novel allosteric regulation of PI4KB activity.

Structural Pharmacokinetics of Polymethoxylated Flavones in Rat Plasma Using HPLC-MS/MS

The purpose of this study was to investigate the pharmacokinetics of the polymethoxylated flavonoids kumatakenin, pachypodol, and retusin, which contain two, three, or four methoxy substitutions, using a validated ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method in rats. The pharmacokinetic results demonstrated that the elimination half-lives for kumatakenin, pachypodol, and retusin were 30 ± 11.6, 39.4 ± 19.5, and 106.9 ± 26 min, respectively, for the low dose group and 54.5 ± 16.5, 33.8 ± 10, and 134.6 ± 34.7 min for the high dose group. The results suggested that the area under the curve values (AUC) for the analytes did not correlate with the number of methoxy groups. Pachypodol had the lowest AUC, which may have been correlated with lipophilicity, for both the low and high dose groups. In conclusion, the polymethoxylated flavonoid pachypodol is more hydrophilic than kumatakenin or retusin, which were correlated with the pharmacokinetic results.

Uncovering oxysterol-binding protein (OSBP) as a target of the anti-enteroviral compound TTP-8307

The genus Enterovirus (e.g. poliovirus, coxsackievirus, rhinovirus) of the Picornaviridae family of positive-strand RNA viruses includes many important pathogens linked to a range of acute and chronic diseases for which no approved antiviral therapy is available. Targeting a step in the life cycle that is highly conserved provides an attractive strategy for developing broad-range inhibitors of enterovirus infection. A step that is currently explored as a target for the development of antivirals is the formation of replication organelles, which support replication of the viral genome. To build replication organelles, enteroviruses rewire cellular machinery and hijack lipid homeostasis pathways. For example, enteroviruses exploit the PI4KIIIβ-PI4P-OSBP pathway to direct cholesterol to replication organelles. Here, we uncover that TTP-8307, a known enterovirus replication inhibitor, acts through the PI4KIIIβ-PI4P-OSBP pathway by directly inhibiting OSBP activity. However, despite a shared mechanism of TTP-8307 with established OSBP inhibitors (itraconazole and OSW-1), we identify a number of notable differences between these compounds. The antiviral activity of TTP-8307 extends to other viruses that require OSBP, namely the picornavirus encephalomyocarditis virus and the flavivirus hepatitis C virus.

Anti-enteroviral triple combination of viral replication inhibitors: activity against coxsackievirus B1 neuroinfection in mice

BACKGROUND

Chemotherapy is an important tool for controlling enterovirus infections, but clinically effective anti-enterovirus drugs do not currently exist, mainly due to the development of drug resistance. We investigated the combination effects of enterovirus replication inhibitors in order to limit this process. In previous studies, we showed the efficacy of consecutive alternating administration of the triple combinations disoxaril/guanidine/oxoglaucine and pleconaril/guanidine/oxoglaucine against coxsackievirus B1 infection in newborn mice. Drug sensitivity tests of the viral brain isolates showed that these drug combinations prevented the development of drug resistance.

METHODS

In the current study, we replaced guanidine-HCl with enteroviral RNA synthesis inhibitor MDL-860 to test the effect of a new triple combination-pleconaril/MDL-860/oxoglaucine-applied via consecutive alternating administration in newborn mice infected subcutaneously with 20 MLD₅₀ of coxsackievirus B1.

RESULTS

The pleconaril/MDL-860/oxoglaucine combination via consecutive alternating administration showed high activity at the 75 mg/kg MDL-860 dose: a protective effect of 50% and a pronounced suppression of brain virus titers. Moreover, along with prevention of drug resistance, a phenomenon of increased drug sensitivity was established. MDL-860 sensitivity in pleconaril/MDL-860/oxoglaucine increased 8.2 times vs. placebo (29 times vs. monotherapy) on day 7 and oxoglaucine sensitivity-4.9 times vs. placebo (by 6.8 times vs. monotherapy) on day 13. As concerns pleconaril, a demonstrable prevention of drug resistance was registered without increase of drug sensitivity. Daily, simultaneous administration of pleconaril/MDL-860/oxoglaucine showed no protective effects and led to a rapid development of drug resistance.

CONCLUSIONS

These results add new support for using consecutive alternating administration treatment courses to achieve clinically effective chemotherapy of enterovirus infections.

