Apoptosis is a common host response to virus infection. The extent and timing of apoptosis following infection is controlled by the balance between the strength of signals that activate death signaling and those that promote the survival of cells. In many cell types, infection with Mammalian orthoreovirus (reovirus) results in induction of cell death by apoptosis late in infection. In this study, we uncovered that WD repeat-containing protein 81 (WDR81) is required for apoptosis induction after reovirus infection. The requirement for WDR81 for apoptosis induction is not unique to reovirus because cells lacking WDR81 are also resistant to apoptosis induced by other agonists that trigger the extrinsic apoptotic pathway. We find that in cells deficient in WDR81, expression of several pro-survival genes is upregulated. The expression of these genes is controlled by the inhibitor of kB kinase complex (IKK)-Nuclear Factor of kB (NFκB) signaling pathway. When IKK signaling is blocked in WDR81-deficient cells, pro-survival gene expression is restored to normal levels and the cells regain their susceptibility to reovirus-induced death receptor-triggered apoptosis. Our work uncovers a new function for WDR81 in controlling apoptosis. Additionally, it reveals a previously unknown link between endosomally localized protein WDR81 and IKK-NFκB signaling.
