| Autor: |
Mühlemann, Andreas, Diener, Catherine, Fischer, Christophe, Piussi, Jenny, Stucki, Andy, Porter, Richard H. |
| Předmět: |
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| Zdroj: |
British Journal of Pharmacology; Apr2005, Vol. 144 Issue 8, p1118-1125, 8p |
| Abstrakt: |
Several combinations of cysteine to serine mutations at positions 57, 93, 99 and 129 in the extracellular N-terminal domain of human metabotropic 5a (hmGlu5a) receptors were produced and expressed in HEK293 cells. Quisqualic acid-induced intracellular calcium ([Ca2+]i) mobilization and inositol phosphates (IP) accumulation revealed an apparent increased efficacy and decreased potency for hmGlu5a mutants C57S, C99S and C57/99S, as well as a total loss of function for the mutant C57/93/99/129S.[3H]Quisqualate saturation analysis revealed mutants C57S, C99S, C57/99S and the tetramutant C57/93/99/129S to have unchanged KD but reduced Bmax values.[3H]MPEP saturation analysis on the same membrane preparations revealed no difference in KD for any mutant, but a decrease in Bmax value for the C57/93/99/129S receptor.Inverse agonism of MPEP at hmGlu5a receptors was partially reduced by mutation C57S, significantly reduced by C99S and C57/99S mutations and totally abolished in the tetramutant.We confirmed the surface expression of all the mutated receptors using[3H]MPEP binding analysis on whole cells. However, Bmax values were increased for mutant C57S, C99S, and C57/99S but decreased in the C57/93/99/129S receptor.The 24?h preincubation of cells expressing hmGlu5a receptors with 1?µM MPEP followed by extensive washing dramatically increased the wild-type receptor efficacy to quisqualate, to the same levels seen with C57/99S receptors. MPEP preincubation did not affect C57/99S function.We conclude that cysteines 57 and 99 are key residues necessary for modulating hmGlu5a receptor function.British Journal of Pharmacology (2005) 144, 1118-1125. doi:10.1038/sj.bjp.0706152 [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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