Neuronal Depolarization Drives Increased Dopamine Synaptic Vesicle Loading via VGLUT

Abstract

SUMMARY The ability of presynaptic dopamine terminals to tune neurotransmitter release to meet the demands of neuronal activity is critical to neurotransmission. Although vesicle content has been assumed to be static, in vitro data increasingly suggest that cell activity modulates vesicle content. Here, we use a coordinated genetic, pharmacological, and imaging approach in Drosophila to study the presynaptic machinery responsible for these vesicular processes in vivo. We show that cell depolarization increases synaptic vesicle dopamine content prior to release via vesicular hyperacidification. This depolarization-induced hyperacidification is mediated by the vesicular glutamate transporter (VGLUT). Remarkably, both depolarization-induced dopamine vesicle hyperacidification and its dependence on VGLUT2 are seen in ventral midbrain dopamine neurons in the mouse. Together, these data suggest that in response to depolarization, dopamine vesicles utilize a cascade of vesicular transporters to dynamically increase the vesicular pH gradient, thereby increasing dopamine vesicle content.

Role for VGLUT2 in selective vulnerability of midbrain dopamine neurons

“…This conclusion is based on our finding that loss of VGLUT2 increased susceptibility to the DA-selective neurotoxins 6-OHDA and MPTP. We have previously observed that the vesicular coentry of glutamate through VGLUT can increase the driving force for VMAT2-mediated exchange in both mice and flies (6,54). This mechanism can increase the quantal content of DA and other cationic transmitters (6,(55)(56)(57)(58), but could also help sequester toxic VMAT2 substrates, such as 6-OHDA or 1-methyl-4-phenylpyridinium (MPP + ), away from sensitive cellular compartments or processes.…”

The intertwined roles of circadian rhythmsand neuronal metabolism fueling drug reward and addiction

“…We are just beginning to understand the role of astrocyte specific molecular clocks and their role in relevant neural circuits and behaviors [142,143]. Intriguingly, we have recently shown that DA neurons projecting to the NAc from the VTA can tune vesicular DA content and release in response to increases in firing [144]. These neurons concomitantly load DA vesicles with glutamate to facilitate this activity-dependent increase in DA loading and release.…”

Membrane composition influences the conformation and function of the dopamine transporter in vivo

“…FSCV was performed as previously described (Aguilar et al, 2017). Briefly, coronal brain slices with thickness of 250-300 µm containing cortex and striatum were prepared from 8-12 week old mice using a vibratome (Leica) and ice-cold cutting solution consisting of (in mM): glucose (10), NaCl (125.2), NaHCO3 (26), KCl (2.5), MgSO4 (3.7), NaH2PO4·6H2O (0.3), KH2PO4·6H2O (0.3).…”