ROLE OF HOST CELL GLYCOLYTIC PROTEINS; ALPHA ENOLASE AND PYRUVATE KINASE IN INFLUENZA A VIRUS INFECTED CELLS

Influenza A virus, a respiratory pathogen known to manipulate various cellular metabolic processes including glycolysis. Our earlier studies demonstrated the interaction of influenza A viral structural proteins; nucleoprotein and matrix protein with glycolytic enzymes; pyruvate kinase and alpha enolase in infected cells. Here, the role of these two glycolytic proteins in virus infection was studied. The expression and activity of pyruvate kinase, alpha enolase, rate of glycolysis, glucose uptake and the expression of glucose transporters were measured in A549 cells expressing recombinant virus nucleoprotein and matrix protein. Results were further validated in virus infected cells. Rate of glycolysis, glucose uptake, expression of glucose transporters 1 and 4 were observed to be increased in cells expressing recombinant viral nucleoprotein and matrix protein. Specifically, glucose transporter 4 expression was found to be high in cells expressing nucleoprotein as compared to cells expressing matrix protein alone or nucleoprotein and matrix protein together. Paradoxically, inhibition of alpha enolase and pyruvate kinase activity significantly increased the expression of viral genes at transcript and protein level. However, alpha enolase and pyruvate kinase protein levels remained unaltered in mock vs. virus infected/transfected cells. It is reported that glycolysis promotes the replication of various viruses, and is modulated through interaction of viral proteins with rate limiting enzymes of glycolysis. Differential expression of glucose transporter 4 in cells transfected with recombinant viral nucleoprotein vs. matrix protein suggests the regulatory role of these structural proteins in glucose transporter expression for increased glucose uptake. While the enhanced viral gene expression following inhibition of alpha enolase and pyruvate kinase activity proposes a link between viral replication and glycolytic control of cells. Our results indicate that there is an interplay between viral structural proteins and glycolytic enzymes to establish influenza A virus infection in the host which needs to be investigated in detail.