Acidification is required for the function of many intracellular organelles, but methods to acutely manipulate their intraluminal pH have not been available.

Researchers in the journal Nature Neuroscience present a targeting strategy to selectively express the light-driven proton pump Arch3 on synaptic vesicles.

This new tool, pHoenix, can functionally replace endogenous proton pumps, enabling optogenetic control of vesicular acidification and neurotransmitter accumulation.

Under physiological conditions, glutamatergic vesicles are nearly full, as additional vesicle acidification with pHoenix only slightly increased the quantal size.

By contrast, authors found that incompletely filled vesicles exhibited a lower release probability than full vesicles, suggesting preferential exocytosis of vesicles with high transmitter content.

This subcellular targeting approach can be transferred to other organelles, as demonstrated for a pHoenix variant that allows light-activated acidification of lysosomes.

http://www.nature.com/neuro/journal/vaop/ncurrent/full/nn.4161.html