Jeong Su Ji, Sim Bo-Woong, Kim Sun-Uk, Park Chan Young
Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan, Korea.
Futuristic Animal Resource & Research Center (FARRC), Korea Research Institute of Bioscience and Biotechnology (KRIBB), Cheongju, Korea.
FEBS J. 2025 Aug;292(15):4018-4038. doi: 10.1111/febs.70118. Epub 2025 May 9.
Intracellular Ca is crucial in the regulation of adipocyte lipid metabolism and adipogenesis. In this study, we aimed to investigate the regulation mechanism of intracellular Ca levels ([Ca]) during adipocyte differentiation. We found that the expression of stromal interaction molecule 2 beta (STIM2β), which is the inhibitor of store-operated Ca entry (SOCE), is upregulated throughout the differentiation process. Evaluation of [Ca] in 3 T3-L1 and primary stromal vascular fraction (SVF) cells revealed that the basal Ca level is downregulated after differentiation. Knockout (KO) of STIM2β in 3T3-L1 and primary SVF cells showed increased [Ca], indicating the involvement of STIM2β in the regulation of [Ca] during adipogenesis. We further evaluated the function of STIM2β-mediated [Ca] in early and terminal differentiation of adipogenesis. Analysis of cell proliferation rate during mitotic clonal expansion (MCE) in wild-type and STIM2β KO 3T3-L1 cell lines revealed that a larger population of KO cells underwent G1 arrest, suggesting that reduced [Ca] by STIM2β induces MCE. Additionally, ablation of STIM2β increased differentiation efficiency, with more lipid accumulation and rapid transcriptional activation of adipogenic genes, especially proliferator-activator receptor γ2 (PPARG2). We found that PPARG2 transcription is regulated by store-operated calcium entry (SOCE) downstream transcription factors, confirming that increased [Ca] by STIM2β ablation promotes PPARG2 transcription during adipogenesis. Additionally, STIM2β KO mice showed hypertrophic adipose tissue development. Our data suggest that STIM2β-mediated [Ca] plays a pivotal role in the regulation of mitotic clonal expansion and PPARG2 gene activation and provides evidence that MCE is not a prerequisite process for terminal differentiation during adipogenesis.
细胞内钙在脂肪细胞脂质代谢和脂肪生成的调节中至关重要。在本研究中，我们旨在探究脂肪细胞分化过程中细胞内钙水平（[Ca]）的调节机制。我们发现，作为储存式钙内流（SOCE）抑制剂的基质相互作用分子2β（STIM2β）的表达在整个分化过程中上调。对3T3-L1和原代基质血管成分（SVF）细胞中[Ca]的评估显示，分化后基础钙水平下调。在3T3-L1和原代SVF细胞中敲除（KO）STIM2β显示[Ca]增加，表明STIM2β参与脂肪生成过程中[Ca]的调节。我们进一步评估了STIM2β介导的[Ca]在脂肪生成早期和终末分化中的功能。对野生型和STIM2β基因敲除的3T3-L1细胞系在有丝分裂克隆扩增（MCE）期间细胞增殖率的分析表明，更多的基因敲除细胞发生G1期阻滞，这表明STIM2β降低[Ca]诱导MCE。此外，敲除STIM2β提高了分化效率，有更多的脂质积累和脂肪生成基因特别是增殖激活受体γ2（PPARG2）的快速转录激活。我们发现PPARG2转录受储存式钙内流（SOCE）下游转录因子调节，证实敲除STIM2β导致[Ca]增加促进脂肪生成过程中PPARG2转录。此外，STIM2β基因敲除小鼠表现出肥大性脂肪组织发育。我们的数据表明，STIM2β介导的[Ca]在有丝分裂克隆扩增和PPARG2基因激活的调节中起关键作用，并提供了证据表明MCE不是脂肪生成过程中终末分化的先决条件。
