Understanding How Sequence Differences Among Glutamate Transporters Might Contribute to their Differential Function in Glutamate Clearance in C. elegans
In the nervous system, high circuit resolution requires efficient post-signaling clearance of the neurotransmitter. Glutamate-mediated neurotransmission involves the release of glutamate (Glu) into the synaptic cleft by the presynaptic cell and binding to glutamate receptors (GluR) on the postsynaptic cell, leading to activation of a signal transduction cascade. Neurotransmission is eventually terminated by Glu uptake via glutamate transporters (GluT). Inefficient Glu clearance is detrimental to precise rapid signaling, can lead to blurring of circuit resolution by inadvertent Glu spillover to nearby circuits, and may even be neurotoxic. While classical views depict synapses as insulated by glia, recent technological advances show that synaptic organization in critical brain regions deviate from this doctrine. Instead, these studies show synapses with far less glial coverage and a wider extracellular space. How these regions still manage to maintain circuit fidelity is not clear. Furthermore, Glu clearance is mediated by a number of different GluTs, each with its specialized sequence, location, and slightly different physiological properties. The significance of this GluT specialization remains unclear. In this study we propose that robust Glu clearance is achieved despite poor anatomical insulation through a dynamic interaction between specialized clearance strategies and specific functional characteristics of GluTs that stem from their differential sequence/structure. We use transgenics and optogenetics in intact animals to study this relationship in the transparent nematode C. elegans. We examine sequence differences between different nematode GluTs and ask if these variations might have functional consequences, by swapping the expression of one GluT with that of another. We also examine the role of these GluTs in their native locations by assessing their role in specific synapses. Understanding the differential role of GluTs in diverse synaptic organizations will promote our comprehension of critical aspects of neurophysiology and might suggest target sites for the development of therapeutic interventions in Glu-associated neurodegenerative disorders.
Glutamate, Glutamate Transporters, GluTs, C.elegans, MosSCI, GCaMP Imaging, Molecular and Cellular Neuroscience
City University of New York - City College
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