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Appearance of Depolarization‐ and Maitotoxin‐Induced [Ca 2+ ] i Elevation in Single LAN‐1 Human Neuroblastoma Cells on Exposure to Retinoic Acid
Author(s) -
Fatatis Alessandro,
Bassi Antonella,
Iannotti Elodia,
Caso Nino,
Mita Gustavo D.,
Di Renzo Gianfranco,
Annunziato Lucio
Publication year - 1994
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1994.63051900.x
Subject(s) - depolarization , phorbol , retinoic acid , chemistry , activator (genetics) , fura 2 , membrane potential , cell culture , calcium , voltage dependent calcium channel , biophysics , microbiology and biotechnology , medicine , endocrinology , biology , protein kinase c , biochemistry , receptor , kinase , cytosol , genetics , enzyme
LAN‐1 is a human neuroblastoma cell line that, in the undifferentiated state, does not respond to membrane depolarization with an elevation of [Ca 2+ ] i , monitored by fura‐2 single‐cell microfluorimetry. The exposure of LAN‐1 cells to the differentiating agent retinoic acid induced the appearance of [Ca 2+ ] i elevation elicited by 55 m M K + . Maitotoxin, a putative activator of voltage‐sensitive Ca 2+ channels, did not evoke an elevation of [Ca 2+ ] i in undifferentiated LAN‐1 cells, but produced a marked and sustained increase in [Ca 2+ ] i when superfused in retinoic acid‐treated cells. Both high K + ‐ and maitotoxin‐induced [Ca 2+ ] i elevation in retinoic acid‐differentiated LAN‐1 cells was reversed by the lanthanide Gd 3+ , an inorganic Ca 2+ ‐entry blocker, and by the snail toxin ω‐conotoxin GVIA, which interacts with the N sub‐type of voltage‐sensitive Ca 2+ channels. In contrast, both Bay K 8644 and nimodipine, dihydropyridines that selectively activate or block, respectively, the L‐channel sub‐type, were completely ineffective. The tumor promoter phorbol 12‐myristate 13‐acetate (100 n M ), a protein kinase C activator, inhibited the elevation of [Ca 2+ ] i due to Ca 2+ influx elicited by membrane depolarization. K + ‐induced [Ca 2+ ] i elevation appeared 24 h after the addition of retinoic acid and reached the highest magnitude after 72 h. Furthermore, 8 days after the removal of the differentiating agent from the culture medium, the high K + ‐induced increase of [Ca 2+ ] i was still present. In conclusion, the results of the present study demonstrated that retinoic acid‐induced differentiation of LAN‐1 cells, which lack a high K + ‐evoked [Ca 2+ ] i increase in the undifferentiated state, induces the functional expression of an ω‐conotoxin GVIA‐sensitive, dihydropyridine‐insensitive N‐type voltage‐sensitive Ca 2+ channel that can be activated by maitotoxin and negatively modulated by protein kinase C.