Allostatic conditions in human glioblastoma stem cells are maintained with the contribution of CLIC1 membrane protein functional expression

Allostasis is a cellular condition physiologically occurring during transient hyper-activated state of the cell. When stress is persistent, cells are unable to restore a basal homeostatic state and allostasis become chronic. Most of the cells are not able to cope with these prolonged conditions and die. Conversely, solid tumors reveal a persistent stress state strengthen by chronic overexpression of several elements and hyper-activation of intracellular pathways. In glioblastoma stem cells (GSCs), the most evident allostatic outcome is a high rate of cell division. Several proteins present in the allostatic GSC plasma membrane are deregulated in either expression or function. Altering any of these proteins disrupts the allostatic equilibrium, causing drastic functional changes and, in some cases, cell death. Several of these proteins, potentially used as valuable pharmacological targets, are also crucial for the physiological activity of the cells. Consequently, modifying their functions would affect the survival of both cancer and healthy cell population. On the contrary, chloride intracellular protein 1 (CLIC1) is active as a membrane charge carrier only during periods of chronic stress, while during homeostatic conditions it is essentially irrelevant. Inhibition of NADPH oxidase or the NHE1 proton pump, both overexpressed in CSCs, causes death of both GSCs and normal mesenchymal stem cells. Conversely, impairing CLIC1 activity delays GSC cycle progression but leaves healthy cells functions unaltered. Our work suggests that CLIC1 protein and its associated chloride permeability are a crucial element involved in the stabilization of GB CSC allostasis.