PIEZO1 encodes a mechanoreceptor, a cation channel activated by mechanical stimuli. Gain-of-function (GoF) variants in PIEZO1 cause dehydrated hereditary stomatocytosis (DHS), or xerocytosis, a pleiotropic syndrome characterized by anemia and iron overload. DHS patients develop hepatic iron overload independent of the degree of anemia and transfusion regimen. PIEZO1-GoF variants suppress hepcidin expression in both hepatic cellular model and constitutive/macrophage-specific Piezo1-GoF mice model. Therefore, PIEZO1-GoF variants regulate hepcidin expression by a crosstalk between hepatocytes (HCs) and macrophages with a still unknown mechanism. Transcriptomic and proteomics analysis in the human hepatic Hep3B cells engineered for the PIEZO1-R2456H variant (PIEZO1-KI) revealed alterations in the actin cytoskeleton regulation, MAPK cascade, and RAS signaling. These changes mainly occur through a novel key regulator, RRAS, whose protein and mRNA levels are regulated by PIEZO1 activation and inhibition. This regulation was further confirmed in C57BL/6 mouse primary HCs treated with Yoda-1 and/or GsMTx-4. Indeed, PIEZO1-KI cells exhibited hyper-activated RAS-GTPase activity that is rescued by PIEZO1 inhibition, restoring expression of the hepcidin gene HAMP. A negative correlation between RAS signaling and HAMP regulation was confirmed by inhibiting RAS-GTPase and MEK1-2 activity. Conversely, rescued HAMP gene expression requires downregulation of RRAS, confirming negative feedback between RAS-MAPK and BMP/SMADs pathways in HAMP regulation. We demonstrated that PIEZO1-GoF variants influence the actin cytoskeleton organization by activating the hepatic RAS signaling system. Understanding the role of RAS signaling in regulating iron metabolism could pave the way for new therapeutic strategies in DHS and other conditions characterized by iron overload.

中文翻译：

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RAS 信号通路在脱水遗传性口红细胞增多症中调节 PIEZO1 介导的肝铁过载中至关重要


PIEZO1 编码机械感受器，即由机械刺激激活的阳离子通道。PIEZO1 中的功能获得性 （GoF） 变体会导致脱水遗传性口红细胞增多症 （DHS） 或干红细胞增多症，这是一种以贫血和铁过载为特征的多效性综合征。DHS 患者出现肝铁超负荷，与贫血程度和输血方案无关。PIEZO1-GoF 变体在肝细胞模型和组成型/巨噬细胞特异性 Piezo1-GoF 小鼠模型中抑制铁调素表达。因此，PIEZO1-GoF 变体通过肝细胞 （HCs） 和巨噬细胞之间的串扰来调节铁调素表达，但机制尚不清楚。针对 PIEZO1-R2456H 变体 （PIEZO1-KI） 工程的人肝 Hep3B 细胞的转录组学和蛋白质组学分析揭示了肌动蛋白细胞骨架调节、MAPK 级联反应和 RAS 信号传导的改变。这些变化主要通过一种新的关键调节因子 RRAS 发生，其蛋白质和 mRNA 水平受 PIEZO1 激活和抑制的调节。这种调节在用 Yoda-1 和/或 GsMTx-4 处理的 C57BL/6 小鼠原代 HCs 中得到进一步证实。事实上，PIEZO1-KI 细胞表现出高度激活的 RAS-GTP 酶活性，该活性被 PIEZO1 抑制挽救，恢复了铁调素基因 HAMP 的表达。通过抑制 RAS-GTP 酶和 MEK1-2 活性证实 RAS 信号转导与 HAMP 调节呈负相关。相反，拯救的 HAMP 基因表达需要下调 RRAS，从而证实 HAMP 调控中 RAS-MAPK 和 BMP/SMADs 通路之间的负反馈。我们证明 PIEZO1-GoF 变体通过激活肝脏 RAS 信号系统来影响肌动蛋白细胞骨架组织。 了解 RAS 信号转导在调节铁代谢中的作用可能为 DHS 和其他以铁过载为特征的疾病的新治疗策略铺平道路。