Essential role of Ca2+ -dependent phospholipase A2 in estradiol-induced lysosome activation.
The mechanism of lysosome activation by 17beta-estradiol has been studied in mussel blood cells. Cell treatment with estradiol induced a sustained increase of cytosolic free Ca2+ that was completely prevented by preincubating the cells with the Ca2+ chelator BAPTA-AM. Estradiol treatment was also followed by destabilization of the lysosomal membranes, as detected in terms of the lysosomes' increased permeability to neutral red. The effect of estradiol on lysosomes was almost completely prevented by preincubation with the inhibitor of cytosolic Ca2+ -dependent PLA2 (cPLA2), arachidonyl trifluoromethyl ketone (AACOCF3), and was significantly reduced by preincubation with BAPTA-AM. In contrast, it was virtually unaffected by preincubation with the inhibitor of Ca2+ -independent PLA2, (E)-6-(bromomethylene)tetrahydro-3-(1-naphtalenyl)-2H-pyran-2-one (BEL). The Ca2+ ionophore A-23187 yielded similar effects on [Ca2+](i) and lysosomes. Exposure to estradiol also resulted in cPLA2 translocation from cytosol to membranes, lysosome enlargement, and increased protein degradation. These results suggest that the destabilization of lysosomal membranes following cell exposure to estradiol occurs mainly through a Ca2+ -dependent mechanism involving activation of Ca2+ -dependent PLA2. This mechanism promotes lysosome fusion and catabolic activities and may mediate short-term estradiol effects.
Burlando
Bruno
B
Dipartimento di Scienze e Tecnologie Avanzate, Università del Piemonte Orientale Amedeo Avogadro, 15100 Alessandria, Biologia e Genetica, Università di Genova, 16132 Genoa, Italy. burlando@unipmn.it
Marchi
Barbara
B
Panfoli
Isabella
I
Viarengo
Aldo
A
D000199:Actins / Q000378:metabolism; D000818:Animals; D001095:Arachidonic Acids / Q000494:pharmacology; D049872:Bivalvia; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects*; D002250:Carbon Radioisotopes; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology*; D008247:Lysosomes / Q000201:enzymology*; D018613:Microscopy, Confocal; D009281:Naphthalenes / Q000494:pharmacology; D010590:Phalloidine / Q000031:analogs & derivatives*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D011753:Pyrones / Q000494:pharmacology; D014633:Valine / Q000493:pharmacokinetics
D000199:Actins; D001095:Arachidonic Acids; D002250:Carbon Radioisotopes; D004791:Enzyme Inhibitors; D009281:Naphthalenes; D010726:Phosphodiesterase Inhibitors; D011753:Pyrones; C037191:fluorescein isothiocyanate-phalloidin; C081565:arachidonyltrifluoromethane; D010590:Phalloidine; D004958:Estradiol; C068314:6-(bromomethylene)tetrahydro-3-(1-naphthaleneyl)-2H-pyran-2-one; D010741:Phospholipases A; D054467:Phospholipases A2; D014633:Valine; D002118:Calcium