Analysis of apolipoprotein E nuclear localization using green fluorescent protein and biotinylation approaches

Woojin S Kim, David A Elliott, Maaike Kockx, Leonard Kritharides, Kerry-Anne Rye, David Andrew Jans, Brett Garner

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19 Citations (Scopus)

Abstract

Previous data indicates apoE may be associated with the nucleus in specific cell types particularly under stress conditions such as serum starvation. In addition, nuclear apoE localisation in ovarian cancer was recently shown to be correlated with patient survival. In order to better understand the factors associated with apoE nuclear localisation we examined intracellular apoE trafficking using live cell imaging of CHO cells that constitutively express apoE-GFP. In addition, we used biotinylated apoE (in a lipid-free state and as a lipidated discoidal complex) to track the uptake and potential nuclear targeting of exogenous apoE. Our data indicate that a small proportion of apoE-GFP is detected in the nucleus of living apoE-GFP expressing CHO cells and that nuclear apoE-GFP level is increased with serum starvation. Exposure of control CHO cells to exogenous apoE-GFP did not result in nuclear apoE-GFP localisation in the recipient cells. Similarly, biotinylated apoE did not reach the nucleus of control CHO cells or SK-N-SH neurons. In contrast, when biotinylated apoE was delivered to recipient cells as a lipidated apoE-disc, apoE was detected in the nucleus; suggesting that the lipoprotein complex alters the intracellular degradation or trafficking of apoE. Biotinylated apoE discs containing each of the three common human apoE isoforms (E2, E3, and E4) were also tested for nuclear trafficking. All three apoE isoforms were equally detected in the nucleus. These studies provide new evidence that apoE may be targeted to the nucleus and shed light on factors that regulate this process.
Original languageEnglish
Pages (from-to)701 - 709
Number of pages8
JournalBiochemical Journal
Volume409
Publication statusPublished - 2008

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