VMAT2 is the protein that packs dopamine, serotonin, and other monoamines into synaptic vesicles. A study in Cell Reports captures high-resolution structures of VMAT2 in multiple states, revealing how it works - and how amphetamines reverse it.
The Vesicular Transporter
Before neurotransmitters can be released at synapses, they must be packaged into vesicles. VMAT2 uses the energy from proton gradients to pump monoamines into vesicles, concentrating them for release.
VMAT2 is also a drug target. Tetrabenazine and valbenazine, used for movement disorders, block it. And amphetamines hijack it to reverse monoamine flow.
Structures Across the Transport Cycle
Using cryo-electron microscopy, the researchers solved structures of VMAT2 bound to serotonin, histamine, amphetamine, tetrabenazine, and in unbound states. The structures reveal how the transporter opens to each side of the membrane and how substrates bind.
Serotonin and histamine bind in opposite orientations within the same pocket. Amphetamine binds differently, not engaging the protonation site that powers normal transport.
How Amphetamines Work
The structural data suggested that amphetamine might directly reverse VMAT2, causing monoamines to leak out of vesicles. Experiments with artificial membranes confirmed this: amphetamine directly induced release of a fluorescent monoamine analog via VMAT2.
This "exchange mechanism" - amphetamine goes in, monoamines come out - explains how amphetamines cause massive monoamine release and their psychostimulant effects.
Therapeutic Implications
Understanding VMAT2's structure and mechanism could inform development of new drugs for neurological diseases involving monoamine dysfunction, including Parkinson's disease, depression, and substance abuse.
Reference: Singh SK, et al. (2025). Molecular basis of vesicular monoamine transport and neurological drug interactions. Cell Reports. doi: 10.1016/j.celrep.2025.116490 | PMID: 41166311
Disclaimer: The image accompanying this article is for illustrative purposes only and does not depict actual experimental results, data, or biological mechanisms.