Submitted on August 4, 2008
Revised on October 7, 2008
Accepted on October 7, 2008
Both TASK3 and TREK1 2-pore loop K channels are expressed in H295R cells and modulate their membrane potential and aldosterone secretion
Tanja Brenner1 and Kevin M O'Shaughnessy1*
1 University of Cambridge
* To whom correspondence should be addressed. E-mail: kmo22{at}medschl.cam.ac.uk.
The rate of aldosterone synthesis by adrenal glomerulosa cells relies on the selective permeability of the glomerulosa cell to K+ ions. In rodent and bovine adrenal glomerulosa cells this background potassium current is provided by a 2-pore loop potassium (K2P) channel: largely TASK3 in the rat and TREK1 in the cow. The nature of the K2P channel in the human adrenal cortex is not known, and we have addressed this issue here using the H295R human adrenal cell line. We show that these cells express mRNA and protein for both TASK3 and TREK1 K2P channels. Using a potentiometric dye (FMP) we also show that TASK3 and TREK1 channel modulators can affect the membrane potential of H295R cells. Transfecting H295R cells with TASK3 or TREK1 dominant-negative mutants (TASK3 G95E or TREK1 G144E) produced depolarisation of H295R cells and altered K-stimulated aldosterone secretion. Finally, transfection of a constitutively active mutant of G
q into H295R cells (GTPase deficient Gq-QL) depolarised them and increased basal aldosterone secretion. Taken together our data supports both TASK3 and TREK1 as being functionally operational in the H295R cell line. This suggests that human adrenal glomerulosa cells may utilise both of these K2P channels for their background potassium current.
