Nguyen Lap P, Svensmark Julius, Jiang Xin, Jordan Alexander, Brakebusch Cord
Biotech Research and Innovation Center (BRIC), University of Copenhagen, Ole Maaløes Vej 5, 2200 Copenhagen, Denmark.
Cells. 2025 Mar 10;14(6):404. doi: 10.3390/cells14060404.
RhoA is a major regulator of the actin cytoskeleton. Its function in the nucleus, however, is unclear. Fusing wildtype, fast cycling, constitutively active, and dominant negative forms of RhoA with tags promoting nuclear or cytoplasmic location and allowing specific detection, we established a platform to distinguish the functions of nuclear and cytoplasmic RhoA. Our data show that nuclear but not cytoplasmic activation of RhoA regulates DNA amount and nuclear size. This is mediated by sequential nuclear activation of the RhoA effector ROCK and Erk, a major cell cycle regulating kinase. The inhibition of ROCK or Erk activation in untransfected cells reduced DNA amounts to a similar extent, suggesting that endogenous activation levels of nuclear RhoA-ROCK-Erk signaling are sufficient for regulation. We reveal, furthermore, that GDP-bound, but not activated RhoA, translocates to the nucleus, indicating relatively separated cytoplasmic and nuclear RhoA signaling. Moreover, even the massive nuclear activation of RhoA does not cause an obvious increase in nuclear F-actin, indicating that RhoA activation is not critical for nuclear F-actin formation.
RhoA是肌动蛋白细胞骨架的主要调节因子。然而，其在细胞核中的功能尚不清楚。我们将野生型、快速循环型、组成型激活型和显性负性形式的RhoA与促进核定位或胞质定位并允许特异性检测的标签融合，建立了一个区分核RhoA和胞质RhoA功能的平台。我们的数据表明，RhoA的核激活而非胞质激活调节DNA含量和核大小。这是由RhoA效应器ROCK和Erk（一种主要的细胞周期调节激酶）的顺序核激活介导的。在未转染细胞中抑制ROCK或Erk激活会使DNA含量降低到相似程度，这表明核RhoA-ROCK-Erk信号的内源性激活水平足以进行调节。此外，我们发现结合GDP的RhoA（而非激活的RhoA）易位至细胞核，这表明胞质和核RhoA信号相对分离。此外，即使RhoA大量核激活也不会导致核F-肌动蛋白明显增加，这表明RhoA激活对核F-肌动蛋白形成并不关键。
