title: NGEP, a prostate-specific plasma membrane protein that promotes the association of LNCaP cells.
abstract: NGEP is a prostate-specific gene identified by analysis of expressed sequence tag databases. RNA analysis revealed two spliced forms of NGEP mRNA: a short form encoding a soluble protein (NGEP-S) and a long form encoding a polytopic membrane protein (NGEP-L). Transient expression of myc epitope-tagged NGEP-L showed that it was localized to the plasma membrane. We have now produced a specific antibody to the COOH terminus of NGEP-L and showed that it detects an approximately 100-kDa protein in extracts of normal prostate and prostate cancers that contain high levels of NGEP mRNA. The antibody detects a protein that is highly expressed on the apical and the lateral surfaces of normal prostate and prostate cancer cells by immunohistochemistry. The antibody does not detect a protein in the prostate cancer cell line LNCaP, which has very low NGEP mRNA levels. To study NGEP function, two stable LNCaP cell lines were prepared by transfection with NGEP-L and shown to contain similar amounts of NGEP-L protein as human prostate. Confocal immunofluorescence showed that NGEP-L is present on the plasma membrane of the transfected LNCaP cells and is highly concentrated at cell:cell contact regions. Furthermore, as the cell density increased, the cells formed large aggregates. A specific RNA interference that lowered NGEP-L levels prevented formation of cell aggregates. Our results suggest that NGEP-L has a role in promoting cell contact-dependent interactions of LNCaP prostate cancer cells and also that NGEP is a promising immunotherapy target for prostate cancer.
authors.affiliation: Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute/NIH, 37 Convent Drive, Bethesda, MD 20892, USA.
authors.forename: Sudipto
authors.initials: S
authors.lastname: Das
authors.forename: Yoonsoo
authors.initials: Y
authors.lastname: Hahn
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nagata
authors.forename: Mark C
authors.initials: MC
authors.lastname: Willingham
authors.forename: Tapan K
authors.initials: TK
authors.lastname: Bera
authors.forename: Byungkook
authors.initials: B
authors.lastname: Lee
authors.forename: Ira
authors.initials: I
authors.lastname: Pastan
mesh_terms: D000595:Amino Acid Sequence; D000075368:Anoctamins; D000906:Antibodies / Q000276:immunology; D002450:Cell Communication / Q000502:physiology; D045744:Cell Line, Tumor; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D034622:RNA Interference; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics
chemical_list: C498181:ANO7 protein, human; D000075368:Anoctamins; D000906:Antibodies; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D012333:RNA, Messenger