Fujimoto Muneya, Masuzaki Hiroaki, Yamamoto Yuji, Norisada Nobuyoshi, Imori Makoto, Yoshimoto Masako, Tomita Tsutomu, Tanaka Tomohiro, Okazawa Kayoko, Fujikura Junji, Chusho Hideki, Ebihara Ken, Hayashi Tatsuya, Hosoda Kiminori, Inoue Gen, Nakao Kazuwa
Division of Endocrinology and Metabolism, Department of Medicine and Clinical Science, Kyoto University Graduate School of Medicine, 54, Sakyo-ku, Kyoto, 606-8507, Japan.
Biochim Biophys Acta. 2005 Aug 15;1745(1):38-47. doi: 10.1016/j.bbamcr.2004.12.007. Epub 2005 Jan 19.
In 3T3-L1 preadipocytes, hormonal induction causes adipose conversion and facilitates the expression of insulin-sensitive glucose transporter, GLUT4. Evidence has accumulated that, in 3T3-L1 preadipocytes, the formation of GLUT4 storage vesicle and its translocation to plasma membrane precede both lipid accumulation and expression of GLUT4 and C/EBPalpha, a key transcription factor for adipose differentiation. On the other hand, 3T3-C2 fibroblastic cells, a subline of 3T3-L1, follow adipogenic process till mitotic clonal expansion stage (2 days after hormonal induction), but do not proceed to terminal differentiation stage (8 days after the induction), resulting in a lack of adipose conversion and GLUT4 expression. Here we show that, when myc-tagged GLUT4 was retrovirally expressed in 3T3-C2 cells, insulin-stimulated GLUT4 translocation did occur on day 2 after the induction. On day 8 after the induction, however, neither GLUT4 translocation nor the expression of C/EBPalpha was observed. We also created 3T3-C2 cells stably expressing both myc-tagged GLUT4 and C/EBPalpha, demonstrating that co-expressed cells showed insulin-stimulated GLUT4 translocation on day 8 after the induction, as well as adipose conversion coupling with PPARgamma expression. Our results provide evidence that C/EBPalpha has the potential to maintain the ability of insulin-stimulated GLUT4 translocation in C/EBPalpha-deficient 3T3-C2 fibroblastic cells.
在3T3-L1前脂肪细胞中，激素诱导可导致脂肪转化，并促进胰岛素敏感型葡萄糖转运蛋白GLUT4的表达。越来越多的证据表明，在3T3-L1前脂肪细胞中，GLUT4储存囊泡的形成及其向质膜的转位先于脂质积累以及GLUT4和C/EBPα（脂肪分化的关键转录因子）的表达。另一方面，3T3-C2成纤维细胞是3T3-L1的一个亚系，其遵循脂肪生成过程直至有丝分裂克隆扩增阶段（激素诱导后2天），但不会进入终末分化阶段（诱导后8天），导致缺乏脂肪转化和GLUT4表达。在此我们表明，当用逆转录病毒在3T3-C2细胞中表达myc标签的GLUT4时，诱导后第2天确实发生了胰岛素刺激的GLUT4转位。然而，在诱导后第8天，既未观察到GLUT4转位，也未观察到C/EBPα的表达。我们还创建了稳定表达myc标签的GLUT4和C/EBPα的3T3-C2细胞，证明共表达细胞在诱导后第8天显示出胰岛素刺激的GLUT4转位，以及与PPARγ表达相关的脂肪转化。我们的结果提供了证据，表明C/EBPα有潜力在缺乏C/EBPα的3T3-C2成纤维细胞中维持胰岛素刺激的GLUT4转位能力。