Poliovirus Studies during the Endgame of the Polio Eradication Program

Since the beginning of Global Polio Eradication Initiative in 1988, poliomyelitis cases caused by wild poliovirus (PV) have been drastically reduced, with only 74 cases reported in 2 endemic countries in 2015. The current limited PV transmission suggests that we are in the endgame of the polio eradication program. However, specific challenges have emerged in the endgame, including tight budget, switching of the vaccines, and changes in biorisk management of PV. To overcome these challenges, several PV studies have been implemented in the eradication program. Some of the responses to the emerging challenges in the polio endgame might be valuable in other infectious diseases eradication programs. Here, I will review challenges that confront the polio eradication program and current research to address these challenges.

Design and Structural Characterization of Potent and Selective Inhibitors of Phosphatidylinositol 4 Kinase IIIβ

Type III phosphatidylinositol 4-kinase (PI4KIIIβ) is an essential enzyme in mediating membrane trafficking and is implicated in a variety of pathogenic processes. It is a key host factor mediating replication of RNA viruses. The design of potent and specific inhibitors of this enzyme will be essential to define its cellular roles and may lead to novel antiviral therapeutics. We previously reported the PI4K inhibitor PIK93, and this compound has defined key functions of PI4KIIIβ. However, this compound showed high cross reactivity with class I and III PI3Ks. Using structure-based drug design, we have designed novel potent and selective (>1000-fold over class I and class III PI3Ks) PI4KIIIβ inhibitors. These compounds showed antiviral activity against hepatitis C virus. The co-crystal structure of PI4KIIIβ bound to one of the most potent compounds reveals the molecular basis of specificity. This work will be vital in the design of novel PI4KIIIβ inhibitors, which may play significant roles as antiviral therapeutics.

Mechanism of Poliovirus Resistance to Host Phosphatidylinositol-4 Kinase III β Inhibitor

Phosphatidylinositol-4 kinase III β (PI4KB) and oxysterol-binding protein (OSBP) family I have been identified as the major targets of anti-enterovirus drug candidates. Resistance mutations in poliovirus (PV) to these inhibitors have been identified in viral 3A protein, represented by a G5318A (3A-Ala70Thr) mutation, but the mechanism of viral resistance to host PI4KB/OSBP inhibitors remained unknown. In this study, we found that a G5318A mutation enhances the basal levels of phosphatidylinositol 4-phosphate (PI4P) and of the 3A protein and decreases the levels of the 3AB protein during PV replication. The 3A protein acted as a major effector responsible for the resistance to PI4KB inhibitor, but did not enhance the PI4KB activity in vitro in contrast to the 2C, 2BC, 3AB, and 3D proteins. The 3AB protein acted as the primary target of a G5318A mutation and also as an effector. We identified novel resistance mutations to a PI4KB inhibitor [C5151U (3A-T14M) and C5366U (3A-H86Y) mutations] and found that there is a positive correlation between the extent of the resistance phenotype and the levels of the 3A proteins. These results suggested that the 3A protein overproduced by enhanced processing of the 3AB protein with the resistance mutations overcomes the inhibitory effect of PI4KB inhibitor on PV replication independently of the hyperactivation of the PI4KB/OSBP pathway.

Using hydrogen deuterium exchange mass spectrometry to engineer optimized constructs for crystallization of protein complexes: Case study of PI4KIIIβ with Rab11

The ability of proteins to bind and interact with protein partners plays fundamental roles in many cellular contexts. X‐ray crystallography has been a powerful approach to understand protein‐protein interactions; however, a challenge in the crystallization of proteins and their complexes is the presence of intrinsically disordered regions. In this article, we describe an application of hydrogen deuterium exchange mass spectrometry (HDX‐MS) to identify dynamic regions within type III phosphatidylinositol 4 kinase beta (PI4KIIIβ) in complex with the GTPase Rab11. This information was then used to design deletions that allowed for the production of diffraction quality crystals. Importantly, we also used HDX‐MS to verify that the new construct was properly folded, consistent with it being catalytically and functionally active. Structures of PI4KIIIβ in an Apo state and bound to the potent inhibitor BQR695 in complex with both GTPγS and GDP loaded Rab11 were determined. This hybrid HDX‐MS/crystallographic strategy revealed novel aspects of the PI4KIIIβ‐Rab11 complex, as well as the molecular mechanism of potency of a PI4K specific inhibitor (BQR695). This approach is widely applicable to protein‐protein complexes, and is an excellent strategy to optimize constructs for high‐resolution structural approaches.

PDB Code(s): 5C46; 5C4G

Chinese herbal medicines as a source of molecules with anti-enterovirus 71 activity

Enterovirus 71 (EV71) is one of the causative agents of hand, foot, and mouth disease (HFMD), which sometimes leads to severe neurological disease and death in the Asia-Pacific region. In Chinese medicine, HFMD is caused mainly by an accumulation of damp-heat and toxicity in the body. No effective drugs are currently available for the treatment and prevention of EV71 infection. This review summarizes the potential Chinese herbal extracts and isolated compounds with antiviral activity against EV71 and their clinical applications, especially those categorized as heat-clearing and detoxifying.

