TY - JOUR
T1 - Q/R site interactions with the M3 helix in GluK2 kainate receptor channels revealed by thermodynamic mutant cycles
AU - Lopez, Melany N.
AU - Wilding, Timothy J.
AU - Huettner, James E.
PY - 2013
Y1 - 2013
N2 - RNA editing at the Q/R site near the apex of the pore loop of AMPA and kainate receptors controls a diversearray of channel properties, including ion selectivity and unitary conductance and susceptibility to inhibition by polyamines and cis-unsaturated fatty acids, as well as subunit assembly into tetramers and regulation by auxiliary subunits. How these different aspects of channel function are all determined by a single amino acid substitution remains poorly understood; however, several lines of evidence suggest that interaction between the pore helix (M2) and adjacent segments of the transmembrane inner (M3) and outer (M1) helices may be involved. In the present study, we have used double mutant cycle analysis to test for energetic coupling between the Q/R site residue and amino acid side chains along the M3 helix. Our results demonstrate interaction with several M3 locationsand particularly strong coupling to substitution for L614 at the level of the central cavity. In this location,replacement with smaller side chains completely and selectively reverses the effect of fatty acids on gating of edited channels, converting strong inhibition of wild-type GluK2(R) to nearly 10-fold potentiation of GluK2(R) L614A.
AB - RNA editing at the Q/R site near the apex of the pore loop of AMPA and kainate receptors controls a diversearray of channel properties, including ion selectivity and unitary conductance and susceptibility to inhibition by polyamines and cis-unsaturated fatty acids, as well as subunit assembly into tetramers and regulation by auxiliary subunits. How these different aspects of channel function are all determined by a single amino acid substitution remains poorly understood; however, several lines of evidence suggest that interaction between the pore helix (M2) and adjacent segments of the transmembrane inner (M3) and outer (M1) helices may be involved. In the present study, we have used double mutant cycle analysis to test for energetic coupling between the Q/R site residue and amino acid side chains along the M3 helix. Our results demonstrate interaction with several M3 locationsand particularly strong coupling to substitution for L614 at the level of the central cavity. In this location,replacement with smaller side chains completely and selectively reverses the effect of fatty acids on gating of edited channels, converting strong inhibition of wild-type GluK2(R) to nearly 10-fold potentiation of GluK2(R) L614A.
UR - http://www.scopus.com/inward/record.url?scp=84883246984&partnerID=8YFLogxK
U2 - 10.1085/jgp.201311000
DO - 10.1085/jgp.201311000
M3 - Article
C2 - 23940260
AN - SCOPUS:84883246984
VL - 142
SP - 225
EP - 239
JO - Journal of General Physiology
JF - Journal of General Physiology
SN - 0022-1295
IS - 3
ER -