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Substrate-induced modulation of glutamate uptake in human platelets
Barbara Begni1, Lucio Tremolizzo, Cristina D'Orlando
1Department of Neuroscience and Biomedical Technologies, University of Milano-Bicocca, Via Cadore, Monza (MI) 48-20052, Italy.
British Journal of Pharmacology
|May 10, 2005
Summary
Human platelets show increased glutamate uptake after glutamate exposure, suggesting a novel regulatory mechanism for excitatory amino-acid transporters (EAATs). This finding supports using platelets to study neurological disorders.
Area of Science:
- Neuroscience
- Biochemistry
- Cell Biology
Background:
- Glutamate is a key neurotransmitter in the central nervous system (CNS).
- Excitatory amino-acid transporters (EAATs) regulate glutamate levels to prevent excitotoxicity.
- Platelets possess glutamate uptake activity and express major glutamate transporters, offering a model for CNS studies.
Purpose of the Study:
- To investigate substrate-induced modulation of glutamate uptake in human platelets.
- To determine if platelet glutamate transporters are regulated similarly to those in the CNS.
- To explore the molecular mechanisms underlying glutamate uptake regulation in platelets.
Main Methods:
- Measured [3H]-glutamate uptake in platelets preincubated with glutamate.
- Utilized Western blotting to assess transporter expression changes.
- Employed cycloheximide (CEM), L-serine-O-sulphate, and dihydrokainic acid to investigate molecular pathways.
Main Results:
- Platelet glutamate uptake increased up to two-fold with glutamate preincubation, primarily by increasing maximal velocity.
- Glutamate preincubation elevated EAAT1 expression by ~70%, blocked by CEM.
- Evidence suggests EAAT2 involvement, though not via translocation, indicating a novel regulatory mechanism.
Conclusions:
- Human platelets exhibit substrate-dependent glutamate uptake modulation via distinct molecular mechanisms.
- Ex vivo platelets serve as a reliable model for investigating glutamate uptake dysregulation in neurological disorders.
- The findings reveal a new regulatory pathway for EAAT2 activity.