Endosomal and lysosomal pH-regulating mechanisms

Endosomal and lysosomal pH-regulating mechanisms encompass the suite of proteins and processes responsible for maintaining the acidic environment within the endocytic and autophagic pathways. The primary driver of this acidification is the vacuolar-type H+-ATPase (V-ATPase), a multi-subunit ATP-dependent proton pump that translocates protons from the cytosol into the organelle lumen (Forgac, 2007). This acidic gradient is critical for the activation of lysosomal hydrolases, the sorting of endosomal cargo, and the regulation of metabolic signaling through the mTORC1 pathway (Mindell, 2012). Other components, such as chloride channels (e.g., ClC-7) and sodium-hydrogen exchangers (e.g., NHE6/9), act as shunts or exchangers to fine-tune the luminal pH and membrane potential. Dysregulation of these pH-regulating mechanisms is a hallmark of several major diseases. In cancer, V-ATPase is often upregulated or relocated to the plasma membrane, contributing to an acidic tumor microenvironment that facilitates metastasis and immune evasion (Spugnini et al., 2015). Conversely, in neurodegenerative disorders like Alzheimer's and Parkinson's diseases, a failure to maintain lysosomal acidity leads to defective autophagy and the accumulation of undigested protein aggregates (Colacurcio & Nixon, 2016). Furthermore, many viruses, including influenza and coronaviruses, exploit the low pH of endosomes to trigger conformational changes in their envelope proteins, enabling membrane fusion and viral entry into the host cell (Hu et al., 2020). Consequently, targeting these mechanisms with V-ATPase inhibitors or lysosomotropic agents like chloroquine represents a therapeutic strategy for treating infections, cancer, and metabolic disorders, although systemic toxicity remains a significant challenge.

Other names

Endosomal acidificationLysosomal acidificationVacuolar acidificationV-ATPase-mediated pH regulationOrganelle pH regulation

Inhibition of the vacuolar-type H+-ATPase (V-ATPase) proton pump or neutralization of luminal pH via lysosomotropic accumulation of weak bases.