Dong Yewei, Liu Lijie, Li Mengmeng, Xie Dizhi, Zhao Jianhong, Wang Shuqi, You Cuihong, Li Yuanyou
College of Marine Sciences of South China Agricultural University & Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou 510642, China; College of Animal Sciences and Technology, Zhongkai University of Agriculture and Engineering, Guangzhou, Guangdong, 510225, China.
Guangdong Provincial Key Laboratory of Marine Biotechnology, Shantou University, Shantou, Guangdong, 515063, China.
Gene. 2022 Oct 5;840:146755. doi: 10.1016/j.gene.2022.146755. Epub 2022 Jul 26.
The rabbitfish Siganus canaliculatus is the first marine teleost found to have the biosynthetic ability of long-chain polyunsaturated fatty acids (LC-PUFA) from C precursors catalyzed by fatty acyl desaturases (Δ6/Δ5 Fads, Δ4 Fads) and elongases of very long chain fatty acids (Elovls). Previously, we predicted the existence of insulin (INS) response elements (IREs) including nuclear factor Y (NF-Y) and sterol regulatory element (SRE) in the core promoter region of rabbitfish Δ6/Δ5 fads and Δ4 fads. To clarify the potential regulatory effect and mechanism of INS in LC-PUFA biosynthesis, INS responding region was identified at -456 bp to + 51 bp of Δ6/Δ5 fads core promoter, but not in Δ4 fads promoter. Moreover, a unique stimulatory protein 1 (Sp1) element was predicted in the INS responding region of Δ6/Δ5 fads. Subsequently, SRE, NF-Y and Sp1 elements were proved as IREs in Δ6/Δ5 fads promoter. The up-regulation of INS on gene expression of Srebp-1c, Sp1, Δ6/Δ5 fads and elovl5 as well as the LC-PUFA biosynthesis was further demonstrated in S. canaliculatus hepatocyte line (SCHL) cells, but no influence was detected on Δ4 fads. Besides, inhibitors of transcription factors Srebp-1c (Fatostatin, PF-429242) and Sp1 (Mithramycin) could inhibit the gene expression of Srebp-1c, Δ6/Δ5 fads and elovl5, and abolish the up-regulation of INS on these genes' expression and LC-PUFA biosynthesis. These results indicated that INS could up-regulate LC-PUFA biosynthesis with the involvement of Srebp-1c and Sp1 in rabbitfish S. canaliculatus, which is the first report in teleost.
黄斑蓝子鱼是首个被发现具有由脂肪酸去饱和酶（Δ6/Δ5脂肪酸去饱和酶、Δ4脂肪酸去饱和酶）和极长链脂肪酸延长酶（Elovls）催化从碳前体生物合成长链多不饱和脂肪酸（LC-PUFA）能力的海洋硬骨鱼。此前，我们预测在黄斑蓝子鱼Δ6/Δ5脂肪酸去饱和酶和Δ4脂肪酸去饱和酶的核心启动子区域存在包括核因子Y（NF-Y）和固醇调节元件（SRE）在内的胰岛素（INS）反应元件（IREs）。为阐明INS在LC-PUFA生物合成中的潜在调节作用及机制，在Δ6/Δ5脂肪酸去饱和酶核心启动子的-456 bp至+51 bp处鉴定出INS反应区域，但在Δ4脂肪酸去饱和酶启动子中未鉴定出。此外，在Δ6/Δ5脂肪酸去饱和酶的INS反应区域预测到一个独特的刺激蛋白1（Sp1）元件。随后，SRE、NF-Y和Sp1元件在Δ6/Δ5脂肪酸去饱和酶启动子中被证明为IREs。在黄斑蓝子鱼肝细胞系（SCHL）细胞中进一步证明了INS对Srebp-1c、Sp1、Δ6/Δ5脂肪酸去饱和酶和elovl5基因表达以及LC-PUFA生物合成的上调作用，但对Δ4脂肪酸去饱和酶未检测到影响。此外，转录因子Srebp-1c（法托他汀、PF-429242）和Sp1（光神霉素）的抑制剂可抑制Srebp-1c、Δ6/Δ5脂肪酸去饱和酶和elovl5的基因表达，并消除INS对这些基因表达和LC-PUFA生物合成的上调作用。这些结果表明，在黄斑蓝子鱼中，INS可在Srebp-1c和Sp1的参与下上调LC-PUFA生物合成，这在硬骨鱼中尚属首次报道。
