Apolipoprotein[a] secretion from hepatoma cells is regulated in a size-dependent manner by alterations in disulfide bond formation
Apolipoprotein[a] (apo[a]) is a large disulfide linked glycoprotein synthesized by hepatocytes. We have examined the role of disulfide bond formation in the processing of apo[a] using human and rat hepatoma cells expressing apo[a] isoforms containing varying numbers of kringle 4 (K4) domains, follow...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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Elsevier
2003-04-01
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| Series: | Journal of Lipid Research |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S002222752031172X |
| _version_ | 1818385204560003072 |
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| author | Fatiha Nassir Yan Xie Nicholas O. Davidson |
| author_facet | Fatiha Nassir Yan Xie Nicholas O. Davidson |
| author_sort | Fatiha Nassir |
| collection | DOAJ |
| description | Apolipoprotein[a] (apo[a]) is a large disulfide linked glycoprotein synthesized by hepatocytes. We have examined the role of disulfide bond formation in the processing of apo[a] using human and rat hepatoma cells expressing apo[a] isoforms containing varying numbers of kringle 4 (K4) domains, following treatment with DTT. Hepatoma cells expressing 6- or 9-K4 isoforms revealed ∼90% inhibition of apo[a] secretion following DTT treatment, although larger isoforms containing 13- or 17-K4 domains demonstrated continued secretion (up to 30% of control values), suggesting that a fraction of the larger isoforms is at least partially DTT resistant. Wash-out experiments demonstrated that these effects were completely reversible for all isoforms studied, with no enhanced degradation associated with prolonged intracellular retention. DTT treatment was associated with enhanced binding of apo[a] with the endoplasmic reticulum-associated chaperone proteins calnexin, calreticulin, and BiP, which was reversible upon DTT removal. The chemical chaperone 6-aminohexanoic acid, previously demonstrated by others to rescue defective apo[a] secretion associated with alterations in glycosylation, failed to alter the secretion of apo[a] following DTT treatment.The demonstration that DTT modulates apo[a] secretion in a manner influenced by both the type and number of K4 repeats extends understanding of the mechanisms that regulate its exit from the endoplasmic reticulum. |
| first_indexed | 2024-12-14T03:34:26Z |
| format | Article |
| id | doaj.art-d8250213e24f4ba8927d1a95238009eb |
| institution | Directory Open Access Journal |
| issn | 0022-2275 |
| language | English |
| last_indexed | 2024-12-14T03:34:26Z |
| publishDate | 2003-04-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Journal of Lipid Research |
| spelling | doaj.art-d8250213e24f4ba8927d1a95238009eb2022-12-21T23:18:40ZengElsevierJournal of Lipid Research0022-22752003-04-01444816827Apolipoprotein[a] secretion from hepatoma cells is regulated in a size-dependent manner by alterations in disulfide bond formationFatiha Nassir0Yan Xie1Nicholas O. Davidson2Departments of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110; Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, MO 63110Departments of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110; Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, MO 63110Departments of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110; Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, MO 63110Apolipoprotein[a] (apo[a]) is a large disulfide linked glycoprotein synthesized by hepatocytes. We have examined the role of disulfide bond formation in the processing of apo[a] using human and rat hepatoma cells expressing apo[a] isoforms containing varying numbers of kringle 4 (K4) domains, following treatment with DTT. Hepatoma cells expressing 6- or 9-K4 isoforms revealed ∼90% inhibition of apo[a] secretion following DTT treatment, although larger isoforms containing 13- or 17-K4 domains demonstrated continued secretion (up to 30% of control values), suggesting that a fraction of the larger isoforms is at least partially DTT resistant. Wash-out experiments demonstrated that these effects were completely reversible for all isoforms studied, with no enhanced degradation associated with prolonged intracellular retention. DTT treatment was associated with enhanced binding of apo[a] with the endoplasmic reticulum-associated chaperone proteins calnexin, calreticulin, and BiP, which was reversible upon DTT removal. The chemical chaperone 6-aminohexanoic acid, previously demonstrated by others to rescue defective apo[a] secretion associated with alterations in glycosylation, failed to alter the secretion of apo[a] following DTT treatment.The demonstration that DTT modulates apo[a] secretion in a manner influenced by both the type and number of K4 repeats extends understanding of the mechanisms that regulate its exit from the endoplasmic reticulum.http://www.sciencedirect.com/science/article/pii/S002222752031172Xlipoprotein[a]apolipoprotein B-100dithiothreitol |
| spellingShingle | Fatiha Nassir Yan Xie Nicholas O. Davidson Apolipoprotein[a] secretion from hepatoma cells is regulated in a size-dependent manner by alterations in disulfide bond formation Journal of Lipid Research lipoprotein[a] apolipoprotein B-100 dithiothreitol |
| title | Apolipoprotein[a] secretion from hepatoma cells is regulated in a size-dependent manner by alterations in disulfide bond formation |
| title_full | Apolipoprotein[a] secretion from hepatoma cells is regulated in a size-dependent manner by alterations in disulfide bond formation |
| title_fullStr | Apolipoprotein[a] secretion from hepatoma cells is regulated in a size-dependent manner by alterations in disulfide bond formation |
| title_full_unstemmed | Apolipoprotein[a] secretion from hepatoma cells is regulated in a size-dependent manner by alterations in disulfide bond formation |
| title_short | Apolipoprotein[a] secretion from hepatoma cells is regulated in a size-dependent manner by alterations in disulfide bond formation |
| title_sort | apolipoprotein a secretion from hepatoma cells is regulated in a size dependent manner by alterations in disulfide bond formation |
| topic | lipoprotein[a] apolipoprotein B-100 dithiothreitol |
| url | http://www.sciencedirect.com/science/article/pii/S002222752031172X |
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