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Inhibition of alpha-glucosidases I and II increases the cell surface expression of functional class A macrophage scavenger receptor (SR-A) by extending its half-life

Inhibition of alpha-glucosidases I and II increases the cell surface expression of functional class A macrophage scavenger receptor (SR-A) by extending its half-life
Inhibition of alpha-glucosidases I and II increases the cell surface expression of functional class A macrophage scavenger receptor (SR-A) by extending its half-life
The class A scavenger receptor (SR-A) is a multifunctional trimeric membrane glycoprotein involved in atherogenesis. The mature receptor can mediate the binding and internalization of a number of specific ligands, including modified low-density lipoprotein. We have investigated the effects of inhibiting N-glycan processing on SR-A expression, distribution, and activity in the murine macrophage cell line RAW264.7. We have found that SR-A normally interacts with calnexin in the endoplasmic reticulum and in its mature form carries complex N-glycans. The imino sugar, N-butyldeoxynojirimycin (NB-DNJ) is an inhibitor of the N-glycan processing enzymes -glucosidases I and II. Following NB-DNJ treatment SR-A became Endo H-sensitive, consistent with inhibition of N-glycan processing. A dose-dependent increase in cell surface expression of SR-A was observed in response to NB-DNJ treatment. The receptor on inhibitor-treated cells was still functional because the increased surface expression resulted in a proportional enhancement in the endocytosis of the ligand, acetylated low-density lipoprotein. The expression of SR-A on NB-DNJ cultured cells was further enhanced by co-treatment with interferon-. Quantitative reverse transcriptase-PCR analysis did not show a significant difference in the amount of SR-A mRNA in NB-DNJ-treated RAW264.7 cells. However, the half-life of SR-A protein was significantly increased. These data indicate the retention of glucosylated N-glycans does not result in gross misfolding and degradation of this receptor or prevent its transport to the cell surface. SR-A interacts with calnexin and when the association is prevented changes in the recycling kinetics and rate of turnover of the receptor result, leading to enhanced cell surface expression.
0021-9258
39303-39309
Tian, G.
ea24fc04-c420-41d0-8e31-0ddc8b8896a2
Wilcockson, D.
5d01a633-d527-448f-8c41-141b3bef250c
Perry, V.H.
8f29d36a-8e1f-4082-8700-09483bbaeae4
Rudd, P.M.
61889150-348c-4c38-b0ca-25f84641584f
Dwek, R.A.
06a873cf-f7f5-467f-99f3-d168b896da27
Platt, F.M.
6a662d9c-7f35-47c6-b095-6f104f081c3a
Platt, N.
85f5bff6-a1b9-4b60-acff-828638bcac7c
Tian, G.
ea24fc04-c420-41d0-8e31-0ddc8b8896a2
Wilcockson, D.
5d01a633-d527-448f-8c41-141b3bef250c
Perry, V.H.
8f29d36a-8e1f-4082-8700-09483bbaeae4
Rudd, P.M.
61889150-348c-4c38-b0ca-25f84641584f
Dwek, R.A.
06a873cf-f7f5-467f-99f3-d168b896da27
Platt, F.M.
6a662d9c-7f35-47c6-b095-6f104f081c3a
Platt, N.
85f5bff6-a1b9-4b60-acff-828638bcac7c

Tian, G., Wilcockson, D., Perry, V.H., Rudd, P.M., Dwek, R.A., Platt, F.M. and Platt, N. (2004) Inhibition of alpha-glucosidases I and II increases the cell surface expression of functional class A macrophage scavenger receptor (SR-A) by extending its half-life. The Journal of Biological Chemistry, 279 (38), 39303-39309. (doi:10.1074/jbc.M405219200).

Record type: Article

Abstract

The class A scavenger receptor (SR-A) is a multifunctional trimeric membrane glycoprotein involved in atherogenesis. The mature receptor can mediate the binding and internalization of a number of specific ligands, including modified low-density lipoprotein. We have investigated the effects of inhibiting N-glycan processing on SR-A expression, distribution, and activity in the murine macrophage cell line RAW264.7. We have found that SR-A normally interacts with calnexin in the endoplasmic reticulum and in its mature form carries complex N-glycans. The imino sugar, N-butyldeoxynojirimycin (NB-DNJ) is an inhibitor of the N-glycan processing enzymes -glucosidases I and II. Following NB-DNJ treatment SR-A became Endo H-sensitive, consistent with inhibition of N-glycan processing. A dose-dependent increase in cell surface expression of SR-A was observed in response to NB-DNJ treatment. The receptor on inhibitor-treated cells was still functional because the increased surface expression resulted in a proportional enhancement in the endocytosis of the ligand, acetylated low-density lipoprotein. The expression of SR-A on NB-DNJ cultured cells was further enhanced by co-treatment with interferon-. Quantitative reverse transcriptase-PCR analysis did not show a significant difference in the amount of SR-A mRNA in NB-DNJ-treated RAW264.7 cells. However, the half-life of SR-A protein was significantly increased. These data indicate the retention of glucosylated N-glycans does not result in gross misfolding and degradation of this receptor or prevent its transport to the cell surface. SR-A interacts with calnexin and when the association is prevented changes in the recycling kinetics and rate of turnover of the receptor result, leading to enhanced cell surface expression.

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Published date: 2004

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Local EPrints ID: 41141
URI: http://eprints.soton.ac.uk/id/eprint/41141
ISSN: 0021-9258
PURE UUID: 121bdce0-8682-438f-bd86-ee99dceebaa9

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Date deposited: 21 Jul 2006
Last modified: 08 Jan 2022 18:58

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Contributors

Author: G. Tian
Author: D. Wilcockson
Author: V.H. Perry
Author: P.M. Rudd
Author: R.A. Dwek
Author: F.M. Platt
Author: N. Platt

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