Proceedings of The Physiological Society
University of Birmingham (2010) Proc Physiol Soc 20, C01 and PC01
AMP-activated protein kinase inhibits recombinant TASK-3 K+ channels
M. L. Dallas1, F. Ross2, J. L. Scragg1, C. N. Wyatt3, D. Hardie2, C. Peers1, A. Evans4
1. Universiy of Leeds, Leeds, United Kingdom. 2. University of Dundee, Dundee, United Kingdom. 3. Wright State University, Dayton, Iowa, United States. 4. University of Edinburgh, Edinburgh, United Kingdom.
Hypoxia excites the carotid body by causing depolarization of type I cells, triggering voltage-gated Ca2+ influx and secretion of transmitters to excite afferent sensory neurons. In the rat, hypoxic depolarization of type I cells arises from inhibition of a ‘leak’ K current and BKCa channels . The leak current has recently been proposed to be carried by TASK-1, TASK-3 and, predominantly, TASK-1/3 heterodimers . We have previously proposed that hypoxia inhibits these currents via activation of AMP-activated protein kinase (AMPK) , and have also provided preliminary pharmacological evidence that heterologously expressed TASK-3 (but not TASK-1) channels are inhibited by AMPK activation. However, a recent study has suggested that neither channel type is regulated by AMPK activation . Here we report new evidence to indicate that recombinant TASK-3 channels (stably expressed in HEK293 cells) are inhibited by AMPK. Data are expressed as mean ± s.e.m. Whole-cell TASK-3 currents recorded at 37oC were inhibited by bath application of 100μM A-769662, a specific AMPK activator (45.8 ± 6.6% inhibition, n=5, P<0.01, paired t-test). However, in the presence of the AMPK inhibitor compound C (20μM), A-769662 failed to inhibit TASK-3 currents (n=6). Over a 20 min period, TASK-3 currents were reduced in amplitude by 46.7 ± 2.7% (n=7) when a bacterially-derived, active (thiophosphorylated) recombinant AMPK heterotrimer (α2β2γ1) was included in the pipette solution. By contrast, inclusion of an inactive (α2D157A) AMPK heterotrimer led to a reduction in current amplitude of only 9.0 ± 4.1% (n=5) over the same time period. These data indicate that TASK-3 is inhibited by activation by AMPK, and further support our suggestion that AMPK mediates hypoxic inhibition of leak K+ channels in the carotid body.
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