Zika virus NS4A hijacks host ANKLE2 to promote viral replication

Zika virus (ZIKV) is infamous among flaviviruses for its unique association with congenital birth defects, notably microcephaly. We previously mapped ZIKV-host protein interactions and identified the interaction between ZIKV NS4A and host ANKLE2, which itself has established ties to congenital microcephaly. In fruit flies, NS4A induces microcephaly phenotypes in an ANKLE2-dependent manner. This suggests that NS4A interacts with ANKLE2 to dysregulate cell behavior and contributes to abnormal host neurodevelopment. Here, we explore the role of ANKLE2 in ZIKV replication to understand the biological significance of the interaction from the viral perspective. We show that knockdown of ANKLE2 reduces replication of two ZIKV strains, across multiple MOIs and timepoints. We observe that localization of ANKLE2 is drastically shifted to sites of NS4A accumulation during infection. We investigate which domains of ANKLE2 mediate this behavior and the interaction with NS4A. Using co-immunoprecipitation, we show that deletion of either the transmembrane or LEM domain has little impact on the interaction, but deletion of both significantly reduces interaction with NS4A. We show that the C-terminal transmembrane domains of NS4A stabilize the interaction with ANKLE2. Finally, we explore this interaction in other flaviviruses and observe ANKLE2 interacts with NS4A across four additional mosquito-borne flaviviruses. Together, these results suggest NS4A interacts with ANKLE2 through a combination of its transmembrane and LEM domains, bringing it to sites of ZIKV replication to promote replication through an unknown mechanism. Taken together with our previous results, our findings indicate that, in the process of hijacking ANKLE2 for replication, ZIKV disrupts its physiological function to cause disease. ImportanceThe ZIKV epidemic led to the astonishing revelation that congenital ZIKV infection is associated with devastating birth defects, including microcephaly. Microcephaly is the condition in which head and brain size are severely reduced, and is often accompanied by intellectual disability. The molecular mechanisms by which ZIKV replicates and causes microcephaly are still incompletely understood. We previously identified the protein interaction between ZIKV NS4A and host ANKLE2, which is associated with congenital microcephaly. In flies, NS4A induces microcephaly in an ANKLE2-dependent manner, suggesting this interaction is crucial for ZIKV pathogenesis. Here, we explore the relevance of this physical interaction for virus replication. We find that ANKLE2 promotes ZIKV replication, concentrates at sites of NS4A accumulation during infection, and interacts with NS4A via its N-terminal domain. Thus, this represents a rare example of a ZIKV-host protein interaction that impacts both disease and virus replication.