TABLE 1

Summary of results

The first column gives the subunits injected. The first set of four rows gives results for receptors predicted to contain three copies of α4 and two copies of β2, while the second set gives results for two copies of α4 and three of β2. The third set of four rows shows data for receptors containing the α5 subunit, again ordered based on the predicted number of copies of α4. The final set of two rows shows data for dimeric concatemers expressed in the absence of a free subunit; the pattern of properties is distinct from a dimer expressed with a free subunit (although closest to receptors formed with a free α4 subunit). The second column gives the number of α4 subunits predicted to be in the receptor, while the third and fourth columns give the ACh EC50 and the response to 1 μM 5I A85380 relative to the response of the same oocyte to 1 mM ACh. The fifth and sixth columns give whether the predicted receptor has adjacent α4 subunits and the observed effect of physostigmine. The seventh and eighth columns give the predicted number of untethered α4 C termini in the receptor and the observed effect of 17β-estradiol. The final column gives the response to 1 mM ACh. All data are mean ± S.E. (number of observations).

SubunitsNo. of α4 SubunitsACh EC505I A85380 Relative ResponseAdjacent α4?Physostigmine EffectNo. of Free α4 C Termini17 β-Estradiol EffectMaximal Response
μMrelative to AChfoldfold−nA
α4&β2 8:13135 ± 11 (32)0.17 ± 0.02 (17)Yes1.52 ± 0.09 (18)32.54 ± 0.18 (23)13,451 ± 1459 (45)
α4-β2&α4387 ± 7 (46)0.16 ± 0.01 (41)Yes1.57 ± 0.18 (21)11.38 ± 0.05 (35)7238 ± 1179 (68)
β2-α4&α43135 ± 12 (52)0.17 ± 0.01 (56)Yes1.33 ± 0.04 (34)33.77 ± 0.20 (11)14,454 ± 1301 (77)
β2-α4-β2-α4-α43153 ± 12 (9)0.15 ± 0.01 (12)Yes1.43 ± 0.23 (8)11.13 ± 0.02 (20)2020 ± 265 (25)
α4&β2 1:826 ± 1 (18)1.49 ± 0.13 (18)No0.67 ± 0.04 (11)22.70 ± 0.11 (4)1103 ± 208 (43)
α4-β2&β223 ± 1 (14)1.83 ± 0.07 (19)No0.71 ± 0.06 (6)01.04 ± 0.03 (5)341 ± 98 (32)
β2-α4&β225 ± 1 (40)1.72 ± 0.05 (60)No0.56 ± 0.03 (15)23.73 ± 0.32 (7)819 ± 114 (73)
β2-α4-β2-α4-β223 ± 1 (16)1.79 ± 0.11 (7)No0.64 ± 0.03 (14)00.88 ± 0.02 (8)110 ± 23 (20)
β2-α4-α5-α4-α4334 ± 9 (2)0.47 ± 0.03 (8)Yes1.87 ± 0.20 (6)11.43 ± 0.12 (12)24 ± 5 (30)
β2-α4&α524 ± 1 (20)1.07 ± 0.06 (31)No0.64 ± 0.04 (20)21.68 ± 0.06 (7)399 ± 67 (45)
α4-β2&α524 ± 1 (9)1.15 ± 0.08 (15)No0.56 ± 0.02 (19)00.69 ± 0.03 (5)436 ± 124 (20)
β2-α4-α5-α4-β229 ± 1 (13)1.65 ± 0.06 (17)No0.78 ± 0.11 (9)00.86 ± 0.03 (10)27 ± 4 (36)
β2-α4?127 ± 15 (52)0.41 ± 0.04 (72)No1.09 ± 0.10 (13)≥23.17 ± 0.25 (6)5155 ± 781 (82)
α4-β2?111 ± 18 (24)0.19 ± 0.01 (24)No0.98 ± 0.09 (9)00.87 ± 0.05 (8)859 ± 160 (37)