The objective of this developmental/exploratory R21 proposal is to develop a new direction for studying GABAA receptor trafficking and regulation at synapses. A genetic model organism approach will be taken, using the nematode Caenorhabditis elegans. GABAA receptors are the major inhibitory neurotransmitter receptors in the brain, and play important roles in most brain functions. The abundance of GABAA receptors at synapses is an important factor in normal nervous system function, and in the progression of nervous system disease, particularly anxiety disorders. Studies in mammalian systems suggest that receptor abundance is regulated by controlling receptor biosynthesis, trafficking to synapses, and degradation. However, results to date have been largely descriptive. We lack an understanding of how these processes occur, and how they may be regulated. Progress has been slowed by the difficulty of perturbing mammalian gene expression, the anatomical complexity of the mammalian nervous system, and the structural heterogeneity of mammalian GABAA receptors. One solution is to take a genetic approach in a simple model organism. C. elegans is well suited for this purpose: GABAA receptors, and their regulation at synapses, are conserved in C. elegans; genetic manipulation of C. elegans is rapid and efficient; the C. elegans nervous system is relatively simple; and the C. elegans GABAA receptor is uniform and well characterized.
The specific aims of this proposal are two-fold: First, the points along the biosynthetic, trafficking, and degradation pathways that control GABAA receptor abundance at synapses will be determined. To achieve this aim, these points will be perturbed genetically, and the effects on the regulation of receptor abundance will be determined. Measurements of receptor function (using electrophysiology), receptor subcellular localization, and receptor mRNA and protein levels will be performed. Second, the genes that are important at each of these potential regulatory points will be determined.
This aim will be achieved by forward genetic screening using a functional GFP-tagged receptor. These initial data will form the basis of a substantial future research program to understand how GABAA receptor abundance at synapses is regulated. Because cellular processes are generally well-conserved between C. elegans and humans, insights from these studies could lead to improved treatments for anxiety disorders based on modulating GABAA receptor abundance at synapses.
| Rowland, Aaron M; Richmond, Janet E; Olsen, Jason G et al. (2006) Presynaptic terminals independently regulate synaptic clustering and autophagy of GABAA receptors in Caenorhabditis elegans. J Neurosci 26:1711-20 |
| Wardell, Bryan; Marik, Purba S; Piper, David et al. (2006) Residues in the first transmembrane domain of the Caenorhabditis elegans GABA(A) receptor confer sensitivity to the neurosteroid pregnenolone sulfate. Br J Pharmacol 148:162-72 |
| Bamber, Bruce A; Twyman, Roy E; Jorgensen, Erik M (2003) Pharmacological characterization of the homomeric and heteromeric UNC-49 GABA receptors in C. elegans. Br J Pharmacol 138:883-93 |
