Bocchinfuso W P, Warmels-Rodenhiser S, Hammond G L
Department of Obstetrics and Gynecology, University of Western Ontario, London, Canada.
Mol Endocrinol. 1991 Nov;5(11):1723-9. doi: 10.1210/mend-5-11-1723.
The human sex hormone-binding globulin (SHBG) gene is responsible for the production of plasma SHBG by the liver and androgen-binding protein in the testis. Cell-specific glycosylation events during synthesis may account for minor differences in the biochemical properties of SHBG and androgen-binding protein, and we have, therefore, expressed a human SHBG cDNA in chinese hamster ovary (CHO) cells and a mouse hepatoma cell line (BW-1), and compared the products to SHBG in serum. The SHBG produced in this way is a homodimer of subunits that exhibit size microheterogeneity similar to SHBG in human serum, and its affinity for 5 alpha-dihydrotestosterone (Kd = 0.6 nM) and other steroids is essentially identical to that of natural SHBG. When medium from transfected CHO and BW-1 cells was subjected to Concanavalin-A (Con-A) chromatography, the relative amounts of SHBG retained by Con-A were 74% and 86%, respectively. In addition, when SHBG produced by CHO cells was separated into two fractions by Con-A chromatography and analyzed by polyacrylamide gel electrophoresis, SHBG that did not interact with Con-A migrated with a slightly larger apparent mol wt than that of SHBG that binds Con-A; this can be explained by the presence of triantennary, rather than biantennary, N-linked oligosaccharide chains. These data also demonstrate that the subunit microheterogeneity associated with plasma SHBG reflects differences in glycosylation during synthesis, which appear to be cell type specific.
人类性激素结合球蛋白（SHBG）基因负责肝脏产生血浆SHBG以及睾丸中产生雄激素结合蛋白。合成过程中细胞特异性的糖基化事件可能导致SHBG和雄激素结合蛋白在生化特性上存在细微差异。因此，我们在中华仓鼠卵巢（CHO）细胞和小鼠肝癌细胞系（BW-1）中表达了人类SHBG cDNA，并将产物与血清中的SHBG进行比较。以这种方式产生的SHBG是亚基的同二聚体，表现出与人血清中SHBG相似的大小微异质性，其对5α-二氢睾酮（Kd = 0.6 nM）和其他类固醇的亲和力与天然SHBG基本相同。当转染的CHO和BW-1细胞的培养基进行伴刀豆球蛋白A（Con-A）层析时，Con-A保留的SHBG相对量分别为74%和86%。此外，当CHO细胞产生的SHBG通过Con-A层析分离成两个组分并通过聚丙烯酰胺凝胶电泳分析时，不与Con-A相互作用的SHBG迁移时的表观分子量略大于与Con-A结合的SHBG；这可以通过存在三触角而非双触角的N-连接寡糖链来解释。这些数据还表明，与血浆SHBG相关的亚基微异质性反映了合成过程中糖基化的差异，这似乎具有细胞类型特异性。
