Journal of Biological Chemistry
Volume 277, Issue 33, 16 August 2002, Pages 29919-29926
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LIPIDS AND LIPOPROTEINS
Apolipoprotein E (ApoE) Isoform-dependent Lipid Release from Astrocytes Prepared from Human ApoE3 and ApoE4 Knock-in Mice*

https://doi.org/10.1074/jbc.M203934200Get rights and content
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We have reported previously (Michikawa, M., Fan, Q.-W., Isobe, I., and Yanagisawa, K. (2000) J. Neurochem. 74, 1008–1016) that exogenously added recombinant human apolipoprotein E (apoE) promotes cholesterol release in an isoform-dependent manner. However, the molecular mechanism underlying this isoform-dependent promotion of cholesterol release remains undetermined. In this study, we demonstrate that the cholesterol release is mediated by endogenously synthesized and secreted apoE isoforms and clarify the mechanism underlying this apoE isoform-dependent cholesterol release using cultured astrocytes prepared from human apoE3 and apoE4 knock-in mice. Cholesterol and phospholipids were released into the culture media, resulting in the generation of two types of high density lipoprotein (HDL)-like particles; one was associated with apoE and the other with apoJ. The amount of cholesterol released into the culture media from the apoE3-expressing astrocytes was ∼2.5-fold greater than that from apoE4-expressing astrocytes. In contrast, the amount of apoE3 released in association with the HDL-like particles was similar to that of apoE4, and the sizes of the HDL-like particles released from apoE3- and apoE4-expressing astrocytes were similar. The molar ratios of cholesterol to apoE in the HDL fraction of the culture media of apoE3- and apoE4-expressing astrocytes were 250 ± 6.0 and 119 ± 5.1, respectively. These data indicate that apoE3 has an ability to generate similarly sized lipid particles with less number of apoE molecules than apoE4, suggesting that apoE3-expressing astrocytes can supply more cholesterol to neurons than apoE4-expressing astrocytes. These findings provide a new insight into the issue concerning the putative alteration of apoE-related cholesterol metabolism in Alzheimer's disease.

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Published, JBC Papers in Press, May 31, 2002, DOI 10.1074/jbc.M203934200

*

This work was supported by a Research Grant for Longevity Sciences 8A-1, the Program for Promotion of Fundamental Studies in Health Sciences of the Organization for Pharmaceutical Safety and Research, and Research on Brain Science from the Ministry of Health and Welfare, CREST, Japan.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.