Effect of Dynamic and Static Load on the Concentration of Myokines in the Blood Plasma and Content of Sodium and Potassium in Mouse Skeletal Muscles

G-Quadruplexes as Sensors of Intracellular Na+/K+ Ratio: Potential Role in Regulation of Transcription and Translation

Data on the structure of G-quadruplexes, noncanonical nucleic acid forms, supporting an idea of their potential participation in regulation of gene expression in response to the change in intracellular Na+i/K+i ratio are considered in the review. Structural variety of G-quadruplexes, role of monovalent cations in formation of this structure, and thermodynamic stability of G-quadruplexes are described. Data on the methods of their identification in the cells and biological functions of these structures are presented. Analysis of information about specific interactions of G-quadruplexes with some proteins was conducted, and their potential participation in the development of some pathological conditions, in particular, cancer and neurodegenerative diseases, is considered. Special attention is given to the plausible role of G-quadruplexes as sensors of intracellular Na+i/K+i ratio, because alteration of this parameter affects folding of G-quadruplexes changing their stability and, thereby, organization of the regulatory elements of nucleic acids. The data presented in the conclusion section demonstrate significant change in the expression of some early response genes under certain physiological conditions of cells and tissues depending on the intracellular Na+i/K+i ratio.

Sodium Ions as Regulators of Transcription in Mammalian Cells

The maintenance of an uneven distribution of Na+ and K+ ions between the cytoplasm and extracellular medium is the basis for the functioning of any animal cell. Changes in the intracellular ratio of these cations occur in response to numerous stimuli and are important for the cell activity regulation. Numerous experimental data have shown that gene transcription in mammalian cells can be regulated by changes in the intracellular [Na+]_i/[K+]_i ratio. Here, we discuss possible mechanisms of such regulation in various cell types, with special attention to the [Ca2+]-independent signaling pathways that suggest the presence of an intracellular sensor of monovalent cations. As such sensor, we propose the secondary structures of nucleic acids called G-quadruplexes. They are widely represented in mammalian genomes and are often found in the promoters of genes encoding transcription factors.