N-Glycosylation is required for Na+-dependent vitamin C transporter functionality

Veedamali S. Subramanian; Jonathan S. Marchant; Jack C. Reidling; Hamid M. Said

doi:10.1016/j.bbrc.2008.06.120

N-Glycosylation is required for Na⁺-dependent vitamin C transporter functionality

Veedamali S. Subramanian, Jonathan S. Marchant, Jack C. Reidling, Hamid M. Said

Research output: Contribution to journal › Article › peer-review

41 Scopus citations

Abstract

The human sodium-dependent vitamin C transporters (hSVCT1 and hSVCT2) mediate cellular uptake of ascorbic acid. Both these transporters contain potential sites for N-glycosylation in their extracellular domains (Asn-138, Asn-144 [hSVCT1]; Asn-188, Asn-196 [hSVCT2]), however the role of N-glycosylation in transporter function is unexplored. On the basis of the result that tunicamycin decreased ¹⁴C-ascorbic acid uptake in HepG2 cells, we systematically ablated all consensus N-glycosylation sites in hSVCT1 and hSVCT2 to resolve any effects on ascorbic acid uptake, transporter expression and targeting. We show that removal of individual N-glycosylation sites significantly impairs protein expression and consequently ascorbic acid uptake for hSVCT1 mutants (N138Q is retained intracellularly) and for hSVCT2 mutants (all of which reach the cell surface). N-Glycosylation is therefore essential for vitamin C transporter functionality.

Original language	English (US)
Pages (from-to)	123-127
Number of pages	5
Journal	Biochemical and Biophysical Research Communications
Volume	374
Issue number	1
DOIs	https://doi.org/10.1016/j.bbrc.2008.06.120
State	Published - Sep 12 2008

Bibliographical note

Funding Information:
This study is supported by the Department of VA, NIH grants DK 056061 (H.M.S.), DK-73032 (J.C.R.) and DK-71538 (V.S.S.). Work in the Marchant lab is supported by NIH (#NS046783) and NSF (CAREER #0237946). Appendix A

Keywords

Ascorbic acid
Transport
hSVCT1
hSVCT2

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abstract = "The human sodium-dependent vitamin C transporters (hSVCT1 and hSVCT2) mediate cellular uptake of ascorbic acid. Both these transporters contain potential sites for N-glycosylation in their extracellular domains (Asn-138, Asn-144 [hSVCT1]; Asn-188, Asn-196 [hSVCT2]), however the role of N-glycosylation in transporter function is unexplored. On the basis of the result that tunicamycin decreased 14C-ascorbic acid uptake in HepG2 cells, we systematically ablated all consensus N-glycosylation sites in hSVCT1 and hSVCT2 to resolve any effects on ascorbic acid uptake, transporter expression and targeting. We show that removal of individual N-glycosylation sites significantly impairs protein expression and consequently ascorbic acid uptake for hSVCT1 mutants (N138Q is retained intracellularly) and for hSVCT2 mutants (all of which reach the cell surface). N-Glycosylation is therefore essential for vitamin C transporter functionality.",

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AU - Reidling, Jack C.

AU - Said, Hamid M.

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