Feuchter F A, Tabet A J, Green M F
Department of Anatomy, School of Medicine, University of New Mexico, Albuquerque 87131.
Am J Anat. 1988 Jan;181(1):67-76. doi: 10.1002/aja.1001810108.
We report here recent findings on the sperm maturation antigen SMA4, which is secreted by holocrine cells of the distal caput epididymis and binds to the flagellar surface of mouse sperm during epididymal transit. Washed sperm from the caput and corpus epididymides of mice were examined by immunofluorescence and SDS-PAGE using wheat germ agglutinin, which binds specifically to SMA4 as a primary probe. Results indicate that sperm first exhibit WGA reactivity on their flagellae in the region of the distal caput, and that the appearance of WGA receptors is due to the binding of a 54-Kd glycoprotein (SMA4) to the cell surface. Extracts of epididymis containing SMA4 were tested for their ability to bind to the surfaces of caput and corpus sperm. Caput sperm surfaces bound SMA4 in a temperature-independent manner, and binding occurred in the presence of enzyme inhibitors, suggesting a nonenzymatic process. Biochemical studies revealed that SMA4 contains disulfide bonds which stabilize it on the sperm surface and restrict its mobility. Terminal carbohydrate residues of the molecule are sialic acids. The addition of SMA4 to caput sperm flagellae prevented tail-to-tail agglutination, normally seen when caput sperm are diluted into saline; and SMA4 was able to disperse clumps of agglutinated caput sperm. The data suggest that a primary function of SMA4 is to prevent tail-to-tail agglutination of sperm during storage in the epididymis.
我们在此报告关于精子成熟抗原SMA4的最新研究结果，该抗原由附睾头远端的全浆分泌细胞分泌，并在附睾转运过程中与小鼠精子的鞭毛表面结合。使用小麦胚凝集素（它作为主要探针特异性结合SMA4），通过免疫荧光和SDS - PAGE对来自小鼠附睾头和附睾体的洗涤精子进行检测。结果表明，精子首先在附睾头远端区域的鞭毛上表现出小麦胚凝集素反应性，并且小麦胚凝集素受体的出现是由于一种54 - Kd糖蛋白（SMA4）与细胞表面结合所致。对含有SMA4的附睾提取物结合附睾头和附睾体精子表面的能力进行了测试。附睾头精子表面以不依赖温度的方式结合SMA4，并且在存在酶抑制剂的情况下也会发生结合，这表明是一个非酶促过程。生化研究表明，SMA4含有二硫键，这些二硫键使其在精子表面稳定并限制其移动性。该分子的末端碳水化合物残基是唾液酸。将SMA4添加到附睾头精子鞭毛上可防止尾对尾凝集，而当附睾头精子稀释到盐水中时通常会出现这种凝集现象；并且SMA4能够分散凝集的附睾头精子团块。数据表明，SMA4的主要功能是在精子储存在附睾期间防止其尾对尾凝集。
