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Bowton E, Saunders C, Reddy IA, Campbell NG, Hamilton PJ, Henry LK, Coon H, Sakrikar D, Veenstra-VanderWeele JM, Blakely RD, Sutcliffe J, Matthies HJG, Erreger K, Galli A. SLC6A3 coding variant Ala559Val found in two autism probands alters dopamine transporter function and trafficking. Transl Psychiatry 2014; 4:e464. [PMID: 25313507 PMCID: PMC4350523 DOI: 10.1038/tp.2014.90] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Revised: 08/11/2014] [Accepted: 08/12/2014] [Indexed: 12/12/2022] Open
Abstract
Emerging evidence associates dysfunction in the dopamine (DA) transporter (DAT) with the pathophysiology of autism spectrum disorder (ASD). The human DAT (hDAT; SLC6A3) rare variant with an Ala to Val substitution at amino acid 559 (hDAT A559V) was previously reported in individuals with bipolar disorder or attention-deficit hyperactivity disorder (ADHD). We have demonstrated that this variant is hyper-phosphorylated at the amino (N)-terminal serine (Ser) residues and promotes an anomalous DA efflux phenotype. Here, we report the novel identification of hDAT A559V in two unrelated ASD subjects and provide the first mechanistic description of its impaired trafficking phenotype. DAT surface expression is dynamically regulated by DAT substrates including the psychostimulant amphetamine (AMPH), which causes hDAT trafficking away from the plasma membrane. The integrity of DAT trafficking directly impacts DA transport capacity and therefore dopaminergic neurotransmission. Here, we show that hDAT A559V is resistant to AMPH-induced cell surface redistribution. This unique trafficking phenotype is conferred by altered protein kinase C β (PKCβ) activity. Cells expressing hDAT A559V exhibit constitutively elevated PKCβ activity, inhibition of which restores the AMPH-induced hDAT A559V membrane redistribution. Mechanistically, we link the inability of hDAT A559V to traffic in response to AMPH to the phosphorylation of the five most distal DAT N-terminal Ser. Mutation of these N-terminal Ser to Ala restores AMPH-induced trafficking. Furthermore, hDAT A559V has a diminished ability to transport AMPH, and therefore lacks AMPH-induced DA efflux. Pharmacological inhibition of PKCβ or Ser to Ala substitution in the hDAT A559V background restores AMPH-induced DA efflux while promoting intracellular AMPH accumulation. Although hDAT A559V is a rare variant, it has been found in multiple probands with neuropsychiatric disorders associated with imbalances in DA neurotransmission, including ADHD, bipolar disorder, and now ASD. These findings provide valuable insight into a new cellular phenotype (altered hDAT trafficking) supporting dysregulated DA function in these disorders. They also provide a novel potential target (PKCβ) for therapeutic interventions in individuals with ASD.
