Kolmer M, Pelto-Huikko M, Parvinen M, Höög C, Alho H
University of Tampere, Medical School, Finland.
DNA Cell Biol. 1997 Jan;16(1):59-72. doi: 10.1089/dna.1997.16.59.
The diazepam binding inhibitor [DBI, also known as acyl-CoA-binding protein, (ACBP), or endozepine] is a 10-kD protein that has been suggested to be involved in the regulation of several biological processes such as acyl-CoA metabolism, steroidogenesis, insulin secretion, and gamma-aminobutyric acid type A (GABA(A))/benzodiazepine receptor modulation. DBI has been cloned from vertebrates, insects, plants, and yeasts. In mammals, DBI is expressed in almost all the tissues studied. Nevertheless, DBI expression is restricted to specific cell types. Here we have studied DBI gene expression in the germ-line cells of rat testis. The DBI gene was intensively transcribed in postmeiotic round spermatids from stages VI to VIII of the seminiferous epithelial cycle. A prominent, spermatid-specific upstream transcription initiation site was identified in addition to the multiple common transcriptional initiation sites found in the somatic tissues. However, no DBI protein was detected in round spermatids, suggesting that the DBI transcripts were translationally arrested. The DBI protein was detected in the late spermatogenic stages starting from elongating spermatids from step 18 (stage VI) onward. The DBI protein was also detected in mature spermatozoa and in ejaculated human sperms. The majority of DBI was located at the middle piece of the spermatozoons tail enriched with mitochondria. On the basis of this observation and the well-established role of DBI in acyl-CoA metabolism, we propose that DBI expression in spermatozoa reflects the usage of fatty acids as a primary energy source by spermatozoa. The biological function of DBI in spermatozoa could thus be related to the motility function of sperm.
地西泮结合抑制剂[DBI，也称为酰基辅酶A结合蛋白（ACBP）或内源性苯二氮䓬]是一种10千道尔顿的蛋白质，有人认为它参与多种生物学过程的调节，如酰基辅酶A代谢、类固醇生成、胰岛素分泌以及A型γ-氨基丁酸（GABA(A)）/苯二氮䓬受体调节。DBI已从脊椎动物、昆虫、植物和酵母中克隆出来。在哺乳动物中，DBI在几乎所有研究过的组织中都有表达。然而，DBI的表达仅限于特定的细胞类型。在此，我们研究了大鼠睾丸生殖系细胞中DBI基因的表达。在生精上皮周期VI至VIII阶段的减数分裂后圆形精子细胞中，DBI基因被大量转录。除了在体细胞组织中发现的多个常见转录起始位点外，还鉴定出一个突出的、精子细胞特异性的上游转录起始位点。然而，在圆形精子细胞中未检测到DBI蛋白，这表明DBI转录本的翻译被阻断。从第18步（VI阶段）开始的伸长精子细胞起，在精子发生后期检测到了DBI蛋白。在成熟精子和射出的人类精子中也检测到了DBI蛋白。大多数DBI位于富含线粒体的精子尾部中段。基于这一观察结果以及DBI在酰基辅酶A代谢中已确立的作用，我们提出精子中DBI的表达反映了精子将脂肪酸作为主要能量来源的利用情况。因此，DBI在精子中的生物学功能可能与精子的运动功能有关。
