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ω‐Conotoxin binding and effects on calcium channel function in human neuroblastoma and rat pheochromocytoma cell lines
Author(s) -
Sher E.,
Pandiella A.,
Clementi F.
Publication year - 1988
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(88)81258-4
Subject(s) - nitrendipine , verapamil , depolarization , calcium channel , chemistry , biophysics , neuroblastoma , calcium , endocrinology , medicine , cell culture , pharmacology , biology , genetics
Binding of ω‐conotoxin, a peptide toxin specific for some subtypes of voltage‐operated calcium channels (VOCCs), was investigated in IMR32 neuroblastoma and PC12 pheochromocytoma cell lines. In both cell types, binding was specific, saturable and of high affinity. Association was rapid and dissociation almost non‐existent. Dihydropyridines and verapamil failed to affect toxin binding, while high concentrations of CaCl 2 completely antagonized it. Depolarization with high K + induced a [Ca 2+ ] i rise (revealed by the fura‐2 fluorimetric technique) that consisted of an initial (0.5–1 min) peak followed by a prolonged (several minutes) plateau phase. ω‐Conotoxin blocked mainly the first phase, while the dihydropyridine Ca 2+ channel blocker, nitrendipine, primarily affected the plateau. This result suggests that in the two cell lines investigated, ω‐conotoxin acts mainly on a subgroup of VOCCs that is resistant to dihydropyridines.