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4‐aminopyridine causes apoptosis and blocks an outward rectifier K + channel in malignant astrocytoma cell lines
Author(s) -
Chin Lawrence S.,
Park Charles C.,
Zitnay Kevin M.,
Sinha Manoj,
DiPatri Arthur J.,
Perillán Pablo,
Simard J. Marc
Publication year - 1997
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/(sici)1097-4547(19970415)48:2<122::aid-jnr4>3.0.co;2-e
Subject(s) - charybdotoxin , 4 aminopyridine , tetraethylammonium , chemistry , potassium channel , channel blocker , patch clamp , cell growth , apoptosis , potassium channel blocker , cell culture , biophysics , ion channel , microbiology and biotechnology , biology , biochemistry , potassium , receptor , genetics , organic chemistry , calcium
Among the ion channels and pumps activated by growth factor stimulation, K + channels have been implicated in the growth and proliferation of several cancer cell lines. The role of these channels in central nervous system tumors, however, has not been described. This study used the malignant astrocytoma cell lines U87 and A172. 4‐Aminopyridine (4‐AP) inhibition of proliferation was dose dependent, and assessment using a TUNEL in situ assay revealed that apoptosis occurred in U87 cells with wild‐type p53 but not in A172 cells with mutant p53 (24‐hr incubation with 4 mM 4‐AP). In patch clamp experiments, we identified two types of K + currents in both cell lines, a charybdotoxin‐sensitive Ca 2+ ‐activated K + channel and a 4‐AP‐sensitive outward rectifier K + current. The outward rectifier current was blocked by 4‐AP in a dose‐dependent manner, with half‐maximal block occurring at 3.9 mM. The blocking effect of 4 mM 4‐AP was noticeable at potentials as low as −65 mV and was statistically significant at −60 mV and above, suggesting that 4‐AP‐sensitive current is active at physiological potentials. By contrast, charybdotoxin (1 μM) and tetraethylammonium · Cl (2 mM) blocked the Ca 2+ ‐activated K + channel in both cell lines but had no appreciable effect on cell growth. Our findings reveal that 4‐AP inhibits proliferation and the outward rectifier K + channel in both U87 and A172 cells. More studies are needed, however, to describe the mechanism by which K + channels influence proliferation and induce apoptosis. J. Neurosci. Res. 48:122–127, 1997. © 1997 Wiley‐Liss, Inc.