Influenza A: Understanding the Viral Life Cycle

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Abstract

Influenza A virus belongs to the family of Orthomyxoviridae. It is an enveloped virus with a negative sense RNA segmented genome that encodes for 11 viral genes. This virus has evolved a number of mechanisms that enable it to invade host cells and subvert the host cell machinery for its own purpose, that is, for the sole production of more virus. Two of the mechanisms that the virus uses are “cap-snatching” and preventing the host cell from expressing its own genes. This mini-review provides a brief overview as to how the virus is able to invade host cells, replicate itself, and exit the host cell.

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Most cited references 51

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Receptor binding and membrane fusion in virus entry: the influenza hemagglutinin.

J J Skehel, D C Wiley (2000)

Hemagglutinin (HA) is the receptor-binding and membrane fusion glycoprotein of influenza virus and the target for infectivity-neutralizing antibodies. The structures of three conformations of the ectodomain of the 1968 Hong Kong influenza virus HA have been determined by X-ray crystallography: the single-chain precursor, HA0; the metastable neutral-pH conformation found on virus, and the fusion pH-induced conformation. These structures provide a framework for designing and interpreting the results of experiments on the activity of HA in receptor binding, the generation of emerging and reemerging epidemics, and membrane fusion during viral entry. Structures of HA in complex with sialic acid receptor analogs, together with binding experiments, provide details of these low-affinity interactions in terms of the sialic acid substituents recognized and the HA residues involved in recognition. Neutralizing antibody-binding sites surround the receptor-binding pocket on the membrane-distal surface of HA, and the structures of the complexes between neutralizing monoclonal Fabs and HA indicate possible neutralization mechanisms. Cleavage of the biosynthetic precursor HA0 at a prominent loop in its structure primes HA for subsequent activation of membrane fusion at endosomal pH (Figure 1). Priming involves insertion of the fusion peptide into a charged pocket in the precursor; activation requires its extrusion towards the fusion target membrane, as the N terminus of a newly formed trimeric coiled coil, and repositioning of the C-terminal membrane anchor near the fusion peptide at the same end of a rod-shaped molecule. Comparison of this new HA conformation, which has been formed for membrane fusion, with the structures determined for other virus fusion glycoproteins suggests that these molecules are all in the fusion-activated conformation and that the juxtaposition of the membrane anchor and fusion peptide, a recurring feature, is involved in the fusion mechanism. Extension of these comparisons to the soluble N-ethyl-maleimide-sensitive factor attachment protein receptor (SNARE) protein complex of vesicle fusion allows a similar conclusion.

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Influenza virus NS1 protein interacts with the cellular 30 kDa subunit of CPSF and inhibits 3'end formation of cellular pre-mRNAs.

Martin E. Nemeroff, Silvia M.L. Barabino, Yongzhong Li … (1998)

Inhibition of the nuclear export of poly(A)-containing mRNAs caused by the influenza A virus NS1 protein requires its effector domain. Here, we demonstrate that the NS1 effector domain functionally interacts with the cellular 30 kDa subunit of CPSF, an essential component of the 3' end processing machinery of cellular pre-mRNAs. In influenza virus-infected cells, the NS1 protein is physically associated with CPSF 30 kDa. Binding of the NS1 protein to the 30 kDa protein in vitro prevents CPSF binding to the RNA substrate and inhibits 3' end cleavage and polyadenylation of host pre-mRNAs. The NS1 protein also inhibits 3' end processing in vivo, and the uncleaved pre-mRNA remains in the nucleus. Via this novel regulation of pre-mRNA 3' end processing, the NS1 protein selectively inhibits the nuclear export of cellular, and not viral, mRNAs.

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Influenza virus M2 protein has ion channel activity.

L H Pinto, L J Holsinger, R A Lamb (1992)

The influenza virus M2 protein was expressed in Xenopus laevis oocytes and shown to have an associated ion channel activity selective for monovalent ions. The anti-influenza virus drug amantadine hydrochloride significantly attenuated the inward current induced by hyperpolarization of oocyte membranes. Mutations in the M2 membrane-spanning domain that confer viral resistance to amantadine produced currents that were resistant to the drug. Analysis of the currents of these altered M2 proteins suggests that the channel pore is formed by the transmembrane domain of the M2 protein. The wild-type M2 channel was found to be regulated by pH. The wild-type M2 ion channel activity is proposed to have a pivotal role in the biology of influenza virus infection.

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Author and article information

Journal

Journal ID (nlm-ta): Yale J Biol Med

Journal ID (pmc): yjbm

Journal ID (publisher-id): YJBM

Title: The Yale Journal of Biology and Medicine

Publisher: YJBM

ISSN (Print): 0044-0086

ISSN (Electronic): 1551-4056

Publication date (Electronic): December 2009

Publication date (Print): December 2009

Volume: 82

Issue: 4

Pages: 153-159

Affiliations

Graduate student, Department of Microbiology, Yale University School of Medicine, New Haven. Connecticut

Author notes

To whom all correspondence should be addressed: Tasleem Samji, Department of Microbiology, Yale University School of Medicine, New Haven. Connecticut; E-mail: tasleem.samji@ 123456yale.edu .

Article

PMC ID: 2794490

PubMed ID: 20027280

SO-VID: 39e2d3a4-debc-439a-8ff6-d83da3f52860

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This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License, which permits for noncommercial use, distribution, and reproduction in any digital medium, provided the original work is properly cited and is not altered in any way.

Influenza A: Understanding the Viral Life Cycle

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Zika Virus

Most cited references 51

Receptor binding and membrane fusion in virus entry: the influenza hemagglutinin.

Influenza virus NS1 protein interacts with the cellular 30 kDa subunit of CPSF and inhibits 3'end formation of cellular pre-mRNAs.

Influenza virus M2 protein has ion channel activity.

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