Receptor | Expression | IP | Epinephrine | ||
---|---|---|---|---|---|
Basal | Epinephrine-Induced | IC50 | EC50 | ||
fmol/well | % | μM | nM | ||
Wild-type (low) | 128 ± 9 | 14 ± 2 | 313 ± 69 | 4.7 ± 0.6 | 29 ± 6 |
Wild-type (high) | 347 ± 58 | 17 ± 2 | 432 ± 44 | ||
F286A | 155 ± 27 | 59 ± 211-150 | 643 ± 891-150 | 0.03 ± 0.0011-150 | 0.9 ± 0.011-150 |
F286E | 447 ± 23 | 19 ± 5 | 291 ± 351-150 | 0.04 ± 0.0021-150 | 6.6 ± 0.11-150 |
E289A | 162 ± 16 | 426 ± 721-150 | 1633 ± 1941-150 | 0.19 ± 0.041-150 | 0.7 ± 0.11-150 |
E289Q | 242 ± 43 | 25 ± 3 | 669 ± 621-150 | 1.9 ± 0.1 | 32 ± 6 |
E289F | 69 ± 18 | 252 ± 111-150 | 976 ± 431-150 | 0.07 ± 0.0021-150 | 0.9 ± 0.21-150 |
E289D | 275 ± 44 | 167 ± 721-150 | 726 ± 1301-150 | 0.13 ± 0.011-150 | 0.7 ± 0.021-150 |
E289R | 234 ± 27 | 301 ± 901-150 | 1054 ± 2971-150 | 0.09 ± 0.021-150 | 0.9 ± 0.31-150 |
E289K | 121 ± 37 | 1386 ± 2921-150 | 2385 ± 791-150 | 0.06 ± 0.011-150 | 0.2 ± 0.011-150 |
E289R/ R143E | 420 ± 34 | 28 ± 15 | 30 ± 161-150 | 0.07 ± 0.021-150 | N.D. |
A292E | 352 ± 75 | 44 ± 16 | 89 ± 271-150 | 3.2 ± 1 | N.D |
L296A | 512 ± 96 | 13 ± 6 | 106 ± 221-150 | 4 ± 0.5 | N.D. |
L296F | 478 ± 70 | 14 ± 4 | 120 ± 311-150 | 3.2 ± 0.5 | N.D. |
V299A | 380 ± 69 | 52 ± 24 | 441 ± 43 | 1.2 ± 0.1 | 9 ± 0.4 |
V299F | 411 ± 92 | 39 ± 7 | 449 ± 47 | 0.04 ± 0.011-150 | 5.5 ± 0.51-150 |
V300A | 317 ± 24 | 27 ± 8 | 415 ± 101 | 6 ± 0.8 | 13 ± 2 |
V300F | 246 ± 10 | 36 ± 19 | 309 ± 35 | 1.2 ± 0.2 | 23 ± 0.5 |
F303G | 355 ± 185 | 7 ± 4 | 8 ± 21-150 | 0.09 ± 0.011-150 | N.D |
F303A | 379 ± 92 | 8 ± 4 | 48 ± 181-150 | 0.12 ± 0.011-150 | n.d. |
F303L | 443 ± 88 | 225 ± 731-150 | 652 ± 1651-150 | 0.16 ± 0.031-150 | 1.5 ± 0.21-150 |
F303Y | 409 ± 56 | 9 ± 7 | 227 ± 911-150 | 10 ± 0.2 | 520 ± 51-150 |
The receptors were expressed in COS-7 cells. Receptor expression was measured using 250 pM [125I]HEAT on membrane preparations derived from transfected cells from one well of a six-well dish (approximately 150 μg of protein). IP accumulation was measured after incubation in the absence (basal) or presence of 10−4 M epinephrine (epinephrine-induced IP) for 45 min. The IP accumulation is expressed as the percentage increase in IP levels above those of mock-transfected cells. For determining the EC50values. the concentrations of epinephrine ranged from 10−12 to 10−4 M. Results for receptor expression and IP accumulation are the mean ± S.E. of at least three independent experiments. The IC50 values (mean ± S.E) of epinephrine are from 15 and 3 independent experiments for the wild-type and mutated receptors, respectively. The EC50 values (mean ± S.E) are from nine and three independent experiments for the wild-type and mutated receptors, respectively.
↵1-150 P < 0.05 paired Student'st test compared with the wild-type receptor.
N.D., not determined.