Monocarboxylate Transport in Drosophila Larval Brain during Low and High Neuronal Activity

Abstract

The transport of lactate and pyruvate between glial cells and neurons plays an important role in the nervous system metabolic coupling. However, the mechanisms and characteristics that underlie the transport of monocarboxylates (MC-T) in vivo are poorly described. Here we use Drosophila expressing genetically-encoded FRET sensors to provide an ex vivo characterization of the MC-T in motor neurons and glial cells from the ventral nerve cord. We show that lactate/pyruvate transport on glial cells is coupled to protons and is more efficient than in neurons. Glial cells maintain higher levels of intracellular lactate generating a positive gradient towards neurons. Moreover, our results show that under increased activity lactate and pyruvate rise on motor neurons and suggest that this depends on the transfer of lactate from glial cells mediated in part by the previously described MC transporter Chaski, giving support to the in vivo glia to neurons lactate shuttling during activity.