Martínez-Rendón Jacqueline, Hinojosa Lorena, Xoconostle-Cázares Beatriz, Ramírez-Pool José Abrahán, Castillo Aída, Cereijido Marcelino, Ponce Arturo
Department of Physiology, Biophysics and Neurosciences, Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de Mexico 07360, Mexico.
Molecular Medicine Laboratory, Unidad Académica de Medicina Humana y C.S., Campus UAZ Siglo XXI-L1, Universidad Autónoma de Zacatecas, Zacatecas 98160, Mexico.
Curr Issues Mol Biol. 2023 Sep 14;45(9):7538-7556. doi: 10.3390/cimb45090475.
Ouabain, an organic compound with the ability to strengthen the contraction of the heart muscle, was originally derived from plants. It has been observed that certain mammalian species, including humans, naturally produce ouabain, leading to its classification as a new type of hormone. When ouabain binds to Na/K-ATPase, it elicits various physiological effects, although these effects are not well characterized. Previous studies have demonstrated that ouabain, within the concentration range found naturally in the body (10 nmol/L), affects the polarity of epithelial cells and their intercellular contacts, such as tight junctions, adherens junctions, and gap junctional communication. This is achieved by activating signaling pathways involving cSrc and Erk1/2. To further investigate the effects of ouabain within the hormonally relevant concentration range (10 nmol/L), mRNA-seq, a high-throughput sequencing technique, was employed to identify differentially expressed transcripts. The discovery that the transcript encoding MYO9A was among the genes affected prompted an exploration of whether RhoA and its downstream effector ROCK were involved in the signaling pathways through which ouabain influences cell-to-cell contacts in epithelial cells. Supporting this hypothesis, this study reveals the following: (1) Ouabain increases the activation of RhoA. (2) Treatment with inhibitors of RhoA activation (Y27) and ROCK (C3) eliminates the enhancing effect of ouabain on the tight junction seal and intercellular communication via gap junctions. These findings further support the notion that ouabain acts as a hormone to emphasize the epithelial phenotype.
哇巴因是一种能够增强心肌收缩能力的有机化合物，最初从植物中提取。据观察，包括人类在内的某些哺乳动物物种会自然产生哇巴因，因此它被归类为一种新型激素。当哇巴因与钠钾-ATP酶结合时，会引发各种生理效应，尽管这些效应尚未得到充分表征。先前的研究表明，在体内自然发现的浓度范围内（10 nmol/L），哇巴因会影响上皮细胞的极性及其细胞间连接，如紧密连接、黏着连接和缝隙连接通讯。这是通过激活涉及cSrc和Erk1/2的信号通路来实现的。为了进一步研究在激素相关浓度范围（10 nmol/L）内哇巴因的作用，采用了mRNA测序这一高通量测序技术来鉴定差异表达的转录本。编码MYO9A的转录本是受影响的基因之一，这一发现促使人们探索RhoA及其下游效应物ROCK是否参与了哇巴因影响上皮细胞间接触的信号通路。本研究支持这一假设，揭示了以下内容：（1）哇巴因增加RhoA的激活。（2）用RhoA激活抑制剂（Y27）和ROCK抑制剂（C3）处理可消除哇巴因对紧密连接密封和通过缝隙连接的细胞间通讯的增强作用。这些发现进一步支持了哇巴因作为一种激素来强化上皮表型的观点。
