Investigation of SYD-2 Protein as a Substrate of the Anaphase-Promoting Complex Enzyme at the C.elegans Neuromuscular Junction

Neurons communicate at specialized junctions called synapses. Tightly regulation of synapses is vital to proper neuronal function. Several cellular mechanisms regulate the amount of neuronal proteins controlling synaptic signaling. One molecule that regulates protein activity and abundance is ubiquitin. Ubiquitin ligase enzymes tag proteins for degradation by adding a chain of ubiquitin peptides. We recently showed that one ubiquitin ligase, the Anaphase-Promoting Complex (APC), inhibits signaling for muscle contraction at the neuromuscular junction (NMJ) in Caenorhabditis elegans roundworms. These animals have a simple nervous system, yet share similar genes and proteins with humans. The C. elegans NMJ uses a balance of excitatory and inhibitory neuronal signaling to control muscle contraction. Although we know the APC acts in inhibitory neurons to control NMJ function, much is still unknown about its relevant target proteins . My focus is to define the relationship between the APC and the synaptic protein SYD-2. SYD-2 is a possible APC substrate because it contains an APC recognition site and promotes NMJ signaling. SYD-2 also accumulates at inhibitory synapses in APC mutants. Initial studies testing total SYD-2 abundance in C. elegans lacking the APC versus wild type animals revealed no difference in SYD-2 protein levels, suggesting local effects on synaptic SYD-2 abundance. Behavioral assays confirmed the requirement for SYD-2 in muscle contraction. Future studies will test if the APC and SYD-2 control muscle contraction by acting in the same genetic pathway. Since synaptic regulation is disrupted in neurological disorders, investigatingthese proteins may aid our understanding of these disorders