The Investigation of SYD-2 as a Potential Substrate of the Anaphase Promoting Complex in Promoting GABA release at the C. elegans Neuromuscular Junction

Lauryn Campagnoli Butler University, Daniel Lester University of South Florida
Faculty Sponsor(s): Jennifer Kowalski Butler University
Neurons communicate at synaptic junctions via chemical neurotransmitters that elicit either excitatory or inhibitory responses in postsynaptic cells. Balance of excitatory to inhibitory signaling (E:I) is governed by the abundance of synaptic proteins. Ubiquitin ligase enzymes tag target proteins with ubiquitin polypeptides, which alters protein location, activity, and abundance. Defects in E:I balance and the ubiquitin system occur in neurological disorders. To study ubiquitin enzyme regulation of E:I balance, we use the neuromuscular junction (NMJ) in Caenorhabditis elegans. At the C. elegans NMJ, acetylcholine (Ach) neurotransmitter release causes muscle excitation (contraction) whereas GABA neurotransmitter release inhibits muscle excitation (relaxation). These phenotypes can be measured using aldicarb, which causes synaptic Ach buildup, leading to muscle hypercontraction and paralysis. Using aldicarb assays, we showed that the Anaphase Promoting Complex (APC)—a conserved ubiquitin ligase—acts in C. elegans GABA-releasing motor neurons to promote GABA release. We hypothesize the APC negatively regulates SYD-2 Liprinα, a conserved protein that acts at GABA neuron presynapses, to promote GABA release. SYD-2 has two APC recognition sequences, and SYD-2 protein levels increase at NMJs in APC loss of function (APC LoF) mutants. SYD-2 LoF and APC LoF;SYD-2 LoF double mutants are both aldicarb resistant, consistent with SYD-2 acting downstream of the APC at the NMJ. SYD-2 overexpression causes aldicarb hypersensitivity, as does APC LoF, also consistent with our model. Current experiments are examining synaptic vesicle accumulation in SYD-2 overexpression animals. Future experiments will test effects of mutating APC recognition motifs within SYD-2 on SYD-2 synaptic protein levels.
Biology
Oral Presentation

When & Where

12:45 PM
Gallahue Hall 101