Origin of the 1918 pandemic H1N1 influenza A virus as studied by codon usage patterns and phylogenetic analysis.

The pandemic of 1918 was caused by an H1N1 influenza A virus, which is a negative strand RNA virus; however, little is known about the nature of its direct ancestral strains. Here we applied a broad genetic and phylogenetic analysis of a wide range of influenza virus genes, in particular the PB1 gene, to gain information about the phylogenetic relatedness of the 1918 H1N1 virus. We compared the RNA genome of the 1918 strain to many other influenza strains of different origin by several means, including relative synonymous codon usage (RSCU), effective number of codons (ENC), and phylogenetic relationship.

Interplay between influenza A virus and the innate immune signaling.

Pathogens such as influenza A viruses (IAV) have to overcome a number of barriers defined and maintained by the host, to successfully establish an infection. One of the initial barriers is collectively characterized as the innate immune system. This is a broad anti-pathogen defense program that ranges from the action of natural killer cells to the induction of an antiviral cytokine response.

MEK5/ERK5 signaling modulates endothelial cell migration and focal contact turnover.

The formation of new blood vessels from pre-existing ones requires highly coordinated restructuring of endothelial cells (EC) and the surrounding extracellular matrix. Directed EC migration is a central step in this process and depends on cellular signaling cascades that initiate and control the structural rearrangements. On the basis of earlier findings that ERK5 deficiency in mouse EC results in massive defects in vessel architecture, we focused on the impact of the MEK5/ERK5 signaling pathway on EC migration.

A new player in a deadly game: influenza viruses and the PI3K/Akt signalling pathway.

Upon influenza A virus infection of cells, a wide variety of antiviral and virus-supportive signalling pathways are induced. Phosphatidylinositol-3-kinase (PI3K) is a recent addition to the growing list of signalling mediators that are activated by these viruses. Several studies have addressed the role of PI3K and the downstream effector protein kinase Akt in influenza A virus-infected cells.

Influenza A virus inhibits type I IFN signaling via NF-kappaB-dependent induction of SOCS-3 expression.

The type I interferon (IFN) system is a first line of defense against viral infections. Viruses have developed various mechanisms to counteract this response. So far, the interferon antagonistic activity of influenza A viruses was mainly observed on the level of IFNbeta gene induction via action of the viral non-structural protein 1 (NS1).

Influenza viruses and the NF-kappaB signaling pathway - towards a novel concept of antiviral therapy.

Influenza A virus remains a major public health concern, both in its annual toll in death and debilitation and its potential to cause devastating pandemics. Like any other virus, influenza A viruses are strongly dependent on cellular factors for replication. One of the hallmark signaling factors activated by viral pathogens is the transcription factor NF-kappaB.

The proapoptotic influenza A virus protein PB1-F2 regulates viral polymerase activity by interaction with the PB1 protein.

The 11th influenza A virus protein PB1-F2 was previously shown to enhance apoptosis in response to cytotoxic stimuli. The 87 amino acid protein that is encoded by an alternative reading frame of the PB1 polymerase gene was described to localize to mitochondria consistent with its proapoptotic function. However, PB1-F2 is also found diffusely distributed in the cytoplasm and in the nucleus suggesting additional functions of the protein.

Activation of phosphatidylinositol 3-kinase signaling by the nonstructural NS1 protein is not conserved among type A and B influenza viruses.

Recently it has been shown by several laboratories that the influenza A virus nonstructural protein 1 (A/NS1) binds and activates phosphatidylinositol 3-kinase (PI3K). This function of the protein is likely to prevent premature apoptosis induction during viral propagation. Here we show that the B/NS1 protein completely lacks the capacity to induce PI3K signaling.

Bivalent role of the phosphatidylinositol-3-kinase (PI3K) during influenza virus infection and host cell defence.

Infections with influenza A viruses result in the activation of a variety of intracellular signalling pathways. Recent findings suggest that in response to double-stranded RNA (dsRNA), which is commonly used as a mimic for accumulating viral RNA, the phosphatidylinositol-3-kinase (PI3K) is activated and mediates activation of the transcription factor interferon regulatory factor 3 (IRF-3). Thus, we investigated the function of PI3K during influenza virus infection.

Ringing the alarm bells: signalling and apoptosis in influenza virus infected cells.

Small RNA viruses such as influenza viruses extensively manipulate host-cell functions to support their replication. At the same time the infected cell induces an array of defence mechanisms to fight the invader. These processes are mediated by a variety of intracellular signalling cascades.