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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.

SUBMITTER: Chichkova NV

PROVIDER: S-EPMC2845272 | biostudies-literature | 2010 Mar

REPOSITORIES: biostudies-literature

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Phytaspase, a relocalisable cell death promoting plant protease with caspase specificity.

Chichkova Nina V NV Shaw Jane J Galiullina Raisa A RA Drury Georgina E GE Tuzhikov Alexander I AI Kim Sang Hyon SH Kalkum Markus M Hong Teresa B TB Gorshkova Elena N EN Torrance Lesley L Vartapetian Andrey B AB Taliansky Michael M

The EMBO journal 20100128 6

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 ma ...[more]

PMID: 20111004

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Project description:3C proteases, the main proteases of picornaviruses, play the key role in viral life cycle by processing polyproteins. In addition, 3C proteases digest certain host cell proteins to suppress antiviral defense, transcription, and translation. The activity of 3C proteases per se induces host cell death, which makes them critical factors of viral cytotoxicity. To date, cytotoxic effects have been studied for several 3C proteases, all of which induce apoptosis. This study for the first time describes the cytotoxic effect of 3C protease of human hepatitis A virus (3Cpro), the only proteolytic enzyme of the virus.Individual expression of 3Cpro induced catalytic activity-dependent cell death, which was not abrogated by the pan-caspase inhibitor (z-VAD-fmk) and was not accompanied by phosphatidylserine externalization in contrast to other picornaviral 3C proteases. The cell survival was also not affected by the inhibitors of cysteine proteases (z-FA-fmk) and RIP1 kinase (necrostatin-1), critical enzymes involved in non-apoptotic cell death. A substantial fraction of dying cells demonstrated numerous non-acidic cytoplasmic vacuoles with not previously described features and originating from several types of endosomal/lysosomal organelles. The lysosomal protein Lamp1 and GTPases Rab5, Rab7, Rab9, and Rab11 were associated with the vacuolar membranes. The vacuolization was completely blocked by the vacuolar ATPase inhibitor (bafilomycin A1) and did not depend on the activity of the principal factors of endosomal transport, GTPases Rab5 and Rab7, as well as on autophagy and macropinocytosis.3Cpro, apart from other picornaviral 3C proteases, induces caspase-independent cell death, accompanying by cytoplasmic vacuolization. 3Cpro-induced vacuoles have unique properties and are formed from several organelle types of the endosomal/lysosomal compartment. The data obtained demonstrate previously undocumented morphological characters of the 3Cpro-induced cell death, which can reflect unknown aspects of the human hepatitis A virus-host cell interaction.

Dataset Information

Phytaspase, a relocalisable cell death promoting plant protease with caspase specificity.

Publications

Phytaspase, a relocalisable cell death promoting plant protease with caspase specificity.

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