GLYCAN PROFILE OF GLYCOPROTEINS SECRETED BY THE PROSTATE AND PROSTATIC URETHRA OF THE DONKEY

[Background-aim] The male urethra has a dual function, serving as both a passageway for urine and a conduit for seminal fluid. The pelvic urethra is characterised by the presence of glands (urethral glands of Littré) whose secretory glycoproteins lubricate the epithelial lining of the urethra. Seminal fluid is rich in glycoproteins, mainly secreted by the prostate gland, which play a critical role in male fertility by regulating sperm extracellular quality control, capacitation, sperm-egg recognition, and, ultimately, fertilisation. To our knowledge, the glycan pattern in the urethra and prostate of donkeys has been studied using traditional histochemical methods, such as PAS and Alcian Blue staining, which reveal the presence of neutral or acidic glycans, but not with lectins, which are useful tools for investigating glycosylation in greater depth. Lectins can distinguish between N- and O-linked glycosylation, sugar isomers, branching, linkage, and terminal modifications of complex glycans. Previously, our histological investigations had revealed the presence of glycoproteins both on the apical surface and free in the lumen of the prostatic urethra of the donkey. [Methods] To study the contribution of the lumen glycoproteins of pelvic urethra to the glycan composition of seminal fluid, this research analysed the glycan pattern of the prostatic secretion and the luminal content the prostatic urethra of the donkey using twelve HRP-labelled lectins (Con A, DBA, GSA I-B4, GSA II, HPA, LTA, MAL II, PNA, SBA, SNA, UEA I, WGA), in combination with the cleavage of sialic acids by saponification and digestion with sialidase (Ks). [Results] The comparison of the lectin binding pattern of prostate and urethral secretion displayed that: 1) prostate secrete characteristic glycans terminating with N-acetylglucosamine (GlcNAc) (GSA II); 2) uretral secretion is characterized by 􀄯Galactose (GSA I-B4), terminal 􀄯-Nacetylgalactosamine (GalNAc) (HPA, DBA, SBA), and sialylated 􀄯GalNAc (KsDBA) in O-linked glycan; 3) high mannosylated N-glycans (Con A) and 􀁖􀁌􀁄􀁏􀁜􀁏􀁄􀁗􀁈􀁇􀀃 􀇃􀀪􀁄􀁏􀀱􀀤􀁆􀀃 􀀋􀀮􀁖􀀶􀀥􀀤􀀌􀀃 􀁖􀁌􀁊􀁑􀁌􀁉􀁌􀁆􀁄􀁑􀁗􀁏􀁜􀀃 􀁓􀁕􀁈􀁙􀁄􀁏􀁈􀁇􀀃 􀁌􀁑􀀃 􀁗􀁋􀁈􀀃 prostate secretion; 4) O-glycans containing sialylated Tn antigen (KsHPA), sialylated T-antigen (KsPNA), and 􀄯2- 3sialylated lactosamine (MAL II) significantly prevaled in the urethral secretion; 5) glycans with internal GlcNAc (KsWGA) and N-glycans with terminal 􀄯2,6-sialylated (SNA) were equally contained in both the prostate and urethral secretions; 6) terminal T-antigen (PNA) and fucosylated glycans (UEA I and LTA) were absent in both the prostate and urethral secretion. [Conclusions] These findings suggest that the prostatic urethral glands may contribute to the composition and function of seminal plasma by mixing their secretory glycoproteins with the prostatic glycoproteins during ejaculation.