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Original Article Effect of Oxidized LDL on the Amount of Insulin Receptor and Gi-proteins in the Caveolae of Bovine Aortic Endothelial Cells (BAEC).
Sung Yoon Jeon, Hyun Shik Son, Jung Min Lee, Sung Dae Moon, Kun Ho Yoon, Bong Yun Cha, Kwang Woo Lee, Ho Young Son, Sung Koo Kang
Diabetes & Metabolism Journal 2001;25(1):71-82
Published online: February 1, 2001
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Catholic Research Institutes of Medical Science, Seoul, Korea.

AND AIMS: Oxidized LDL (ox-LDL) may induce endothelial cell dysfunction and suggested to have an association with atherosclerosis or insulin resistance. Several studies have shown that ox-LDL inhibits signaling pathways mediated by inhibitory GTP-binding proteins (Gi-proteins). G-protein coupled receptors (GPCRs) can be internalized via caveolae. Caveolae are small flask-shaped invaginations of the plasma membrane, characterized by high levels of cholesterol and glycosphingolipids and also by the presence of caveolin, a 20-24 kDa integral membrane protein. G-proteins are enriched within caveolae membranes, where caveolin-1 directly interacts with the -subunits of G-proteins. It is reported that functional changes of G-proteins such as mutational or pharmacological activation of G-proteins affect direct interaction between G-proteins and caveolin-1. Thus, we investigated the effect of ox-LDL on the change of the amount of insulin receptor and Gi proteins in the caveolae. MATERIALS AND METHODS: ox-LDL was prepared by exposing samples of native LDL (n-LDL) to CuSO4 for 24 hours. Caveolae were extracted after treating BAECs at several concentrations of ox-LDL (10, 50, 100 g/mL) for various durations (0-48 hr), and we investigated the changes of the amount of caveolin-1, Gi -proteins and insulin receptor using immunoblot. RESULTS: While the amount of caveolin-1 was decreased, the amount of insulin receptor, Gi 2 and Gi 3 proteins in caveolae were also decreased after treatment of ox-LDL on the BAECs (insulin receptor: 66%; Gi 2 protein: 33%; Gi 3 protein: 66%, p<0.05). The amount of caveolin-1 was increased for the first 6 hours and then decreased, however, the amount of Gi -proteins and insulin receptor were vice versa during 48 hours incubation. CONCLUSION: These results indicate that ox-LDL can affect the change of the amount of insulin receptor and Gi-proteins in caveolae and it may induce endothelial cell dysfunction.

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    • Citation for the content below
    Effect of Oxidized LDL on the Amount of Insulin Receptor and Gi-proteins in the Caveolae of Bovine Aortic Endothelial Cells (BAEC).
    Korean Diabetes J. 2001;25(1):71-82.   Published online February 1, 2001
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