A DELETION IN THE 2ND CYTOPLASMIC LOOP OF GLUR3 PRODUCES A DOMINANT-NEGATIVE MUTANT OF ALPHA-AMINO-3-HYDROXY-5-METHYL-4-ISOXAZOLE PROPIONIC-ACID RECEPTOR
M. Sekiguchi et al., A DELETION IN THE 2ND CYTOPLASMIC LOOP OF GLUR3 PRODUCES A DOMINANT-NEGATIVE MUTANT OF ALPHA-AMINO-3-HYDROXY-5-METHYL-4-ISOXAZOLE PROPIONIC-ACID RECEPTOR, The Journal of biological chemistry, 269(20), 1994, pp. 14559-14565
We have characterized a GluR3 mutant (sGluR3) which has a 33-amino aci
d deletion in its second cytoplasmic loop (deficit from Tyr-715 to Gly
-747 of GluR3-flop). Xenopus oocytes injected with cRNA transcribed fr
om cDNA for this mutant did not respond to kainate and glutamate (each
100 mu M) at a holding potential of -70 mV. In oocytes coinjected wit
h cRNAs for this mutant and for normal alpha-amino-3-hydroxy-5-methyl-
4-isoxazole propionic acid (AMPA) receptor subunits, the current respo
nse to both kainate and glutamate was much weaker than that observed i
n oocytes injected with cRNA for the normal subunits alone. This inhib
itory action was not accompanied by a significant change of ED(50) val
ue and shape of the I-V curve and was AMPA receptor-specific, A compar
able deletion in GluR1 produced a mutant with properties similar to th
ose of sGluR3, while a 33-amino acid deletion elsewhere in the second
cytoplasmic loop of GluR3 (Met-674 to Phe-706) gave a mutant with a we
aker effect. These results suggest that sGluR3 acts as a dominant nega
tive mutant on the functional expression of normal AMPA receptors in o
ocytes by assembling with the normal subunits to produce an essentiall
y nonfunctional receptor complex.