XXII. BIOCHEMICKÝ ZJAZD - Jesseniova lekárska fakulta

Lectures
GATING OF THE T-TYPE CALCIUM CHANNELS
Ľubica Lacinová and Mária Karmažínová
Institute of Molecular Physiology and Genetics, SAV, Bratislava, Slovak Republic
T-type calcium channels are distinguished by relatively low voltage threshold for an activation
and steep voltage dependence of activation and inactivation kinetics just above
the activation threshold. Further, while macroscopic current kinetics of Ca V
3.1 and Ca V
3.2
channels are virtually identical, kinetics of the Ca V
3.3 channel is almost one order more
slow. Kinetics and voltage dependence of macroscopic inward calcium current through
Ca V
3 channels was described in a detail. In contrast, very little information is available
on gating current of these channels. Therefore we compared gating currents measured
from all three Ca V
3.1, Ca V
3.2 and Ca V
3.3 channels.
Voltage dependencies of macroscopic current activation are similar for all three Ca V
3
channels. While gating kinetics of macroscopic calcium current is virtually identical for
Ca V
3.1 and Ca V
3.2 channels it is about one order slower for the Ca V
3.3 channel. Voltage
dependencies of charge movement differ dramatically from those for macroscopic current.
First, their slope factors are several-fold bigger that slope factors of macroscopic
current activation. Second, activation mid-point for Ca V
3.3 channels on-gating is shifted
to more positive membrane potentials by about 20 mV compare to Ca V
3.1 and Ca V
3.2
channels, whose activation mid-points are similar. The same is truth for off-gating voltage
dependences. Kinetics of both on- and off-gating is remarkably faster for Ca V
3.1 and
Ca V
3.2 channels compare to Ca V
3.3 channels. Further, more charge is moved per unit of
macroscopic current amplitude in Ca V
3.3 channels compare to Ca V
3.1 and Ca V
3.2 channels.
Acknowledgement: Supported by VVCE-0064-07 and VEGA 2/0195/10.
74 XXII. Biochemistry Congress, Martin