Muir, J. (2012) Molecular mechanisms controlling GABAA receptor clustering and lateral mobility. Doctoral thesis, UCL (University College London).
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γ-aminobutyric acid type A receptors (GABAARs) are the major mediators of inhibitory neurotransmission in the mammalian CNS. They play a critical role in regulating the excitatory/inhibitory balance required for correct brain function. Inhibitory synaptic strength depends on the number of GABAARs at the synapse, which can be regulated by trafficking mechanisms controlled by protein-protein interactions and post-translational modifications. Recently, it has become clear that neurotransmitter receptors can undergo lateral exchange between synaptic and extrasynaptic regions. This thesis is centred on the study of GABAAR surface trafficking with live-cell imaging techniques in cultured hippocampal neurons. GABAAR clustering at inhibitory synapses is monitored via super-ecliptic pHluorin tagging, and single particle tracking with quantum dot labelling is used to image GABAAR lateral mobility. Computational tools developed for single particle tracking of GABAARs are described herein. Characterisation of GABAAR clustering and lateral mobility under baseline conditions reveals that GABAAR clusters are stable, but that single GABAARs can move rapidly into and out of synapses. GABAAR surface trafficking is found to be activity-dependent. Ca2+ in ux through NMDA receptors drives the rapid dispersal of GABAAR clusters from synapses and increases GABAAR lateral mobility. This requires activation of calcineurin and dephosphorylation of serine 327 on the GABAAR γ2 subunit. Finally, GABAAR clustering and lateral mobility in the axon initial segment (AIS) is analysed. A chronic depolarisation stimulus which shifts the AIS away from the cell body is then used. GABAAR cluster positions remain xed along the axon, but GABAAR lateral mobility in the AIS and proximal axon is increased. These effects require activation of voltage-gated Ca2+ channels. In summary, this work reveals that GABAAR surface trafficking can be modulated by multiple molecular mechanisms, which may have important functional consequences for information processing in the brain.
|Title:||Molecular mechanisms controlling GABAA receptor clustering and lateral mobility|
|Additional information:||Permission for digitisation not received|
|UCL classification:||UCL > School of Life and Medical Sciences > Faculty of Life Sciences > Biosciences (Division of) > Neuroscience, Physiology and Pharmacology|
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