Department of Biotechnology, College of Veterinary Medicine, Seoul National University, Seoul, Republic of Korea.
Stem Cells Dev. 2012 Jul 1;21(10):1736-48. doi: 10.1089/scd.2011.0388. Epub 2012 Jan 6.
Argonaute2 (Ago2) is a well-known factor that has intrinsic endonuclease activity and is a part of the fundamental gene regulatory machinery. Recently, we showed that nuclear Ago2 regulates voltage-gated potassium (Kv) channels and that Ago2/Kv1.3 has crucial functions in the self-renewal and cell de-aging processes in adipose tissue-derived stromal cells (ATSCs). In the nucleus, Ago2 bound to the promoter regions of calcium-activated potassium channel 3, potassium channel subfamily K member 1 (KCNK1), and voltage-gated potassium channel 2, and the expression of these genes was significantly upregulated at the level of transcription. We detected an active K+ channel that plays a critical role in Ago2-mediated ATSC self-renewal through the control of membrane potential during cell self-renewal and differentiation. Among the several regulatory subunits of voltage-dependent K+ (Kv) channels, Kv1.3 and Kv1.5 have been shown to impact tissue differentiation and cell growth in cultured ATSCs following their direct binding to the regulatory region of the Kv channel gene. In ATSCs, interference with Ago2 or K+ channel gene expression or treatment with tetraethylammonium significantly downregulated stemness gene expression, induced cell cycle arrest, and inhibited the ability of cells to transdifferentiate into neurons or β-cells via Oct4 knockdown. Blockage of the K+ channel significantly induced protein kinase C (PKC) α, β, and δ phosphorylation and negatively affected Ago2 and Oct4 expression. This K+ channel blockage also resulted in the upregulation of p53 and p21 expression and the inactivation of mitogen-activated protein kinase (MEK), extracellular signal-regulated kinase 1/2 (ERK 1/2), AKT, β-catenin, and STAT3. Our results suggest that the nuclear Ago2 regulation of the K+ channel or stemness-related gene expression plays a critical role in adult stem cell self-renewal and differentiation.
Argonaute2 (Ago2) 是一种具有内在内切酶活性的众所周知的因子，是基本基因调控机制的一部分。最近，我们表明核 Ago2 调节电压门控钾 (Kv) 通道，Ago2/Kv1.3 在脂肪组织来源的基质细胞 (ATSCs) 的自我更新和细胞衰老过程中具有至关重要的功能。在核内，Ago2 与钙激活钾通道 3、钾通道亚家族 K 成员 1 (KCNK1) 和电压门控钾通道 2 的启动子区域结合，这些基因的表达在转录水平上显著上调。我们检测到一种活性 K+通道，该通道通过在细胞自我更新和分化过程中控制膜电位，在 Ago2 介导的 ATSC 自我更新中发挥关键作用。在几种电压依赖性 K+ (Kv) 通道的调节亚基中，Kv1.3 和 Kv1.5 已被证明通过直接结合 Kv 通道基因的调节区，影响培养的 ATSC 中的组织分化和细胞生长。在 ATSCs 中，干扰 Ago2 或 K+通道基因表达或用四乙铵处理可显著下调干性基因表达，诱导细胞周期停滞，并抑制细胞通过 Oct4 敲低分化为神经元或 β 细胞的能力。阻断 K+通道可显著诱导蛋白激酶 C (PKC) α、β 和 δ 磷酸化，并负性影响 Ago2 和 Oct4 表达。这种 K+通道阻断还导致 p53 和 p21 表达上调以及丝裂原活化蛋白激酶 (MEK)、细胞外信号调节激酶 1/2 (ERK 1/2)、AKT、β-连环蛋白和 STAT3 的失活。我们的结果表明，核 Ago2 对 K+通道或干性相关基因表达的调节在成体干细胞自我更新和分化中起关键作用。
