AtSERPIN1 is an inhibitor of the metacaspase AtMC1-mediated cell death and autocatalytic processing in planta.
The hypersensitive response (HR) is a localized programmed cell death phenomenon that occurs in response to pathogen recognition at the site of attempted invasion. Despite more than a century of research on HR, little is known about how it is so tightly regulated and how it can be contained spatially to a few cells. AtMC1 is an Arabidopsis thaliana plant metacaspase that positively regulates the HR. Here, we used an unbiased approach to identify new AtMC1 regulators. Immunoaffinity purification of AtMC1-containing complexes led us to the identification of the protease inhibitor AtSerpin1. Our data clearly showed that coimmunoprecipitation between AtMC1 and AtSerpin1 and formation of a complex between them was lost upon mutation of the AtMC1 catalytic site, and that the AtMC1 prodomain was not required for the interaction. AtSerpin1 blocked AtMC1 self-processing and inhibited AtMC1-mediated cell death. Our results constitute an in vivo example of a Serpin acting as a suicide inhibitor in plants, reminiscent of the activity of animal or viral serpins on immune/cell death regulators, including caspase-1. These results indicate a conserved function of a protease inhibitor on cell death regulators from different kingdoms with unrelated modes of action (i.e. caspases vs metacaspases).
Centre for Research in Agricultural Genomics (CRAG), CSIC-IRTA-UAB-UB, Campus UAB, Bellaterra, Barcelona, 08193, Spain.
Saul
S
Lema Asqui
Department of Plant Systems Biology, VIB, Ghent, 9052, Belgium.|Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, 9052, Belgium.
Dominique
D
Vercammen
LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France.
Irene
I
Serrano
Department of Genetics, Universitat de Barcelona and Centre for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB) Edifici CRAG, Campus UAB, Bellaterra, Catalonia, 08193, Spain.
Marc
M
Valls
LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France.
Susana
S
Rivas
Department of Plant Systems Biology, VIB, Ghent, 9052, Belgium.|Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, 9052, Belgium.|Department of Medical Protein Research, VIB, Ghent, 9000, Belgium.|Department of Biochemistry, Ghent University, Ghent, 9000, Belgium.
Frank
F
Van Breusegem
Department of Biology, University of North Carolina, Chapel Hill, NC, 27599, USA.|Department of Genetics, University of North Carolina, Chapel Hill, NC, 27599, USA.|McAllister Heart Institute, University of North Carolina, Chapel Hill, NC, 27599, USA.|Lineberger Cancer Center, University of North Carolina, Chapel Hill, NC, 27599, USA.
Frank L
FL
Conlon
Department of Biology, University of North Carolina, Chapel Hill, NC, 27599-3280, USA.|Howard Hughes Medical Institute, University of North Carolina, Chapel Hill, NC, 27599-3280, USA.|Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC, 27599-3280, USA.|Carolina Center for Genome Sciences, University of North Carolina, Chapel Hill, NC, 27599-3280, USA.|Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC, 27599-3280, USA.
Jeffery L
JL
Dangl
Centre for Research in Agricultural Genomics (CRAG), CSIC-IRTA-UAB-UB, Campus UAB, Bellaterra, Barcelona, 08193, Spain.
Núria S
0000-0002-8889-0399
NS
Coll
D017209:Apoptosis; D017360:Arabidopsis / Q000166:cytology* / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D055162:Biocatalysis; D020169:Caspases / Q000737:chemistry / Q000378:metabolism*; D047468:Immunoprecipitation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding; D000072417:Protein Domains; D015843:Serpins / Q000378:metabolism*
D029681:Arabidopsis Proteins; C549571:Serpin1 protein, Arabidopsis; D015843:Serpins; D020169:Caspases; C554451:MC1 protein, Arabidopsis; D046988:Proteasome Endopeptidase Complex
hypersensitive response (HR); metacaspase; plant-pathogen interactions; programmed cell death; protease; serpin