School of Biological Sciences, Louisiana Tech University, Ruston, Louisiana, USA.
Pennington Biomedical Research Center, Baton Rouge, Louisiana, USA.
Stem Cells Dev. 2022 Mar;31(5-6):119-131. doi: 10.1089/scd.2021.0302. Epub 2022 Jan 28.
The mediator kinase module plays a critical role in the regulation of transcription during metabolic processes. Here we demonstrate that in human adipose-derived stem cells (hASCs), kinase module subunits have distinct mRNA and protein expression profiles during different stages of adipogenesis. In addition, siRNA-mediated loss of MED12 results in decreased adipogenesis as evident through decreased lipid accumulation and decreased expression of PPARγ, a master regulator of adipogenesis. Moreover, the decrease in adipogenesis and reduced PPARγ expression are observed only during the early stages of MED12 knockdown. At later stages, knockdown of MED12 did not have any significant effects on adipogenesis or PPARγ expression. We also observed that MED12 was present in a protein complex with PPARγ and C/EBPα during all stages of adipogenesis in hASCs. In 3T3-L1 preadipocytes and adipocytes, MED12 is present in protein complexes with PPARγ1, C/EBPα, and STAT5A. CDK8, another member of the kinase module, was only found to interact with C/EBPα. We found that the expression of all kinase module subunits decreased in inguinal, gonadal, and retroperitoneal white adipose tissue (WAT) depots in the fed state after an overnight fast, whereas the expression of kinase module subunits remained consistent in mesenteric WAT (mWAT) and brown adipose tissue. These data demonstrate that the kinase module undergoes physiologic regulation during fasting and feeding in specific mouse adipose tissue depots, and that MED12 likely plays a specific role in initiating and maintaining adipogenesis.
介导体激酶模块在代谢过程中的转录调控中起着关键作用。在这里，我们证明在人类脂肪来源干细胞（hASCs）中，激酶模块亚基在脂肪生成的不同阶段具有不同的 mRNA 和蛋白表达谱。此外，siRNA 介导的 MED12 缺失导致脂肪生成减少，表现为脂质积累减少和脂肪生成主调控因子 PPARγ 的表达降低。此外，只有在 MED12 敲低的早期阶段才观察到脂肪生成减少和 PPARγ 表达降低。在后期阶段，MED12 的敲低对脂肪生成或 PPARγ 表达没有任何显著影响。我们还观察到，在 hASCs 的脂肪生成的所有阶段，MED12 与 PPARγ 和 C/EBPα 存在于蛋白质复合物中。在 3T3-L1 前脂肪细胞和脂肪细胞中，MED12 与 PPARγ1、C/EBPα 和 STAT5A 存在于蛋白质复合物中。激酶模块的另一个成员 CDK8 仅与 C/EBPα 相互作用。我们发现，在禁食过夜后的进食状态下，腹股沟、性腺和腹膜后白色脂肪组织（WAT）中的所有激酶模块亚基的表达均降低，而肠系膜 WAT（mWAT）和棕色脂肪组织中的激酶模块亚基的表达保持一致。这些数据表明，激酶模块在特定的小鼠脂肪组织中经历了禁食和进食过程中的生理调节，并且 MED12 可能在启动和维持脂肪生成中发挥特定作用。
