title: Nonclassical, distinct endocytic signals dictate constitutive and PKC-regulated neurotransmitter transporter internalization.
abstract: Neurotransmitter transporters are critical for synaptic neurotransmitter inactivation. Transporter inhibitors markedly increase the duration and magnitude of synaptic transmission, underscoring the importance of transporter activity in neurotransmission. Recent studies indicate that membrane trafficking dynamically governs neuronal transporter cell-surface presentation in a protein kinase C-regulated manner, suggesting that transporter trafficking profoundly affects synaptic signaling. However, the molecular architecture coupling neurotransmitter transporters to the endocytic machinery is not defined. Here, we identify nonclassical, distinct endocytic signals in the dopamine transporter (DAT) that are necessary and sufficient to drive constitutive and protein kinase C-regulated DAT internalization. The DAT internalization signal is conserved across SLC6 neurotransmitter carriers and is functional in the homologous norepinephrine transporter, suggesting that this region is likely to be the endocytic signal for all SLC6 neurotransmitter transporters. The DAT endocytic signal does not conform to classic internalization motifs, suggesting that SLC6 neurotransmitter transporters may have evolved unique endocytic mechanisms.
authors.affiliation: Brudnick Neuropsychiatric Research Institute, Department of Psychiatry, University of Massachusetts Medical School, 303 Belmont Street, Worcester, Massachusetts 01604, USA.
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Holton
authors.forename: Merewyn K
authors.initials: MK
authors.lastname: Loder
authors.forename: Haley E
authors.initials: HE
authors.lastname: Melikian
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D017124:Conserved Sequence; D006224:Cricetinae; D003412:Cricetulus; D050483:Dopamine Plasma Membrane Transport Proteins; D004705:Endocytosis / Q000502:physiology*; D050485:GABA Plasma Membrane Transport Proteins; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics / Q000502:physiology*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000502:physiology*; D016716:PC12 Cells; D011493:Protein Kinase C / Q000502:physiology*; D017434:Protein Structure, Tertiary / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D050483:Dopamine Plasma Membrane Transport Proteins; D050485:GABA Plasma Membrane Transport Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; C493214:SLC6A3 protein, human; C493216:Slc6a3 protein, rat; D011493:Protein Kinase C