BAJEC, MR*; PEARCE, J; STEWART, BA; Div. of Life Sciences, University of Toronto at Scarborough; Div. of Life Sciences, University of Toronto at Scarborough; Div. of Life Sciences, University of Toronto at Scarborough: Ultrastructural Analysis of Drosophila NSF Mutants with Impaired Synaptic Transmission

A key molecule regulating neurotransmitter secretion is the ATPase, n-ethylmaleimide sensitive fusion protein (NSF). The main activity of this molecule is thought to be disassembly of the SNARE protein complex. We have previously shown (Stewart et al. 2002, J. Neurobiol. 51, 261-271), using site-directed mutagenesis, that a dominant-negative form of Drosophila melanogaster NSF2 greatly suppresses synaptic transmission at the larval neuromuscular junction, when the construct is expressed in neurons. Interestingly, this phenotype occurs independently of any change in SNARE complex abundance. Further physiological analysis revealed that the population of readily-releasable synaptic vesicles was greatly reduced in the larvae expressing the NSF2 construct. Here we address the possibility that there has been a redistribution of synaptic vesicles away from release sites in the mutant NSF2 larvae using electron microscopy. Our results indicate that there is not a reduction in the total population of synaptic vesicles, and we are now analyzing the size of the vesicle population in sub-compartments of the nerve terminal. These results will allow us to determine if one effect of the mutant NSF2 construct is a relocalization of synaptic vesicles away from the synaptic active zone of Drosophila melanogaster larval synapses.