Sodium-dependent vitamin C transporter 2 (SVCT2) is necessary for the uptake of

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Glia. 2009 Aug 11.

Sodium-dependent vitamin C transporter 2 (SVCT2) is necessary for the uptake of

L-ascorbic acid into Schwann cells.

Gess B, Lohmann C, Halfter H, Young P.

Department of Neurology, University of Muenster, 48129 Muenster, Germany.

Ascorbic acid has been shown to be an essential component for in vitro

myelination and to improve the clinical and pathological phenotype of a mouse

model of Charcot-Marie-tooth disease 1A.

The mechanism of ascorbic acid uptake into peripheral nerves, however, has not

been addressed so far.

Hence, we studied the expression and activity of sodium-dependent vitamin C

transporters 1 and 2 (SVCT1 and 2) in the peripheral nervous system.

Using immunohistochemistry, immunoblotting, and reverse transcription PCR, we

could show that SVCT1 and 2 were differentially expressed in myelinated

peripheral nerve fibers and Schwann cell (SC) cultures.

SVCT1 was expressed at very low levels confined to the axons, whereas SVCT2 was

highly expressed both in the axons and in the SCs. SVCT2 was localized

particularly in SC compartments of uncompacted myelin. Uptake assays using

(14)C-labeled ascorbic acid showed transport of ascorbic acid into SC cultures.

Ascorbic acid transport was dependent on the concentration of sodium, magnesium,

and calcium in the extracellular medium. Treatment with the flavonoid phloretin,

a known inhibitor of SVCT1 and 2, and specific RNA interference with SVCT2

caused significant reductions in ascorbic acid uptake into SCs. P

hloretin-inhibited uptake of ascorbic acid was further shown in freshly

dissected, cell-culture-naïve rat sciatic nerves. These results provide evidence

for the first time that uptake of ascorbic acid in the peripheral nervous system

is crucially dependent on the expression and activity of SVCT2.