Presenilin 1 Maintains Lysosomal Ca²⁺ Homeostasis via TRPML1 by Regulating vATPase-Mediated Lysosome Acidification

Highlights

• PS1 is essential for V0a1 subunit glycosylation, stability, and vATPase assembly

• PS1 deficiency depletes vATPase, impairing lysosomal acidification and proteolysis

• Defective lysosome acidification in PS1KO cells causes lysosomal Ca²⁺ efflux

• TRPML1 mediates lysosomal Ca²⁺ efflux and cytosolic Ca²⁺ elevation in PS1KO cells

Summary

Presenilin 1 (PS1) deletion or Alzheimer’s disease (AD)-linked mutations disrupt lysosomal acidification and proteolysis, which inhibits autophagy. Here, we establish that this phenotype stems from impaired glycosylation and instability of vATPase V0a1 subunit, causing deficient lysosomal vATPase assembly and function. We further demonstrate that elevated lysosomal pH in Presenilin 1 knockout (PS1KO) cells induces abnormal Ca²⁺ efflux from lysosomes mediated by TRPML1 and elevates cytosolic Ca²⁺. In WT cells, blocking vATPase activity or knockdown of either PS1 or the V0a1 subunit of vATPase reproduces all of these abnormalities. Normalizing lysosomal pH in PS1KO cells using acidic nanoparticles restores normal lysosomal proteolysis, autophagy, and Ca²⁺ homeostasis, but correcting lysosomal Ca²⁺ deficits alone neither re-acidifies lysosomes nor reverses proteolytic and autophagic deficits. Our results indicate that vATPase deficiency in PS1 loss-of-function states causes lysosomal/autophagy deficits and contributes to abnormal cellular Ca²⁺ homeostasis, thus linking two AD-related pathogenic processes through a common molecular mechanism.