AMPA glutamate receptors and their flip and flop mRNAs in human hippocampus
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S L Eastwood1, P W Burnet, J Beckwith
1University Department of Psychiatry, Warneford Hospital, Oxford, UK.
Abstract:
AMPA-preferring glutamate receptor genes gluR1-4 undergo alternative splicing into flip and flop mRNA isoforms. In the rodent hippocampus, gluR1 and gluR2 isoforms are differentially expressed. We have studied their distribution in human hippocampus. As in the rat, flop isoforms predominate over flip in dentate gyrus, whereas gluR1 flip is prominent only in CA3. In contrast to the rat, flop mRNAs are clearly present in CA3. At a cellular level, pyramidal neurones express moderate amounts of each isoform. In several hippocampal fields, scattered non-pyramidal cells--putatively interneurones and glia--show abundant expression. The findings are supported by immunocytochemical detection of gluR1 and gluR2/3. As the four encoded isoforms have distinct properties, their differential expression within the hippocampus, and between species, should be taken into account when considering the roles of AMPA receptors in normal and abnormal brain states.
Insights
Glutamate receptor flip and flop isoforms show distinct human hippocampal distribution. Differential expression in pyramidal and non-pyramidal cells impacts AMPA receptor function understanding.
Area of Science:
- Neuroscience
- Molecular Biology
- Genetics
Background:
- AMPA-preferring glutamate receptor genes (gluR1-4) exhibit alternative splicing, producing distinct flip and flop mRNA isoforms.
- Differential expression of gluR1 and gluR2 isoforms is known in rodent hippocampus.
- Understanding human hippocampal AMPA receptor distribution is crucial for neuroscience research.
Purpose of the Study:
- To investigate the distribution of AMPA receptor flip and flop isoforms in the human hippocampus.
- To compare human hippocampal AMPA receptor isoform expression with rodent models.
- To identify cellular localization of these isoforms within the human hippocampus.
Main Methods:
- In situ hybridization to detect flip and flop mRNA isoforms of gluR1-4.
- Immunocytochemistry to confirm protein expression of gluR1 and gluR2/3.
- Comparative analysis between human and rodent hippocampal expression patterns.
Main Results:
- Similar to rodents, flop isoforms predominate in the human dentate gyrus.
- GluR1 flip isoform is prominent in CA3, with flop mRNAs also present in CA3.
- Pyramidal neurons show moderate expression, while interneurons and glia exhibit abundant expression of certain isoforms.
Conclusions:
- The differential expression of AMPA receptor isoforms in the human hippocampus varies between regions and cell types.
- Human-specific expression patterns, particularly in CA3, contrast with rodent models.
- Considering these distinct isoform properties and distributions is essential for understanding AMPA receptor roles in brain function and disease.