The lysosomal compartment as intracellular calcium store in MDCK cells: a possible involvement in InsP3-mediated Ca2+ release

To test for a possible role of lysosomes in intracellular Ca2+ homeostasis, the effects of glycyl-L-phenylalanine-beta-naphthylamide (GPN), known to permeabilize these organelles by osmotic swelling, were studied in single MDCK cells. Fluorescence of acridine orange, rhodol green dextran, lysotracke...

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Bibliographic Details
Published in:Cell calcium (Edinburgh) 1996-02, Vol.19 (2), p.157-165
Main Authors: Haller, T, Dietl, P, Deetjen, P, Völkl, H
Format: Article
Language:English
Subjects:
Adenosine Triphosphate - pharmacology
Ammonia - pharmacology
Animals
Calcium - metabolism
Cell Compartmentation - drug effects
Cell Compartmentation - physiology
Cell Line
Cell Membrane Permeability - drug effects
Dipeptides - pharmacology
Dogs
Enzyme Inhibitors - pharmacology
Inositol 1,4,5-Trisphosphate - metabolism
Kidney - cytology
Lysosomes - drug effects
Lysosomes - metabolism
Terpenes - pharmacology
Thapsigargin
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Summary:To test for a possible role of lysosomes in intracellular Ca2+ homeostasis, the effects of glycyl-L-phenylalanine-beta-naphthylamide (GPN), known to permeabilize these organelles by osmotic swelling, were studied in single MDCK cells. Fluorescence of acridine orange, rhodol green dextran, lysotracker green and FITC-dextran indicated that GPN (0.2 mmol/l) elicited a reversible permeabilization of lysosomes. Cytosolic Ca2+ ([Ca2+]i) as determined by Fura-2 fluorescence increased from 60 +/- 11 to 534 +/- 66 nmol/l (n = 41) in the presence of GPN. Whereas only a single intracellular Ca2+ release could be induced by GPN in a Ca(2+)-free perfusate, repetitive release could be evoked in Ca2+ containing solutions suggesting reuptake of Ca2+ into lysosomal stores. GPN-induced Ca2+ release was blunted after pretreatment with thapsigargin (TG), an inhibitor of Ca(2+)-ATPase, or repeated applications of ATP inducing Ca2+ release from inositol trisphosphate (InsP3) sensitive Ca2+ stores. The effect of ATP on Ca2+ release was, however, not abolished by preceding GPN treatment. GPN-induced Ca2+ release from lysosomes was independent of InsP3 formation or Ca(2+)-induced Ca2+ release, since it was unaffected by the phospholipase C inhibitor U-73, 122 or by caffeine and ruthenium red. These results suggest that Ca2+ largely accumulates in lysosomal vesicles. Moreover, these organelles seem to be part or functionally coupled with InsP3-sensitive Ca2+ stores.
ISSN:0143-4160
DOI:10.1016/s0143-4160(96)90084-6