Differential Phosphatidylinositol-3-Kinase-Akt-mTOR activation by Semliki forest and Chikungunya viruses is dependent on nsP3 and connected to replication complex internalization
Autor(es): Thaa Bastian, Biasiotto Roberta, Eng Kai, Neuvonen Maarit, Götte Benjamin, Rheinemann Lara, Mutso Margit, Utt Age, Varghese Finny, Balistreri Giuseppe, Merits Andres, Ahola Tero, McInerney Gerald M
Resumo: Many viruses affect or exploit the phosphatidylinositol-3-kinase (PI3K)-Akt-mammalian target of rapamycin (mTOR) pathway, a crucial prosurvival signaling cascade. We report that this pathway was strongly activated in cells upon infection with the Old World alphavirus Semliki Forest virus (SFV), even under conditions of complete nutrient starvation. We mapped this activation to the hyperphosphorylated/acidic domain in the C-terminal tail of SFV nonstructural protein nsP3. Viruses with a deletion of this domain (SFV-?50) but not of other regions in nsP3 displayed a clearly delayed - reduced capacity of Akt stimulation. Ectopic expression of the nsP3 of SFV wild type (nsP3-wt), but not nsP3-?50, equipped with a membrane anchor was sufficient to activate Akt. We linked PI3K-Akt-mTOR stimulation to the intracellular dynamics of viral replication complexes, which are formed at the plasma membrane - subsequently internalized in a process blocked by the PI3K inhibitor wortmannin. Replication complex internalization was observed upon infection of cells with SFV-wt - SFV mutants with deletions in nsP3 but not with SFV-?50, where replication complexes were typically accumulated at the cell periphery. In cells infected with the closely related chikungunya virus (CHIKV), the PI3K-Akt-mTOR pathway was only moderately activated. Replication complexes of CHIKV were predominantly located at the cell periphery. Exchanging the hypervariable C-terminal tail of nsP3 between SFV - CHIKV induced the phenotype of strong PI3K-Akt-mTOR activation - replication complex internalization in CHIKV. In conclusion, infection with SFV but not CHIKV boosts PI3K-Akt-mTOR through the hyperphosphorylated/acidic domain of nsP3 to drive replication complex internalization. SFV - CHIKV are very similar in terms of molecular - cell biology, e.g., regarding replication - molecular interactions, but are strikingly different regarding pathology: CHIKV is a relevant human pathogen, causing high fever - joint pain, while SFV is a low-pathogenic model virus, albeit neuropathogenic in mice. We show that both SFV - CHIKV activate the prosurvival PI3K-Akt-mTOR pathway in cells but greatly differ in their capacities to do so: Akt is strongly - persistently activated by SFV infection but only moderately activated by CHIKV. We mapped this activation capacity to a region in nonstructural protein 3 (nsP3) of SFV - could functionally transfer this region to CHIKV. Akt activation is linked to the subcellular dynamics of replication complexes, which are efficiently internalized from the cell periphery for SFV but not CHIKV. This difference in signal pathway stimulation - replication complex localization may have implications for pathology.
Imprenta: Journal of Virology, v. 89, n. 22, p. 11420-11437, 2015
Identificador do objeto digital: 10.1128/JVI.01579-15
Descritores: Chikungunya virus - Biosynthesis ; Chikungunya virus - Cell ; Chikungunya virus - Cytopathology ; Chikungunya virus - Molecular structure ; Chikungunya virus - Pathogenesis ; Chikungunya virus - Proteins ; Chikungunya virus - RNA ; Chikungunya virus - Viral infections ; Chikungunya Virus - Virus ; Chikungunya virus - Chikungunya fever
Data de publicação: 2015
