Author/Editor		Cocucci, Emanuele; Racchetti, Gabriella; Podini, Paola; Rupnik, Marjan; Meldolesi, Jacopo
Title		Enlargeosome, an exocytic vesicle resistant to nonionic detergents, undergoes endocytosis via a nonacidic route
Type		članek
Source		Mol Biol Cell
Vol. and No.		Letnik 15, št. 12
Publication year		2004
Volume		str. 5356-68
Language		eng
Abstract		Enlargeosomes, a new type of widely expressed cytoplasmic vesicles, undergo tetanus toxin-insensitive exocytosis in response to cytosolic Ca2+ concentration ([Ca2+];) rises. Cell biology of enlargeosomes is still largely unknown. By combining immunocytochemistry (marker desmoyokin-Ahnak, d/A) to capacitance electrophysiology in the enlargeosome-rich, neurosecretion-defective clone PC12-27, we show that 1) the two responses, cell surface enlargement and d/A surface appearance, occur with similar kinetics and in the same low micromolar [Ca2+]; range, no matter whether induced by photolysis of the caged Ca2+ compound o-nitrophenyl EGTA or by the Ca2+ ionophore ionomycin. Thus, enlargeosomes seem to account, at least in large part, for the exocytic processes triggered by the two stimulations. 2. The enlargeosome membranes are resistant to nonionic detergents but distinct from other resistant membranes, rich in caveolin, Thy1, and/or flotillinl. 3. Cell cholesterol depletion, which affects many membrane fusions, neither disrupts enlargeosomes nor affects their regulated exocytosis. 4. The postexocytic cell surface decline is [Ca2+]; dependent. 5. Exocytized d/A-rich membranes are endocytized and trafficked along an intracellular pathway by nonacidic organelles, distinct from classical endosomes and lysosomes. Our data define specific aspects of enlargeosomes and suggest their participation, in addition to cell differentiation and repair, for which evidence already exists, to other physiological and pathological processes.
Descriptors		EXOCYTOSIS IONOMYCIN ENDOSOMES ENDOCYTOSIS DETERGENTS RATS NEOPLASM PROTEINS MICROSCOPY, ELECTRON MEMBRANE PROTEINS KINETICS IONS INTRACELLULAR MEMBRANES HYDROGEN-ION CONCENTRATION CHOLESTEROL CELL LINE CALCIUM