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Gating of the expressed T‐type Ca v 3.1 calcium channels is modulated by Ca 2+
Author(s) -
Lacinová L.,
Kurejová M.,
Klugbauer N.,
Hofmann F.
Publication year - 2006
Publication title -
acta physiologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.591
H-Index - 116
eISSN - 1748-1716
pISSN - 1748-1708
DOI - 10.1111/j.1748-1716.2006.01539.x
Subject(s) - intracellular , extracellular , chemistry , egta , calcium , biophysics , time constant , gating , patch clamp , analytical chemistry (journal) , ion , voltage dependent calcium channel , membrane potential , reversal potential , biochemistry , chromatography , biology , receptor , organic chemistry , electrical engineering , engineering
Abstract Aim: We have investigated the influence of Ca 2+ ions on the basic biophysical properties of T‐type calcium channels. Methods: The Ca v 3.1 calcium channel was transiently expressed in HEK 293 cells. Current was measured using the whole cell patch clamp technique. Ca 2+ or Na + ions were used as charge carriers. The intracellular Ca 2+ was either decreased by the addition of 10 m m ethyleneglycoltetraacetic acid (EGTA) or increased by the addition of 200 μ m Ca 2+ into the non‐buffered intracellular solution. Various combinations of extra‐ and intracellular solutions yielded high, intermediate or low intracellular Ca 2+ levels. Results: The amplitude of the calcium current was independent of intracellular Ca 2+ concentrations. High levels of intracellular Ca 2+ accelerated significantly both the inactivation and the activation time constants of the current. The replacement of extracellular Ca 2+ by Na + as charge carrier did not affect the absolute value of the activation and inactivation time constants, but significantly enhanced the slope factor of the voltage dependence of the inactivation time constant. Slope factors of voltage dependencies of channel activation and inactivation were significantly enhanced. The recovery from inactivation was faster when Ca 2+ was a charge carrier. The number of available channels saturated for membrane voltages more negative than −100 mV for the Ca 2+ current, but did not reach steady state even at −150 mV for the Na + current. Conclusions: Ca 2+ ions facilitate transitions of Ca v 3.1 channel from open into closed and inactivated states as well as backwards transition from inactivated into closed state, possibly by interacting with its voltage sensor.