Machado Sergio A, Kadirvel Govindasamy, Daigneault Bradford W, Korneli Claudia, Miller Paul, Bovin Nicolai, Miller David J
Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois.
Shemyakin Institute of Bioorganic Chemistry RAS, Moscow, Russia.
Biol Reprod. 2014 Dec;91(6):140. doi: 10.1095/biolreprod.114.119503. Epub 2014 Oct 22.
In many mammals, after semen deposition, a subpopulation of the sperm is transported to the lower oviduct, or isthmus, to form a functional sperm reservoir that provides sperm to fertilize oocytes. The precise molecular interactions that allow formation of this reservoir are unclear. It is proposed that binding of sperm receptors (lectins) to their oviductal cell ligands is accomplished by glycans. Previous results indicated that Lewis trisaccharides are present in glycosphingolipids and O- and N-linked glycans of the porcine isthmus and that Le(X)-containing molecules bind porcine sperm. Immunohistochemistry indicated that the Lewis structures identified by mass spectrometry were, in fact, Lewis X (Le(X)) trisaccharides. These motifs were localized to the luminal border of the isthmus. Assays using fluoresceinated glycans showed that 3-O-sulfated Le(X) (suLe(X)) bound to receptors localized on the head of nearly 60% of uncapacitated boar sperm but that the positional isomer 3-O-sulfo-Le(A) (suLe(A)) bound to <5% of sperm. Sperm also bound preferentially to suLe(X) made insoluble by coupling to beads. Capacitation reduced the ability of suLe(X) to bind sperm to <10%, perhaps helping to explain why sperm are released at capacitation. Pretreatment of oviduct cell aggregates with the Le(X) antibody blocked 57% of sperm binding to isthmic aggregates. Blocking putative receptors on sperm with soluble Le(X) and suLe(X) glycans specifically reduced sperm binding to oviduct cells up to 61%. These results demonstrate that the oviduct isthmus contains Le(X)-related moieties and that sperm binding to these oviduct glycans is necessary and sufficient for forming the sperm reservoir.
在许多哺乳动物中，精液沉积后，一部分精子会被运输到输卵管下部或峡部，形成一个功能性精子库，为卵母细胞受精提供精子。目前尚不清楚形成这个精子库的精确分子相互作用。有人提出精子受体（凝集素）与其输卵管细胞配体的结合是通过聚糖完成的。先前的结果表明，猪输卵管峡部的糖鞘脂以及O-连接和N-连接聚糖中存在Lewis三糖，且含Le(X)的分子可结合猪精子。免疫组织化学表明，质谱鉴定出的Lewis结构实际上是Lewis X（Le(X)）三糖。这些基序定位于峡部的管腔边界。使用荧光聚糖的实验表明，3-O-硫酸化Le(X)（suLe(X)）与近60%未获能的公猪精子头部的受体结合，但位置异构体3-O-磺基-Le(A)（suLe(A)）与不到5%的精子结合。精子还优先与偶联到珠子上而变得不溶的suLe(X)结合。获能使suLe(X)与精子结合的能力降低至10%以下，这或许有助于解释为什么精子在获能时会释放出来。用Le(X)抗体预处理输卵管细胞聚集体可阻断57%的精子与峡部聚集体的结合。用可溶性Le(X)和suLe(X)聚糖封闭精子上的假定受体可使精子与输卵管细胞的结合特异性降低高达61%。这些结果表明，输卵管峡部含有与Le(X)相关的部分，精子与这些输卵管聚糖的结合对于形成精子库是必要且充分的。
