Figure 1.

Increased efficacy but decreased potency in C57S, C99S and C57/99S mutants of hmGlu5a receptor upon quisqualate- or glutamate-induced activation. HEK293 cells were transiently transfected with cDNAs coding for hmGlu5a WT or the indicated mutated receptors. (a) Quisqualate- or (b) glutamate-induced [Ca²⁺]_i mobilization was assessed using the Ca²⁺-sensitive dye Fluo-4 and FLIPR. In all, 100% correspond to 13 688 fluorescence units. (c) IP production concentration–response curve of quisqualate applied on HEK293 expressing the indicated cysteine to serine mutants together with rat glutamate transporter rEAAC1 and the G protein α_q subunit. Data represent the mean±s.e.m. of three (a and b) or four (c) measurements performed in quadruplicates from three or four independent transfections, respectively. Note that the tetramutant 4C-S displays total loss of function even at high concentration of the agonist.