title: Podocalyxin-like protein is an E-/L-selectin ligand on colon carcinoma cells: comparative biochemical properties of selectin ligands in host and tumor cells.
abstract: Selectins facilitate metastasis and tumor cell arrest in the microvasculature by mediating binding of selectin-expressing host cells to ligands on tumor cells. We recently identified CD44 variant isoforms as functional P-, but not E-/L-, selectin ligands on colon carcinoma cells. Furthermore, a approximately 180-kDa sialofucosylated glycoprotein(s) mediated selectin binding in CD44-knockdown cells. Using immunoaffinity chromatography and tandem mass spectrometry, we identify podocalyxin-like protein (PCLP) as an alternative selectin ligand. Blot rolling and cell-free flow-based adhesion assays disclose that PCLP on LS174T colon carcinoma cells possesses E-/L-, but not P-, selectin binding activity. The selectin-binding determinants on LS174T PCLP are non-MECA-79-reactive sialofucosylated structures displayed on O-linked glycans, distinct from the MECA-79-reactive O-glycans on PCLP expressed by high endothelial venules, which is an L-selectin ligand. PCLP on CD44-knockdown LS174T cells exhibits higher HECA-452 immunoreactivity than PCLP on wild-type cells, suggesting that PCLP functions as an alternative acceptor for selectin-binding glycans. The enhanced expression of HECA-452 reactivity on PCLP from CD44-knockdown cells correlates with the increased avidity of PCLP for E- but not L-selectin. The novel finding that PCLP is an E-/L-selectin ligand on carcinoma cells offers a unifying perspective on the apparent enhanced metastatic potential associated with tumor cell PCLP overexpression and the role of selectins in metastasis.
authors.affiliation: Dept. of Chemical and Biomolecular Engineering, The Johns Hopkins Univ., 3400 N. Charles St., Baltimore, MD 21218, USA.
authors.forename: Susan N
authors.initials: SN
authors.lastname: Thomas
authors.forename: Ronald L
authors.initials: RL
authors.lastname: Schnaar
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Konstantopoulos
mesh_terms: D000818:Animals; D016466:CHO Cells; D002277:Carcinoma / Q000378:metabolism* / Q000473:pathology; D002448:Cell Adhesion; D045744:Cell Line, Tumor; D002846:Chromatography, Affinity; D015179:Colorectal Neoplasms / Q000378:metabolism* / Q000473:pathology; D006224:Cricetinae; D003412:Cricetulus; D019040:E-Selectin / Q000235:genetics / Q000378:metabolism*; D006031:Glycosylation; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism; D019041:L-Selectin / Q000235:genetics / Q000378:metabolism*; D008024:Ligands; D009362:Neoplasm Metastasis; D019007:P-Selectin / Q000378:metabolism; D010449:Peptide Mapping; D011485:Protein Binding; D012795:Sialoglycoproteins / Q000378:metabolism*; D053719:Tandem Mass Spectrometry; D014162:Transfection; D015854:Up-Regulation
chemical_list: C497483:CD44 protein, human; D019040:E-Selectin; D018960:Hyaluronan Receptors; D008024:Ligands; D019007:P-Selectin; D012795:Sialoglycoproteins; C001643:podocalyxin; D019041:L-Selectin