Loss Of Membrane Cholesterol Influences Lysosomal Permeability To Potassium Ions And Protons

Cholesterol is an essential component of lysosomal membranes. In this study, we investigated effects of membrane cholesterol on the lysosomal permeability to K+ and H+, and the organelle stability.Through measurements of lysosomalβ-hexosaminidase free activity, membrane potential, membrane fluidity, intra-lysosomal pH, and lysosomal proton leakage, we established that methyl-β-cyclodextrin (MβCD)-produced loss of membrane cholesterol could increase lysosomal permeability to both potassium ions and protons, and fluidize lysosomal membranes.As a result, potassium ions entered lysosomes through K+/H+ exchange, which produced osmotic imbalance across the membranes and osmotically destabilized the lysosomes. In addition, treatment of lysosomes with MβCD caused lysosomal proton leakage and raised intra-lysosomal pH.The results indicate that membrane cholesterol plays important roles in the maintenance of lysosomal limited permeability to K+ and H+. Loss of this membrane sterol is critical for the organelle acidification and stability.