Related Experiment Video
Updated: Jun 26, 2026
Antibody Binding Specificity for Kappa (Vκ) Light Chain-containing Human (IgM) Antibodies: Polysialic Acid (PSA) Attached to NCAM as a Case Study
Published on: June 29, 2016
Prostate-specific membrane antigen and its truncated form PSM'
Petra Mlcochová1, Cyril Barinka, Jan Tykvart
1Gilead Sciences and IOCB Research Centre, Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
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.
Insights
Prostate specific membrane antigen (PSMA) variant PSM' is found in the cytosol and is proteolytically active. Data suggest PSM' arises from PSMA cleavage, not alternative splicing, impacting prostate cancer research.
Area of Science:
- Molecular Biology
- Cancer Research
- Biochemistry
Background:
- Prostate specific membrane antigen (PSMA) is overexpressed in prostate cancer and tumor neovasculature.
- PSMA splice variants exist, with PSM' prevalent in healthy prostate.
- The PSMA/PSM' mRNA ratio correlates with prostate cancer progression.
Purpose of the Study:
- Investigate the origin and localization of PSMA/PSM' variants.
- Clarify the mechanism of PSM' protein generation.
- Understand PSM' protein function and trafficking.
Main Methods:
- Differential ultracentrifugation and cell surface biotinylation.
- Western blotting and enzyme activity assays.
- N-glycosylation analysis and site-directed mutagenesis.
Main Results:
- PSM' protein expressed in LNCaP and HEK293 cells.
- PSM' localized to the cytosol and showed proteolytic activity.
- PSM' is N-glycosylated and trafficked beyond the cis-Golgi.
Conclusions:
- PSM' protein is likely generated by endoproteolytic cleavage of full-length PSMA.
- Alternative splicing is not the probable mechanism for PSM' generation.
- Findings offer new insights into PSMA biology and prostate cancer.
