科研之友
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摘要
Background: The mutation P290R in the excitatory amino acid transporter 1 (EAAT1) causes episodic ataxia type 6. Results: Voltage clamp fluorometry demonstrates changes in the time course of EAAT3 fluorescence signals by the homologous P259R mutation. Conclusion: P259R alters EAAT3 transport functions by decelerating conformational changes associated with sodium binding. Significance: Studying naturally occurring mutations promises identification of unexpected determinants of transporter functions. %26lt;br%26gt;Excitatory amino acid transporters (EAATs) are crucial for glutamate homeostasis in the mammalian central nervous system. They are not only secondary active glutamate transporters but also function as anion channels, and different EAATs vary considerably in glutamate transport rates and associated anion current amplitudes. A naturally occurring mutation, which was identified in a patient with episodic ataxia type 6 and that predicts the substitution of a highly conserved proline at position 290 by arginine (P290R), was recently shown to reduce glutamate uptake and to increase anion conduction by hEAAT1. We here used voltage clamp fluorometry to define how the homologous P259R mutation modifies the functional properties of hEAAT3. P259R inverts the voltage dependence, changes the sodium dependence, and alters the time dependence of hEAAT3 fluorescence signals. Kinetic analysis of fluorescence signals indicate that P259R decelerates a conformational change associated with sodium binding to the glutamate-free mutant transporters. This alteration in the glutamate uptake cycle accounts for the experimentally observed changes in glutamate transport and anion conduction by P259R hEAAT3.
- 出版日期2013-12-20
