Vacuolar-type H+-transporting ATPase (V-ATPase) (V-ATPase)

The endosomal/lysosomal acidification machinery, primarily driven by the Vacuolar-type H+-ATPase (V-ATPase), is a sophisticated multi-subunit enzyme complex that utilizes ATP hydrolysis to pump protons across membranes into the lumen of organelles (Forgac, M. Nat Rev Mol Cell Biol, 2007). This process is fundamental for maintaining the acidic pH (ranging from 4.5 to 6.5) required for the proper functioning of the endocytic and secretory pathways, including receptor recycling, protein sorting, and the activation of acid hydrolases for macromolecular degradation (Maxson, M. E., & Grinstein, S. Front Cell Dev Biol, 2014). In the context of human disease, this machinery plays a critical role in viral pathogenesis, as many enveloped viruses, such as influenza and coronaviruses, rely on endosomal acidification to trigger membrane fusion and genome release (Yao, J., et al. Cell Biosci, 2021). Furthermore, in cancer, V-ATPases are often upregulated and redistributed to the plasma membrane, where they contribute to an acidic extracellular microenvironment that facilitates tumor invasion, metastasis, and resistance to chemotherapy (Spugnini, E. P., et al. J Exp Clin Cancer Res, 2015). While small molecule inhibitors like bafilomycin and lysosomotropic agents like chloroquine have demonstrated therapeutic potential by disrupting these processes, the ubiquitous and essential nature of V-ATPase function in normal physiology presents significant challenges for achieving a favorable safety profile in clinical applications.

Other names

Endosomal/lysosomal acidification machineryVacuolar proton pumpH+-transporting ATPaseV-type ATPaseV-ATPase complex

The primary mechanism involves the inhibition of the V-ATPase enzyme complex, which prevents the ATP-driven translocation of protons from the cytosol into the lumen of endosomes and lysosomes (Forgac, M. Nat Rev Mol Cell Biol, 2007). This leads to an increase in organellar pH, thereby inhibiting the activity of acid-dependent hydrolases, preventing the pH-triggered conformational changes required for viral fusion, and disrupting the sorting and recycling of membrane receptors (Yao, J., et al. Cell Biosci, 2021). Additionally, lysosomotropic agents like chloroquine act as weak bases that accumulate in acidic compartments and directly buffer the pH, achieving a similar end-result of neutralizing the acidification machinery.