Toxicity of eosinophil MBP is repressed by intracellular crystallization and promoted by extracellular aggregation.
Eosinophils are white blood cells that function in innate immunity and participate in the pathogenesis of various inflammatory and neoplastic disorders. Their secretory granules contain four cytotoxic proteins, including the eosinophil major basic protein (MBP-1). How MBP-1 toxicity is controlled within the eosinophil itself and activated upon extracellular release is unknown. Here we show how intragranular MBP-1 nanocrystals restrain toxicity, enabling its safe storage, and characterize them with an X-ray-free electron laser. Following eosinophil activation, MBP-1 toxicity is triggered by granule acidification, followed by extracellular aggregation, which mediates the damage to pathogens and host cells. Larger non-toxic amyloid plaques are also present in tissues of eosinophilic patients in a feedback mechanism that likely limits tissue damage under pathological conditions of MBP-1 oversecretion. Our results suggest that MBP-1 aggregation is important for innate immunity and immunopathology mediated by eosinophils and clarify how its polymorphic self-association pathways regulate toxicity intra- and extracellularly.
UCLA-DOE Institute, HHMI, and Departments of Biological Chemistry and Chemistry and Biochemistry, 611 Charles E. Young Drive, University of California, Los Angeles, Los Angeles, CA 90095-1570, USA; Institute of Pharmacology, University of Bern, Friedbuehlstrasse 49, 3010 Bern, Switzerland; Department of Physical Chemistry, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich, Switzerland.
Alice
A
Soragni
Institute of Pharmacology, University of Bern, Friedbuehlstrasse 49, 3010 Bern, Switzerland.
Shida
S
Yousefi
Institute of Pharmacology, University of Bern, Friedbuehlstrasse 49, 3010 Bern, Switzerland.
Christina
C
Stoeckle
UCLA-DOE Institute, HHMI, and Departments of Biological Chemistry and Chemistry and Biochemistry, 611 Charles E. Young Drive, University of California, Los Angeles, Los Angeles, CA 90095-1570, USA.
Angela B
AB
Soriaga
UCLA-DOE Institute, HHMI, and Departments of Biological Chemistry and Chemistry and Biochemistry, 611 Charles E. Young Drive, University of California, Los Angeles, Los Angeles, CA 90095-1570, USA.
Michael R
MR
Sawaya
Institute of Pharmacology, University of Bern, Friedbuehlstrasse 49, 3010 Bern, Switzerland.
Evelyne
E
Kozlowski
Institute of Pharmacology, University of Bern, Friedbuehlstrasse 49, 3010 Bern, Switzerland.
Inès
I
Schmid
Institute of Pharmacology, University of Bern, Friedbuehlstrasse 49, 3010 Bern, Switzerland.
Susanne
S
Radonjic-Hoesli
Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025.
Sebastien
S
Boutet
Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025.
Garth J
GJ
Williams
National Science Foundation BioXFEL Science and Technology Center, 700 Ellicott Street, Buffalo, NY 14203, USA.
Marc
M
Messerschmidt
Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025.
M Marvin
MM
Seibert
UCLA-DOE Institute, HHMI, and Departments of Biological Chemistry and Chemistry and Biochemistry, 611 Charles E. Young Drive, University of California, Los Angeles, Los Angeles, CA 90095-1570, USA.
Duilio
D
Cascio
Department of Physics, Arizona State University, Tempe, AZ 85287, USA.
Nadia A
NA
Zatsepin
European Synchrotron Radiation Facility (ESRF), rue Jules Horowitz, 38043 Grenoble Cedex, France; Department of Analytical Chemistry, Ghent University, Krijgslaan 281, S12B, 9000 Ghent, Belgium.
Manfred
M
Burghammer
European Synchrotron Radiation Facility (ESRF), rue Jules Horowitz, 38043 Grenoble Cedex, France.
Christian
C
Riekel
University Grenoble Alpes, IBS, 38044 Grenoble, France; CNRS, IBS, 38044 Grenoble, France; CEA, IBS, 38044 Grenoble, France.
Jacques-Philippe
JP
Colletier
Department of Physical Chemistry, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich, Switzerland. Electronic address: roland.riek@phys.chem.ethz.ch.
Roland
R
Riek
UCLA-DOE Institute, HHMI, and Departments of Biological Chemistry and Chemistry and Biochemistry, 611 Charles E. Young Drive, University of California, Los Angeles, Los Angeles, CA 90095-1570, USA.
David S
DS
Eisenberg
Institute of Pharmacology, University of Bern, Friedbuehlstrasse 49, 3010 Bern, Switzerland. Electronic address: hus@pki.unibe.ch.
Hans-Uwe
HU
Simon
D000818:Animals; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects; D002481:Cellulitis / Q000378:metabolism / Q000473:pathology; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism* / Q000633:toxicity; D003876:Dermatitis, Atopic / Q000378:metabolism / Q000473:pathology; D004802:Eosinophilia / Q000378:metabolism / Q000473:pathology; D004804:Eosinophils / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D004926:Escherichia coli / Q000187:drug effects; D054884:Host-Pathogen Interactions; D006801:Humans; D007113:Immunity, Innate / Q000502:physiology; D008810:Mice, Inbred C57BL; D053758:Nanoparticles / Q000378:metabolism / Q000633:toxicity; D022142:Secretory Vesicles / Q000378:metabolism; D012867:Skin / Q000187:drug effects / Q000473:pathology
C088830:DENND4A protein, human; D004268:DNA-Binding Proteins