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Prostate‐specific membrane antigen and its truncated form PSM′
Author(s) -
Mlčochová Petra,
Bařinka Cyril,
Tykvart Jan,
Šácha Pavel,
Konvalinka Jan
Publication year - 2008
Publication title -
the prostate
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.295
H-Index - 123
eISSN - 1097-0045
pISSN - 0270-4137
DOI - 10.1002/pros.20894
Subject(s) - lncap , biology , hek 293 cells , microbiology and biotechnology , prostate cancer , cell culture , transfection , transmembrane protein , cancer research , biochemistry , cancer , genetics , receptor
BACKGROUND Prostate specific membrane antigen (PSMA) is a type II transmembrane protein overexpressed in prostate cancer as well as in the neovasculature of several non‐prostatic solid tumors. In addition to full‐length PSMA, several splice variants exist in prostatic tissue. Notably, the N‐terminally truncated PSMA variant, termed PSM′, is prevalent in healthy prostate, and the ratio of PSMA/PSM′ mRNA has been shown to correlate with cancer progression. The widely accepted hypothesis is that the PSM′ protein is a translation product arising from the alternatively spliced PSM′ mRNA. METHODS Differential ultracentrifugation, cell surface biotinylation, Western blotting, and enzyme activity measurement were used to study the origin and localization of the PSMA/PSM′ variants in prostatic (LNCaP; lymph‐node carcinoma of the prostate) and non‐prostatic (HEK293) cell lines. These experiments were further complemented by analysis of the N ‐glycosylation patterns of the PSMA/PSM′ proteins and by site‐directed mutagenesis. RESULTS We identified PSM′ protein expression in both the LNCaP cell line and a non‐cancerous HEK293 human cell line transfected with a plasmid encoding full‐length PSMA. Differential centrifugation revealed that PSM′ is localized predominantly to the cytosol of both these cell lines and is proteolytically active. Furthermore, the PSM′ protein is N ‐glycosylated by a mixture of high‐mannose and complex type oligosaccharides and therefore trafficked beyond the cis ‐Golgi compartment. CONCLUSIONS Our data suggest that the PSM′ protein is likely not generated by alternative splicing of the PSMA gene but by different mechanism, probably via an endoproteolytic cleavage of the full‐length PSMA. Prostate 69:471–479, 2009. © 2008 Wiley‐Liss, Inc.