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Degree

Doctor of Philosophy, Case Western Reserve University, Pharmacology, 1996.

Abstract

The GABAA receptor mediates the action of γ-aminobutyric acid, the major inhibitory neurotransmitter in the CNS. Multiple receptor subtypes, with distinct subunit compositions, exist in the brain. While 16 different receptor subunits have been identified by molecular cloning, the α1, β2/3, and γ2 subunits are thought to form a major GABAA receptor population. To understand how GABAA receptors are assembled and how their expression is regulated, we analyzed the α1, β2/3, and γ2 subunit polypeptides in the cerebellum and in cultured cerebellar granule neurons. The expression of GABAA receptor subunit polypeptides was examined using subunit-specific antibodies. In the cerebellum, β2/3 and γ2 polypeptide expression increased several-fold during the second and third postnatal weeks. Moreover, levels of the β2/3 and γ2 polypeptides increased between 2 and 6 days in cultured cerebellar granule neurons. These patterns were very similar to those previously determined for their encoding mRNAs. However, expression of the α1 subunit was more complex. Two α1-related polypeptide species of Mr 39 kDa and 51 kDa d isplayed reciprocal temporal profiles in cultured granule neurons, despite no significant change in the α1 mRNA level. Additional findings demonstrated that the 39 kDa polypeptide is also present in vivo and suggested that it is a novel form of the α1 subunit which contains a shortened N-terminal domain. These studies suggest that GABAA receptor subunit expression is regulated in part at the level of the mRNA, although α1 subunit expression may also be regulated at the level of receptor assembly. The relationship between subunit polypeptide expression and that of GABAA receptor complexes was assessed in radioligand binding assays. These studies showed that levels of receptor complexes increase in parallel with the 51 kDa α1, β2/3, and γ2 subunits both in vivo and in culture. Moreover, immunoprecipitation studies suggested the physical association of these subunits in one type of receptor oligomer. However, pharmacological experiments demonstrated the presence of multiple GABAA receptor subtypes in cultured granule neurons. Taken together, this work provides a first step towards the elucidation of GABAA receptor composition and assembly in identified neurons

Subject Headings

Biology, Neuroscience

Keywords

Cerebellum; Neurons; Receptors, GABA-A

Advisor

Ruth E. Siegel

Pages

178p.

Document number: case1057672368
Permalink: http://rave.ohiolink.edu/etdc/view?acc_num=case1057672368

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