Lysosomal acidification through membrane contacts with mitochondria.

Mitochondria act as a previously unrecognized proton source that drives lysosomal acidification, as uncovered by two independent studies.

• Why it matters: Lysosomal acidification is central to lysosome function, yet the upstream proton sources were not fully understood, limiting mechanistic insight and disease relevance.
• What they did: The Viewpoint summarizes two independent studies, examining associated proteins and functional mechanisms linking mitochondria to lysosomal acidification.
• The result: The findings suggest a new mechanistic framework for how lysosomes become acidic, enabling further exploration of disease relevance tied to this pathway.