Prolactin Regulatory Element Binding Protein Is Involved in Hepatitis C Virus Replication by Interaction with NS4B

It has been proposed that the hepatitis C virus (HCV) NS4B protein triggers the membranous HCV replication compartment, but the underlying molecular mechanism is not fully understood. Here, we screened for NS4B-associated membrane proteins by tandem affinity purification and proteome analysis and identified 202 host proteins. Subsequent screening of replicon cells with small interfering RNA identified prolactin regulatory element binding (PREB) to be a novel HCV host cofactor. The interaction between PREB and NS4B was confirmed by immunoprecipitation, immunofluorescence, and proximity ligation assays. PREB colocalized with double-stranded RNA and the newly synthesized HCV RNA labeled with bromouridine triphosphate in HCV replicon cells. Furthermore, PREB shifted to detergent-resistant membranes (DRMs), where HCV replication complexes reside, in the presence of NS4B expression in Huh7 cells. However, a PREB mutant lacking the NS4B-binding region (PREBd3) could not colocalize with double-stranded RNA and did not shift to the DRM in the presence of NS4B. These results indicate that PREB locates at the HCV replication complex by interacting with NS4B. PREB silencing inhibited the formation of the membranous HCV replication compartment and increased the protease and nuclease sensitivity of HCV replicase proteins and RNA in DRMs, respectively. Collectively, these data indicate that PREB promotes HCV RNA replication by participating in the formation of the membranous replication compartment and by maintaining its proper structure by interacting with NS4B. Furthermore, PREB was induced by HCV infection in vitro and in vivo. Our findings provide new insights into HCV host cofactors.

IMPORTANCE

The hepatitis C virus (HCV) protein NS4B can induce alteration of the endoplasmic reticulum and the formation of a membranous web structure, which provides a platform for the HCV replication complex. The molecular mechanism by which NS4B induces the membranous HCV replication compartment is not understood. We screened for NS4B-associated membrane proteins by tandem affinity purification and proteome analysis, followed by screening with small interfering RNA. We identified prolactin regulatory element binding (PREB) to be a novel HCV host cofactor. PREB is induced by HCV infection and recruited into the replication complex by interaction with NS4B. Recruited PREB promotes HCV RNA replication by participating in the formation of the membranous HCV replication compartment. To our knowledge, the effect of NS4B-binding protein on the formation of the membranous HCV replication compartment is newly described in this report. Our findings are expected to provide new insights into HCV host cofactors.

Effect of consecutive alternating administration (CAA) of a triple anti-enteroviral combination on Coxsackievirus B1 neuroinfection in mice

Currently, clinically effective antivirals for use in the treatment of enteroviral (EV) infections do not exist. The main reason is the development of drug resistance, the principle obstacle in the development of EV infection chemotherapy, based til now on monotherapy. The most important achievement of our previous studies was the development of a novel scheme for in vivo application of a triple combination of EV inhibitors with different modes of action against Coxsackievirus B (CVB) infections in mice. It consists of consecutive alternating administration (CAA) of the substances in the combination. Here, we tested the effect of the triple combination pleconaril, guanidine-HCl, and oxoglaucine (PGO) via CAA in newborn mice infected with a neurotropic strain of CVB1 (20 LD50 per mouse). This combination manifested a considerable protective effect with pleconaril doses of 25-200mg/kg: it decreased mortality rate (protection index, PI, between 31.3% and 67.7%) and increased mean survival time (MST) by 4-6days. Pleconaril monotherapy demonstrated activity similar to that of PGO via CAA, as measured by PI values, but MST values were slightly lower. However, it also greatly suppressed growth of infected suckling mice, especially at 200mg/kg. This toxic effect was avoided with CAA of PGO at pleconaril doses of 25-100mg/kg. Pleconaril monotherapy administered every 3days was ineffective. The PGO with CAA treatment course decreased infectious virus content, whereas pleconaril monotherapy did not. Analysis of drug-sensitivity in brain samples from CVB1 infected mice, based on IC50 (50% inhibitory concentration) values from cell culture experiments, showed that the CAA course counteracted the development of drug resistance to pleconaril and oxoglaucine in the triple PGO combination and increased drug sensitivity. In contrast, pleconaril and oxoglaucine monotherapies resulted in drug resistance. This data clearly proves the effectiveness of the proposed novel approach-the CAA treatment course-for combined application of EV replication inhibitors.