Solution Structure, Self-Assembly, and Membrane Interactions of the Matrix Protein from Newcastle Disease Virus at Neutral and Acidic pH

Structural Insights into Plant Viruses Revealed by Small-Angle X-ray Scattering and Atomic Force Microscopy

The structural study of plant viruses is of great importance to reduce the damage caused by these agricultural pathogens and to support their biotechnological applications. Nowadays, X-ray crystallography, NMR spectroscopy and cryo-electron microscopy are well accepted methods to obtain the 3D protein structure with the best resolution. However, for large and complex supramolecular structures such as plant viruses, especially flexible filamentous ones, there are a number of technical limitations to resolving their native structure in solution. In addition, they do not allow us to obtain structural information about dynamics and interactions with physiological partners. For these purposes, small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM) are well established. In this review, we have outlined the main principles of these two methods and demonstrated their advantages for structural studies of plant viruses of different shapes with relatively high spatial resolution. In addition, we have demonstrated the ability of AFM to obtain information on the mechanical properties of the virus particles that are inaccessible to other experimental techniques. We believe that these under-appreciated approaches, especially when used in combination, are valuable tools for studying a wide variety of helical plant viruses, many of which cannot be resolved by classical structural methods.

Newcastle disease virus: the past and current situation in Indonesia

The Newcastle disease virus (NDV) outbreak was first reported in Java Island, Indonesia, in 1926, which was then reported further in Newcastle-upon-Tyne, England. Nevertheless, the NDV is still endemic in Indonesia, with outbreaks occurring in free-range and commercial chicken farms. The dynamic evolution of the NDV has led to the further development of vaccines and diagnostic tools for more effective control of this virus. This paper discusses the history of the NDV occurrence, vaccines, the development of diagnostic tools, and the epidemiological condition of the NDV in Indonesia. Indonesia, which has the largest poultry population in the world after China, has challenges in preventing and controlling this virus that causes economic losses to the farmers and has an impact on the welfare of the poultry farming community in Indonesia.

Multifunctionality of matrix protein in the replication and pathogenesis of Newcastle disease virus: A review

As an important structural protein in virion morphogenesis, the matrix (M) protein of Newcastle disease virus (NDV) is demonstrated to be a nuclear-cytoplasmic trafficking protein and plays essential roles in viral assembly and budding. In recent years, increasing lines of evidence have indicated that the M protein has obvious influence on the pathotypes of NDV, and the interaction of M protein with cellular proteins is also closely associated with the replication and pathogenicity of NDV. Although substantial progress has been made in the past 40 years towards understanding the structure and function of NDV M protein, the available information is scattered. Therefore, this review article summarizes and updates the research progress on the structural feature, virulence and pathotype correlation, and nucleocytoplasmic transport mechanism of NDV M protein, as well as the functions of M protein and cellular protein interactions in M's intracellular localization, viral RNA synthesis and transcription, viral protein synthesis, viral immune evasion, and viral budding and release, which will provide an in-depth understanding of the biological functions of M protein in the replication and pathogenesis of NDV, and also contribute to the development of effective antiviral strategies aiming at blocking the early or late steps of NDV lifecycles.

Mutation of Phenylalanine 23 of Newcastle Disease Virus Matrix Protein Inhibits Virus Release by Disrupting the Interaction between the FPIV L-Domain and Charged Multivesicular Body Protein 4B

The matrix (M) protein FPIV L-domain is conserved among multiple paramyxoviruses; however, its function and the associated mechanism remain unclear. In this study, the paramyxovirus Newcastle disease virus (NDV) was employed to study the FPIV L-domain. Two recombinant NDV strains, each carrying a single amino acid mutation at the Phe (F23) or Pro (P24) site of 23FPIV/I26 L-domain, were rescued. Growth defects were observed in only the recombinant SG10-F23A (rSG10-F23A) strain. Subsequent studies focused on rSG10-F23A revealed that the virulence, pathogenicity, and replication ability of this strain were all weaker than those of wild-type strain rSG10 and that a budding deficiency contributed to those weaknesses. To uncover the molecular mechanism underlying the rSG10-F23A budding deficiency, the bridging proteins between the FPIV L-domain and endosomal sorting complex required for transported (ESCRT) machinery were explored. Among 17 candidate proteins, only the charged multivesicular body protein 4 (CHMP4) paralogues were found to interact more strongly with the NDV wild-type M protein (M-WT) than with the mutated M protein (M-F23A). Overexpression of M-WT, but not of M-F23A, changed the CHMP4 subcellular location to the NDV budding site. Furthermore, a knockdown of CHMP4B, the most abundant CHMP4 protein, inhibited the release of rSG10 but not that of rSG10-F23A. From these findings, we can reasonably infer that the F23A mutation of the FPIV L-domain blocks the interaction between the NDV M protein and CHMP4B and that this contributes to the budding deficiency and consequent growth defects of rSG10-F23A. This work lays the foundation for further study of the FPIV L-domain in NDV and other paramyxoviruses. IMPORTANCE Multiple viruses utilize a conserved motif, termed the L-domain, to act as a cellular adaptor for recruiting host ESCRT machinery to their budding site. Despite the FPIV type L-domain having been identified in some paramyxoviruses 2 decades ago, its function in virus life cycles and its method of recruiting the ESCRT machinery are poorly understood. In this study, a single amino acid mutation at the F23 site of the 23FPIV26 L-domain was found to block NDV budding at the late stage. Furthermore, CHMP4B, a core component of the ESCRT-III complex, was identified as a main factor that links the FPIV L-domain and ESCRT machinery together. These results extend previous understanding of the FPIV L-domain and, therefore, not only provide a new approach for attenuating NDV and other paramyxoviruses but also lay the foundation for further study of the FPIV L-domain.

