Table 2. Comparison of affinity and cooperativity estimates for allosteric modulation of DHPG and glutamate-mediated iCa2+ mobilization following 1 min vs 30 min pre-incubation of mGlu5 allosteric ligands in HEK293A-rat mGlu5-low cells.
Data represent mean ± SEM of indicated number (n) of independent experiments performed in duplicate.
| Glutamate | DHPG | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 min | 30 min | 1 min | 30 min | |||||||||
| pKBa | log βb | n | pKB | log β | n | pKB | log β | n | pKB | log β | n | |
| MPEP | 8.39±0.13 | Full NAMc | 7 | 7.90±0.08 | Full NAM | 4 | 9.08±0.14d,f | full NAM | 7 | 8.29 ±0.16e | full NAM | 5 |
| fenobam | 7.04±0.09 | Full NAM | 9 | 7.31±0.08 | Full NAM | 7 | 6.91±0.13 | full NAM | 5 | 6.98 ±0.14 | full NAM | 5 |
| VU0409106 | 7.27±0.12 | Full NAM | 7 | 7.38±0.12 | Full NAM | 6 | 7.03±0.14 | full NAM | 5 | 7.67 ±0.21e | full NAM | 3 |
| VU0366248 | 7.22±0.09 | −0.90±0.12 | 7 | 6.57±0.18e | −0.58±0.08 | 7 | 7.43±0.19 | −1.23±0.48 | 5 | 6.45 ±0.24e | −0.40 ±0.08 | 4 |
| VU0366058 | 6.98±0.11 | Full NAM | 5 | 7.11±0.28 | Full NAM | 5 | 6.71±0.13 | full NAM | 5 | 7.02 ±0.24 | full NAM | 4 |
| M-5MPEP | 7.00±0.07 | −0.59±0.03 | 3 | 6.72±0.26 | −0.52±0.06 | 3 | 6.70±0.15 | −0.97±0.24 | 5 | 6.49 ±0.24 | −0.47 ±0.09 | 3 |
| dipraglurant | 8.16±0.06d | Full NAM | 6 | 7.47±0.07e | Full NAM | 6 | 8.06±0.14d | full NAM | 6 | 7.31 ±0.16e | full NAM | 4 |
| MTEP | 7.83±0.09 | Full NAM | 3 | 6.97±0.15e | Full NAM | 6 | 8.37±0.14d | full NAM | 6 | 7.81 ±0.18f | full NAM | 5 |
pKB, negative logarithm of the equilibrium dissociation constant determined using an operational model of allosterism
log β, logarithm of the efficacy cooperativity scaling factor determined using an operational model of allosterism where α was assumed to be equal to 1
“full NAM” denotes complete inhibition of DHPG response, such that β approaches zero.
Denotes p<0.05, One-way ANOVA, Tukey’s multiple comparisons test, compared to binding pKi estimates
Denotes p<0.05, One-way ANOVA, Tukey’s multiple comparisons test, compared to pKB estimate derived from iCa2+ mobilization assays (1 min versus 30 min paradigm)
Denotes p<0.05, One-way ANOVA, Tukey’s multiple comparisons test, compared to pKB estimate derived from glutamate iCa2+ mobilization assays (equivalent incubation paradigm)