Loss of membrane cholesterol influences lysosomal permeability to potassium ions and protons

Abstract

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

SNAPIN is critical for lysosomal acidification and autophagosome maturation in macrophages

“…Additionally, lysosomal cholesterol may be important in preventing proton leak since treatment of lysosomes with methyl-b-cyclodextrin results in the loss of cholesterol and increased pH through increased exchange of H C and K C . 73 However, there has been no description of how SNAPIN might affect cholesterol content of any organelle. Recently it has been demonstrated the position of lysosomes within cells relative to the nucleus was a determinant of the lysosomal pH.…”

Is Endothelial Nitric Oxide Synthase a Moonlighting Protein Whose Day Job is Cholesterol Sulfate Synthesis? Implications for Cholesterol Transport, Diabetes and Cardiovascular Disease

“…We suggest for the first time here, based on reasonable theoretical inferences from empirical research findings, that the atheroma in cardiovascular disease enables a repair system to synthesize both Ch-S and HS, alleviating deficiencies and protecting from thrombosis. Lysosomes, evolving from the budding-off of membrane caveolae, as is known, depend upon adequate supplies of both cholesterol and sulfate to function [24][25][26][27][28][29].…”

Lysosomal membrane stability plays a major role in the cytotoxic activity of the anti-proliferative agent, di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT)

“…6B), these results were not as pronounced as the protective effect of U18666A against the deleterious activity of Dp44mT. This effect may also be due to the ability of MβCD to cause leakage of lysosomal protons through the lysosomal membrane that subsequently increases intra-lysosomal pH [35]. The retention of Dp44mT within lysosomes relies on its ionization characteristics and the acidic pH of lysosomes [5,6].…”

“…On the other hand, cholesterol plays a vital role in the maintenance of lysosomal membrane stability and reduces their membrane permeability [32]. Accordingly, reduced lysosomal membrane cholesterol levels are associated with increased permeability that leads to lysosomal membrane destabilization [32,35,36].…”

“…Several molecules have been reported to protect lysosomal membranes against permeabilization, including heat shock protein 70 (HSP70) and cholesterol [32,[35][36][37][38]. HSP70 may prevent LMP by scavenging lysosomal labile iron, protecting the lysosomal membrane from ROS-induced permeabilization [32,37,38].…”