文章基本信息

标题：Conditional steroidogenic cell-targeted deletion of TSPO unveils a crucial role in viability and hormone-dependent steroid formation
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作者：Jinjiang Fan ; Enrico Campioli ; Andrew Midzak 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：23
页码：7261-7266
DOI：10.1073/pnas.1502670112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceCholesterol-derived steroid hormones are critical mediators in development, reproduction, behavior, and stress response. Steroid biosynthesis occurs in hormone-dependent steroidogenic cells, which are defined by their ability to cleave cholesterol to pregnenolone in mitochondria, the adrenal cortex, and gonads. The rate-limiting step in steroid biosynthesis is the transport of cholesterol from intracellular stores into mitochondria. Translocator protein (TSPO) is a high-affinity drug- and cholesterol-binding protein important for cholesterol import into mitochondria. Two distinct genetically engineered Tspo mouse mutants were generated to induce gonadal and steroidogenic cell-specific Tspo deletion. Our studies show the importance of TSPO for murine development as well as for hormone-induced steroidogenesis, suggesting a key role for TSPO in the development and function of the mammalian acute stress response. Translocator protein (TSPO) is a key member of the mitochondrial cholesterol transport complex in steroidogenic tissues. To assess the function of TSPO, we generated two lines of Cre-mediated Tspo conditional knockout (cKO) mice. First, gonadal somatic cell-targeting Amhr2-Cre mice were crossed with Tspo-floxed mice to obtain F1 Tspo Amhr2 cKO mice (Tspofl/fl;Amhr2-Cre/+). The unexpected Mendelian ratio of 4.4% cKO mice was confirmed by genotyping of 12.5-day-postcoitum (dpc) embryos. As Amhr2-Cre is expressed in gonads at 12.5 dpc, these findings suggest preimplantation selection of embryos. Analysis of expression databases revealed elevated levels of Amhr2 in two- and eight-cell zygotes, suggesting ectopic Tspo silencing before the morula stage and demonstrating elevated embryonic lethality and involvement of TSPO in embryonic development. To circumvent this issue, steroidogenic cell-targeting Nr5a1-Cre mice were crossed with Tspo-floxed mice. The resulting Tspofl/fl;Nr5a1-Cre/+ mice were born at a normal Mendelian ratio. Nr5a1-driven Tspo cKO mice exhibited highly reduced Tspo levels in adrenal cortex and gonads. Treatment of mice with human chorionic gonadotropin (hCG) resulted in increased circulating testosterone levels despite extensive lipid droplet depletion. In contrast, Nr5a1-driven Tspo cKO mice lost their ability to form corticosterone in response to adrenocorticotropic hormone (ACTH). Important for ACTH-dependent steroidogenesis, Mc2r, Stard1, and Cypa11a1 levels were unaffected, whereas Scarb1 levels were increased and accumulation of lipid droplets was observed, indicative of a blockade of cholesterol utilization for steroidogenesis. TSPO expression in the adrenal medulla and increased epinephrine production were also observed. In conclusion, TSPO was found necessary for preimplantation embryo development and ACTH-stimulated steroid biosynthesis.
关键词：translocator protein ; anti-Mullerian hormone receptor type II ; nuclear receptor subfamily 5 group A member 1 ; knockout mice ; steroidogenesis