Arabidopsis Accelerated Cell Death 11, ACD11, Is a Ceramide-1-Phosphate Transfer Protein and Intermediary Regulator of Phytoceramide Levels
Dhirendra K. Simanshu,
Xiuhong Zhai,
David Munch,
Daniel Hofius,
Jonathan E. Markham,
Jacek Bielawski,
Alicja Bielawska,
Lucy Malinina,
Julian G. Molotkovsky,
John W. Mundy,
Dinshaw J. Patel,
Rhoderick E. Brown
Affiliations
Dhirendra K. Simanshu
Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
Xiuhong Zhai
Hormel Institute, University of Minnesota, Austin, MN 55912, USA
David Munch
Department of Biology, BioCenter, University of Copenhagen, 2200 Copenhagen N, Denmark
Daniel Hofius
Department of Biology, BioCenter, University of Copenhagen, 2200 Copenhagen N, Denmark
Jonathan E. Markham
Department of Biochemistry, University of Nebraska, N146 Beadle Center, Lincoln, NE 68588, USA
Jacek Bielawski
Department of Biochemistry and Molecular Biology, Lipidomics Shared Resource Mass Spectrometry Lab, Medical University of South Carolina, Charleston, SC 29425, USA
Alicja Bielawska
Department of Biochemistry and Molecular Biology, Lipidomics Shared Resource Mass Spectrometry Lab, Medical University of South Carolina, Charleston, SC 29425, USA
Lucy Malinina
Structural Biology Unit, CIC bioGUNE, Technology Park of Bizkaia, 48160 Derio-Bilbao, Spain
Julian G. Molotkovsky
Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
John W. Mundy
Department of Biology, BioCenter, University of Copenhagen, 2200 Copenhagen N, Denmark
Dinshaw J. Patel
Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
Rhoderick E. Brown
Hormel Institute, University of Minnesota, Austin, MN 55912, USA
The accelerated cell death 11 (acd11) mutant of Arabidopsis provides a genetic model for studying immune response activation and localized cellular suicide that halt pathogen spread during infection in plants. Here, we elucidate ACD11 structure and function and show that acd11 disruption dramatically alters the in vivo balance of sphingolipid mediators that regulate eukaryotic-programmed cell death. In acd11 mutants, normally low ceramide-1-phosphate (C1P) levels become elevated, but the relatively abundant cell death inducer phytoceramide rises acutely. ACD11 exhibits selective intermembrane transfer of C1P and phyto-C1P. Crystal structures establish C1P binding via a surface-localized, phosphate headgroup recognition center connected to an interior hydrophobic pocket that adaptively ensheaths lipid chains via a cleft-like gating mechanism. Point mutation mapping confirms functional involvement of binding site residues. A π helix (π bulge) near the lipid binding cleft distinguishes apo-ACD11 from other GLTP folds. The global two-layer, α-helically dominated, “sandwich” topology displaying C1P-selective binding identifies ACD11 as the plant prototype of a GLTP fold subfamily.
