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

Cell Calcium. 1996 Feb;19(2):157-65. doi: 10.1016/s0143-4160(96)90084-6.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 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

Substances

  • Dipeptides
  • Enzyme Inhibitors
  • Terpenes
  • glycylphenylalanine 2-naphthylamide
  • Thapsigargin
  • Ammonia
  • Inositol 1,4,5-Trisphosphate
  • Adenosine Triphosphate
  • Calcium