Catalysis of ACAT may be completed within the plane of the membrane: a working hypothesis
Two ACAT sharing protein sequence homology near their C termini have been identified. Both proteins may span the endoplasmic reticulum (ER) membrane several times. There is good evidence implicating the role of ACAT1 in macrophage foam cell formation, and ACAT2 in intestinal cholesterol absorption....
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Elsevier
2001-12-01
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| Series: | Journal of Lipid Research |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S0022227520315212 |
| _version_ | 1818739305856630784 |
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| author | Ta Yuan Chang Catherine C.Y. Chang Xiaohui Lu Song Lin |
| author_facet | Ta Yuan Chang Catherine C.Y. Chang Xiaohui Lu Song Lin |
| author_sort | Ta Yuan Chang |
| collection | DOAJ |
| description | Two ACAT sharing protein sequence homology near their C termini have been identified. Both proteins may span the endoplasmic reticulum (ER) membrane several times. There is good evidence implicating the role of ACAT1 in macrophage foam cell formation, and ACAT2 in intestinal cholesterol absorption. On the other hand, the functional roles of ACAT1 and ACAT2 in the VLDL or chylomicron assembly process are less clear. It is possible that both enzymes are able to form lipid droplets (which are present in the cytoplasm), and participate in lipoprotein assembly (which occurs in the ER lumen). To link the site of ACAT catalysis with its function, we propose that part of the ACAT catalytic site may reside within the lipid bilayer, allowing catalysis to be completed within the plane of the membrane. Cholesteryl esters (CE) produced in situ may burst into cytoplasmic lipid droplets, carrying phospholipid monolayers as their outer coats. In cells engaged in lipoprotein assembly and secretion, CE in the bilayer may be recognized by the specific protein microsomal triacylglycerol transfer protein (MTP), reaching out from the lumenal side of the membrane. MTP then lipidates the growing apolipoprotein B (apoB) chain with CE and TG during the early stages of apoB lipoprotein assembly.—Chang, T. Y., C. C. Y. Chang, X. Lu, and S. Lin. Catalysis of ACAT may be completed within the plane of the membrane: a working hypothesis. J. Lipid Res. 2001. 42: 1933–1938. |
| first_indexed | 2024-12-18T01:22:44Z |
| format | Article |
| id | doaj.art-6f3a29747d1c497d9ae4ad04d4a0cb50 |
| institution | Directory Open Access Journal |
| issn | 0022-2275 |
| language | English |
| last_indexed | 2024-12-18T01:22:44Z |
| publishDate | 2001-12-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Journal of Lipid Research |
| spelling | doaj.art-6f3a29747d1c497d9ae4ad04d4a0cb502022-12-21T21:25:47ZengElsevierJournal of Lipid Research0022-22752001-12-01421219331938Catalysis of ACAT may be completed within the plane of the membrane: a working hypothesisTa Yuan Chang0Catherine C.Y. Chang1Xiaohui Lu2Song Lin3To whom correspondence should be addressed.; Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755-3844Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755-3844Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755-3844Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755-3844Two ACAT sharing protein sequence homology near their C termini have been identified. Both proteins may span the endoplasmic reticulum (ER) membrane several times. There is good evidence implicating the role of ACAT1 in macrophage foam cell formation, and ACAT2 in intestinal cholesterol absorption. On the other hand, the functional roles of ACAT1 and ACAT2 in the VLDL or chylomicron assembly process are less clear. It is possible that both enzymes are able to form lipid droplets (which are present in the cytoplasm), and participate in lipoprotein assembly (which occurs in the ER lumen). To link the site of ACAT catalysis with its function, we propose that part of the ACAT catalytic site may reside within the lipid bilayer, allowing catalysis to be completed within the plane of the membrane. Cholesteryl esters (CE) produced in situ may burst into cytoplasmic lipid droplets, carrying phospholipid monolayers as their outer coats. In cells engaged in lipoprotein assembly and secretion, CE in the bilayer may be recognized by the specific protein microsomal triacylglycerol transfer protein (MTP), reaching out from the lumenal side of the membrane. MTP then lipidates the growing apolipoprotein B (apoB) chain with CE and TG during the early stages of apoB lipoprotein assembly.—Chang, T. Y., C. C. Y. Chang, X. Lu, and S. Lin. Catalysis of ACAT may be completed within the plane of the membrane: a working hypothesis. J. Lipid Res. 2001. 42: 1933–1938.http://www.sciencedirect.com/science/article/pii/S0022227520315212apoBcholesterol absorptioncholesteryl ester lipid dropletslipoprotein assemblymicrosomal triacylglycerol transfer protein |
| spellingShingle | Ta Yuan Chang Catherine C.Y. Chang Xiaohui Lu Song Lin Catalysis of ACAT may be completed within the plane of the membrane: a working hypothesis Journal of Lipid Research apoB cholesterol absorption cholesteryl ester lipid droplets lipoprotein assembly microsomal triacylglycerol transfer protein |
| title | Catalysis of ACAT may be completed within the plane of the membrane: a working hypothesis |
| title_full | Catalysis of ACAT may be completed within the plane of the membrane: a working hypothesis |
| title_fullStr | Catalysis of ACAT may be completed within the plane of the membrane: a working hypothesis |
| title_full_unstemmed | Catalysis of ACAT may be completed within the plane of the membrane: a working hypothesis |
| title_short | Catalysis of ACAT may be completed within the plane of the membrane: a working hypothesis |
| title_sort | catalysis of acat may be completed within the plane of the membrane a working hypothesis |
| topic | apoB cholesterol absorption cholesteryl ester lipid droplets lipoprotein assembly microsomal triacylglycerol transfer protein |
| url | http://www.sciencedirect.com/science/article/pii/S0022227520315212 |
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