title: Antibacterial membrane attack by a pore-forming intestinal C-type lectin.
abstract: Human body-surface epithelia coexist in close association with complex bacterial communities and are protected by a variety of antibacterial proteins. C-type lectins of the RegIII family are bactericidal proteins that limit direct contact between bacteria and the intestinal epithelium and thus promote tolerance to the intestinal microbiota. RegIII lectins recognize their bacterial targets by binding peptidoglycan carbohydrate, but the mechanism by which they kill bacteria is unknown. Here we elucidate the mechanistic basis for RegIII bactericidal activity. We show that human RegIIIα (also known as HIP/PAP) binds membrane phospholipids and kills bacteria by forming a hexameric membrane-permeabilizing oligomeric pore. We derive a three-dimensional model of the RegIIIα pore by docking the RegIIIα crystal structure into a cryo-electron microscopic map of the pore complex, and show that the model accords with experimentally determined properties of the pore. Lipopolysaccharide inhibits RegIIIα pore-forming activity, explaining why RegIIIα is bactericidal for Gram-positive but not Gram-negative bacteria. Our findings identify C-type lectins as mediators of membrane attack in the mucosal immune system, and provide detailed insight into an antibacterial mechanism that promotes mutualism with the resident microbiota.
authors.affiliation: Department of Immunology, The University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
authors.forename: Sohini
authors.initials: S
authors.lastname: Mukherjee
authors.affiliation: Department of Cell Biology, The University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
authors.forename: Hui
authors.initials: H
authors.lastname: Zheng
authors.affiliation: Department of Immunology, The University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
authors.forename: Mehabaw G
authors.initials: MG
authors.lastname: Derebe
authors.affiliation: Department of Biological Sciences, University of Pittsburgh, and Joint Carnegie Mellon University-University of Pittsburgh PhD Program in Computational Biology, Pittsburgh, Pennsylvania 15261, USA.
authors.forename: Keith M
authors.initials: KM
authors.lastname: Callenberg
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, USA.
authors.forename: Carrie L
authors.initials: CL
authors.lastname: Partch
authors.affiliation: Department of Immunology, The University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
authors.forename: Darcy
authors.initials: D
authors.lastname: Rollins
authors.affiliation: Department of Immunology, The University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Propheter
authors.affiliation: Department of Biochemistry and Department of Pharmacology, The University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
authors.forename: Josep
authors.initials: J
authors.lastname: Rizo
authors.affiliation: 1] Department of Biological Sciences, University of Pittsburgh, and Joint Carnegie Mellon University-University of Pittsburgh PhD Program in Computational Biology, Pittsburgh, Pennsylvania 15261, USA [2] Cardiovascular Research Institute, University of California, San Francisco, San Francisco, California 94143, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Grabe
authors.affiliation: 1] Department of Cell Biology, The University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA [2].
authors.forename: Qiu-Xing
authors.initials: QX
authors.lastname: Jiang
authors.affiliation: 1] Department of Immunology, The University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA [2] The Howard Hughes Medical Institute, The University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA [3].
authors.forename: Lora V
authors.initials: LV
authors.lastname: Hooper
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000276:immunology / Q000378:metabolism* / Q000494:pharmacology; D000951:Antigens, Neoplasm / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D014408:Biomarkers, Tumor / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects; D020285:Cryoelectron Microscopy; D018360:Crystallography, X-Ray; D006090:Gram-Negative Bacteria / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D006801:Humans; D018928:Immunity, Mucosal / Q000187:drug effects / Q000276:immunology; D007422:Intestines / Q000737:chemistry* / Q000276:immunology / Q000382:microbiology; D037181:Lectins, C-Type / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008089:Listeria monocytogenes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D050296:Microbial Viability / Q000187:drug effects; D008958:Models, Molecular; D000073718:Pancreatitis-Associated Proteins; D010457:Peptidoglycan / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D018272:Porins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D013559:Symbiosis
chemical_list: D000900:Anti-Bacterial Agents; D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D037181:Lectins, C-Type; D008070:Lipopolysaccharides; D000073718:Pancreatitis-Associated Proteins; D010457:Peptidoglycan; D010743:Phospholipids; D018272:Porins; C000612141:REG3A protein, human