Acidic dileucine motifs in the cylindrical inclusion protein of turnip mosaic virus are crucial for endosomal targeting and viral replication

Abstract

Previously we reported that the multifunctional cylindrical inclusion (CI) protein of turnip mosaic virus (TuMV) is targeted to endosomes through the interaction with the medium subunit of adaptor protein complex 2 (AP2β), which is essential for viral infection. Although several functionally important regions in the CI have been identified, little is known about the determinant(s) for endosomal trafficking. The CI protein contains seven conserved acidic dileucine motifs [(D/E)XXXL(L/I)] typical of endocytic sorting signals recognized by AP2β. Here, we selected five motifs for further study and identified that they all were located in the regions of CI interacting with AP2β. Coimmunoprecipitation assays revealed that alanine substitutions in the each of these acidic dileucine motifs decreased binding with AP2β. Moreover, these CI mutants also showed decreased accumulation of punctate bodies, which enter endocytic‐tracking styryl‐stained endosomes. The mutations were then introduced into a full‐length infectious clone of TuMV, and each mutant had reduced viral replication and systemic infection. The data suggest that the acidic dileucine motifs in CI are indispensable for interacting with AP2β for efficient viral replication. This study provides new insights into the role of endocytic sorting motifs in the intracellular movement of viral proteins for replication.

Manipulation of the Cellular Membrane-Cytoskeleton Network for RNA Virus Replication and Movement in Plants

“…These viral proteins are recognized as cargoes by AP2β (adaptor protein complex-2β) and knockout AtAP2β interferes with VPg and CI endosomal trafficking [ 118 ]. CI interacts with AP2β through the acidic dileucine motifs, which are crucial for endosomal targeting and viral replication, suggesting that viral proteins bind to AP2β to mediate intracellular trafficking for viral replication [ 166 ].…”