N-linked glycoproteome of human seminal plasma

N-linked glycosylation is an important type of post-translational modification. This modification plays important roles in many cellular functions including cell-cell and receptor-ligand interactions, immune response, apoptosis, and pathogenesis of many diseases. Seminal plasma is a mixture of secretions from several male accessory glands. Glycoproteins in seminal plasma can reflect the states of reproductive organs or diseases. Using isotope labeling and high-resolution mass spectrometry, we identified 720 N-glycosylated sites on 372 N-glycosylated proteins, corresponding to 365 genes. Analysis of variations among five individuals revealed similar compositions of N-glycosylated proteins in seminal plasma. Consistent composition of N-linked glycoproteins in human seminal plasma provides evidences that seminal plasma glycoproteins are of significant value to be candidates of biomarkers. Bioinformatics annotation of the identified seminal plasma glycoproteins showed that more than 43.0% of these glycoproteins are known secreted proteins according to UniProt. Such a high proportion of secreted glycoproteins in seminal plasma may play important roles in seminal plasma function such as making sure for sperm nutrition and function.

N-糖基化（N-linked glycosylation）是一类重要的翻译后修饰（post-translational modification）。该修饰在诸多细胞功能中发挥关键作用，涵盖细胞间相互作用、受体-配体结合、免疫应答、细胞凋亡以及多种疾病的发病机制。精浆是多种男性附属性腺分泌物的混合体系。精浆中的糖蛋白可反映生殖器官的生理状态或疾病进程。本研究采用同位素标记结合高分辨质谱（high-resolution mass spectrometry）技术，在372个N-糖基化蛋白上共鉴定出720个N-糖基化位点，对应365个编码基因。对5名个体的组间差异分析显示，不同个体精浆中的N-糖基化蛋白组成具有高度相似性。人精浆中N-连接糖蛋白组成的一致性，表明精浆糖蛋白可作为极具研究价值的生物标志物候选物。对鉴定得到的精浆糖蛋白进行生物信息学注释后发现，依据UniProt数据库，超过43.0%的此类糖蛋白为已报道的分泌型蛋白。精浆中如此高占比的分泌型糖蛋白，可能在精浆功能中发挥关键作用，例如为精子提供营养支持并维持其正常生理功能。