Mass spectrometry-based identification of the tumor antigen UN1 as the transmembrane CD43 sialoglycoprotein

Annamaria De Laurentiis, Marco Gaspari, Camillo Palmieri, Cristina Falcone, Enrico Iaccino, Giuseppe Fiume, Ornella Massa, Mariorosario Masullo, Franca Maria Tuccillo, Laura Roveda, Ubaldo Prati, Olga Fierro, Immacolata Cozzolino, Giancarlo Troncone, Pierfrancesco Tassone, Giuseppe Scala, Ileana Quinto

Research output: Contribution to journalArticlepeer-review

Abstract

The UN1 monoclonal antibody recognized the UN1 antigen as a heavily sialylated and O-glycosylated protein with the apparent molecular weight of 100-120 kDa; this antigen was peculiarly expressed in fetal tissues and several cancer tissues, including leukemic T cells, breast, and colon carcinomas. However, the lack of primary structure information has limited further investigation on the role of the UN1 antigen in neoplastic transformation. In this study, we have identified the UN1 antigen as CD43, a transmembrane sialoglycoprotein involved in cell adhesion, differentiation, and apoptosis. Indeed, mass spectrometry detected two tryptic peptides of the membrane-purified UN1 antigen that matched the amino acidic sequence of the CD43 intracellular domain. Immunological cross-reactivity, migration pattern in mono- and bi-dimensional electrophoresis, and CD43 gene-dependent expression proved the CD43 identity of the UN1 antigen. Moreover, the monosaccharide GalNAc-O-linked to the CD43 peptide core was identified as an essential component of the UN1 epitope by glycosidase digestion of specific glycan branches. UN1-type CD43 glycoforms were detected in colon, sigmoid colon, and breast carcinomas, whereas undetected in normal tissues from the same patients, confirming the cancer-association of the UN1 epitope. Our results highlight UN1 monoclonal antibody as a suitable tool for cancer immunophenotyping and analysis of CD43 glycosylation in tumorigenesis.

Original languageEnglish
JournalMolecular and Cellular Proteomics
Volume10
Issue number5
DOIs
Publication statusPublished - May 2011

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Analytical Chemistry
  • Medicine(all)

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