title: Metacaspase activity of Arabidopsis thaliana is regulated by S-nitrosylation of a critical cysteine residue.
abstract: Nitric oxide (NO) regulates a number of signaling functions in both animals and plants under several physiological and pathophysiological conditions. S-Nitrosylation linking a nitrosothiol on cysteine residues mediates NO signaling functions of a broad spectrum of mammalian proteins, including caspases, the main effectors of apoptosis. Metacaspases are suggested to be the ancestors of metazoan caspases, and plant metacaspases have previously been shown to be genuine cysteine proteases that autoprocess in a manner similar to that of caspases. We show that S-nitrosylation plays a central role in the regulation of the proteolytic activity of Arabidopsis thaliana metacaspase 9 (AtMC9) and hypothesize that this S-nitrosylation affects the cellular processes in which metacaspases are involved. We found that AtMC9 zymogens are S-nitrosylated at their active site cysteines in vivo and that this posttranslational modification suppresses both AtMC9 autoprocessing and proteolytic activity. However, the mature processed form is not prone to NO inhibition due to the presence of a second S-nitrosylation-insensitive cysteine that can replace the S-nitrosylated cysteine residue within the catalytic center of the processed AtMC9. This cysteine is absent in caspases and paracaspases but is conserved in all reported metacaspases.
authors.affiliation: Department of Plant Systems Biology, Flanders Interuniversity Institute for Biotechnology, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium.
authors.forename: Beatrice
authors.initials: B
authors.lastname: Belenghi
authors.forename: Maria C
authors.initials: MC
authors.lastname: Romero-Puertas
authors.forename: Dominique
authors.initials: D
authors.lastname: Vercammen
authors.forename: Anouk
authors.initials: A
authors.lastname: Brackenier
authors.forename: Dirk
authors.initials: D
authors.lastname: Inzé
authors.forename: Massimo
authors.initials: M
authors.lastname: Delledonne
authors.forename: Frank
authors.initials: F
authors.lastname: Van Breusegem
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020169:Caspases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D003545:Cysteine / Q000378:metabolism; D004789:Enzyme Activation / Q000502:physiology; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009569:Nitric Oxide / Q000378:metabolism*; D017434:Protein Structure, Tertiary
chemical_list: D029681:Arabidopsis Proteins; D009569:Nitric Oxide; D020169:Caspases; C516211:metacaspase 9, Arabidopsis; D003545:Cysteine