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

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 Ca(2+)-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.

CHOLINE TRANSPORTER-LIKE1 is required for sieve plate development to mediate long-distance cell-to-cell communication

“…This process has been shown to regulate the abundance and polarity of various transporters, such as CHT1 in human embryonic kidney and neuroblastoma cells 39,[55][56][57][58] , aquaporins 59 and PIN-FORMED (PIN) auxin efflux carriers [60][61][62] in Arabidopsis. Our observation that CHER1 is rapidly endocytosed at forming cell plates suggests that a specific vesicle transport machinery is employed to continuously target CHER1 to the forming sieve plates.…”

Metabotropic Glutamate Receptor-Mediated Cell Signaling Pathways Are Altered in a Mouse Model of Huntington's Disease

“…Plasma membrane proteins of striatal prisms prepared as described above were biotinylated with sulfo-NHS-SS-biotin for 1 h on ice, as described previously (Ribeiro et al, 2007). To quench the biotinylation reaction, slices were washed and incubated for 30 min with cold 100 mM glycine in HBSS, followed by 3 washes with cold HBSS.…”

Substrate-Induced Internalization of the High-Affinity Choline Transporter

“…Depolarization induces an increase in the maximal uptake rate of choline (Murrin and Kuhar, 1976) or in the maximal binding capacity of HC-3 (Saltarelli et al, 1987), suggesting the increase in cell-surface expression of CHT1. This has recently been explained by activity-dependent vesicular trafficking of the intracellular pool of CHT1 to the plasma membrane Ribeiro et al, 2003Ribeiro et al, , 2007Ivy et al, 2010). Cellular trafficking of CHT1 may also be regulated by its phosphorylation (Gates et al, 2004) or its interaction with other proteins, such as the amyloid-␤ precursor protein (Wang et al, 2007).…”