Atlastin Endoplasmic Reticulum-Shaping Proteins Facilitate Zika Virus Replication

Abstract

The endoplasmic reticulum (ER) is the site for Zika virus (ZIKV) replication and is central to the cytopathic effects observed in infected cells. ZIKV induces the formation of ER-derived large cytoplasmic vacuoles followed by “implosive” cell death. Little is known about the nature of the ER factors that regulate flavivirus replication. Atlastins (ATL1, -2, and -3) are dynamin-related GTPases that control the structure and the dynamics of the ER membrane. We show here that ZIKV replication is significantly decreased in the absence of ATL proteins. The appearance of infected cells is delayed, the levels of intracellular viral proteins and released virus are reduced, and the cytopathic effects are strongly impaired. We further show that ATL3 is recruited to viral replication sites and interacts with the nonstructural viral proteins NS2A and NS2B3. Thus, proteins that shape and maintain the ER tubular network ensure efficient ZIKV replication. IMPORTANCE Zika virus (ZIKV) is an emerging virus associated with Guillain-Barré syndrome, and fetal microcephaly as well as other neurological complications. There is no vaccine or specific antiviral treatment against ZIKV. We found that endoplasmic reticulum (ER)-shaping atlastin proteins (ATL1, -2, and -3), which induce ER membrane fusion, facilitate ZIKV replication. We show that ATL3 is recruited to the viral replication site and colocalize with the viral proteins NS2A and NS2B3. The results provide insights into host factors used by ZIKV to enhance its replication.

The entanglement between flaviviruses and ER-shaping proteins

“…ATL3 depletion did not change the morphology of the DENVinduced vesicles but resulted in an increased accumulation of intracellular viral particles in the ER lumen ( Fig 2D) [17]. The GTPase function of ATLs is important for DENV and ZIKV replication [30] [17].…”

“…ATL2 depletion affected formation of ER-derived DENV-replication organelles, distorting the size and shape of the vesicles and condensing them into a small perinuclear region (Fig 2D) [17]. The depletion of ATL3 reduced the titers of ZIKV and DENV (but not WNV) and had no effect on viral-RNA levels [17] [30]. ATL3 depletion did not change the morphology of the DENVinduced vesicles but resulted in an increased accumulation of intracellular viral particles in the ER lumen ( Fig 2D) [17].…”

“…Two recent investigations examined the relationship between the three ATLs and different flaviviruses and found varying effects based on the virus [17] [30]. Silencing ATL2 resulted in a significant reduction of DENV, WNV, and ZIKV titers and viral RNA [17].…”

“…The different ATL proteins exhibit variation in their interaction with flavivirus proteins. ATL3 relocates to the ZIKV-replication site and directly interacts with nonstructural protein 3 (NS3; Fig 1B) and NS2B3, that belong to the viral-replication complex (Fig 2B) [30]. Both ATL2 and ATL3 interact with DENV NS3, NS5, and NS2B proteins, though interactions with ATL2 are relatively weak (Fig 2B) [17].…”

“…Future investigations could examine the role of other ER-shaping proteins including Spastin, Lunapark, and other REEP proteins that are involved in the regulation of ER shape through microtubule dynamics, stabilization of three-way ER tubular junctions, and formation and stabilization of the ER curvature, respectively. It will be worth investigating if ER-shaping proteins are involved in ZIKV-induced cytoskeleton modifications [12] and the formation of vacuoles to understand if these proteins are related to ER stress, innate sensing of infection, and viral replication [30] [8] [29]. The interplay between different ER-shaping proteins [31] within the context of viral infection is also of potential interest.…”