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- Title
Proteomic identification of galectin-3 binding ligands and characterization of galectin-3 proteolytic cleavage in human prostasomes.
- Authors
Kovak, M. R.; Saraswati, S.; Goddard, S. D.; Diekman, A. B.
- Abstract
Galectin-3 is a multifunctional carbohydrate-binding protein that was previously characterized as a proteolytic substrate for prostate-specific antigen ( PSA) and was shown to be associated with prostasomes in human semen. Prostasomes are exosome-like vesicles that are secreted by the prostatic epithelium and have multiple proposed functions in normal reproduction and prostate cancer. In the current study, galectin-3 binding ligands in human prostasomes were identified and characterized with the goal to investigate galectin-3 function in prostasomes. Galectin-3 binding proteins were isolated by affinity column chromatography. Candidate ligands identified by MS/ MS were PSA, prostatic acid phosphatase ( PAP), zinc alpha-2-glycoprotein ( ZAG), dipeptidyl peptidase-4 ( CD26), aminopeptidase N ( CD13), neprilysin, clusterin, antibacterial protein ( FALL-39) and alpha-1-acid glycoprotein ( ORM1). Biochemical methods were used to characterize the ability of galectin-3 to bind to selected ligands, and galectin-3 cleavage assays were utilized to investigate the protease(s) in prostasomes that cleaves galectin-3. CD26, CD13, PSA, PAP and ZAG immunoreactivity were detected in extracts of purified prostasomes. One-dimensional electroblot analysis of prostasomes demonstrated that CD26, PAP and CD13 immunoreactivity co-migrated with galectin-3-reactive protein bands. PSA and ZAG were found to be associated with the surface of prostasomes. Both intact and cleaved galectin-3 were detected in prostate and prostasome extracts. Cleavage and inhibition assays indicated that PSA in prostasomes proteolytically cleaves galectin-3. The identification of these glycoproteins as galectin-3 ligands lays the groundwork for future studies of galectin-3 and prostasome function in reproduction and prostate cancer.
- Subjects
PROTEOMICS; GALECTINS; LIGAND binding (Biochemistry); PROTEOLYTIC enzymes; CLEAVAGE (Embryology); EXOSOMES; CARBOHYDRATE-binding proteins
- Publication
Andrology, 2013, Vol 1, Issue 5, p682
- ISSN
2047-2919
- Publication type
Article
- DOI
10.1111/j.2047-2927.2013.00099.x