scholarly journals Molecular recognition of a host protein by NS1 of pandemic and seasonal influenza A viruses

2020 ◽  
Vol 117 (12) ◽  
pp. 6550-6558 ◽  
Author(s):  
Jae-Hyun Cho ◽  
Baoyu Zhao ◽  
Jie Shi ◽  
Nowlan Savage ◽  
Qingliang Shen ◽  
...  
Keyword(s):  
Molecular Recognition ◽  
Influenza A ◽  
Nonstructural Protein ◽  
Conformational Dynamics ◽  
Relaxation Dispersion ◽  
Binding Kinetics ◽  
Host Protein ◽  
Dynamics Simulation ◽  
Nonstructural Protein 1 ◽  
Strain Dependent

The 1918 influenza A virus (IAV) caused the most severe flu pandemic in recorded human history. Nonstructural protein 1 (NS1) is an important virulence factor of the 1918 IAV. NS1 antagonizes host defense mechanisms through interactions with multiple host factors. One pathway by which NS1 increases virulence is through the activation of phosphoinositide 3-kinase (PI3K) by binding to its p85β subunit. Here we present the mechanism underlying the molecular recognition of the p85β subunit by 1918 NS1. Using X-ray crystallography, we determine the structure of 1918 NS1 complexed with p85β of human PI3K. We find that the 1918 NS1 effector domain (1918 NS1ED) undergoes a conformational change to bind p85β. Using NMR relaxation dispersion and molecular dynamics simulation, we identify that free 1918 NS1EDexists in a dynamic equilibrium between p85β-binding–competent and –incompetent conformations in the submillisecond timescale. Moreover, we discover that NS1EDproteins of 1918 (H1N1) and Udorn (H3N2) strains exhibit drastically different conformational dynamics and binding kinetics to p85β. These results provide evidence of strain-dependent conformational dynamics of NS1. Using kinetic modeling based on the experimental data, we demonstrate that 1918 NS1EDcan result in the faster hijacking of p85β compared to Ud NS1ED, although the former has a lower affinity to p85β than the latter. Our results suggest that the difference in binding kinetics may impact the competition with cellular antiviral responses for the activation of PI3K. We anticipate that our findings will increase the understanding of the strain-dependent behaviors of influenza NS1 proteins.

Influenza A viruses balance ER stress with host protein synthesis shutoff

2021 ◽  
Vol 118 (36) ◽  
pp. e2024681118
Author(s):  
Beryl Mazel-Sanchez ◽  
Justyna Iwaszkiewicz ◽  
Joao P. P. Bonifacio ◽  
Filo Silva ◽  
Chengyue Niu ◽  
...  
Keyword(s):  
Viral Replication ◽  
Er Stress ◽  
Host Cell ◽  
Messenger Rna ◽  
Influenza A ◽  
Nonstructural Protein ◽  
Host Protein ◽  
Stress Induction ◽  
Nonstructural Protein 1

Excessive production of viral glycoproteins during infections poses a tremendous stress potential on the endoplasmic reticulum (ER) protein folding machinery of the host cell. The host cell balances this by providing more ER resident chaperones and reducing translation. For viruses, this unfolded protein response (UPR) offers the potential to fold more glycoproteins. We postulated that viruses could have developed means to limit the inevitable ER stress to a beneficial level for viral replication. Using a relevant human pathogen, influenza A virus (IAV), we first established the determinant for ER stress and UPR induction during infection. In contrast to a panel of previous reports, we identified neuraminidase to be the determinant for ER stress induction, and not hemagglutinin. IAV relieves ER stress by expression of its nonstructural protein 1 (NS1). NS1 interferes with the host messenger RNA processing factor CPSF30 and suppresses ER stress response factors, such as XBP1. In vivo viral replication is increased when NS1 antagonizes ER stress induction. Our results reveal how IAV optimizes glycoprotein expression by balancing folding capacity.

scholarly journals Influenza A Virus Protein NS1 Exhibits Strain-Independent Conformational Plasticity

2019 ◽  
Vol 93 (21) ◽  
Author(s):  
Sayantan Mitra ◽  
Dilip Kumar ◽  
Liya Hu ◽  
Banumathi Sankaran ◽  
Mahdi Muhammad Moosa ◽  
...  
Keyword(s):  
Influenza A Virus ◽  
Influenza A ◽  
Nonstructural Protein ◽  
Major Group ◽  
Cellular Proteins ◽  
Conformational Preference ◽  
Nonstructural Protein 1 ◽  
Open Conformation ◽  
Cellular Factors ◽  
Strain Dependent

