title: A BAR-domain protein SH3P2, which binds to phosphatidylinositol 3-phosphate and ATG8, regulates autophagosome formation in Arabidopsis.
abstract: Autophagy is a well-defined catabolic mechanism whereby cytoplasmic materials are engulfed into a structure termed the autophagosome. In plants, little is known about the underlying mechanism of autophagosome formation. In this study, we report that SH3 DOMAIN-CONTAINING PROTEIN2 (SH3P2), a Bin-Amphiphysin-Rvs domain-containing protein, translocates to the phagophore assembly site/preautophagosome structure (PAS) upon autophagy induction and actively participates in the membrane deformation process. Using the SH3P2-green fluorescent protein fusion as a reporter, we found that the PAS develops from a cup-shaped isolation membranes or endoplasmic reticulum-derived omegasome-like structures. Using an inducible RNA interference (RNAi) approach, we show that RNAi knockdown of SH3P2 is developmentally lethal and significantly suppresses autophagosome formation. An in vitro membrane/lipid binding assay demonstrates that SH3P2 is a membrane-associated protein that binds to phosphatidylinositol 3-phosphate. SH3P2 may facilitate membrane expansion or maturation in coordination with the phosphatidylinositol 3-kinase (PI3K) complex during autophagy, as SH3P2 promotes PI3K foci formation, while PI3K inhibitor treatment inhibits SH3P2 from translocating to autophagosomes. Further interaction analysis shows that SH3P2 associates with the PI3K complex and interacts with ATG8s in Arabidopsis thaliana, whereby SH3P2 may mediate autophagy. Thus, our study has identified SH3P2 as a novel regulator of autophagy and provided a conserved model for autophagosome biogenesis in Arabidopsis.
authors.affiliation: School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Zhuang
authors.forename: Hao
authors.initials: H
authors.lastname: Wang
authors.forename: Sheung Kwan
authors.initials: SK
authors.lastname: Lam
authors.forename: Caiji
authors.initials: C
authors.lastname: Gao
authors.forename: Xiangfeng
authors.initials: X
authors.lastname: Wang
authors.forename: Yi
authors.initials: Y
authors.lastname: Cai
authors.forename: Liwen
authors.initials: L
authors.lastname: Jiang
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001343:Autophagy / Q000502:physiology*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D010588:Phagosomes / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D030821:Plants, Genetically Modified; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D049452:Green Fluorescent Proteins; D019869:Phosphatidylinositol 3-Kinases; D018129:Phosphatidylinositol Phosphates; D000081082:Phosphoinositide-3 Kinase Inhibitors; D000077191:Wortmannin; C000597559:SH3P2 protein, Arabidopsis; C055525:phosphatidylinositol 3-phosphate