title: Dual function of novel pollen coat (surface) proteins: IgE-binding capacity and proteolytic activity disrupting the airway epithelial barrier.
abstract: BACKGROUND
  The pollen coat is the first structure of the pollen to encounter the mucosal immune system upon inhalation. Prior characterizations of pollen allergens have focused on water-soluble, cytoplasmic proteins, but have overlooked much of the extracellular pollen coat. Due to washing with organic solvents when prepared, these pollen coat proteins are typically absent from commercial standardized allergenic extracts (i.e., "de-fatted"), and, as a result, their involvement in allergy has not been explored.
  
  
  RESULTS
  Using a unique approach to search for pollen allergenic proteins residing in the pollen coat, we employed transmission electron microscopy (TEM) to assess the impact of organic solvents on the structural integrity of the pollen coat. TEM results indicated that de-fatting of Cynodon dactylon (Bermuda grass) pollen (BGP) by use of organic solvents altered the structural integrity of the pollen coat. The novel IgE-binding proteins of the BGP coat include a cysteine protease (CP) and endoxylanase (EXY). The full-length cDNA that encodes the novel IgE-reactive CP was cloned from floral RNA. The EXY and CP were purified to homogeneity and tested for IgE reactivity. The CP from the BGP coat increased the permeability of human airway epithelial cells, caused a clear concentration-dependent detachment of cells, and damaged their barrier integrity.
  
  
  CONCLUSIONS
  Using an immunoproteomics approach, novel allergenic proteins of the BGP coat were identified. These proteins represent a class of novel dual-function proteins residing on the coat of the pollen grain that have IgE-binding capacity and proteolytic activity, which disrupts the integrity of the airway epithelial barrier. The identification of pollen coat allergens might explain the IgE-negative response to available skin-prick-testing proteins in patients who have positive symptoms. Further study of the role of these pollen coat proteins in allergic responses is warranted and could potentially lead to the development of improved diagnostic and therapeutic tools.
authors: Section of Otolaryngology-Head and Neck Surgery, Department of Surgery, The University of Chicago, Chicago, Illinois, United States of America. mbashir@surgery.bsd.uchicago.edu
authors: Mohamed Elfatih H
authors: ME
authors: Bashir
authors: Jason M
authors: JM
authors: Ward
authors: Matthew
authors: M
authors: Cummings
authors: Eltayeb E
authors: EE
authors: Karrar
authors: Michael
authors: M
authors: Root
authors: Abu Bekr A
authors: AB
authors: Mohamed
authors: Robert M
authors: RM
authors: Naclerio
authors: Daphne
authors: D
authors: Preuss
mesh_terms: D001483:Base Sequence; D002448:Cell Adhesion / Q000187:drug effects; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D005591:Chemical Fractionation; D031744:Cynodon / Q000737:chemistry* / Q000276:immunology / Q000648:ultrastructure; D057056:Cysteine Proteases / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D043364:Endo-1,4-beta Xylanases / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007073:Immunoglobulin E / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*; D011058:Pollen / Q000737:chemistry* / Q000276:immunology / Q000648:ultrastructure; D011485:Protein Binding; D020545:Respiratory Mucosa / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D006255:Rhinitis, Allergic, Seasonal / Q000276:immunology; D012997:Solvents
chemical_list: D010940:Plant Proteins; D012997:Solvents; D007073:Immunoglobulin E; D043364:Endo-1,4-beta Xylanases; D057056:Cysteine Proteases