Regulated recycling and plasma membrane recruitment of the high-affinity choline transporter

Authors

  • Fabiola M. Ribeiro,

    1. Cell Biology Research Group, Robarts Research Institute London, Ontario, Canada
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  • Metta Pinthong,

    1. Cell Biology Research Group, Robarts Research Institute London, Ontario, Canada
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  • Stefanie A. G. Black,

    1. Cell Biology Research Group, Robarts Research Institute London, Ontario, Canada
    2. Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
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  • Alexis C. Gordon,

    1. Cell Biology Research Group, Robarts Research Institute London, Ontario, Canada
    2. Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
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  • Vania F. Prado,

    1. Departamento de Bioquimica-Imunologia ICB, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
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  • Marco A. M. Prado,

    1. Departamento de Farmacologia, ICB, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
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  • R. Jane Rylett,

    1. Cell Biology Research Group, Robarts Research Institute London, Ontario, Canada
    2. Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
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  • Stephen S. G. Ferguson

    1. Cell Biology Research Group, Robarts Research Institute London, Ontario, Canada
    2. Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
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Dr S.S.G. Ferguson, 1Cell Biology Research Group, as above.
E-mail: ferguson@robarts.ca

Abstract

The high-affinity choline transporter (CHT1) is responsible for uptake of choline from the synaptic cleft and supplying choline for acetylcholine synthesis. CHT1 internalization by clathrin-coated vesicles is proposed to represent a mechanism by which high-affinity choline uptake can be modulated. We show here that internalized CHT1 is rapidly recycled back to the cell surface in both human embryonic kidney cells (HEK 293 cells) and SH-SY5Y neuroblastoma cells. This rapidly recycling pool of CHT1 comprises about 10% of total CHT1 protein. In the SH-SY5Y neuroblastoma cell line K+-depolarization promotes Ca2+-dependent increase in the rate of CHT1 recycling to the plasma membrane without affecting the rate of CHT1 internalization. K+-depolarization also increases the size of the pool of CHT1 protein that can be mobilized to the plasma membrane. Thus, the activity-dependent increase in plasma membrane CHT1 localization appears to be regulated by two mechanisms: (i) an increase in the rate of externalization of the intracellular CHT1 pool; and (ii) the recruitment of additional intracellular transporters to the recycling pool.

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