Investigation of -Acetyllactosamine and ,-Diacetyllactosamine Residues of Seminal Plasma Prolactin-Induced Protein as Ligands Recognized by Galectin-3.

Prolactin induced-protein (PIP) has been found to be rich in immunomodulatory epitopes, including -acetyllactosamine (LacNAc) and ,-diacetyllactosamine (LacdiNAc) residues, which may constitute ligands for galecin-3 (Gal-3). In the current study, we aimed to investigate the reactivity of galactose- and -acetylgalactosamine-specific lectins with human seminal plasma PIP. Subsequently, we examined the direct interaction between seminal plasma PIP and galectin-3, and next analyzed whether there are any differences in the interaction associated with impaired semen parameters. The reactivity of terminal galactose-presenting glycans in seminal plasma PIP with agglutinin I in the asthenozoospermic group was significantly higher compared to the normozoospermic fertile subjects. Investigating the reactivity of lectin with PIP glycans, we found likewise significantly higher relative reactivity in the normozoospermic infertile as well as the oligoasthenozoopermic group compared to the control group. These results are related to the expression of LacdiNAc epitopes in the oligosaccharide chain of PIP. Finally, we observed that PIP reactivity with lectin correlates positively with the interaction between galectin-3 and PIP in the seminal plasma. This can suggest that LacdiNAc residues are engaged in the interaction between PIP and galectin-3.