The A/ENTH Domain-Containing Protein AtECA4 Is an Adaptor Protein Involved in Cargo Recycling from the trans-Golgi Network/Early Endosome to the Plasma Membrane

• Published in: Molecular plant 2018-04, Vol.11 (4), p.568-583
• Main Authors: Nguyen, Hong Hanh, Lee, Myoung Hui, Song, Kyungyoung, Ahn, Gyeongik, Lee, Jihyeong, Hwang, Inhwan
• Format: Article
• Language: English
• Subjects: A/ENTH; abiotic stress; Arabidopsis - cytology; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Calcium-Transporting ATPases - genetics; Calcium-Transporting ATPases - metabolism; cargo recycling; Cell Membrane - metabolism; Droughts; Endosomes - metabolism; Gene Expression Regulation, Plant; Osmotic Pressure; Protein Transport; Pyridinium Compounds - metabolism; Quaternary Ammonium Compounds - metabolism; Salinity; trans-Golgi Network - metabolism
• ISSN: 1674-2052; 1752-9867
• DOI: 10.1016/j.molp.2018.01.001

Endocytosis and subsequent trafficking pathways are crucial for regulating the activity of plasma membrane-localized proteins. Depending on cellular and physiological conditions, the internalized cargoes are sorted at (and transported from) the trans-Golgi network/early endosome (TGN/EE) to the vacuole for degradation or recycled back to the plasma membrane. How this occurs at the molecular level remains largely elusive. Here, we provide evidence that the ENTH domain-containing protein AtECA4 plays a crucial role in recycling cargoes from the TGN/EE to the plasma membrane in Arabidopsis thaliana. AtECA4:sGFP primarily localized to the TGN/EE and plasma membrane (at low levels). Upon NaCl or mannitol treatment, AtECA4:sGFP accumulated at the TGN/EE at an early time point but was released from the TGN/EE to the cytosol at later time points. The ateca4 mutant showed higher resistance to osmotic stress and more sensitive to exogenous abscisic acid (ABA) than the wild type, as well as increased expression of ABA-inducible genes RD29A and RD29B. Consistently, ABCG25, a plasma membrane-localized ABA exporter, accumulated at the prevacuolar compartment in ateca4, indicating a defect in recycling to the plasma membrane. However, the role of AtECA4 in cargo recycling is not specific to ABCG25, as it also functions in the recycling of BRI1. These results suggest that AtECA4 plays a crucial role in the recycling of endocytosed cargoes from the TGN/EE to the plasma membrane. AtECA4 primarily localizes to the TGN/EE and plays a role in recycling of proteins from the TGN/EE to the plasma membrane. This AtECA4-mediated recycling of cargo proteins ABCG25 and BRI1 is crucial for homeostasis of cellular ABA levels and brassinolide-mediated signaling for plant growth.