LBPO.MCB02 · 分子与细胞生物学 · Late-Breaking
ERK 脉冲性丧失通过 Akt 介导的信号绝缘崩溃驱动结肠类器官转化
Loss of ERK pulsatility drives transformation of colonic organoids through collapse of Akt-mediated signaling insulation
作者与单位 Authors & Affiliations
摘要 Abstract
中文摘要
结肠干细胞（CSC）位于空间组织化的微环境中，暴露于生长因子信号的梯度中，包括由隐窝基底部间质细胞分泌的 EGF。尽管存在这一梯度，CSC 却表现出偏离经典配体-受体模型的悖论性信号模式，维持高 Akt 活性和受抑制的 ERK 激活。利用患者来源的结肠类器官（PDCO），我们发现分化细胞表现出脉冲性 ERK 活性，而干细胞区室则通过 Akt 导向的对 Raf-1 丝氨酸 259 位点的抑制性磷酸化而处于 ERK 沉默状态。因此，Raf-1S259 磷酸化使干细胞区室在丰富的 EGF 刺激下免受过度的 MAPK 激活。破坏这种 Raf-1S259 绝缘作用——无论是通过瞬时 ERK 激活还是 Akt 抑制——都会导致干细胞快速分化。相反，致癌突变如 KRAS G12V 或不可磷酸化的 Raf-1 S259A 消除了这种调控控制，产生组成型高 ERK 激活以及持续的 Akt 信号。这种双重激活驱动上皮模式化丧失、未分化细胞扩增以及类似早期结直肠癌的形态学异型增生。定量活细胞成像揭示了决定细胞命运的不同 ERK 动力学：健康分化的特征是非干细胞中的脉冲性 ERK 活性，而持续的 ERK 激活则标志着转化的 CSC。值得注意的是，瞬时重新引入 ERK 脉冲性或抑制 Akt 即使在致癌条件下也能挽救分化。总之，这些发现提示由 Akt-Raf-1 绝缘回路维持的 ERK 活性时间动力学对于维持上皮组织结构至关重要，并可被利用以逆转结直肠癌中的早期转化。
查看英文原文 English abstract
Colonic stem cells (CSCs) reside within spatially organized niches exposed to a gradient of growth factor signals, including EGF secreted by stromal cells at the crypt base. Despite this gradient, CSCs exhibit paradoxical signaling patterns that deviate from canonical ligand-receptor models, maintaining high Akt activity and suppressed ERK activation. Using patient-derived colonic organoids (PDCOs), we find that differentiated cells display pulsatile ERK activity, whereas stem cell compartments are ERK-silent through an Akt-directed inhibitory phosphorylation of Raf-1 at serine 259. Raf-1S259 phosphorylation thereby insulates the stem cell compartment from excessive MAPK activation despite abundant EGF stimulation. Disruption of this Raf‑1S259 insulation, either through transient ERK activation or Akt inhibition, leads to rapid stem cell differentiation. Conversely, oncogenic mutations such as KRAS G12V or non-phosphorylatable Raf‑1 S259A abolish this regulatory control, producing constitutively high ERK activation along with sustained Akt signaling. This dual activation drives loss of epithelial patterning, expansion of undifferentiated cells, and morphological dysplasia reminiscent of early colorectal cancer. Quantitative live-cell imaging reveals distinct ERK dynamics underlying cell fates: healthy differentiation is characterized by pulsatile ERK activity in non-stem cells, whereas sustained ERK activation marks transformed CSCs. Remarkably, transient reintroduction of ERK pulsatility or Akt suppression rescues differentiation even under oncogenic conditions. Together, these findings suggest that the temporal dynamics of ERK activity, maintained by an Akt-Raf-1 insulation circuit, are critical for preserving epithelial organization and could be leveraged to reverse early transformation in colorectal cancers.
利益披露 Disclosure
L. Riede, None..
A. Borowiec, None..
W. March-Steinman, None..
J. Chakrabarti, None..
S. Mallick, None.
C. Thorne,
ProxyBio Inc Employment, g., Board of Directors, non-salaried role), Stock, Other Business Ownership, Trademark, Other Intellectual Property.
Branch Therapeutics Inc Employment, g., Board of Directors, non-salaried role), Stock, Other Business Ownership, Trademark, Other Intellectual Property.
A. Paek, None.
K. Pond,
ProxyBio, Inc Employment, g., Board of Directors, non-salaried role), Stock, Other Securities, Other Business Ownership, Patent, Other Intellectual Property.