Metacaspase Activity of Arabidopsis thaliana Is Regulated by S-Nitrosylation of a Critical Cysteine Residue

Beatrice Belenghi,Maria C Romero-Puertas,Dominique Vercammen,Anouk Brackenier,Dirk Inzé,Massimo Delledonne,Frank Van Breusegem

doi:10.1074/jbc.m608931200

Beatrice Belenghi, Maria C Romero-Puertas + Show 5 more

Open Access

https://doi.org/10.1074/jbc.m608931200

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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.

Highlights

Many more examples of protein S-nitrosylation and consequent modifications in activity have been reported in animal systems [7]
We demonstrate that Nitric oxide (NO) regulates the proteolytic activity of the Arabidopsis thaliana type-II metacaspase Arabidopsis thaliana metacaspase 9 (AtMC9) and that NO blocks autoprocessing and activation of the AtMC9 zymogen through S-nitrosylation of the catalytic cysteine residue
In Arabidopsis, mere overproduction of AtMC9 does not lead to obvious cell death-related phenotypes, suggesting that its proteolytic activity is inhibited

Summary

Introduction

Many more examples of protein S-nitrosylation and consequent modifications in activity have been reported in animal systems [7]. We demonstrate that NO regulates the proteolytic activity of the Arabidopsis thaliana type-II metacaspase AtMC9 and that NO blocks autoprocessing and activation of the AtMC9 zymogen through S-nitrosylation of the catalytic cysteine residue.

Results

Conclusion