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Differential modulation of Kv1 channel-mediated currents by co-expression of Kvbeta3 subunit in a mammalian cell-line
Robert Bähring1, Vitya Vardanyan, Olaf Pongs
1Institut für Neurale Signalverarbeitung, Zentrum für Molekulare Neurobiologie der Universität Hamburg, Germany. baehring@zmnh.uni-hamburg.de
Abstract:
The effect of Kvbeta3 subunit co-expression on currents mediated by the Shaker-related channels Kv1.1 to Kv1.6 in Chinese hamster ovary (CHO) cells was studied with patch-clamp techniques. In the presence of Kvbeta3, differences in the voltage dependence of activation for Kv1.1, Kv1.3 and Kv1.6 were detected, but not for Kv1.2- and Kv1.4-mediated currents. Co-expression of Kvbeta3 did not cause a significant increase in current density for any of the tested channels. In contrast to previous studies in Xenopus oocyte expression system, Kvbeta3 confered a rapid inactivation to all except Kv1.3 channels. Also, Kv1.6 channels that possess an N-type inactivation prevention (NIP) domain for Kvbeta1.1, inactivated rapidly when co-expressed with Kvbeta3. Onset and recovery kinetics of channel inactivation distinctly differed for the various Kv1alpha/Kvbeta3 subunit combinations investigated in this study. The results indicate that the choice of expression system may critically determine Kvbeta3 inactivating activity. This suggests that the presence of an inactivating domain and a receptor in a channel pore, although necessary, may not be sufficient for an effective rapid N-type inactivation of Kv1 channels in heterologous expression systems.
Insights
Kvbeta3 subunit co-expression altered voltage dependence and rapid inactivation in Shaker-related Kv1 channels, but effects varied by Kv1 subtype and expression system. This highlights the importance of the expression system in Kvbeta3 channel modulation.
Area of Science:
- Molecular and Cellular Neuroscience
- Ion Channel Physiology
- Biophysics
Background:
- Kv1 channels are crucial for neuronal excitability.
- Kvbeta subunits modulate Kv1 channel function.
- Kvbeta3's role in modulating Kv1 channel inactivation is not fully understood.
Purpose of the Study:
- To investigate the effects of Kvbeta3 subunit co-expression on Kv1.1-Kv1.6 channel function.
- To compare Kvbeta3 effects in Chinese hamster ovary (CHO) cells versus previous Xenopus oocyte studies.
- To elucidate the mechanisms underlying Kvbeta3-mediated modulation of Kv1 channel inactivation.
Main Methods:
- Patch-clamp electrophysiology in CHO cells.
- Co-expression of Kv1.1-Kv1.6 alpha subunits with Kvbeta3 subunits.
- Analysis of voltage dependence of activation and channel inactivation kinetics.
Main Results:
- Kvbeta3 altered voltage dependence of activation for Kv1.1, Kv1.3, and Kv1.6, but not Kv1.2 or Kv1.4.
- Kvbeta3 induced rapid inactivation in Kv1.1, Kv1.2, Kv1.4, Kv1.5, and Kv1.6 channels, unlike in Xenopus oocytes.
- Kv1.6 channels, despite having an N-type inactivation prevention domain, showed rapid inactivation with Kvbeta3.
- Onset and recovery kinetics of inactivation varied significantly among Kv1alpha/Kvbeta3 combinations.
Conclusions:
- The expression system critically influences Kvbeta3's inactivating activity.
- An inactivating domain and receptor in the channel pore may be necessary but not sufficient for rapid N-type inactivation.
- Kvbeta3's modulatory effects on Kv1 channels are complex and system-dependent.
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