Oko R, Hermo L, Chan P T, Fazel A, Bergeron J J
Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada.
J Cell Biol. 1993 Nov;123(4):809-21. doi: 10.1083/jcb.123.4.809.
The cytoplasmic droplet of epididymal spermatozoa is a small localized outpouching of cytoplasm of the tail of unknown significance. EM revealed flattened saccular elements as the near exclusive membranous component of the droplet. Light and electron microscopic immunolabeling for Golgi/TGN markers showed these saccules to be reactive for antibodies to TGN38, protein affinity-purified alpha 2,6 sialyltransferase, and anti-human beta 1,4 galactosyltransferase. The saccules were isolated by subcellular fractionation and antibodies raised against this fraction immunolabeled the saccules of the droplet in situ as well as the Golgi region of somatic epithelial cells lining the epididymis. The isolated droplet fraction was enriched in galactosyltransferase and sialyltransferase activities, and endogenous glycosylation assays identified the modification of several endogenous glycopeptides. EM lectin staining in situ demonstrated galactose and N-acetyl galactosamine constituents in the saccules. Endocytic studies with cationic and anionic ferritin as well as HRP failed to identify the saccules as components of the endocytic apparatus. Epididymal spermatozoa were devoid of markers for the ER as well as the Golgi-associated coatamer protein beta-COP. It is therefore unlikely that the saccular elements of the droplet participate in vesicular protein transport. However, the identification of Golgi/TGN glycosylating activities in the saccules may be related to plasma membrane modifications which occur during epididymal sperm maturation.
附睾精子的细胞质滴是尾部细胞质的一个小的局限性膨出，其意义不明。电子显微镜显示扁平囊状结构是该滴几乎唯一的膜性成分。针对高尔基体/反式高尔基体网络（TGN）标志物的光镜和电镜免疫标记显示，这些囊泡对TGN38抗体、蛋白亲和纯化的α2,6唾液酸转移酶抗体及抗人β1,4半乳糖基转移酶抗体呈反应性。通过亚细胞分级分离法分离出这些囊泡，用针对该分级分离物产生的抗体对原位的细胞质滴囊泡以及附睾内衬的体细胞上皮细胞的高尔基体区域进行免疫标记。分离出的细胞质滴分级分离物富含半乳糖基转移酶和唾液酸转移酶活性，内源性糖基化分析鉴定出几种内源性糖肽的修饰。原位的电镜凝集素染色显示囊泡中有半乳糖和N - 乙酰半乳糖胺成分。用阳离子和阴离子铁蛋白以及辣根过氧化物酶进行的内吞研究未能将这些囊泡鉴定为内吞装置的组成部分。附睾精子缺乏内质网标志物以及与高尔基体相关的外被体蛋白β - COP。因此，细胞质滴的囊状结构不太可能参与囊泡蛋白运输。然而，在囊泡中鉴定出高尔基体/TGN糖基化活性可能与附睾精子成熟过程中发生的质膜修饰有关。
