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Title: The role of K2P channels in aldosterone secretion by human adrenal glomerulosa cells
Author: Brenner, Tanja
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2008
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The project was largely undertaken using an established human adrenocortical cell line, H295R, which secretes most adrenocortical steroids. I have shown that these cells express mRNA and protein for both TASK3 and TREK1. In the absence of selective K2P channel blockers, a dominant-negative approach was employed using mutant K2Ps that are non-functional when they homo- or heterodimerise (TASK3-G95E, TREK1-G144E). Constructs containing wild-type (WT) and mutant channels were transfected into H295R cells and the effects on membrane potential and aldosterone release were measured by voltage-sensitive FMP dye and radioimmunoassay, respectively. These findings suggest both channels are involved in aldosterone secretion by H295R cells (and by implication adrenal zona glomerulosa cells), since dominant-negative TASK3 and TREK1 GE mutants depolarize cells and also show a significant effect on aldosterone secretion. It is not clear which components of the complex signalling cascade following Gαq activation lead to K2P channel inhibition in the human adrenal cortex. In this study, the effect of Gαq on membrane potential and aldosterone release in H295R cells was investigated by transiently transfecting WT Gαq and two mutant versions (Gαq-QL, Gαq-RTAA). I have found no evidence for direct inhibition through Gαq, but phospholipase C and also protein kinase C seem to be important components of the downstream signalling cascade affecting K2P channel function. Overall, I have shown that aldosterone release in H295R cells depends on a combination of TASK3 and TREK1 channels. I have also shown that the activation of phospholipase C is necessary for K2P channel inhibition via G protein pathways. These findings shed important new light on the regulation of aldosterone secretion in the H295R cell line per se and the possible behaviour of human adrenal glomerulosa cells that are modelled by this cell line.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available