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Endogenous Adipocyte ApoE is Co-localized with Caveolin at the Adipocyte Plasma Membrane

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journal contribution
posted on 07.08.2012, 00:00 authored by Lili Yue, Theodore Mazzone
Apolipoprotein E is well-established as a secreted protein that plays an important role in systemic lipoprotein metabolism and vascular wall homeostasis. Recently, endogenous expression of apoE in adipocytes has been shown to play an important role in adipocyte lipoprotein metabolism and gene expression consistent with a non-secreted cellular itinerary for apoE. We designed studies to evaluate if adipocyte apoE was retained as a constituent protein in adipocytes, and to identify a cellular retention compartment. Using confocal microscopy, coimmunoprecipitation, and sucrose density cellular fractionation, we establish that endogenous apoE shares a cellular itinerary with the constituent protein caveolin-1. Altering adipocyte caveolar number by modulating cellular cholesterol flux or altering caveolin expression regulates the distribution of cellular apoE between cytoplasmic and plasma membrane compartments. A mechanism for co-localization of apoE with caveolin was established by demonstrating a noncovalent interaction between an aromatic amino acid-enriched apoE N-terminal domain with the caveolin scaffolding domain. Absent apoE expression in adipocytes alters caveolar lipid composition. These observations provide evidence for an interaction between two proteins involved in cellular lipid metabolism in a cell specialized for lipid storage and flux, and rationalize a biological basis for the impact of adipocyte apoE expression on adipocyte lipoprotein metabolism.

Funding

This work was supported by grant DK71711 (to TM) from the National Institutes of Health.

History

Publisher Statement

This research was originally published in Journal of Lipid Research. Lili Yue and Theodore Mazzone. Endogenous Adipocyte ApoE is Co-localized with Caveolin at the Adipocyte Plasma Membrane. Journal of Lipid Research. 2011. Vol52:489-498. © the American Society for Biochemistry and Molecular Biology. DOI: 10.1194/jlr.M011809

Publisher

American Society for Biochemistry and Molecular Biology

Language

en_US

issn

0022-2275

Issue date

01/03/2011

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