Regulation Of The Single Channel Conductance Of K2p10.1 (Trek2) By The Amino-terminus

Abstract

K2P2.1 (TREK-1) and K2P10.1 (TREK-2), when expressed in mammalian cell lines, show several single channel conductance levels. Recent studies show that the N-terminus of TREKs controls the unitary conductance levels via alternative translation initiation mechanism that produces isoforms with long and short N-termini. For TREK-2, the isoform with the full length N-terminus (residues 1-69) has a low conductance level, whereas that with the short one (residues 55-69 or 67-69) has a large conductance level. The role of the N-terminus and the putative slide helix region in the control of the unitary conductance was studied further using deletion and substitution TREK-2 mutants. Deletion of the N-terminus up to residue 36 (out of 69 residues) had no effect on conductance levels. Further deletions up to residues 40 (∼150-pS at −40 mV), 44 (∼90-pS), and 49 (>30-pS) produced channels with levels that were different from the levels observed in the wild type TREK-2. A mutation within the putative slide helix region (residues 47-55) to render it non-helical resulted in formation of mainly the low conductance channel, and greatly reduced the open probability. These TREK-2 mutants also inhibited the alternative translation initiation. These results suggest that the distal region of the N-terminus (residues 37-55) including the putative helical region (residues 37-54) controls the unitary conductance of TREK-2 in an unpredictable way. The data also indicate that the putative helical region is important for the control of channel activity.