Ram P A, Cardullo R A, Millette C F
Department of Anatomy & Cellular Biology, Harvard Medical School, Boston, Massachusetts 02115.
Gamete Res. 1989 Mar;22(3):321-32. doi: 10.1002/mrd.1120220309.
We have demonstrated previously that spermatogenic cells in the mouse testis have high levels of fucosyltransferase activity. Furthermore, a significant portion of this activity has been localized to the cell surface (Millette et al.: Cell Biology of the Testis and Epididymis, 1987). Differential expression of fucosyltransferases and their function as ecto-enzymes may be important in the processes of sperm maturation and fertilization in mammals. Accordingly, here we report the activity levels of fucosyltransferase (FT) in spermatozoa isolated from the mouse caput and cauda epididymides. Calculated on a per cell basis, spermatozoa from the caput epididymis have significantly more FT activity than do spermatozoa from the cauda epididymis (18.07 +/- 2.2 pmol/million cells compared with 2.8 +/- 0.09 pmol/million cells). Furthermore, caput sperm exhibit a more significant increase in FT activity when assayed in the presence of Nonidet P-40. Calculated on the basis of cell surface area, however, FT activity remains constant on the head portion of spermatozoa isolated from all portions of the male reproductive tract and from capacitated spermatozoa. Measurements of FT activity in extracts of isolated sperm tails from cells at different stages of maturation indicate a greatly diminished activity in tails from sperm in the cauda epididymis. The total sperm surface area is composed predominantly of the plasma membrane surrounding the flagellar apparatus. Therefore, our data demonstrate that FT activity is retained selectively on the different topological regions of sperm, with losses during sperm maturation in the epididymis being restricted to the tail segment. Maintenance of high levels of FT activity of the plasma membranes of the mouse sperm head raise the possibility that FT is indeed involved in some aspects of sperm-egg recognition.
我们之前已经证明，小鼠睾丸中的生精细胞具有高水平的岩藻糖基转移酶活性。此外，该活性的很大一部分定位于细胞表面（米利特等人：《睾丸和附睾的细胞生物学》，1987年）。岩藻糖基转移酶的差异表达及其作为外切酶的功能在哺乳动物精子成熟和受精过程中可能很重要。因此，我们在此报告从小鼠附睾头和附睾尾分离的精子中岩藻糖基转移酶（FT）的活性水平。以每个细胞计算，附睾头的精子比附睾尾的精子具有显著更高的FT活性（分别为18.07±2.2 pmol/百万个细胞和2.8±0.09 pmol/百万个细胞）。此外，在存在诺乃洗涤剂P - 40的情况下进行检测时，附睾头精子的FT活性增加更为显著。然而，以细胞表面积计算，从雄性生殖道所有部位分离的精子头部以及获能精子的FT活性保持恒定。对不同成熟阶段细胞分离的精子尾部提取物中FT活性的测量表明，附睾尾精子尾部的活性大大降低。精子的总表面积主要由围绕鞭毛装置的质膜组成。因此，我们的数据表明FT活性选择性地保留在精子的不同拓扑区域，在附睾中精子成熟过程中的活性损失仅限于尾部。小鼠精子头部质膜高水平FT活性的维持增加了FT确实参与精卵识别某些方面的可能性。
