The binding characteristics of dopamine and S-(—)-3-PPP with D2L receptor-G protein fusions
Membranes from HEK293 cells transfected to express each of the D2L-G protein fusions transiently were used in competition binding studies using [3H]spiperone and varying concentrations of either dopamine or S-(—)-3PPP. Data were analyzed as described under Materials and Methods. pK values are provided where appropriate for both high (h) and low (l) affinity sites or where the data did not warrant a “two-site” fit simply as pKl. In the cases in which a two-site fit provided a significant improvement in data fit, the proportion of high-affinity sites (% Rh) is provided. In all cases, a one site fit was appropriate for data obtained in the presence of GTP (pKl GTP). Data represent means (±) S.E.M. from a minimum of three independent experiments.
Receptor:G Protein Fusion | D2L Gαi1 | D2L Gαi2 | D2L Gαi3 | D2L Gαo1 | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Dopamine | S-(—)-3-PPP | Dopamine | S-(—)-3-PPP | Dopamine | S-(—)-3-PPP | Dopamine | S-(—)-3-PPP | |||||
| pKh (±S.E.M.) | 7.12 (0.11) | 7.20 (0.12) | 7.52 (0.13) | 7.67 (0.35) | 8.44 (0.15) | |||||||
| pKl (±S.E.M.) | 5.75 (0.08) | 6.27 (0.06) | 5.63 (0.17) | 6.47 (0.11) | 5.58 (0.12) | 6.26 (0.07) | 5.82 (0.18) | 6.24 (0.07) | ||||
| %Rh | 44 (7) | 55 (4) | 36 (4) | 29 (4) | 29 (2) | |||||||
| pKiGTP (±S.E.M.) | 5.53 (0.01) | 6.23 (0.02) | 5.81 (0.01) | 6.52 (0.11) | 5.50 (0.11) | 6.27 (0.11) | 5.86 (0.07) | 6.3 (0.01) | ||||