. 2016 Mar 11;12(2):313–329. doi: 10.1007/s11302-016-9506-7

Table 3.

Affinities of selected ligands for the wt human A_2AAR compared to the cysteine mutant receptors determined in radioligand binding studies versus [³H]CGS21680 (5 nM) or [³H]NECA (3 nM). K _i values were calculated based on the K _D values obtained in homologous competition experiments (see Table 1). Data are mean ± SEM of the three independent experiments, otherwise noted

K _i ± SEM (nM)
[³H]CGS21680	NECA		Fold shift^d	CGS21680	Fold shift^d	PSB-15826	Fold shift^d
hA_2A wt	81.2 ± 11.4^a			130 ± 1^a		118 ± 1
hA_2A C166S	99.4 ± 15.2^ns		1.2	114 ± 4^{b, ns}	0.9	196 ± 1^***	1.7
hA_2A C159S	Low^c 4.92 ± 0.68^*		0.1	50.1 ± 0.7^{b, ***}	0.4	29.2 ± 3.6^{a, ***}	0.3
	High 467 ± 119^*		5.8
	One-site 20.2 ± 0.8		0.3
hA_2A C146S – C159S	2490 ± 3^{b, ***}		31	128 ± 10^{a, ns}	1.0	278 ± 8^{a, ***}	2.4
[³H]NECA
hA_2A wt		7.06 ± 1.27		17.8 ± 3.5		43.5 ± 5.3
hA_2A C146S		39.1 ± 1.3^***	5.5	19.5 ± 3.4^ns	1.1	33.9 ± 2.2^ns	0.8

^a n = 4

^b n = 5

^cLow and high refer to the two K _i values of the biphasic curve of the C159S mutant, while one-site refer to the single K _i value calculated with one-site competition fit

^dThe shift represents the ratio K _i (mutant):K _i (wt)

^ns not significantly different from wt hA_2AAR (determined using the two-tailed t test)

^* p < 0.05

^*** p < 0.001