Influenza A Virus M1 Protein Non-Specifically Deforms Charged Lipid Membranes and Specifically Interacts with the Raft Boundary

Topological rearrangements of biological membranes, such as fusion and fission, often require a sophisticated interplay between different proteins and cellular membranes. However, in the case of fusion proteins of enveloped viruses, even one molecule can execute membrane restructurings. Growing evidence indicates that matrix proteins of enveloped viruses can solely trigger the membrane bending required for another crucial step in virogenesis, the budding of progeny virions. For the case of the influenza A virus matrix protein M1, different studies report both in favor and against M1 being able to produce virus-like particles without other viral proteins. Here, we investigated the physicochemical mechanisms of M1 membrane activity on giant unilamellar vesicles of different lipid compositions using fluorescent confocal microscopy. We confirmed that M1 predominantly interacts electrostatically with the membrane, and its ability to deform the lipid bilayer is non-specific and typical for membrane-binding proteins and polypeptides. However, in the case of phase-separating membranes, M1 demonstrates a unique ability to induce macro-phase separation, probably due to the high affinity of M1's amphipathic helices to the raft boundary. Thus, we suggest that M1 is tailored to deform charged membranes with a specific activity in the case of phase-separating membranes.

Molecular Mechanisms of Anti-Neoplastic and Immune Stimulatory Properties of Oncolytic Newcastle Disease Virus

Oncolytic viruses represent interesting anti-cancer agents with high tumor selectivity and immune stimulatory potential. The present review provides an update of the molecular mechanisms of the anti-neoplastic and immune stimulatory properties of the avian paramyxovirus, Newcastle Disease Virus (NDV). The anti-neoplastic activities of NDV include (i) the endocytic targeting of the GTPase Rac1 in Ras-transformed human tumorigenic cells; (ii) the switch from cellular protein to viral protein synthesis and the induction of autophagy mediated by viral nucleoprotein NP; (iii) the virus replication mediated by viral RNA polymerase (large protein (L), associated with phosphoprotein (P)); (iv) the facilitation of NDV spread in tumors via the membrane budding of the virus progeny with the help of matrix protein (M) and fusion protein (F); and (v) the oncolysis via apoptosis, necroptosis, pyroptosis, or ferroptosis associated with immunogenic cell death. A special property of this oncolytic virus consists of its potential for breaking therapy resistance in human cancer cells. Eight examples of this important property are presented and explained. In healthy human cells, NDV infection activates the RIG-MAVs immune signaling pathway and establishes an anti-viral state based on a strong and uninhibited interferon α,ß response. The review also describes the molecular determinants and mechanisms of the NDV-mediated immune stimulatory effects, in which the viral hemagglutinin-neuraminidase (HN) protein plays a prominent role. The six viral proteins provide oncolytic NDV with a special profile in the treatment of cancer.

Ubiquitination on Lysine 247 of Newcastle Disease Virus Matrix Protein Enhances Viral Replication and Virulence by Driving Nuclear-Cytoplasmic Trafficking

