title: CKAP4/p63 is a receptor for the frizzled-8 protein-related antiproliferative factor from interstitial cystitis patients.
abstract: Antiproliferative factor (APF) is a low molecular weight sialoglycopeptide that is secreted by bladder cells from interstitial cystitis patients and is a potent inhibitor of both normal bladder epithelial and bladder carcinoma cell proliferation. We hypothesized that APF may produce its antiproliferative effects by binding to a transmembrane receptor. This study demonstrates that cytoskeleton-associated protein 4/p63 (CKAP4/p63), a type II transmembrane receptor, binds with high affinity to APF. The antiproliferative activity of APF is effectively inhibited by preincubation with anti-CKAP4/p63-specific antibodies, as well as by short interfering RNA knockdown of CKAP4/p63. Immunofluorescent confocal microscopy showed co-localization of anti-CKAP4/p63 and rhodamine-labeled synthetic APF binding in both cell membrane and perinuclear areas. APF also inhibits the proliferation of HeLa cervical carcinoma cells that are known to express CKAP4/p63. These data indicate that CKAP4/p63 is an important epithelial cell receptor for APF.
authors.affiliation: Laboratory of Proteomics and Analytical Technologies, SAIC-Frederick, Inc., NCI, National Institutes of Health, Frederick, Maryland 21702, USA.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Conrads
authors.forename: Gillian M
authors.initials: GM
authors.lastname: Tocci
authors.forename: Brian L
authors.initials: BL
authors.lastname: Hood
authors.forename: Chen-Ou
authors.initials: CO
authors.lastname: Zhang
authors.forename: Li
authors.initials: L
authors.lastname: Guo
authors.forename: Kristopher R
authors.initials: KR
authors.lastname: Koch
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Michejda
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Veenstra
authors.forename: Susan K
authors.initials: SK
authors.lastname: Keay
mesh_terms: D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal; D001483:Base Sequence; D002478:Cells, Cultured; D018856:Cystitis, Interstitial / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000235:genetics; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D001743:Urinary Bladder / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; C081876:CKAP4 protein, human; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D034741:RNA, Small Interfering; D011956:Receptors, Cell Surface; C490708:antiproliferative factor APF, human