Open AccessGPN does not release lysosomal Ca2+, but evokes ER Ca2+ release by increasing cytosolic pH independent of cathepsin C
Author(s) -
Peace Atakpa,
Laura M. van Marrewijk,
Michael Apta-Smith,
Sumita Chakraborty,
Colin W. Taylor
Publication year - 2019
Publication title -
journal of cell science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.384
H-Index - 278
eISSN - 1477-9137
pISSN - 0021-9533
DOI - 10.1242/jcs.223883
Subject(s) - endoplasmic reticulum , biology , cytosol , cathepsin d , ryanodine receptor , cathepsin , microbiology and biotechnology , lysosome , biochemistry , cleavage (geology) , cathepsin b , enzyme , paleontology , fracture (geology)
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 Ca 2+ concentration ([Ca 2+ ] 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 [Ca 2+ ] c require Ca 2+ within the endoplasmic reticulum (ER), but they are not mediated by ER Ca 2+ channels amplifying Ca 2+ release from lysosomes. GPN increases [Ca 2+ ] c by increasing pH cyt , which then directly stimulates Ca 2+ release from the ER. We conclude that physiologically relevant increases in pH cyt stimulate Ca 2+ release from the ER in a manner that is independent of IP 3 and ryanodine receptors, and that GPN does not selectively target lysosomes.