Hyperexpression of N-acetylglucosaminyltransferase-III in liver tissues of transgenic mice causes fatty body and obesity through severe accumulation of Apo A-I and Apo B
| Autor: | Tae-Hwa Chung, Eun Young Song, Cheorl-Ho Kim, Kyoung-Sook Kim, Tae-Wook Chung, Sung-Koo Kang, Jung-Woong Lee, Young-Il Yeom |
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| Rok vydání: | 2004 |
| Předmět: |
Blood Glucose
Male Genetically modified mouse Glycosylation Apolipoprotein B Transgene Molecular Sequence Data Biophysics Mannose Mice Transgenic N-Acetylglucosaminyltransferases Biochemistry Transaminase Mice chemistry.chemical_compound N-linked glycosylation Lectins Lipid droplet Animals Humans Aspartate Aminotransferases Obesity Molecular Biology Serum Albumin Triglycerides Apolipoproteins B Apolipoprotein A-I biology Body Weight Alanine Transaminase Molecular biology Recombinant Proteins Mice Inbred C57BL Cholesterol Carbohydrate Sequence Liver chemistry Mice Inbred CBA biology.protein Female lipids (amino acids peptides and proteins) Protein Multimerization |
| Zdroj: | Archives of Biochemistry and Biophysics. 426:18-31 |
| ISSN: | 0003-9861 |
| Popis: | N-Acetylglucosaminyltransferase (GnT)-III catalyzes the attachment of an N-acetylglucosamine (GlcNAc) residue to mannose in β(1–4) configuration in the region of N-glycans and forms a bisecting GlcNAc. To investigate the pathophysiological role of dysregulated glycosylation mediated by aberrantly expressed GnT-III, we generated transgenic mice hyperexpressing the human GnT-III in the liver by introducing human GnT-III cDNA under the control of mouse albumin enhancer/promoter. Total five transgenic founder mice (pGnTSVTpA-10, -14, -20, -25, and -51) expressed the human GnT-III in their livers and were characterized by molecular genetic means. The copy number of transgene integrated into the genome of these mice ranged between 1 and 3 copies per haploid genome. Northern and Western blot analyses showed that the transgene is specifically expressed in the liver but not in any other tissues tested. The triglyceride level in GnT-III transgenic mice was significantly decreased, however, no significant differences in the levels of glucose, cholesterol, or albumin were observed between transgenic and nontransgenic mice. Although glutamate oxaloacetic transaminase and glutamic pyruvic transaminase activities of transgenic mice were also higher than those of nontransgenic mice, no differences in total bililubin and total protein were observed between the two animal lines. Large amounts of apolipoprotein (Apo) A-I and Apo B were specifically detected in the intracellular liver of transgenic mice. The accumulation of Apo A-I in hepatocytes may be due to aberrant glycosylation, since glycosylated Apo A-I was not observed in transgenic mice. However, the accumulated Apo B was severely glycosylated. Therefore, it is suggested that highly expressed transgenic GnT-III allowed unknown target proteins to be glycosylated in large amounts, and the resulting target protein(s) disrupted in assembly formation of Apo A-I in the hepatocytes and cause a decrease in the release of lipoproteins and accumulations of Apo A-I and Apo B in the liver. The transgenic mice showed aberrant glycosylation by GnT-III, resulting in numerous lipid droplets in liver tissues and the obesity. These mice showed microvesicular fatty changes with abnormal lipid accumulation in the hepatocytes. Our study provides the basis for future analysis of the role of glycosylation in hepatic pathogenesis. In the transgenic mice, Apo A-I and Apo B were significantly increased compared with levels in nontransgenic liver tissues. |
| Databáze: | OpenAIRE |
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