TABLE 1

Mutations introduced into mGluR8 that correspond to known CaSR activating mutations, and the Go activation abilities of wild-type and mutants Relative Go activation abilities were estimated using the [35S]GTPγS binding assay on transfected HEK293 cell membranes. Data were normalized to wild-type basal activity and expressed as the mean ± S.D. of more than two independent experiments performed in duplicate.

mGluR8 Mutation
Known CaSR Activating Mutation
Receptor Domain
Go Activation
0 mM l-AP4
1 mM l-AP4
WT 1.00 ± 0.05 4.11 ± 0.69
1575K E604K N ter 1.34 ± 0.16 2.22 ± 0.37
W583S F612S Helix I 1.11 ± 0.12 1.62 ± 0.27
R652H Q681H Helix III 1.30 ± 0.03 2.28 ± 0.49
1744K E767K e2 1.10 ± 0.07 2.71 ± 0.20
1750R L773R Helix V N.D. N.D.
T764C F788C Helix V 4.17 ± 1.01* 7.94 ± 1.14
E775K E799K i3 1.15 ± 0.08 2.84 ± 0.14
P782S F806S Helix VI 1.28 ± 0.08 2.82 ± 0.27
L795A I819A Helix VI 0.97 ± 0.08 1.33 ± 0.20
A796F S820F Helix VI 1.08 ± 0.24 1.28 ± 0.17
F797L F821L Helix VI 1.50 ± 0.19* 2.39 ± 0.24
I798A I822A Helix VI 1.35 ± 0.13* 2.18 ± 0.16
I800S A824S Helix VI 1.76 ± 0.24* 2.33 ± 0.04
F801A Y825A Helix VI 1.60 ± 0.16* 2.81 ± 0.17
Q806A G830A e3 1.27 ± 0.12 2.61 ± 0.22
S807A K831A e3 1.24 ± 0.17 3.49 ± 0.61
A808S F832S e3 1.18 ± 0.18 3.08 ± 0.38
M811T A835T e3 1.21 ± 0.23 2.10 ± 0.23
Y812L V836L e3 1.72 ± 0.17* 2.79 ± 0.34
I813K E837K e3 1.21 ± 0.16 1.59 ± 0.09
T819E
A843E
Helix VII
1.40 ± 0.19*
2.29 ± 0.19

  • N ter, amino terminal; e2, extracellular loop 2; e3, extracellular loop 3; i3, intracellular loop 3; N.D., not detectable.

  • ↵* Significant increase of constitutive activity compared with wild-type. (P < 0.05; Student's t test, two-tailed).