title: Phosphoinositide-mediated oligomerization of a defensin induces cell lysis.
abstract: Cationic antimicrobial peptides (CAPs) such as defensins are ubiquitously found innate immune molecules that often exhibit broad activity against microbial pathogens and mammalian tumor cells. Many CAPs act at the plasma membrane of cells leading to membrane destabilization and permeabilization. In this study, we describe a novel cell lysis mechanism for fungal and tumor cells by the plant defensin NaD1 that acts via direct binding to the plasma membrane phospholipid phosphatidylinositol 4,5-bisphosphate (PIP2). We determined the crystal structure of a NaD1:PIP2 complex, revealing a striking oligomeric arrangement comprising seven dimers of NaD1 that cooperatively bind the anionic headgroups of 14 PIP2 molecules through a unique 'cationic grip' configuration. Site-directed mutagenesis of NaD1 confirms that PIP2-mediated oligomerization is important for fungal and tumor cell permeabilization. These observations identify an innate recognition system by NaD1 for direct binding of PIP2 that permeabilizes cells via a novel membrane disrupting mechanism. DOI: http://dx.doi.org/10.7554/eLife.01808.001.
authors.affiliation: Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Australia.
authors.forename: Ivan Kh
authors.initials: IKh
authors.lastname: Poon
authors.forename: Amy A
authors.initials: AA
authors.lastname: Baxter
authors.forename: Fung T
authors.initials: FT
authors.lastname: Lay
authors.forename: Grant D
authors.initials: GD
authors.lastname: Mills
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Adda
authors.forename: Jennifer Ae
authors.initials: JA
authors.lastname: Payne
authors.forename: Thanh Kha
authors.initials: TK
authors.lastname: Phan
authors.forename: Gemma F
authors.initials: GF
authors.lastname: Ryan
authors.forename: Julie A
authors.initials: JA
authors.lastname: White
authors.forename: Prem K
authors.initials: PK
authors.lastname: Veneer
authors.forename: Nicole L
authors.initials: NL
authors.lastname: van der Weerden
authors.forename: Marilyn A
authors.initials: MA
authors.lastname: Anderson
authors.forename: Marc
authors.initials: M
authors.lastname: Kvansakul
authors.forename: Mark D
authors.initials: MD
authors.lastname: Hulett
mesh_terms: D016923:Cell Death; D018360:Crystallography, X-Ray; D023082:Defensins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects / Q000502:physiology; D005670:Fusarium / Q000187:drug effects / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D050296:Microbial Viability / Q000187:drug effects; D016297:Mutagenesis, Site-Directed; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D055503:Protein Multimerization; D014026:Nicotiana / Q000737:chemistry
chemical_list: D023082:Defensins; D019269:Phosphatidylinositol 4,5-Diphosphate
keywords: X-ray crystallography; antimicrobial peptide; fungus; phospholipids; protein structure