EPSIN1 and MTV1 define functionally overlapping but molecularly distinct <i>trans</i> -Golgi network subdomains in <i>Arabidopsis</i>
Laura Heinze, Nina Freimuth, Ann-Kathrin Rößling, Reni Hahnke, Sarah Riebschläger, Anja Fröhlich, Arun Sampathkumar, Heather E. McFarlane, Michael Sauer
Abstract
Epsin-like proteins, which are accessory proteins to APs facilitating vesicle biogenesis. By comprehensive molecular, cellular, and genetic analysis of the EPSIN gene family, we identify EPSIN1 and MODIFIED TRANSPORT TO THE VACUOLE1 (MTV1) as its only TGN-associated members. Despite their large phylogenetic distance, they perform overlapping functions in vacuolar and secretory transport. By probing their relationship with AP complexes, we find that they define two molecularly independent pathways: While EPSIN1 associates with AP-1, MTV1 interacts with AP-4, whose function is required for MTV1 recruitment. Although both EPSIN1/AP-1 and MTV1/AP-4 pairs reside at the TGN, high-resolution microscopy reveals them as spatially separate entities. Our results strongly support the hypothesis of molecularly, functionally, and spatially distinct subdomains of the plant TGN and suggest that functional redundancy can be achieved through parallelization of molecularly distinct but functionally overlapping pathways.