ABSTRACT Influenza A virus (IAV) nonstructural protein 1 (NS1), a potent antagonist of the host immune response, is capable of interacting with RNA and a wide range of cellular proteins. NS1 consists of an RNA-binding domain (RBD) and an effector domain (ED) separated by a flexible linker region (LR). H5N1-NS1 has a characteristic 5-residue deletion in the LR, with either G (minor group) or E (major group) at the 71st position, and non-H5N1-NS1 contains E71 with an intact linker. Based on the orientation of the ED with respect to the RBD, previous crystallographic studies have shown that minor group H5N1-NS1(G71), a non-H5N1-NS1 [H6N6-NS1(E71)], and the LR deletion mutant H6N6-NS1(Δ80-84/E71) mimicking the major group H5N1-NS1 exhibit “open,” “semiopen,” and “closed” conformations, respectively, suggesting that NS1 exhibits a strain-dependent conformational preference. Here we report the first crystal structure of a naturally occurring H5N1-NS1(E71) and show that it adopts an open conformation similar to that of the minor group of H5N1-NS1 [H5N1-NS1(G71)]. We also show that H6N6-NS1(Δ80-84/E71) under a different crystallization condition and H6N6-NS1(Δ80-84/G71) also exhibit open conformations, suggesting that NS1 can adopt an open conformation irrespective of E or G at the 71st position. Our single-molecule fluorescence resonance energy transfer (FRET) analysis to investigate the conformational preference of NS1 in solution showed that all NS1 constructs predominantly exist in an open conformation. Further, our coimmunoprecipitation and binding studies showed that they all bind to cellular factors with similar affinities. Taken together, our studies suggest that NS1 exhibits strain-independent structural plasticity that allows it to interact with a wide variety of cellular ligands during viral infection. IMPORTANCE IAV is responsible for several pandemics over the last century and continues to infect millions annually. The frequent rise in drug-resistant strains necessitates exploring novel targets for developing antiviral drugs that can reduce the global burden of influenza infection. Because of its critical role in the replication and pathogenesis of IAV, nonstructural protein 1 (NS1) is a potential target for developing antivirals. Previous studies suggested that NS1 adopts strain-dependent “open,” “semiopen,” and “closed” conformations. Here we show, based on three crystal structures, that NS1 irrespective of strain differences can adopt an open conformation. We further show that NS1 from different strains primarily exists in an open conformation in solution and binds to cellular proteins with a similar affinity. Together, our findings suggest that conformational polymorphism facilitated by a flexible linker is intrinsic to NS1, and this may be the underlying factor allowing NS1 to bind several cellular factors during IAV replication.

scholarly journals Understanding the Binding Transition State After the Conformational Selection Step: The Second Half of the Molecular Recognition Process Between NS1 of the 1918 Influenza Virus and Host p85β

2021 ◽  
Vol 8 ◽  
Author(s):  
Alyssa Dubrow ◽  
Iktae Kim ◽  
Elias Topo ◽  
Jae-Hyun Cho
Keyword(s):  
Free Energy ◽  
Molecular Recognition ◽  
Transition State ◽  
Hydrophobic Interactions ◽  
Nonstructural Protein ◽  
Conformational Dynamics ◽  
Linear Free Energy Relationship ◽  
Conformational Selection ◽  
Nonstructural Protein 1 ◽  
1918 Influenza

Biomolecular recognition often involves conformational changes as a prerequisite for binding (i.e., conformational selection) or concurrently with binding (i.e., induced-fit). Recent advances in structural and kinetic approaches have enabled the detailed characterization of protein motions at atomic resolution. However, to fully understand the role of the conformational dynamics in molecular recognition, studies on the binding transition state are needed. Here, we investigate the binding transition state between nonstructural protein 1 (NS1) of the pandemic 1918 influenza A virus and the human p85β subunit of PI3K. 1918 NS1 binds to p85β via conformational selection. We present the free-energy mapping of the transition and bound states of the 1918 NS1:p85β interaction using linear free energy relationship and ϕ-value analyses. We find that the binding transition state of 1918 NS1 and p85β is structurally similar to the bound state with well-defined binding orientation and hydrophobic interactions. Our finding provides a detailed view of how protein motion contributes to the development of intermolecular interactions along the binding reaction coordinate.

scholarly journals Relative contribution of nonstructural protein 1 in dengue pathogenesis

2020 ◽  
Vol 217 (9) ◽  
Author(s):  
Pei Xuan Lee ◽  
Donald Heng Rong Ting ◽  
Clement Peng Hee Boey ◽  
Eunice Tze Xin Tan ◽  
Janice Zuo Hui Chia ◽  
...  
Keyword(s):  
Nonstructural Protein ◽  
Critical Role ◽  
Health Concern ◽  
Relative Contribution ◽  
Nonstructural Protein 1 ◽  
Structural Region ◽  
Strain Dependent ◽  
Highly Virulent

