GPN does not release lysosomal Ca²⁺ but evokes Ca²⁺ release from the ER by increasing the cytosolic pH independently of cathepsin C.

ABSTRACT: The dipeptide glycyl-l-phenylalanine 2-naphthylamide (GPN) is widely used to perturb lysosomes because its cleavage by the lysosomal enzyme cathepsin C is proposed to rupture lysosomal membranes. We show that GPN evokes a sustained increase in lysosomal pH (pH_ly), and transient increases in cytosolic pH (pH_cyt) and Ca²⁺ concentration ([Ca²⁺]_c). None of these effects require cathepsin C, nor are they accompanied by rupture of lysosomes, but they are mimicked by structurally unrelated weak bases. GPN-evoked increases in [Ca²⁺]_c require Ca²⁺ within the endoplasmic reticulum (ER), but they are not mediated by ER Ca²⁺ channels amplifying Ca²⁺ release from lysosomes. GPN increases [Ca²⁺]_c by increasing pH_cyt, which then directly stimulates Ca²⁺ release from the ER. We conclude that physiologically relevant increases in pH_cyt stimulate Ca²⁺ release from the ER in a manner that is independent of IP₃ and ryanodine receptors, and that GPN does not selectively target lysosomes.

SUBMITTER: Atakpa P 

PROVIDER: S-EPMC6382017 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature