Localization of TREK-2 K+ channel domains that regulate channel kinetics and sensitivity to pressure, fatty acids and pHi.
TREK-2, a member of the tandem-pore K+ channel family, is activated by membrane stretch, unsaturated free fatty acids and acidic conditions, and exhibits unique open channel kinetics. To identify the regions responsible for these properties, we studied the role of the cytoplasmic regions of TREK-2. Deletion of the N-terminus had no effect on any aspect of TREK-2 function. Deletion of the C-terminus or its substitution with that of TASK-3 abolished the sensitivity to free fatty acids and intracellular pH (pHi), and reduced the sensitivity to pressure. The regions that allow activation by free fatty acids and low pHi were localized to 25- and 10-amino-acid domains, respectively, close to the fourth transmembrane segment. Substitution of KKTKEE, a charged region near the proximal C-terminus, with uncharged amino acids produced little change in TREK-2 function; however, its deletion abolished sensitivity to fatty acids and low pH, indicating that this region is structurally very important. The TREK-2 C-terminus was also found to be critical for its channel opening in bursts as well as for its increased basal activity. Thus, the C-terminus endows TREK-2 with unique channel kinetics and the ability to be gated by free fatty acids and low pHi, and with increased mechanosensitivity.
Kim
Y
Y
Department of Physiology and Biophysics, Finch University of Health Sciences, The Chicago Medical School, IL 60064, USA. donghee.kim@finchcms.edu
Gnatenco
C
C
Bang
H
H
Kim
D
D
D000818:Animals; D019556:COS Cells; D003593:Cytoplasm / Q000737:chemistry; D005227:Fatty Acids / Q000494:pharmacology*; D017353:Gene Deletion; D015870:Gene Expression; D049452:Green Fluorescent Proteins; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008164:Luminescent Proteins / Q000235:genetics; D008465:Mechanoreceptors / Q000502:physiology; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D024683:Potassium Channels, Tandem Pore Domain; D011312:Pressure; D011993:Recombinant Fusion Proteins; D013329:Structure-Activity Relationship; D014162:Transfection
D005227:Fatty Acids; D008164:Luminescent Proteins; D015221:Potassium Channels; D024683:Potassium Channels, Tandem Pore Domain; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins