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Inactivation determinants in segment IIIS6 of Ca(v)3.1
R Marksteiner1, P Schurr, S Berjukow
1Institut für Biochemische Pharmakologie, Peter-Mayr-Strasse 1, A-6020 Innsbruck, Austria.
The Journal of Physiology
|November 17, 2001
Summary
Molecular determinants of Ca(v)3.1 channel inactivation were investigated. Specific amino acids in segment IIIS6 significantly influence inactivation kinetics, suggesting common mechanisms across calcium channel types.
Area of Science:
- Molecular and Cellular Neuroscience
- Ion Channel Physiology
- Biophysics
Background:
- Low threshold, T-type, Ca(2+) channels (Ca(v)3 family) exhibit rapid inactivation kinetics.
- The molecular basis for Ca(v)3.1 channel inactivation remains largely uncharacterized.
- Previous studies implicated segment IIIS6 in the inactivation of high voltage-activated Ca(2+) channels.
Purpose of the Study:
- To determine if segment IIIS6 contains molecular determinants for Ca(v)3.1 channel inactivation.
- To identify specific amino acid residues within IIIS6 that modulate Ca(v)3.1 inactivation kinetics.
Main Methods:
- Site-directed mutagenesis of conserved amino acids in the IIIS6 segment of Ca(v)3.1 channels.
- Two-microelectrode voltage-clamp technique to analyze channel kinetics in Xenopus oocytes.
- Measurement of barium current (I(Ba)) inactivation time constants (tau(inact)) and recovery kinetics.
Main Results:
- Mutations M1510I, F1511A, and V1512A in IIIS6 significantly altered Ca(v)3.1 inactivation kinetics.
- M1510I mutation resulted in a 4.8-fold slowing of inactivation (tau(inact) = 45.7 ms).
- V1512A and F1511A mutations notably affected the recovery of inactivation at -80 mV.
Conclusions:
- Amino acids M1510, F1511, and V1512 in segment IIIS6 are critical for Ca(v)3.1 inactivation.
- These findings suggest conserved molecular elements in the inactivation mechanisms of both low and high threshold Ca(2+) channels.
- The study provides insights into the structural basis of voltage-gated calcium channel inactivation.
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