Basal and CCK-8-induced signaling in COS-7 cells expressing wild-type and mutant CCK-BRs
| Receptor | IP production | |
|---|---|---|
| Basal | CCK-8-induced | |
| % of 3H incorporation | ||
| Wild-type | 1.18 ± 0.07 | 8.71 ± 0.42 (22) |
| T111A | 1.28 ± 0.35 | 10.56 ± 1.95 (6) |
| S131A | 0.65 ± 0.08 | 7.21 ± 1.46 (3) |
| S219A | 0.96 ± 0.21 | 8.86 ± 0.97 (4) |
| W346A | 1.07 ± 0.41 | 7.32 ± 1.11 (4) |
| V349A | 1.45 ± 0.43 | 8.64 ± 1.50 (4) |
| Y350A | 1.26 ± 0.65 | 10.33 ± 2.66 (4) |
| N353L | 1.06 ± 0.16 | 10.20 ± 0.78 (5) |
| S379A | 1.28 ± 0.35 | 8.23 ± 0.87 (4) |
Basal (in the absence of ligand) and CCK-8-induced IP production levels were comparable for wild-type and mutant receptors. Signaling is expressed as [3H]IPs/total cellular 3H × 100 (see Materials and Methods). Basal signaling levels were not significantly different from those measured in cells transfected with the empty expression vector pcDNAI (1.10 ± 0.07% of 3H incorporation, mean ± standard error from 29 experiments). In addition, CCK-8-induced IP production by mutant receptors was not significantly different from the corresponding value of the wild-type CCK-BR. Data represent means ± standard errors from the number of independent experiments indicated in parentheses.