title: Phytaspase, a relocalisable cell death promoting plant protease with caspase specificity.
abstract: Caspases are cysteine-dependent proteases and are important components of animal apoptosis. They introduce specific breaks after aspartate residues in a number of cellular proteins mediating programmed cell death (PCD). Plants encode only distant homologues of caspases, the metacaspases that are involved in PCD, but do not possess caspase-specific proteolytic activity. Nevertheless, plants do display caspase-like activities indicating that enzymes structurally distinct from classical caspases may operate as caspase-like proteases. Here, we report the identification and characterisation of a novel PCD-related subtilisin-like protease from tobacco and rice named phytaspase (plant aspartate-specific protease) that possesses caspase specificity distinct from that of other known caspase-like proteases. We provide evidence that phytaspase is synthesised as a proenzyme, which is autocatalytically processed to generate the mature enzyme. Overexpression and silencing of the phytaspase gene showed that phytaspase is essential for PCD-related responses to tobacco mosaic virus and abiotic stresses. Phytaspase is constitutively secreted into the apoplast before PCD, but unexpectedly is re-imported into the cell during PCD providing insights into how phytaspase operates.
authors.affiliation: A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, Russia.
authors.forename: Nina V
authors.initials: NV
authors.lastname: Chichkova
authors.forename: Jane
authors.initials: J
authors.lastname: Shaw
authors.forename: Raisa A
authors.initials: RA
authors.lastname: Galiullina
authors.forename: Georgina E
authors.initials: GE
authors.lastname: Drury
authors.forename: Alexander I
authors.initials: AI
authors.lastname: Tuzhikov
authors.forename: Sang Hyon
authors.initials: SH
authors.lastname: Kim
authors.forename: Markus
authors.initials: M
authors.lastname: Kalkum
authors.forename: Teresa B
authors.initials: TB
authors.lastname: Hong
authors.forename: Elena N
authors.initials: EN
authors.lastname: Gorshkova
authors.forename: Lesley
authors.initials: L
authors.lastname: Torrance
authors.forename: Andrey B
authors.initials: AB
authors.lastname: Vartapetian
authors.forename: Michael
authors.initials: M
authors.lastname: Taliansky
mesh_terms: D020169:Caspases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016923:Cell Death; D002478:Cells, Cultured; D012275:Oryza / Q000235:genetics / Q000378:metabolism; D010447:Peptide Hydrolases / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D030821:Plants, Genetically Modified; D013379:Substrate Specificity; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D010447:Peptide Hydrolases; D020169:Caspases