Ctr9, a Protein in the Transcription Complex Paf1, Regulates Dopamine Transporter Activity at the Plasma Membrane

J Biol Chem. 2015 Jul 17;290(29):17848-62. doi: 10.1074/jbc.M115.646315. Epub 2015 Jun 5.

Abstract

Dopamine (DA) is a major regulator of sensorimotor and cognitive functions. The DA transporter (DAT) is the key protein that regulates the spatial and temporal activity of DA release into the synaptic cleft via the rapid reuptake of DA into presynaptic termini. Several lines of evidence have suggested that transporter-interacting proteins may play a role in DAT function and regulation. Here, we identified the tetratricopeptide repeat domain-containing protein Ctr9 as a novel DAT binding partner using a yeast two-hybrid system. We showed that Ctr9 is expressed in dopaminergic neurons and forms a stable complex with DAT in vivo via GST pulldown and co-immunoprecipitation assays. In mammalian cells co-expressing both proteins, Ctr9 partially colocalizes with DAT at the plasma membrane. This interaction between DAT and Ctr9 results in a dramatic enhancement of DAT-mediated DA uptake due to an increased number of DAT transporters at the plasma membrane. We determined that the binding of Ctr9 to DAT requires residues YKF in the first half of the DAT C terminus. In addition, we characterized Ctr9, providing new insight into this protein. Using three-dimensional modeling, we identified three novel tetratricopeptide repeat domains in the Ctr9 sequence, and based on deletion mutation experiments, we demonstrated the role of the SH2 domain of Ctr9 in nuclear localization. Our results demonstrate that Ctr9 localization is not restricted to the nucleus, as previously described for the transcription complex Paf1. Taken together, our data provide evidence that Ctr9 modulates DAT function by regulating its trafficking.

Keywords: dopamine transporter; membrane targeting; membrane trafficking; membrane transport; protein-protein interaction; tetratricopeptide domain repeat; transcription factor; uptake activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cell Line
  • Dopamine Plasma Membrane Transport Proteins / analysis
  • Dopamine Plasma Membrane Transport Proteins / metabolism*
  • Humans
  • Molecular Docking Simulation
  • Molecular Sequence Data
  • Nuclear Proteins / analysis
  • Nuclear Proteins / metabolism*
  • Phosphoproteins / analysis
  • Phosphoproteins / metabolism*
  • Protein Interaction Domains and Motifs
  • Protein Transport
  • Rats
  • Transcription Factors
  • src Homology Domains

Substances

  • CTR9 protein, human
  • CTR9 protein, rat
  • Dopamine Plasma Membrane Transport Proteins
  • Nuclear Proteins
  • Phosphoproteins
  • Transcription Factors

Associated data

  • PDB/1VFH
  • PDB/1W3B
  • PDB/1w3b
  • PDB/2NQS
  • PDB/4M48