Department of Molecular Biology and Biotechnology, Tezpur University, Napaam, Assam 784028, India.
Department of Biotechnology, National Institute of Technology, Durgapur, West Bengal 713209, India.
Biochim Biophys Acta Mol Cell Biol Lipids. 2019 Apr;1864(4):596-607. doi: 10.1016/j.bbalip.2018.12.015. Epub 2018 Dec 28.
Protein modification by arginylation regulates protein stability, function and interaction. The loss of arginylation disrupts a diverse set of fundamental cellular processes from proliferation to death. In the current study, role of arginylation in cell differentiation is investigated. Using in vitro preadipocyte differentiation model, it was observed that the inhibition or knockout (KO) of arginyltransferase 1 (ATE1) severely hindered differentiation of preadipocytes into mature adipocytes. Absence of arginylation inhibited expression of two key adipogenic transcription factors PPARγ and C/EBPα, and their downstream adipogenic genes (FABP4, GLUT4, PLN1). Arginylation did not affect the induction of C/EBPβ and C/EBPδ, the up-stream regulators of PPARγ gene. However, absence of arginylation affected PPARγ protein expression, independent of its transcript level. The constitutive expression of PPARγ1 protein in Ate1 KO cells as well as ATE1 inhibitor treated wild type cells were dampened due to increased proteasome mediated degradation of PPARγ1 in the absence of arginylation in the cells. Taken together these observations suggested arginylation mediated transcriptional regulation of PPARγ and C/EBPα was downstream of C/EBPβ and C/EBPδ, and that the arginylation mediated regulation of PPARγ protein expression may play a role in this process. The inhibition of arginylation in mature adipocytes also reduced expression of lipogenesis genes and decreased fat accumulation in differentiated adipocytes. Thus, the current study shows that arginylation is essential for preadipocyte differentiation and maturation which are thought to be key factors in the maintenance of adipose tissue homeostasis.
精氨酸化修饰调控蛋白质的稳定性、功能和相互作用。精氨酸化的缺失会破坏从增殖到死亡的一系列基本细胞过程。在本研究中，研究了精氨酸化在细胞分化中的作用。使用体外前体脂肪细胞分化模型，观察到精氨酸转移酶 1 (ATE1) 的抑制或敲除 (KO) 严重阻碍了前体脂肪细胞向成熟脂肪细胞的分化。精氨酸化的缺失抑制了两个关键的脂肪生成转录因子 PPARγ 和 C/EBPα 及其下游脂肪生成基因 (FABP4、GLUT4、PLN1) 的表达。精氨酸化不影响 C/EBPβ 和 C/EBPδ 的诱导，C/EBPβ 和 C/EBPδ 是 PPARγ 基因的上游调节因子。然而，精氨酸化的缺失影响了 PPARγ 蛋白的表达，而不影响其转录水平。由于细胞中缺乏精氨酸化导致 PPARγ1 蛋白的稳定性降低，通过蛋白酶体介导的降解增加，Ate1 KO 细胞中 PPARγ1 蛋白的组成型表达以及 ATE1 抑制剂处理的野生型细胞中的 PPARγ1 蛋白的组成型表达都受到了抑制。综上所述，这些观察结果表明，PPARγ 和 C/EBPα 的精氨酸化介导的转录调控发生在 C/EBPβ 和 C/EBPδ 之后，而精氨酸化介导的 PPARγ 蛋白表达调控可能在这个过程中发挥作用。在成熟脂肪细胞中抑制精氨酸化也会降低脂肪生成基因的表达，并减少分化的脂肪细胞中的脂肪积累。因此，本研究表明，精氨酸化对于前体脂肪细胞的分化和成熟是必不可少的，这被认为是维持脂肪组织稳态的关键因素。
