title: Identification of a polymeric Ig receptor binding phage-displayed peptide that exploits epithelial transcytosis without dimeric IgA competition.
abstract: The polymeric Ig receptor (pIgR), also called membrane secretory component (SC), mediates epithelial transcytosis of polymeric immunoglobulins (pIgs). J Chain-containing polymeric IgA (pIgA) and pentameric IgM bind pIgR at the basolateral epithelial surface. After transcytosis, the extracellular portion of the pIgR is cleaved at the apical side, either complexed with pIgs as bound SC or unoccupied as free SC. This transport pathway may be exploited to target bioactive molecules to the mucosal surface. To identify small peptide motifs with specific affinity to human pIgR, we used purified free SC and selection from randomized, cysteine-flanked 6- and 9-mer phage-display libraries. One of the selected phages, called C9A, displaying the peptide CVVWMGFQQVC, showed binding both to human free SC and SC complexed with pIgs. However, the pneumococcal surface protein SpsA (Streptococcus pneumoniae secretory IgA-binding protein), which binds human SC at a site distinct from the pIg binding site, competed with the C9A phage for binding to SC. The C9A phage showed greatly increased transport through polarized Madin-Darby canine kidney cells transfected with human pIgR. This transport was not affected by pIgA nor did it inhibit pIgR-mediated pIgA transcytosis. A free peptide of identical amino acid sequence as that displayed by the C9A phage inhibited phage interaction with SC. This implied that the C9A peptide sequence may be exploited for pIgR-mediated epithelial transport without interfering with secretory immunity.
authors.affiliation: Laboratory for Immunohistochemistry and Immunopathology (LIIPAT), Institute of Pathology, University of Oslo, Rikshospitalet University Hospital, N-0027 Oslo, Norway. ranveig.braathen@medisin.uio.no
authors.forename: Ranveig
authors.initials: R
authors.lastname: Braathen
authors.forename: Anders
authors.initials: A
authors.lastname: Sandvik
authors.forename: Gøril
authors.initials: G
authors.lastname: Berntzen
authors.forename: Sven
authors.initials: S
authors.lastname: Hammerschmidt
authors.forename: Burkhard
authors.initials: B
authors.lastname: Fleckenstein
authors.forename: Inger
authors.initials: I
authors.lastname: Sandlie
authors.forename: Per
authors.initials: P
authors.lastname: Brandtzaeg
authors.forename: Finn-Eirik
authors.initials: FE
authors.lastname: Johansen
authors.forename: Vigdis
authors.initials: V
authors.lastname: Lauvrak
mesh_terms: D000818:Animals; D001435:Bacteriophages / Q000378:metabolism; D001665:Binding Sites; D001667:Binding, Competitive; D002460:Cell Line; D003545:Cysteine / Q000737:chemistry; D019281:Dimerization; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D004848:Epithelium / Q000378:metabolism; D006801:Humans; D007070:Immunoglobulin A / Q000737:chemistry*; D051379:Mice; D019151:Peptide Library; D010455:Peptides / Q000737:chemistry*; D011485:Protein Binding; D019056:Receptors, Polymeric Immunoglobulin / Q000737:chemistry*; D013296:Streptococcus pneumoniae / Q000378:metabolism; D014162:Transfection
chemical_list: D007070:Immunoglobulin A; D019151:Peptide Library; D010455:Peptides; D019056:Receptors, Polymeric Immunoglobulin; D003545:Cysteine