title: Novel fluorescence-based approaches for the study of biogenic amine transporter localization, activity, and regulation.
abstract: Pre-synaptic norepinephrine (NE) and dopamine (DA) transporters (NET and DAT) terminate catecholamine synaptic transmission through reuptake of released neurotransmitter. Recent studies reveal that NET and DAT are tightly regulated by receptor and second messenger-linked signaling pathways. Common approaches for studying these transporters involve use of radiolabeled substrates or antagonists, methods possessing limited spatial resolution and that bear limited opportunities for repeated monitoring of living preparations. To circumvent these issues, we have explored two novel assay platforms that permit temporally resolved quantitation of transport activity and transporter protein localization. To monitor the binding and transport function of NET and DAT in real-time, we have investigated the uptake of the fluorescent organic compound 4-(4-diethylaminostyryl)-N-methylpyridinium iodide (ASP+). We have extended our previous single cell level application of this substrate to monitor transport activity via high-throughput assay platforms. Compared to radiotracer uptake methods, acquisition of ASP+ fluorescence is non-isotopic and allows for continuous, repeated transport measurements on both transfected and native preparations. Secondly, we have extended our application of small-molecule-conjugated fluorescent CdSe/ZnS nanocrystals, or quantum dots (Qdots), to utilize antibody and peptide ligands that can identify surface expressed transporters, receptors and other membrane proteins in living cell systems. Unlike typical organic fluorophores, Qdots are highly resistant to bleaching and can be conjugated to multiple ligands. They can also be illuminated by conventional light sources, yet produce narrow, gaussian emission spectra compatible with multiple target visualization (multiplexing). Together, these approaches offer novel opportunities to investigate changes in transporter function and distribution in real-time with superior spatial and temporal resolution.
authors.affiliation: Department of Pharmacology, Vanderbilt University School of Medicine, MRBII, Suite 7140, 465 21st Ave South, Nashville, TN 37232-8548, USA.
authors.forename: J N
authors.initials: JN
authors.lastname: Mason
authors.forename: H
authors.initials: H
authors.lastname: Farmer
authors.forename: I D
authors.initials: ID
authors.lastname: Tomlinson
authors.forename: J W
authors.initials: JW
authors.lastname: Schwartz
authors.forename: V
authors.initials: V
authors.lastname: Savchenko
authors.forename: L J
authors.initials: LJ
authors.lastname: DeFelice
authors.forename: S J
authors.initials: SJ
authors.lastname: Rosenthal
authors.forename: R D
authors.initials: RD
authors.lastname: Blakely
mesh_terms: D000906:Antibodies / Q000737:chemistry; D001681:Biological Assay / Q000379:methods*; D019187:Cadmium Compounds / Q000737:chemistry; D002395:Catecholamines / Q000378:metabolism*; D002460:Cell Line; D050483:Dopamine Plasma Membrane Transport Proteins; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000737:chemistry*; D006801:Humans; D007118:Immunoassay / Q000379:methods; D007700:Kinetics; D008024:Ligands; D008562:Membrane Glycoproteins / Q000032:analysis* / Q000037:antagonists & inhibitors / Q000378:metabolism; D049990:Membrane Transport Modulators; D026901:Membrane Transport Proteins / Q000032:analysis* / Q000037:antagonists & inhibitors / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000032:analysis* / Q000037:antagonists & inhibitors / Q000378:metabolism; D009448:Neurochemistry / Q000379:methods*; D050484:Norepinephrine Plasma Membrane Transport Proteins; D010455:Peptides / Q000737:chemistry; D011726:Pyridinium Compounds / Q000737:chemistry; D018036:Selenium Compounds / Q000737:chemistry; D013440:Sulfides / Q000737:chemistry; D027981:Symporters / Q000032:analysis* / Q000037:antagonists & inhibitors / Q000378:metabolism; D013696:Temperature; D017967:Zinc Compounds / Q000737:chemistry
chemical_list: C032315:4-(4-dimethylaminostyryl)-1-methylpyridinium; D000906:Antibodies; D019187:Cadmium Compounds; D002395:Catecholamines; D050483:Dopamine Plasma Membrane Transport Proteins; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D008024:Ligands; D008562:Membrane Glycoproteins; D049990:Membrane Transport Modulators; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D050484:Norepinephrine Plasma Membrane Transport Proteins; D010455:Peptides; D011726:Pyridinium Compounds; C493227:SLC6A2 protein, human; C493214:SLC6A3 protein, human; D018036:Selenium Compounds; D013440:Sulfides; D027981:Symporters; D017967:Zinc Compounds; C058667:cadmium selenide; C031238:zinc sulfide