Table 1. Pharmacological profiles of the three Dictyostelium ACs.
ND, not determined; NA, not applicable; 0, no effect; −, inhibition; −−, strong inhibition; +, stimulation; ++, strong stimulation; Cm, concentration that yields maximal effect. IC50 values were determined by non-linear curve fitting of the data presented in Figures 1–4 to y=100–[I]×100/(IC50+[I]), where y denotes percentage cAMP accumulation, with t=0 cAMP levels subtracted, and [I] the inhibitor concentration. IC50 values are presented as means ±95% confidence interval. The goodness-of-fit (r2) is indicated in parentheses.
| ACA (6 h starvation) | ACB (vegetative) | ACG (vegetative) | ||||
|---|---|---|---|---|---|---|
| Cells | Lysates | Cells | Lysates | Cells | Lysates | |
| GTP[S] | NA | ++ [43] | NA | 0 [9] | NA | 0 [4] |
| Mg2+ | NA | + [23] | NA | ++ Cm=10 mM [9] | NA | + [23] |
| Mn2+ | NA | ++ Cm=20 mM [23] | NA | + [9] | NA | ++ Cm=1–2 mM [23] |
| Caffeine | −− | −* | −− | + | −− | + |
| IC50=361±113 μM | IC50=825±114 μM | IC50=300±107 μM | EC50=1–2 mM | IC50=207±312 μM | EC50=1–2 mM | |
| (0.99) [17] | (0.99) | (0.99) | (0.79) | |||
| IPA | −− | 0/− | 0 | 0 | 0 | 0 |
| IC50=31±13 μM | IC50=2.18±0.65 mM | |||||
| (0.98) | (0.96) | |||||
| DDA | − | − | + | − | 0/+ | −− |
| IC50=465±217 μM | IC50=274±153 μM | EC50>1 mM | IC50=336±82 μM | IC50=76±25 μM | ||
| (0.97) | (0.98) | (0.99) | (0.99) | |||
| PPi | NA | 0/− | NA | − | NA | − |
| NKY80 | ND | 0/− | ND | 0/− | ND | 0 |
| IC50=1.31±1.36 mM | IC50=5.78±4.97 mM | |||||
| (0.78) | (0.89) | |||||
| MDL- | ND | − | ND | − | ND | −− |
| 12,330A | IC50=329±174 μM | IC50=497±383 μM | IC50=885±258 μM | |||
| (0.95) | (0.93) | (0.99) | ||||
| Tyrphostin | 0/− | 0 | 0/− | 0 | 0/− | −− |
| A25 | 1119±879 μM | 1336±715 μM | IC50=602±336 μM | IC50=16.6±7.4 μM | ||
| (0.94) | (0.89) | (0.95) | (0.97) | |||
| SQ22536 | − | −* | + | 0 | ++ | + |
| IC50=812±280 μM | IC50=247±134 μM | |||||
| (0.99) | (0.96) | |||||
* GTP[S]-stimulated activity.