Dengue is a major public health concern in the tropical and subtropical world, with no effective treatment. The controversial live attenuated virus vaccine Dengvaxia has boosted the pursuit of subunit vaccine approaches, and nonstructural protein 1 (NS1) has recently emerged as a promising candidate. However, we found that NS1 immunization or passive transfer of NS1 antibodies failed to confer protection in symptomatic dengue mouse models using two non–mouse-adapted DENV2 strains that are highly virulent. Exogenous administration of purified NS1 also failed to worsen in vivo vascular leakage in sublethally infected mice. Neither method of NS1 immune neutralization changed the disease outcome of a chimeric strain expressing a vascular leak-potent NS1. Instead, virus chimerization involving the prME structural region indicated that these proteins play a critical role in driving in vivo fitness and virulence of the virus, through induction of key proinflammatory cytokines. This work highlights that the pathogenic role of NS1 is DENV strain dependent, which warrants reevaluation of NS1 as a universal dengue vaccine candidate.

scholarly journals 19F NMR Reveals Multiple Conformations at the Dimer Interface of the Nonstructural Protein 1 Effector Domain from Influenza A Virus

Structure ◽  
2014 ◽  
Vol 22 (4) ◽  
pp. 515-525 ◽  
Author(s):  
James M. Aramini ◽  
Keith Hamilton ◽  
Li-Chung Ma ◽  
G.V.T. Swapna ◽  
Paul G. Leonard ◽  
...  
Keyword(s):  
Influenza A Virus ◽  
Influenza A ◽  
Nonstructural Protein ◽  
19F Nmr ◽  
Effector Domain ◽  
Dimer Interface ◽  
Nonstructural Protein 1 ◽  
Multiple Conformations

scholarly journals Influenza A Virus NS1 Protein Activates the PI3K/Akt Pathway To Mediate Antiapoptotic Signaling Responses

2007 ◽  
Vol 81 (7) ◽  
pp. 3058-3067 ◽  
Author(s):  
Christina Ehrhardt ◽  
Thorsten Wolff ◽  
Stephan Pleschka ◽  
Oliver Planz ◽  
Wiebke Beermann ◽  
...  
Keyword(s):  
Influenza A Virus ◽  
Virus Replication ◽  
Influenza A ◽  
Glycogen Synthase ◽  
Nonstructural Protein ◽  
Akt Pathway ◽  
Ns1 Protein ◽  
Nonstructural Protein 1 ◽  
Cell Death Program ◽  
Pi3k Activation

ABSTRACT Recently we have shown that influenza A virus infection leads to activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway and that this cellular reaction is dependent on the expression of the viral nonstructural protein 1 (NS1). These data also suggested that PI3K activation confers a virus-supporting activity at intermediate stages of the infection cycle. So far it is not known which process is regulated by the kinase that supports virus replication. It is well established that upon infection with influenza A virus, the expression of the viral NS1 keeps the induction of beta interferon and the apoptotic response within a tolerable limit. On a molecular basis, this activity of NS1 has been suggested to preclude the activation of cellular double-stranded RNA receptors as well as impaired modulation of mRNA processing. Here we present a novel mode of action of the NS1 protein to suppress apoptosis induction. NS1 binds to and activates PI3K, which results in the activation of the PI3K effector Akt. This leads to a subsequent inhibition of caspase 9 and glycogen synthase-kinase 3β and limitation of the virus-induced cell death program. Thus, NS1 not only blocks but also activates signaling pathways to ensure efficient virus replication.

scholarly journals Modification of Nonstructural Protein 1 of Influenza A Virus by SUMO1

2010 ◽  
Vol 85 (2) ◽  
pp. 1086-1098 ◽  
Author(s):  
K. Xu ◽  
C. Klenk ◽  
B. Liu ◽  
B. Keiner ◽  
J. Cheng ◽  
...  
Keyword(s):  
Influenza A Virus ◽  
Influenza A ◽  
Nonstructural Protein ◽  
Nonstructural Protein 1

scholarly journals Coronavirus Nsp1: Immune Response Suppression and Protein Expression Inhibition

2021 ◽  
Vol 12 ◽  
Author(s):  
Shuai Yuan ◽  
Shravani Balaji ◽  
Ivan B. Lomakin ◽  
Yong Xiong
Keyword(s):  
Immune Responses ◽  
Protein Expression ◽  
Vaccine Development ◽  
Nonstructural Protein ◽  
Global Gene Expression ◽  
Current Data ◽  
Host Protein ◽  
Host Cells ◽  
Live Attenuated Vaccine ◽  
Nonstructural Protein 1

Coronaviruses have brought severe challenges to public health all over the world in the past 20years. SARS-CoV-2, the causative agent of the COVID-19 pandemic that has led to millions of deaths, belongs to the genus beta-coronavirus. Alpha- and beta-coronaviruses encode a unique protein, nonstructural protein 1 (Nsp1) that both suppresses host immune responses and reduces global gene expression levels in the host cells. As a key pathogenicity factor of coronaviruses, Nsp1 redirects the host translation machinery to increase synthesis of viral proteins. Through multiple mechanisms, coronaviruses impede host protein expression through Nsp1, while escaping inhibition to allow the translation of viral RNA. In this review, we discuss current data about suppression of the immune responses and inhibition of protein synthesis induced by coronavirus Nsp1, as well as the prospect of live-attenuated vaccine development with virulence-attenuated viruses with mutations in Nsp1.

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