Inactive ryanodine receptors sustain lysosomal availability for autophagy by promoting ER-lysosomal contact site formation.

Abstract

Lysosomal and endoplasmic reticulum (ER) Ca²⁺ release mutually influence each other's functions. Recent work revealed that ER-located ryanodine receptor(s) (RyR(s)) Ca²⁺ release channels suppress autophagosome turnover by the lysosomes. In familial Alzheimer's disease, inhibiting RyR hyperactivity restored autophagic flux by normalizing lysosomal vacuolar H⁺-ATPase (vATPase) levels. However, the mechanisms by which RyRs control lysosomal function and how this involves the vATPase remain unknown. Here, we show that RyRs interact with the ATP6v0a1 subunit of the vATPase, contributing to ER-lysosomal contact site formation. This interaction suppresses RyR-mediated Ca²⁺ release, leading to reduced lysosomal exocytosis. Pharmacological inhibition of RyR activity mimics these effects on lysosomal exocytosis. Retaining lysosomes inside cells via RyR inhibition increases ER-lysosomal contact site formation, rendering lysosomes more available for autophagic flux. In summary, these findings establish RyR/ATP6v0a1 complexes as ER-lysosomal tethers that dynamically and Ca²⁺ dependently regulate the intracellular availability of lysosomes to participate in autophagic flux.