Fibrinogen-related protein, FGL2, of hamster cauda epididymal fluid: Purification, kinetic analysis of its prothrombinase activity, and its role in segregation of nonviable spermatozoa.
Fibrinogen-related protein, FGL2, of hamster cauda epididymal fluid: Purification, kinetic analysis of its prothrombinase activity, and its role in segregation of nonviable spermatozoa.
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DOI：
10.1002/mrd.23438
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发表时间：
2020-12
影响因子：
2.5
通讯作者：
Raychoudhuri SS
中科院分区：
文献类型：
--
作者：
Nagdas SK;Wallace S;Eaford D;Baker R;Carr K;Raychoudhuri SS
尽管附睾环境促进精子的成熟和存活，但并非所有精子在通过附睾时都保持活力。附睾是否有保护机制将有活力的精子与有缺陷的精子分开？此前，我们鉴定出260/280kDa寡聚体（称为eFGL-附睾纤维蛋白原样寡聚体）由两个二硫键连接的亚基组成：一个被鉴定为纤维蛋白原样蛋白2（FGL2）的64kDa多肽和一个被鉴定为纤维蛋白原样蛋白1（FGL1）的33kDa多肽。我们的形态学研究表明，附睾尾主细胞分泌的 eFGL 聚合成死亡茧样复合物 (DCF)，掩盖有缺陷的管腔精子，但不能掩盖有活力的精子群。在本研究中，我们从仓鼠附睾尾液中纯化出同质的 FGL2，并检测了其凝血酶原酶催化活性。时程转化研究表明，纯化的仓鼠 FGL2 将所有凝血酶原转化为凝血酶。我们的生化研究表明，FGL2 是一种脂质激活的丝氨酸蛋白酶，通过结合特定的碳水化合物残基发挥凝集素的作用。免疫共沉淀分析表明，附睾尾液中的 FGL2 被泛素化，但 FGL1 未被泛素化。我们认为 FGL2/FGL1 寡聚物代表了一种新颖且独特的机制，可以保护存活的精子群免受管腔内包含的退化精子的影响。
Although the epididymal environment promotes the maturation and survival of spermatozoa, not all spermatozoa remain viable during passage through the epididymis. Does the epididymis has a protective mechanism(s) to segregate the viable sperm from defective spermatozoa? Previously, we identified 260/280kDa oligomers (termed eFGL-epididymal fibrinogen-like oligomer) are composed of two disulfide-linked subunits: a 64kDa polypeptide identified as fibrinogen-like protein-2 (FGL2) and a 33kDa polypeptide identified as fibrinogen-like protein-1 (FGL1). Our morphological studies demonstrated that the eFGL, secreted from the principal cells of the cauda epididymis, is polymerized into a death cocoon-like complex (DCF), masking defective luminal spermatozoa but, not the viable sperm population. In the present study, we purified FGL2 from hamster cauda epididymal fluid towards homogeneity and its prothrombinase catalytic activity was examined. Time-course conversion studies revealed that all prothrombin was converted to thrombin by purified hamster FGL2. Our biochemical studies demonstrate that FGL2 is a lipid–activated serine protease and functions as a lectin by binding specific carbohydrate residues. Co-immunoprecipitation analysis demonstrated that FGL2 of cauda epididymal fluid is ubiquitinated but not the FGL1. We propose that FGL2/FGL1 oligomers represent a novel and unique mechanism to shield the viable sperm population from degenerating spermatozoa contained within the tubule lumen.