Influenza A viral nucleoprotein interacts with cytoskeleton scaffolding protein α‐actinin‐4 for viral replication

Abstract

Influenza A virus (IAV), similar to other viruses, exploits the machinery of human host cells for its survival and replication. We identified a-actinin-4, a host cytoskeletal protein, as an interacting partner of IAV nucleoprotein (NP). We confirmed this interaction using co-immunoprecipitation studies, first in a coupled in vitro transcription-translation assay and then in cells either transiently co-expressing the two proteins or infected with whole IAV. Importantly, the NP-actinin-4 interaction was observed in several IAV subtypes, including the 2009 H1N1 pandemic virus. Moreover, immunofluorescence studies revealed that both NP and actinin-4 co-localized largely around the nucleus and also in the cytoplasmic region of virus-infected A549 cells. Silencing of actinin-4 expression resulted in not only a significant decrease in NP, M2 and NS1 viral protein expression, but also a reduction of both NP mRNA and viral RNA levels, as well as viral titers, 24 h post-infection with IAV, suggesting that actinin-4 was critical for viral replication. Furthermore, actinin-4 depletion reduced the amount of NP localized in the nucleus. Treatment of infected cells with wortmannin, a known inhibitor of actinin-4, led to a decrease in NP mRNA levels and also caused the nuclear retention of NP, further strengthening our previous observations. Taken together, the results of the present study indicate that actinin-4, a novel interacting partner of IAV NP, plays a crucial role in viral replication and this interaction may participate in nuclear localization of NP and/or viral ribonucleoproteins.

Influenza A Virus-induced expression of ISG20 inhibits viral replication by interacting with nucleoprotein

“…NP is a multi-functional protein of IAV, and several host factors were identified to interact with NP, and the interaction between NP and host factors exhibited its diverse role in viral life cycle [37][38][39][40][41][42]. The human anti-apoptosis protein clusterin (CLU) is targeted by NP to induced apoptosis [41].…”

Cervical Alpha-Actinin-4 Is Upregulated in Women with Threatened Preterm Labor and Microbial Invasion of the Amniotic Cavity

“…ACTN-4 is an actin-binding protein which has been described to play a key role in immune response regulation due to infection. It has been involved in the expression of genes encoding proinflammatory cytokines, chemokines and adhesion molecules [39][40][41]. In women with PTL, Romero et al [25] reported a higher presence of ACTN-4 in women with MIAC.…”

Genome-wide screens - a systematic approach to redefine the influenza A virus-host crosstalk

“…Therefore it is not surprising that a large number of host cellular factors have been identified as interacting partners of influenza viral proteins based on this technique. Hsp40, Clusterin, Karyopherin A, actinin-4 and actin are few examples of cellular interactors of viral NP identified using Y2H [45][46][47][48][49]. Similarly, M1 has been reported to interact with Annexin A6 and Cyclophilin A [50,51].…”

“…All viral components including vRNPs, Matrix protein M1, and envelope proteins HA, NA and M2, are transported to and assembled at the apical plasma membrane [28]. NP and M1 have been reported to be associated with host cytoskeleton protein such as actin and actinin-4 which indicates a possible role in vRNP translocation to the budding site [48,49,77]. In the screening carried out by Brass et al, depletion of COPI subunits led to reduced expression of HA on the plasma membrane of the host cell, thus indicating involvement of these proteins in transport of viral glycoproteins (NA and HA) to the cell surface.…”