A Poly-Glutamine Region in theDrosophilaVAChT Dictates Fill-Level of Cholinergic Synaptic Vesicles

Abstract

While the primary role of vesicular transporters is to load neurotransmitters into synaptic vesicles (SVs), accumulating evidence suggests that these proteins also contribute to additional aspects of synaptic function, including vesicle release. In this study, we extend the role of the VAChT to include regulating the transmitter content of SVs. We report that manipulation of a C-terminal poly-glutamine (polyQ) region in the Drosophila VAChT is sufficient to influence transmitter content, and release frequency, of cholinergic vesicles from the terminals of premotor interneurons. Specifically, we find that reduction of the polyQ region, by one glutamine residue ( 13Q to 12Q ), results in a significant increase in both amplitude and frequency of spontaneous cholinergic miniature EPSCs (mEPSCs) recorded in the aCC and RP2 motoneurons. Moreover, this truncation also results in evoked synaptic currents that show increased duration: consistent with increased ACh release. By contrast, extension of the polyQ region by one glutamine ( 13Q to 14Q ) is sufficient to reduce mEPSC amplitude and frequency and, moreover, prevents evoked SV release. Finally, a complete deletion of the polyQ region (13Q to 0Q) has no obvious effects to mEPSCs, but again evoked synaptic currents show increased duration. The mechanisms that ensure SVs are filled to physiologically-appropriate levels remain unknown. Our study identifies the polyQ region of the insect VAChT to be required for correct vesicle transmitter loading and, thus, provides opportunity to increase understanding of this critical aspect of neurotransmission.

Enriched environment attenuates hippocampal theta and gamma rhythms dysfunction in chronic cerebral hypoperfusion via improving imbalanced neural afferent levels

“…The hippocampus receives projections from various types of neurons from different brain regions. Vesicular transporters (VTs) situated on the synaptic vesicles (SVs) at these projecting neurons’ axon terminals, load neurotransmitters into the SVs and contribute to vesicle release ( Vernon et al, 2019 ). Therefore, we examined the VTs levels of three classical neurotransmitters.…”