Proceedings of The Physiological Society
University of Oxford (2011) Proc Physiol Soc 23, PC72
TASK5: a study to determine its physiological role
1. school of medicine - human genetics division, southampton university, Southampton, United Kingdom.
Two-pore domain (K2P) K+ channels are active over physiological voltage ranges resulting in constituent leak of K+ from the cell. These channels are fundamental in setting and regulating the resting membrane potential of cells, are regulated by physiological stimuli and play key roles in several physiological processes. To date fifteen members with distinct functional and pharmacological characteristics have been identified and grouped into distinct subgroups. K2P15.1 (TASK5) was first identified in 2001 by two independent groups [1, 2] and although fails to show functional current in recombinant expression systems was included in the Acid Sensitive subgroup (TASK) of K2P channels primarily due to its sequence homology with other members of this group (K2P3.1 and K2P9.1). TASK channels are characterized by their sensitivity to external pH. At messenger level, K2P15.1 has a wide tissue distribution and shows high levels of expression specifically in pancreas and adrenal glands. While K2P15.1 is predicted to play an important role in both adrenal and pancreatic function, to date the physiological function and pharmacological profile of this channel has been elusive. In this study, tissue distribution at messenger level of hK2P15.1 was determined by performing RT-PCR analysis of human fetal tissues. Subcellular localisation of hK2P15.1 was then examined by immunocytochemistry in HeLa cells transfected with hK2P15.1 and analysed by confocal imaging. Finally, hK2P15.1 interaction with specific proteins was investigated through in vitro pull-down assays using cytosolic domains of hK2P15.1 as bait and specific binding partners were identified by mass-spectrometry. Transcript for hK2P15.1 was detected in human fetal kidney, eye, tongue, stomach and duodenum, but not in lung or muscle. When transiently transfected in HeLa cells hK2P15.1 failed to show robust cell surface expression but appeared to be localized within the golgi and peri-nuclear areas. Candidate binding partners to hK2P15.1 have been identified and work is ongoing to verify the functional significance of these interactions.
Where applicable, experiments conform with Society ethical requirements