Fujimori Haruna, Zhou Yi Jun, Fukumura Keisuke, Matsumoto Sumihiro, Tukamoto Yusuke, Nagata Shinji
Department of Integrated Biosciences, Graduate School of Frontier Sciences, the University of Tokyo, Kashiwa City, Chiba, Japan.
Research Fellow of Japan Society for the Promotion of Science (JSPS), Chiyoda-ku, Tokyo, Japan.
Biosci Biotechnol Biochem. 2020 Jan;84(1):126-133. doi: 10.1080/09168451.2019.1667221. Epub 2019 Sep 20.
Insects must intake sterol compounds because of their inability to synthesize cholesterol . In phytophagous insects, enzymatic conversion of phytosterols to cholesterol involving 24-dehydrocholesterol reductase (DHCR24) exerts to acquire cholesterol. Here, we reported the presence of two DHCR24 homologs in the silkworm , BmDHCR24-1 and -2, with several transcript variants. Consistent with the data of spatial expression analyses by RT-PCR, predominant enzymatic activity of DHCR24 was observed in larval midgut whereas weak activity was observed in the other tissues examined. In addition, BmDHCR24-1 expression in HEK293 cells showed an enzymatic activity, but BmDHCR24-2 did not, although both BmDHCR24s were localized in the endoplasmic reticulum, where the mammalian DHCR24s are located to exert their enzymatic activities. The present data indicated that BmDHCR24-1 but not BmDHCR24-2 contributes to conversion of phytosterols to cholesterol mainly in the midgut of the phytophagous lepidopteran larvae.
由于昆虫自身无法合成胆固醇，所以它们必须摄取甾醇类化合物。在植食性昆虫中，植物甾醇通过24-脱氢胆固醇还原酶（DHCR24）酶促转化为胆固醇，以此来获取胆固醇。在此，我们报道了家蚕中存在两个DHCR24同源物，即BmDHCR24-1和BmDHCR24-2，它们有多个转录变体。与通过RT-PCR进行的空间表达分析数据一致，在幼虫中肠观察到DHCR24的主要酶活性，而在其他检测组织中观察到较弱的活性。此外，尽管两种BmDHCR24都定位于内质网（哺乳动物DHCR24发挥酶活性的部位），但BmDHCR24-1在HEK293细胞中的表达显示出酶活性，而BmDHCR24-2则没有。目前的数据表明，主要在植食性鳞翅目幼虫的中肠中，是BmDHCR24-1而非BmDHCR24-2参与植物甾醇向胆固醇的转化。
