Arabidopsis EXO70A1 recruits Patellin3 to the cell membrane independent of its role as an exocyst subunit

• Published in: Journal of integrative plant biology 2017-12, Vol.59 (12), p.851-865
• Main Authors: Wu, Chengyun, Tan, Lu, van Hooren, Max, Tan, Xiaoyun, Liu, Feng, Li, Yan, Zhao, Yanxue, Li, Bingxuan, Rui, Qingchen, Munnik, Teun, Bao, Yiqun
• Format: Article
• Language: English
• Subjects: Arabidopsis; Arabidopsis - metabolism; Arabidopsis Proteins - metabolism; Carrier Proteins - metabolism; Cell fusion; Cell Membrane - metabolism; Cytoplasm - metabolism; Cytosol; Gold; Localization; Membrane fusion; Membrane vesicles; Mutants; Proteins; Tethering; Tethers; Yeast
• ISSN: 1672-9072; 1744-7909
• DOI: 10.1111/jipb.12578

The exocyst is a well‐known complex which tethers vesicles at the cell membrane before fusion. Whether an individual subunit can execute a unique function is largely unknown. Using yeast‐two‐hybrid (Y2H) analysis, we found that EXO70A1 interacted with the GOLD domain of Patellin3 (PATL3). The direct EXO70A1‐PATL3 interaction was supported by in vitro and in vivo experiments. In Arabidopsis, PATL3‐GFP colocalized with EXO70A1 predominantly at the cell membrane, and PATL3 localization was insensitive to BFA and TryA23. Remarkably, in the exo70a1 mutant, PATL3 proteins accumulated as punctate structures within the cytosol, which did not colocalize with several endomembrane compartment markers, and was insensitive to BFA. Furthermore, PATL3 localization was not changed in the exo70e2, PRsec6 or exo84b mutants. These data suggested that EXO70A1, but not other exocyst subunits, was responsible for PATL3 localization, which is independent of its role in secretory/recycling vesicle‐tethering/fusion. Both EXO70A1 and PATL3 were shown to bind PI4P and PI(4,5)P2 in vitro. Evidence was obtained that the other four members of the PATL family bound to EXO70A1 as well, and shared a similar localization pattern as PATL3. These findings offered new insights into exocyst subunit‐specific function, and provided data and tools for further characterization of PATL family proteins. The octameric exocyst complex is thought to act as a whole to tether vesicles before fusion. In this study, exocyst subunit EXO70A1 was found to play a unique role in recruiting cytosolic PATL3 onto the cell membrane, independent of the conventional role of the exocyst in secretory/recycling vesicle‐tethering.