TABLE 1.

Effects of single- and double-point alanine mutagenesis of aromatic residues in the upper part of P2XR-TM1 domains on receptor functions.

P2XRs	ATP EC50 (µM)	ATP Imax (nA)	ATP τoff (s)	αβ–meATP EC50 (µM)	αβ–meATP efficacy (%)a
P2X2R-WT	5.4±0.8	2.6±0.2	0.34±0.05	>100	44
P2X2R-F49A	10.8±2.1*	2.2±0.2	0.44±0.06	>100	32
P2X2R-Y47A	0.82±0.1*	0.46±0.1*	0.36±0.02	11.8±2*	83
P2X2R-F44A	0.26±0.05*	0.44±0,1*	1±0.07*	3.4±1*	95
P2X2R-Y43A	0.28±0.05*	0.80±0.1*	1.3±0.1*	8.2±1*	94
P2X2R-Y43F	8.2±1.8	2.8±0.4	0.47±0.1	>100	65
P2X3R-WT	0.35±0.12	1.6±0.2	0.55±0.05	0.59±0.1	100
P2X3R-F43A	0.35±0.2	0.9±0.1*	0.75±0.06	0.32±0.2	100
P2X3R-W41A	0,39±0.15	0.7±0.07*	0.67+±0.08	0,56±15	100
P2X3R-F38A	0.31±0.2	0.3±0.05*	1.95±0.27*	0.29±0,05	100
P2X3R-Y37A	0.14±0.1*	1.2±0.2	0.60±0.01 34.±2*b	0.27±0.1	100
P2X4R-WT	4.6±0.3	1.6±0.2	0.42±0.03	57±9	42
P2X4R-W50A	5.1±1.3	1.7±0.2	0.35±0.08	85±15	24
P2X4R-F48A	4.1±0.5	1.5±0.8	0.6±0.04	13.4±2.1*	62
P2X4R-W46A	3.0±0.5	1.0±0.16	0.6±0.1	8.9±1.6*	73
P2X4R-Y42A	0.6±0.1*	0.6±0.3*	24±2.9*	0.6±0.05*	100
P2X4R-42A+V43A	0.9±0.1*	0.3±0.03*	49±2.6*	0.9±0.3*	100
P2X4R-42A+W46A	1.4±0.2*	1.4±0.3	1.2±0.05*	4.7±2.0*	44
P2X4R-42A+F48A	0.3±0.1*	0.2±0.03*	54±5*	0.3±0.1*	100
P2X4R-42A+W50A	1.6±0.3*	1.2±0.4	1.6±0.2*	8.3±2.3*	53
P2X4R-Y42A+I39A	n.d.	0.1±0.05*	n.d.	n.d.	n.d.
P2X4R-42A+V35A	0.6±0.1*	0.4±0.1*	33±4.4*	0.6±0.2*	100
P2X4R-42A+G29A	0.4±0.1*	0.5±0.1*	34±3.4*	0.4±0.05*	77

Data shown are mean±SEM values derived from 5 to 35 cells.

^(*)P<0.01 between WT and mutants

^aαβ-me ATP efficacy was calculated as ratio of I_max at 300 µM αβ-meATP/I_max at 100 µM ATP

^bdeactivation kinetics of this mutant was biexponential and τ_off2 value for slow deactivation component contributed with 36±4 % to the current decay.