Inhibition of Influenza Virus Polymerase by Interfering with Its Protein–Protein Interactions

Abstract

Influenza (flu) virus is a serious threat to global health with the potential to generate devastating pandemics. The availability of broad spectrum antiviral drugs is an unequaled weapon during pandemic events, especially when a vaccine is still not available. One of the most promising targets for the development of new antiflu therapeutics is the viral RNA-dependent RNA polymerase (RdRP). The assembly of the flu RdRP heterotrimeric complex from the individual polymerase acidic protein (PA), polymerase basic protein 1 (PB1), and polymerase basic protein 2 (PB2) subunits is a prerequisite for RdRP functions, such as mRNA synthesis and genome replication. In this Review, we report the known protein–protein interactions (PPIs) occurring by RdRP that could be disrupted by small molecules and analyze their benefits and drawbacks as drug targets. An overview of small molecules able to interfere with flu RdRP functions exploiting the PPI inhibition approach is described. In particular, an update on the most recent inhibitors targeting the well-consolidated RdRP PA–PB1 subunit heterodimerization is mainly reported, together with pioneer inhibitors targeting other virus–virus or virus–host interactions involving RdRP subunits. As demonstrated by the PA–PB1 interaction inhibitors discussed herein, the inhibition of flu RdRP functions by PPI disrupters clearly represents a valid means to identify compounds endowed with a broad spectrum of action and a reduced propensity to develop drug resistance, which are the main issues of antiviral drugs.

Protein-fragment complementation assays for large-scale analysis of protein–protein interactions

“…Alterations in proteinprotein interactions (either by breakdown or the formation of novel PPIs) may lead to various diseases in humans, including cancers [3,4] or neurodegenerative disorders [5]. PPIs are attractive molecular targets with a vast therapeutic potential [6][7][8].…”

Multicolor fluorescence fluctuation spectroscopy in living cells via spectral detection

“…With this approach, it is therefore possible to distinguish specific molecular mechanisms, such as inefficient PA-PB2 interactions in the presence of low PB1 concentration or efficient heterotrimer dimerization when all subunits are present at similar concentrations. The employed experimental scheme offers a powerful tool for future studies, exploring, for example, interaction of the PC with cellular host factors or the development of inhibitors that could interfere with the assembly process of the complex, as a promising therapeutic target for antiviral drugs ( Massari et al, 2021 ).…”

Development and Effects of Influenza Antiviral Drugs

“…The influenza virus polymerase plays a major role in the replication and transcription of influenza virus. Polymerase synthesizes viral mRNA via a unique "cap snapping" mechanism using short-end primers from cellular transcripts [43]. Interference with the activity of the RNA-dependent RNA polymerase (RdRP) is an effective means to reduce viral resistance and inhibit viral replication, and viral RdRP is one of the most promising targets for the development of novel influenza antiviral drugs [43][44][45][46][47].…”

“…Polymerase synthesizes viral mRNA via a unique "cap snapping" mechanism using short-end primers from cellular transcripts [43]. Interference with the activity of the RNA-dependent RNA polymerase (RdRP) is an effective means to reduce viral resistance and inhibit viral replication, and viral RdRP is one of the most promising targets for the development of novel influenza antiviral drugs [43][44][45][46][47]. As a non-structural protein of the influenza virus, NS1 protein can regulate the viral life cycle, the immune function of the host, and play an auxiliary role in the process of influenza virus infection of host cells [48].…”