Old Dog, New Tricks: Influenza A Virus NS1 andIn VitroFibrillogenesis

Abstract

The influenza NS1 protein is involved in suppression of the host immune response. Recently, there is growing evidence that prion-like protein aggregation plays an important role in cellular signaling and immune responses. In this work, we obtained a recombinant, influenza A NS1 protein and showed that it is able to form amyloid-like fibrils in vitro. Using proteolysis and subsequent mass spectrometry, we showed that regions resistant to protease hydrolysis highly differ between the native NS1 form (NS1-N) and fibrillar form (NS1-F); this indicates that significant structural changes occur during fibril formation. The discovery of the ability of NS1 to form amyloid-like fibrils may be relevant to uncovering relationships between influenza A infection and modulation of the immune response.

How the immune mousetrap works: Structural evidence for the immunomodulatory action of a peptide from influenza NS1 protein

“…The use of electron atomic force microscopy, spectrophotometry with Congo red dye, and fluorimetry with thioflavin T dye demonstrated that the T-cell receptor core peptide (CP) and its homologous peptide G51 from the NS1 influenza virus (as was shown by us earlier [24]) can form amyloid-like fibrils in vitro. Additionally, peptide G51 can form heterooligomers with peptide CP and modulate its oligomerization.…”

“…The NS1 protein of the influenza virus is prone to structural polymorphism, which also provides its multifunctionality [51,53], but its ability to form amyloid-like fibrils in vivo has not yet been demonstrated. Previous data suggest that the 140-151 aa region of NS1 may serve as a potential amyloidogenic determinant of this protein [24].…”

“…In experiments studying the biological activity of the NS1 protein of influenza A H1N1 strain that caused the pandemic of 1918, it was found that one of the peptides ( 140 rleylillraft 151 , G51), corresponding to the primary structure of the NS1 protein fragment of influenza A virus [20] and having the highest homology with the CP peptide among the proteins of influenza A virus, is capable of oligomerization and the formation of insoluble fibrillar aggregates in concentrations of 0.2-1 mM after incubation for 24 hours at 55ºC [24].…”

“…However, the sequence of the potential immunosuppressive domain of NS1, given in [20] corresponds to the core region of amyloid-like fibrils formed by the NS1 protein in vitro [24]. The presence of homology in the sequences of CP and the potential immunosuppressive domain, together with the ability of both peptides to form beta-structured oligomers, and in the case of NS1 fragment -amyloid-like fibrils, provides a basis for suggesting that such peptides may influence each other's conformation by a prion-like mechanism.…”

Quench me if you can: Alpha-2-macroglobulin trypsin complexes enable serum biomarker analysis by MALDI mass spectrometry

“…Stained protein bands were cut out, and tryptic hydrolyses were performed as described [44]. Mass spectra of tryptic peptides were registered as described in section 2.4.…”