Metabolism of apoE-free high density lipoproteins in rat hepatoma cells: evidence for a retroendocytic pathway.
The cellular metabolism of apoE-free HDL (HDL) was studied in rat hepatoma cells (FU5AH). Cells incubated with HDL showed a dose-dependent decreased incorporation of [14C]acetate into cell sterol, indicating a net cholesterol delivery to the cells. HDL was localized both at the cell surface and insi...
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Elsevier
1990-02-01
|
| Series: | Journal of Lipid Research |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S0022227520432055 |
| _version_ | 1818449789731209216 |
|---|---|
| author | JG DeLamatre TG Sarphie RC Archibold CA Hornick |
| author_facet | JG DeLamatre TG Sarphie RC Archibold CA Hornick |
| author_sort | JG DeLamatre |
| collection | DOAJ |
| description | The cellular metabolism of apoE-free HDL (HDL) was studied in rat hepatoma cells (FU5AH). Cells incubated with HDL showed a dose-dependent decreased incorporation of [14C]acetate into cell sterol, indicating a net cholesterol delivery to the cells. HDL was localized both at the cell surface and inside the cell. This conclusion was drawn from both the association of 125I-labeled HDL with the cells under different experimental conditions and morphological evidence based on the association of colloidal gold-labeled HDL with the cells. Up to 63% of the 125I-labeled HDL protein initially inside the cell was subsequently recovered in the media as trichloroacetic acid precipitable (TCA-ppt) protein after a 30-min, 37 degrees C chase with a 100-fold concentration of unlabeled HDL. About 27% of the TCA-ppt apoprotein originally inside the cell was recovered as TCA-soluble material. Thus, we conclude that of the HDL apoprotein taken up by the cells, the majority is resecreted by a retroendocytosis pathway. The quantity of HDL apoprotein reappearing in the media was stimulated by the presence of unlabeled HDL in the media, while the amount of TCA-soluble material produced was not. Retroendocytosis of HDL was inhibited at 0 degree C and by the presence of 10 mM NaCN, 20 mM 2-deoxy-D-glucose in the media. Thus, the pathway appears to be both temperature- and energy-sensitive. HDL resecreted by the cell were depleted of cholesteryl ester and showed an altered size distribution, indicative of lipoprotein catabolism and remodeling. This study provides evidence for the existence of an endocytosis-retroendocytosis pathway for HDL apoproteins in a rat hepatoma cell and for the possibility that the endocytosis-retroendocytosis pathway may be involved in lipid delivery to the cell. |
| first_indexed | 2024-12-14T20:41:00Z |
| format | Article |
| id | doaj.art-39fa659fac36404fa63aac5b58d45119 |
| institution | Directory Open Access Journal |
| issn | 0022-2275 |
| language | English |
| last_indexed | 2024-12-14T20:41:00Z |
| publishDate | 1990-02-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Journal of Lipid Research |
| spelling | doaj.art-39fa659fac36404fa63aac5b58d451192022-12-21T22:48:16ZengElsevierJournal of Lipid Research0022-22751990-02-01312191202Metabolism of apoE-free high density lipoproteins in rat hepatoma cells: evidence for a retroendocytic pathway.JG DeLamatre0TG Sarphie1RC Archibold2CA Hornick3Department of Physiology, Louisiana State University Medical Center, New Orleans 70112.Department of Physiology, Louisiana State University Medical Center, New Orleans 70112.Department of Physiology, Louisiana State University Medical Center, New Orleans 70112.Department of Physiology, Louisiana State University Medical Center, New Orleans 70112.The cellular metabolism of apoE-free HDL (HDL) was studied in rat hepatoma cells (FU5AH). Cells incubated with HDL showed a dose-dependent decreased incorporation of [14C]acetate into cell sterol, indicating a net cholesterol delivery to the cells. HDL was localized both at the cell surface and inside the cell. This conclusion was drawn from both the association of 125I-labeled HDL with the cells under different experimental conditions and morphological evidence based on the association of colloidal gold-labeled HDL with the cells. Up to 63% of the 125I-labeled HDL protein initially inside the cell was subsequently recovered in the media as trichloroacetic acid precipitable (TCA-ppt) protein after a 30-min, 37 degrees C chase with a 100-fold concentration of unlabeled HDL. About 27% of the TCA-ppt apoprotein originally inside the cell was recovered as TCA-soluble material. Thus, we conclude that of the HDL apoprotein taken up by the cells, the majority is resecreted by a retroendocytosis pathway. The quantity of HDL apoprotein reappearing in the media was stimulated by the presence of unlabeled HDL in the media, while the amount of TCA-soluble material produced was not. Retroendocytosis of HDL was inhibited at 0 degree C and by the presence of 10 mM NaCN, 20 mM 2-deoxy-D-glucose in the media. Thus, the pathway appears to be both temperature- and energy-sensitive. HDL resecreted by the cell were depleted of cholesteryl ester and showed an altered size distribution, indicative of lipoprotein catabolism and remodeling. This study provides evidence for the existence of an endocytosis-retroendocytosis pathway for HDL apoproteins in a rat hepatoma cell and for the possibility that the endocytosis-retroendocytosis pathway may be involved in lipid delivery to the cell.http://www.sciencedirect.com/science/article/pii/S0022227520432055 |
| spellingShingle | JG DeLamatre TG Sarphie RC Archibold CA Hornick Metabolism of apoE-free high density lipoproteins in rat hepatoma cells: evidence for a retroendocytic pathway. Journal of Lipid Research |
| title | Metabolism of apoE-free high density lipoproteins in rat hepatoma cells: evidence for a retroendocytic pathway. |
| title_full | Metabolism of apoE-free high density lipoproteins in rat hepatoma cells: evidence for a retroendocytic pathway. |
| title_fullStr | Metabolism of apoE-free high density lipoproteins in rat hepatoma cells: evidence for a retroendocytic pathway. |
| title_full_unstemmed | Metabolism of apoE-free high density lipoproteins in rat hepatoma cells: evidence for a retroendocytic pathway. |
| title_short | Metabolism of apoE-free high density lipoproteins in rat hepatoma cells: evidence for a retroendocytic pathway. |
| title_sort | metabolism of apoe free high density lipoproteins in rat hepatoma cells evidence for a retroendocytic pathway |
| url | http://www.sciencedirect.com/science/article/pii/S0022227520432055 |
| work_keys_str_mv | AT jgdelamatre metabolismofapoefreehighdensitylipoproteinsinrathepatomacellsevidenceforaretroendocyticpathway AT tgsarphie metabolismofapoefreehighdensitylipoproteinsinrathepatomacellsevidenceforaretroendocyticpathway AT rcarchibold metabolismofapoefreehighdensitylipoproteinsinrathepatomacellsevidenceforaretroendocyticpathway AT cahornick metabolismofapoefreehighdensitylipoproteinsinrathepatomacellsevidenceforaretroendocyticpathway |