Ehime University School of Medicine, Toon, Japan.
Affiliated Nanhua Hospital, Hengyang Medical School, University of South China, Hengyang, China.
J Histochem Cytochem. 2023 Oct;71(10):537-554. doi: 10.1369/00221554231198570. Epub 2023 Sep 20.
We tracked prosaposin (PSAP), a trophic factor, using an antibody specific to its proteolytic portion and an antibody to sortilin that traffics PSAP only to the lysosome. Immunostaining revealed that PSAP was distributed mainly on the basal side of seminiferous tubules, where many Sertoli cells and pachytene spermatocytes contained PSAP and its distribution differed depending on the stage of the spermatogenic cycle. The PSAP-sortilin complex was sorted to large lysosomes in the basal cytoplasm of Sertoli cells, where it may be processed into saposins. In contrast, in the thinner apical cytoplasm of Sertoli cells, PSAP in small lysosomes was transported to the apical side around sperm heads or into the lumen for secretion. The results of in situ hybridization analyses suggested that immature tubular cells in young animals produce PSAP to self-stimulate proliferation. However, in adults, not only Sertoli cells but also pachytene spermatocytes produce and secrete PSAP around germ cells or into the tubular lumen to stimulate cell proliferation or differentiation in a paracrine or autocrine manner. In summary, PSAP is not only a precursor of lysosomal enzymes but also a pivotal trophic factor in organogenesis in the immature testis and spermatogenesis in the mature testis.
我们使用针对其蛋白水解部分的抗体和仅将 PSAP 转运到溶酶体的分选蛋白抗体来追踪营养因子 prosaposin (PSAP)。免疫染色显示 PSAP 主要分布在生精小管的基底侧，许多支持细胞和粗线期精母细胞含有 PSAP，其分布随精子发生周期的阶段而不同。PSAP-分选蛋白复合物被分选到支持细胞基底细胞质中的大溶酶体中，在那里它可能被加工成脑硫脂。相比之下，在支持细胞较薄的顶细胞质中，小溶酶体中的 PSAP 被运输到精子头部周围的顶侧或进入管腔进行分泌。原位杂交分析的结果表明，年轻动物的未成熟管状细胞产生 PSAP 以自我刺激增殖。然而，在成人中，不仅支持细胞，而且粗线期精母细胞也在生殖细胞周围或管腔中产生和分泌 PSAP，以旁分泌或自分泌方式刺激细胞增殖或分化。总之，PSAP 不仅是溶酶体酶的前体，也是未成熟睾丸器官发生和成熟睾丸精子发生中的关键营养因子。