The Newcastle disease virus (NDV) matrix (M) protein is the pivotal element for viral assembly, budding and proliferation. It traffics through the cellular nucleus but performs its primary function in the cytoplasm. To investigate the biological importance of M's nuclear-cytoplasmic trafficking and the mechanism involved, the regulatory motif nuclear export signal (NES) and nuclear localization signal (NLS) were deeply analyzed. Here, two types of combined NLS and NES signals were identified within NDV-M. The Herts/33-type M was found to mediate efficient nuclear export and stable virus-like particle (VLP) release, while the LaSota-type M was mostly retained in the nuclei and showed retarded VLP production. Two critical residues, 247 and 263, within the motif were identified and associated with nuclear export efficiency. We identified, for the first time, residue 247 as an important monoubiquitination site, the modification of which regulates the nuclear-cytoplasmic trafficking of NDV-M. Subsequently, mutant LaSota strains were rescued via reverse genetics, which contained either single or double amino acid substitutions that were similar to the M of Herts/33. The rescued rLaSota strains rLaSota-R247K, -S263R, and -DM (double mutation) showed about twofold higher HA titers and 10-fold higher EID₅₀ titers than wild-type (wt) rLaSota. Further, the MDT and ICPI values of those recombinant viruses were slightly higher than that of wt rLaSota probably due to their higher proliferation rates. Our findings contribute to a better understanding of the molecular mechanism of the replication and pathogenicity of NDV, and even those of all other paramyxoviruses. It is beneficial for the development of vaccines and therapies for paramyxoviruses. Importance Newcastle disease virus (NDV) is a pathogen that is lethal to birds and causes heavy losses in the poultry industry worldwide. The World Organization for Animal Health (OIE) ranked ND as the third most significant poultry disease and the eighth most important wildlife disease in the World Livestock Disease Atlas in 2011. The matrix (M) protein of NDV is very important for viral assembly and maturation. It is interesting that M proteins enter the cellular nucleus before performing their primary function in the cytoplasm. We found that NDV-M has a combined nuclear import and export signal. The ubiquitin modification of a lysine residue within this signal is critical for quick, efficient nuclear export and subsequent viral production. Our findings shed new light on viral replication and opens up new possibilities for therapeutics against NDV and other paramyxoviruses; furthermore, we demonstrate a novel approach to improving paramyxovirus vaccines.

Advances in the Study of Antitumour Immunotherapy for Newcastle Disease Virus

This article reviews the preclinical research, clinical application and development of Newcastle disease virus (NDV) in the field of cancer therapy. Based on the distinctive antitumour properties of NDV and its positive interaction with the patient's immune system, this biologic could be considered a major breakthrough in cancer treatment. On one hand, NDV infection creates an inflammatory environment in the tumour microenvironment, which can directly activate NK cells, monocytes, macrophages and dendritic cells and promote the recruitment of immune cells. On the other hand, NDV can induce the upregulation of immune checkpoint molecules, which may break immune tolerance and immune checkpoint blockade resistance. In fact, clinical data have shown that NDV combined with immune checkpoint blockade can effectively enhance the antitumour response, leading to the regression of local tumours and distant tumours when injected, and this effect is further enhanced by targeted manipulation and modification of the NDV genome. At present, recombinant NDV and recombinant NDV combined with immune checkpoint blockers have entered different stages of clinical trials. Based on these studies, further research on NDV is warranted.

Activity-dependent conformational transitions of the insulin receptor-related receptor

The insulin receptor (IR), insulin-like growth factor 1 receptor (IGF-1R), and insulin receptor-related receptor (IRR) form a mini family of predimerized receptor-like tyrosine kinases. IR and IGF-1R bind to their peptide agonists triggering metabolic and cell growth responses. In contrast, IRR, despite sharing with them a strong sequence homology, has no peptide-like agonist but can be activated by mildly alkaline media. The spatial structure and activation mechanisms of IRR have not been established yet. The present work represents the first account of a structural analysis of a predimerized receptor-like tyrosine kinase by high-resolution atomic force microscopy in their basal and activated forms. Our data suggest that in neutral media, inactive IRR has two conformations, where one is symmetrical and highly similar to the inactive Λ/U-shape of IR and IGF-1R ectodomains, whereas the second is drop-like and asymmetrical resembling the IRR ectodomain in solution. We did not observe complexes of IRR intracellular catalytic domains of the inactive receptor forms. At pH 9.0, we detected two presumably active IRR conformations, Γ-shaped and T-shaped. Both of conformations demonstrated formation of the complex of their intracellular catalytic domains responsible for autophosphorylation. The existence of two active IRR forms correlates well with the previously described positive cooperativity of the IRR activation. In conclusion, our data provide structural insights into the molecular mechanisms of alkali-induced IRR activation under mild native conditions that could be valuable for interpretation of results of IR and IGF-IR structural studies.

Effects of Sterols on the Interaction of SDS, Benzalkonium Chloride, and A Novel Compound, Kor105, with Membranes

Sterols change the biophysical properties of lipid membranes. Here, we analyzed how sterols affect the activity of widely used antimicrobial membrane-active compounds, sodium dodecyl sulfate (SDS) and benzalkonium chloride (BAC). We also tested a novel benzalkonium-like substance, Kor105. Our data suggest that benzalkonium and Kor105 disturb the ordering of the membrane lipid packaging, and this disturbance is dampened by cholesterol. The disturbance induced by Kor105 is stronger than that induced by BAC because of the higher rigidity of the Kor105 molecule due to a shorter linker between the phenyl group and quaternary nitrogen. On the contrary, individual SDS molecules do not cause the disturbance. Thus, in the tested range of concentrations, SDS-membrane interaction is not influenced by cholesterol. To study how sterols influence the biological effects of these chemicals, we used yeast strains lacking Lam1-4 proteins. These proteins transport sterols from the plasma membrane into the endoplasmic reticulum. We found that the mutants are resistant to BAC and Kor105 but hypersensitive to SDS. Together, our findings show that sterols influence the interaction of SDS versus benzalkonium chloride and Kor105 with the membranes in a completely different manner.