Mitogen-activated protein kinases as key players in osmotic stress signaling

•Osmotic stress causes cell swelling or shrinkage and has deleterious effects on cellular activities.•Cells can adapt to anisosmotic conditions by regulating the intracellular content of inorganic ions and organic osmolytes.•Mitogen-activated protein kinases (MAPKs) play central roles in osmotic stress signaling.•Apoptosis signal-regulating kinase 3 exhibits a unique responsiveness to osmotic stress and has potential importance in osmoregulation.•Studies regarding the upstream factors of MAPK pathways will contribute to reveal the mechanism by which mammalian cells sense osmotic stress.