Miyata Shinji, Sato Chihiro, Kumita Hironobu, Toriyama Masaru, Vacquier Victor D, Kitajima Ken
Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan.
Glycobiology. 2006 Dec;16(12):1229-41. doi: 10.1093/glycob/cwl036. Epub 2006 Aug 3.
A novel alpha2,9-linked polysialic acid (polySia)-containing glycoprotein of sea urchin sperm flagella was identified and named "flagellasialin." Flagellasialin from Hemicentrotus pulcherrimus shows a diverse relative molecular mass on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of 40-80 kDa. Flagellasialin is a 96-amino acid, threonine-rich, heavily O-glycosylated (80-90% by weight) glycoprotein with a single transmembrane segment at its C-terminus and no apparent cytosolic domain. Of 12 extracellular Thr residues, eight are O-glycosylated and three are nonglycosylated. Flagellasialin is highly expressed in the testis but cannot be detected in the ovary. The amino acid sequences of flagellasialin from three sea urchin species (H. pulcherrimus, Strongylocentrotus purpuratus, and Strongylocentrotus franciscanus) are identical, but some species differences exist in the three core glycan structures to which the sulfated alpha2,9-linked polyNeu5Ac chain is linked. Finally, the treatment of sperm with a specific antibody against the alpha2,9-linked polyNeu5Ac structure results in the elevation of intracellular Ca(2+) and inhibition of sperm motility and fertilization, implicating flagellasialin as a regulator of these critical processes.
一种新的、含α2,9-连接的多唾液酸(聚唾液酸)的海胆精子鞭毛糖蛋白被鉴定出来,并命名为“鞭毛唾液酸蛋白”。来自马粪海胆的鞭毛唾液酸蛋白在十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)上显示出40-80 kDa的多种相对分子质量。鞭毛唾液酸蛋白是一种由96个氨基酸组成、富含苏氨酸、高度O-糖基化(重量比为80-90%)的糖蛋白,在其C端有一个单一的跨膜结构域,没有明显的胞质结构域。在12个细胞外苏氨酸残基中,8个被O-糖基化,3个未被糖基化。鞭毛唾液酸蛋白在睾丸中高度表达,但在卵巢中无法检测到。三种海胆物种(马粪海胆、紫海胆和加州紫海胆)的鞭毛唾液酸蛋白的氨基酸序列相同,但在硫酸化的α2,9-连接的聚N-乙酰神经氨酸链连接的三种核心聚糖结构上存在一些物种差异。最后,用针对α2,9-连接的聚N-乙酰神经氨酸结构的特异性抗体处理精子会导致细胞内Ca(2+)升高,并抑制精子活力和受精,这表明鞭毛唾液酸蛋白是这些关键过程的调节因子。