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ARS Home » Southeast Area » Athens, Georgia » U.S. National Poultry Research Center » Exotic & Emerging Avian Viral Diseases Research » Research » Publications at this Location » Publication #337842

Research Project: Intervention Strategies to Prevent and Control Disease Outbreaks Caused by Emerging Strains of Avian Influenza Viruses

Location: Exotic & Emerging Avian Viral Diseases Research

Title: Sequence variation in the M2 ion channel protein influences its intracellular localization during avian influenza replication

Author
item Kapczynski, Darrell
item Murphy, Lita - University Of Edinburgh
item Wise, Helen - University Of Edinburgh
item Smith, Nikki - University Of Edinburgh
item Barr, Andrea - University Of Edinburgh
item Jasim, Seema - University Of Edinburgh
item Pantin-jackwood, Mary
item Vervelde, Lonneke - University Of Edinburgh
item Digard, Paul - University Of Edinburgh

Submitted to: World Veterinary Poultry Association
Publication Type: Abstract Only
Publication Acceptance Date: 4/17/2017
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Avian influenza virus (AIV) is a constant threat to poultry worldwide due to its ability to mutate from a low pathogenic (LP) form into a highly pathogenic (HP) one. It is known that the incorporation of a polybasic cleavage site (PBCS) on the hemagglutinin (HA) gene is a major indicator of pathogenesis. However, while the increased cleavability of the HA broadens the tropism of the virus and raises pathogenicity, it comes at a cost. The addition of a PBCS to HA can decrease the acid stability of the molecule and, because cleavage now occurs intracellularly, there is a risk of premature conformational change of the HA in the exocytic pathway. To alleviate this, the viral proton channel M2 protein functions to protect polybasic HAs from premature flipping into their low pH conformation. Interestingly, the amino acid sequence of the M2 ectodomain is highly conserved amongst most AIV subtypes, however, a splice-variant M42 with an altered ectodomain sequence can functionally replace M2 in the viral lifecycle. We hypothesize that specific alterations to the viral M2 ion channel protein are necessary to support the virulent HA function. Utilizing GFP tagged expression constructs for M2 and M42 we investigated the differential localization pattern of M2 and M42 and confirmed, by quantification and co-localization, a predominately Golgi-based localization of M42. This is in contrast to M2 which is found to be more widespread with a cytoplasmic/plasma membrane based localization. Mutagenic analysis of the polypeptides defined a di-leucine motif present in M2 but absent in M42 that underlies this difference. Antibody internalization experiments suggest that this motif affects retrieval of the ion channel from the plasma membrane. This work defines a new functional motif in the M2 ectodomain that helps explain the functional constraints that underlay its conservation, and may play a role in protecting the HA during its initial progression from LP to HP forms.