| Summary: | Gamma amino-butyric acid type A receptors (GABAA receptors) are the main mediators of inhibitory neurotransmission in the CNS. These chloride permeable ligand-gated ion channels are intrinsic to maintaining the excitatory/inhibitory balance of neuronal circuits, a balance that is essential to ensure proper workings of the nervous system. The strength of the inhibitory synapse can be rapidly altered by GABAA receptor trafficking mechanisms, which are tightly regulated by many interacting proteins and post-translational modifications. The identification of GABAA receptor associated proteins is an important tool for deciphering the function of these receptors and how these functions change in pathology. In this study, the interactions of GABAA receptors with three proteins are investigated. First, the results of a yeast-two hybrid screen revealed two novel GABAA receptor β subunit interacting proteins, Maf1 and Macoco. These proteins were shown to be expressed in the hippocampus and cortex and interact with GABAA receptors in brain. Additionally, altering the function of the Maf1/Macoco complex caused changes in GABAA receptor trafficking in neurons. Secondly, the amino acids that mediate the interaction between the GABAA receptor β3 subunit and the clathrin adaptor protein, AP2 were identified. Futhermore, live imaging experiments demonstrated that inhibiting the endocytosis of GABAA receptors by mutating the AP2 binding amino acids can prevent the down-modulation of surface GABAA receptors observed after ischemic insult. Lastly, GABAA receptors were found to interact in a complex with the scaffold and signalling protein GIT1 (GPCR kinase interacting protein). Experiments utilising an RNAi to GIT1 combined with biochemical and confocal microscopy techniques revealed a role for this protein in signalling pathways that regulate GABAA receptor trafficking. This work highlights the importance of GABAA receptor interacting proteins in the regulation of GABAA receptor trafficking and hence inhibitory synapse strength.
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