Intracellular Potassium in Cell Growth and Proliferation of Human Mesenchymal Stem Cells and Blood Lymphocytes

Many data show that K+ ions are essential for cell proliferation. In this brief review, we summarize our own studies and literature data that characterize the relationship between modulations of intracellular K+ content and the intensity of cell proliferation. Using flame emission assay we compared the transport of monovalent cations in transformed cells and in human mesenchymal stem cells in growing cultures, as well as during stress-induced cell cycle arrest and transition from monolayer (2D) to three-dimensional (3D) spheroids. A decrease in the intracellular content of K+ (evaluated as the ratio of the content of K+ in cells to the mass of cellular protein) associated with the accumulation of G1 cells in the population and accompanied by a stop in proliferation was revealed. The relationship between intracellular K+ and initiation of cell proliferation was further analyzed in human blood lymphocytes (HBL) as a model for the transition of cells from quiescence to proliferation. In HBL stimulated to proliferate, the content of K+ in cells increases during the transition G0/G1/S, accompanying the growth of small lymphocytes into blasts. Cellular water content, calculated from buoyant cell density, is higher in proliferating HBLs and in Jurkat leukemic T cells than in resting HBL. Available data suggest that intracellular K+ is important for successful cell proliferation as the main intracellular ion involved in the regulation of cell volume during the transition from quiescence to proliferation, and high K+ content and associated high water content in the cell are a characteristic feature of cell proliferation and transformation.