Co-expression of two distinct polysialic acids, α2,8- and α2,9-linked polymers of N-acetylneuraminic acid, in distinct glycoproteins and glycolipids in sea urchin sperm

• Published in: Glycobiology (Oxford) 2011-12, Vol.21 (12), p.1596-1605
• Main Authors: Miyata, Shinji, Yamakawa, Nao, Toriyama, Masaru, Sato, Chihiro, Kitajima, Ken
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Antibodies - chemistry; Antibodies - immunology; Antibodies - pharmacology; Biopolymers - chemistry; Biopolymers - immunology; Fertilization - drug effects; Fluorescent Antibody Technique; Glycolipids - chemistry; Glycolipids - immunology; Glycoproteins - chemistry; Glycoproteins - immunology; Life Sciences; Male; N-Acetylneuraminic Acid - chemistry; N-Acetylneuraminic Acid - immunology; Sea Urchins - cytology; Spermatozoa - chemistry; Spermatozoa - drug effects; Spermatozoa - immunology
• ISSN: 0959-6658; 1460-2423
• DOI: 10.1093/glycob/cwr081

Naturally occurring polysialic acid (polySia) structures have a large diversity, primarily arising from the diversity in the sialic acid components as well as in the intersialyl linkages. In 2004, we demonstrated the presence of a new type of polySia, 8-O-sulfated N-acetylneuraminic acid (Neu5Ac) capped α2,9-linked polyNeu5Ac, on the O-glycans of a major 40-80 kDa sialoglycoprotein, flagellasialin, in sea urchin sperm. In this study, we demonstrated that another type of polySia, the α2,8-linked polyNeu5Ac, exclusively occurs on O-glycans of a 190 kDa glycoprotein (190 kDa-gp), whereas the α2,9-linked polyNeu5Ac is exclusively present on flagellasialin. The 190 kDa-gp is localized in both flagellum and head of sperm. We also demonstrated that polysialogangliosides containing the α2,8-linked polyNeu5Ac are present in sperm head. Thus, this study shows two novel features of the occurrence of polySia in nature, the co-localization of polySia with different intersialyl linkages, the α2,8- and α2,9-linkages, in a single cell and the occurrence of α2,8-linked polyNeu5Ac in glycolipids. Anti-α2,8-linked polyNeu5Ac antibody had no effect on fertilization, which contrasted with the previous results that anti-α2,9-linked polyNeu5Ac antibody inhibited sperm motility and fertilization. Based on these properties, distinct functions of α2,8- and α2,9-polySia structures are implicated in fertilization.