Single molecule analysis of serotonin transporter regulation using antagonist-conjugated quantum dots reveals restricted, p38 MAPK-dependent mobilization underlying uptake activation.

Chang JC, Tomlinson ID, Warnement MR, Ustione A, Carneiro AM, Piston DW, Blakely RD, Rosenthal SJ
J Neurosci. 2012 32 (26): 8919-29

PMID: 22745492 · PMCID: PMC3426861 · DOI:10.1523/JNEUROSCI.0048-12.2012

The presynaptic serotonin (5-HT) transporter (SERT) is targeted by widely prescribed antidepressant medications. Altered SERT expression or regulation has been implicated in multiple neuropsychiatric disorders, including anxiety, depression and autism. Here, we implement a generalizable strategy that exploits antagonist-conjugated quantum dots (Qdots) to monitor, for the first time, single SERT proteins on the surface of serotonergic cells. We document two pools of SERT proteins defined by lateral mobility, one that exhibits relatively free diffusion, and a second, localized to cholesterol and GM1 ganglioside-enriched microdomains, that displays restricted mobility. Receptor-linked signaling pathways that enhance SERT activity mobilize transporters that, nonetheless, remain confined to membrane microdomains. Mobilization of transporters arises from a p38 MAPK-dependent untethering of the SERT C terminus from the juxtamembrane actin cytoskeleton. Our studies establish the utility of ligand-conjugated Qdots for analysis of the behavior of single membrane proteins and reveal a physical basis for signaling-mediated SERT regulation.

MeSH Terms (25)

Actins Animals beta-Cyclodextrins Cell Line, Transformed Cholera Toxin Cholesterol Cyclic GMP Cytochalasin D Enzyme Inhibitors Gangliosidosis, GM1 Imidazoles Ligands Membrane Microdomains Microscopy, Confocal Neurons Normal Distribution Nucleic Acid Synthesis Inhibitors p38 Mitogen-Activated Protein Kinases Protein Transport Pyridines Quantum Dots Rats Serotonin Serotonin Plasma Membrane Transport Proteins Thionucleotides

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