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The cellular degradation of the low density lipoprotein receptor and its ligand
The cellular degradation of the low density lipoprotein (LDL) receptor, and its ligand, LDL, were investigated in order to clarify certain mechanistic aspects of these important processes. Long-term lymphoblastoid cell lines and cultured human skin fibroblasts were used to examine the fate of ¹²⁵I-L...
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| Format: | Thesis |
| Language: | English |
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Division of Medical Biochemistry and Structural Biology
2018
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| _version_ | 1867613335670751232 |
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| access_status_str | Open Access |
| author | Casciola, Livia Angela Flavia |
| author2 | Coetzee, G A |
| author_browse | Casciola, Livia Angela Flavia Coetzee, G A |
| author_facet | Coetzee, G A Casciola, Livia Angela Flavia |
| author_sort | Casciola, Livia Angela Flavia |
| collection | Thesis |
| description | The cellular degradation of the low density lipoprotein (LDL) receptor, and its ligand, LDL, were investigated in order to clarify certain mechanistic aspects of these important processes. Long-term lymphoblastoid cell lines and cultured human skin fibroblasts were used to examine the fate of ¹²⁵I-LDL subsequent to its uptake via receptor-mediated endocytosis. In both cases, binding activity was saturable, depended on the presence of calcium ions in the medium, and was calculated to have an equilibrium dissociation constant at 4ᵒC of 2 μg ¹²⁵I-LDL/ml. No high-affinity binding was detected when the ligand was modified by acetylation. After incubating the monolayers at 37°C LDL/LDL receptor complexes were internalized, and the receptors were recycled back to the surface within about 10 minutes. Apolipo-protein B in the LDL particles was largely degraded to the amino acid level: chloroquine, a lysosomotropic agent, inhibited the formation of the ¹²⁵I-LDL degradation products. Cells obtained from a number of heterozygous and homozygous familial hypercholesterolemic patients, as expected, bound markedly reduced amounts of ligand. The half-life of ¹²⁵I-LDL was measured after it had been introduced into cultured fibroblasts by one of the following processes: (i) uptake via receptor-mediated endocytosis in human skin fibroblasts with normal LDL receptors, or (ii) incorporation via scrape-loading into fibroblasts defective in LDL receptor content. The half-lives obtained were about 1 hour and 50 hours, respectively, indicating that efficient degradation of LDL occurred only when it was deIivered to lysosomes via receptor-mediated endocytosis. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/27207 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:34:28.941Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2018 |
| publishDateRange | 2018 |
| publishDateSort | 2018 |
| publisher | Division of Medical Biochemistry and Structural Biology |
| publisherStr | Division of Medical Biochemistry and Structural Biology |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/27207 The cellular degradation of the low density lipoprotein receptor and its ligand Casciola, Livia Angela Flavia Coetzee, G A Cell receptors Lipoproteins Histocytochemistry Ligands Lipoproteins, LDL Receptors, LDL The cellular degradation of the low density lipoprotein (LDL) receptor, and its ligand, LDL, were investigated in order to clarify certain mechanistic aspects of these important processes. Long-term lymphoblastoid cell lines and cultured human skin fibroblasts were used to examine the fate of ¹²⁵I-LDL subsequent to its uptake via receptor-mediated endocytosis. In both cases, binding activity was saturable, depended on the presence of calcium ions in the medium, and was calculated to have an equilibrium dissociation constant at 4ᵒC of 2 μg ¹²⁵I-LDL/ml. No high-affinity binding was detected when the ligand was modified by acetylation. After incubating the monolayers at 37°C LDL/LDL receptor complexes were internalized, and the receptors were recycled back to the surface within about 10 minutes. Apolipo-protein B in the LDL particles was largely degraded to the amino acid level: chloroquine, a lysosomotropic agent, inhibited the formation of the ¹²⁵I-LDL degradation products. Cells obtained from a number of heterozygous and homozygous familial hypercholesterolemic patients, as expected, bound markedly reduced amounts of ligand. The half-life of ¹²⁵I-LDL was measured after it had been introduced into cultured fibroblasts by one of the following processes: (i) uptake via receptor-mediated endocytosis in human skin fibroblasts with normal LDL receptors, or (ii) incorporation via scrape-loading into fibroblasts defective in LDL receptor content. The half-lives obtained were about 1 hour and 50 hours, respectively, indicating that efficient degradation of LDL occurred only when it was deIivered to lysosomes via receptor-mediated endocytosis. 2018-02-01T13:32:37Z 2018-02-01T13:32:37Z 1987 Doctoral Thesis Doctoral PhD http://hdl.handle.net/11427/27207 eng application/pdf Division of Medical Biochemistry and Structural Biology Faculty of Health Sciences University of Cape Town |
| spellingShingle | Cell receptors Lipoproteins Histocytochemistry Ligands Lipoproteins, LDL Receptors, LDL Casciola, Livia Angela Flavia The cellular degradation of the low density lipoprotein receptor and its ligand |
| thesis_degree_str | Doctoral |
| title | The cellular degradation of the low density lipoprotein receptor and its ligand |
| title_full | The cellular degradation of the low density lipoprotein receptor and its ligand |
| title_fullStr | The cellular degradation of the low density lipoprotein receptor and its ligand |
| title_full_unstemmed | The cellular degradation of the low density lipoprotein receptor and its ligand |
| title_short | The cellular degradation of the low density lipoprotein receptor and its ligand |
| title_sort | cellular degradation of the low density lipoprotein receptor and its ligand |
| topic | Cell receptors Lipoproteins Histocytochemistry Ligands Lipoproteins, LDL Receptors, LDL |
| url | http://hdl.handle.net/11427/27207 |
| work_keys_str_mv | AT casciolaliviaangelaflavia thecellulardegradationofthelowdensitylipoproteinreceptoranditsligand AT casciolaliviaangelaflavia cellulardegradationofthelowdensitylipoproteinreceptoranditsligand |