title: Glucosidase II β-subunit, a novel substrate for caspase-3-like activity in rice, plays as a molecular switch between autophagy and programmed cell death.
abstract: Endoplasmic reticulum (ER) stress activates unfolded protein response (UPR) and autophagy. However, prolonged, severe stresses activate programmed cell death (PCD) in both animal and plant cells. Compared to the well-studied UPR pathway, the molecular mechanisms of ER-stress-induced PCD are less understood. Here, we report the identification of Gas2, the glucosidase II β subunit in the ER, as a potential switch between PCD and autophagy in rice. MS analysis identified Gas2, GRP94, and HSP40 protein in a purified caspase-3-like activity from heat stressed rice cell suspensions. The three corresponding genes were down-regulated under DTT-induced ER stress. Gas2 and GRP94 were localized to the ER, while HSP40 localized to the cytoplasm. Compared to wild-type, a Gas2 RNAi cell line was much sensitive to DTT treatment and had high levels of autophagy. Both caspase-3 and heat-stressed cell suspension lysate could cleave Gas2, producing a 14 kDa N-terminal fragment. Conditional expression of corresponding C-terminal fragment resulted in enhanced caspase-3-like activity in the protoplasts under heat stress. We proposed that mild ER stress causes down-regulation of Gas2 and induces autophagy, while severe stress results in Gas2 cleavage by caspase-3-like activity and the cleavage product amplifies this activity, possibly participating in the initiation of PCD.
authors.affiliation: Dept. of Biochemistry &Molecular Biology, College of Life Science, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Cui
authors.affiliation: Dept. of Biochemistry &Molecular Biology, College of Life Science, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China.
authors.forename: Bing
authors.initials: B
authors.lastname: Chen
authors.affiliation: Dept. of Biochemistry &Molecular Biology, College of Life Science, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China.
authors.forename: Hongjuan
authors.initials: H
authors.lastname: Wang
authors.affiliation: Dept. of Biochemistry &Molecular Biology, College of Life Science, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Han
authors.affiliation: Dept. of Biochemistry &Molecular Biology, College of Life Science, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China.
authors.forename: Xi
authors.initials: X
authors.lastname: Chen
authors.affiliation: Dept. of Biochemistry &Molecular Biology, College of Life Science, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
mesh_terms: D001343:Autophagy; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism*; D059865:Endoplasmic Reticulum Stress; D000072817:Eryptosis; D012275:Oryza / Q000201:enzymology* / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D036226:Seedlings / Q000201:enzymology* / Q000235:genetics; D000520:alpha-Glucosidases / Q000235:genetics / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; C034251:4-nitrophenyl-alpha-glucosidase; D000520:alpha-Glucosidases; D053148:Caspase 3