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Affiliation(s)
- E Bowton
- Departments of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN, USA,Vanderbilt Brain Institute, Vanderbilt University Medical Center, Nashville, TN, USA
| | - C Saunders
- Vanderbilt Brain Institute, Vanderbilt University Medical Center, Nashville, TN, USA,Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - I A Reddy
- Departments of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN, USA,Vanderbilt Brain Institute, Vanderbilt University Medical Center, Nashville, TN, USA
| | - N G Campbell
- Departments of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN, USA,Vanderbilt Brain Institute, Vanderbilt University Medical Center, Nashville, TN, USA
| | - P J Hamilton
- Departments of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN, USA,Vanderbilt Brain Institute, Vanderbilt University Medical Center, Nashville, TN, USA
| | - L K Henry
- Department of Basic Sciences, University of North Dakota, Grand Forks, ND, USA
| | - H Coon
- Department of Psychiatry, University of Utah, Salt Lake City, UT, USA
| | - D Sakrikar
- Vanderbilt Brain Institute, Vanderbilt University Medical Center, Nashville, TN, USA,Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - J M Veenstra-VanderWeele
- Vanderbilt Brain Institute, Vanderbilt University Medical Center, Nashville, TN, USA,Department of Psychiatry, Vanderbilt University Medical Center, Nashville, TN, USA
| | - R D Blakely
- Vanderbilt Brain Institute, Vanderbilt University Medical Center, Nashville, TN, USA,Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - J Sutcliffe
- Departments of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN, USA,Vanderbilt Brain Institute, Vanderbilt University Medical Center, Nashville, TN, USA,Department of Psychiatry, Vanderbilt University Medical Center, Nashville, TN, USA
| | - H J G Matthies
- Departments of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN, USA,Vanderbilt Brain Institute, Vanderbilt University Medical Center, Nashville, TN, USA,N-PISA Neuroscience Program In Substance Abuse, Vanderbilt University Medical Center, Nashville, TN, USA,Departments of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, 465 21st Avenue South, MRB3, Room 7124, Nashville, TN 37232, USA E-mail: or
| | - K Erreger
- Departments of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN, USA,Vanderbilt Brain Institute, Vanderbilt University Medical Center, Nashville, TN, USA,N-PISA Neuroscience Program In Substance Abuse, Vanderbilt University Medical Center, Nashville, TN, USA,Departments of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, 465 21st Avenue South, MRB3, Room 7124, Nashville, TN 37232, USA E-mail: or
| | - A Galli
- Departments of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN, USA,Vanderbilt Brain Institute, Vanderbilt University Medical Center, Nashville, TN, USA,N-PISA Neuroscience Program In Substance Abuse, Vanderbilt University Medical Center, Nashville, TN, USA,Departments of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, 465 21st Avenue South, MRB3, Room 7130A, Nashville, TN 37232, USA. E-mail:
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Takahashi H, Namiki H. Mechanism of membrane redistribution of protein kinase C by its ATP-competitive inhibitors. Biochem J 2007; 405:331-40. [PMID: 17373912 PMCID: PMC1904528 DOI: 10.1042/bj20070299] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
ATP-competitive inhibitors of PKC (protein kinase C) such as the bisindolylmaleimide GF 109203X, which interact with the ATP-binding site in the PKC molecule, have also been shown to affect several redistribution events of PKC. However, the reason why these inhibitors affect the redistribution is still controversial. In the present study, using immunoblot analysis and GFP (green fluorescent protein)-tagged PKC, we showed that, at commonly used concentrations, these ATP-competitive inhibitors alone induced redistribution of DAG (diacylglycerol)-sensitive PKCalpha, PKCbetaII, PKCdelta and PKCepsilon, but not atypical PKCzeta, to the endomembrane or the plasma membrane. Studies with deletion and point mutants showed that the DAG-sensitive C1 domain of PKC was required for membrane redistribution by these inhibitors. Furthermore, membrane redistribution was prevented by the aminosteroid PLC (phospholipase C) inhibitor U-73122, although an ATP-competitive inhibitor had no significant effect on acute DAG generation. Immunoblot analysis showed that an ATP-competitive inhibitor enhanced cell-permeable DAG analogue- or phorbol-ester-induced translocation of endogenous PKC. Furthermore, these inhibitors also enhanced [3H]phorbol 12,13-dibutyrate binding to the cytosolic fractions from PKCalpha-GFP-overexpressing cells. These results clearly demonstrate that ATP-competitive inhibitors cause redistribution of DAG-sensitive PKCs to membranes containing endogenous DAG by altering the DAG sensitivity of PKC and support the idea that the inhibitors destabilize the closed conformation of PKC and make the C1 domain accessible to DAG. Most importantly, our findings provide novel insights for the interpretation of studies using ATP-competitive inhibitors, and, especially, suggest caution about the interpretation of the relationship between the redistribution and kinase activity of PKC.
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Affiliation(s)
- Hideyuki Takahashi
- Department of Biology, School of Education, Waseda University, Shinjuku-ku, Tokyo 169-0051, Japan.
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