Научно-исследовательский институт физико-химической биологии им. А.Н. Белозерского
Stimulus-dependent elevation of intracellular Ca<sup>2+</sup> affects gene expression via well-documented calmodulin-mediated signaling pathways. Recently, we found that the addition of extra- and intracellular Ca<sup>2+</sup> chelators increased, rather than decreased, the number of genes expressed, and that this is affected by the elevation of [Na<sup>+</sup>]<sub>i</sub>/[K<sup>+</sup>]<sub>i</sub>-ratio. This assumes the existence of a novel Na<sup>+</sup><sub>i</sub>/K<sup>+</sup><sub>i</sub>-mediated Ca<sup>2+</sup><sub>i</sub>-independent mechanism of excitation-transcription coupling. To identify upstream Na<sup>+</sup><sub>i</sub>/K<sup>+</sup><sub>i</sub>-sensitive genes, we examined the kinetics of transcriptomic changes in human umbilical vein endothelial cells (HUVEC) subjected to Na,K-ATPase inhibition by ouabain or K<sup>+</sup>-free medium. According to our data, microRNAs, transcription factors, and proteins involved in immune response and inflammation might be considered as key components of Na<sup>+</sup><sub>i</sub>/K<sup>+</sup><sub>i</sub>-mediated excitation-transcription coupling. Special attention was focused on the <i>FOS</i> gene and the possible mechanism of transcription regulation via G-quadruplexes, non-canonical secondary structures of nucleic acids, whose stability depends on [Na<sup>+</sup>]<sub>i</sub>/[K<sup>+</sup>]<sub>i</sub>-ratio. Verification of the [Na<sup>+</sup>]<sub>i</sub>/[K<sup>+</sup>]<sub>i</sub>-sensitive transcription regulation mechanism should be continued in forthcoming studies.