# APOE isoform affects protein structure and function in normal brain

> **NIH NIH R01** · GEORGETOWN UNIVERSITY · 2021 · $385,698

## Abstract

The role of APOE genotype in the pathogenesis of Alzheimer's disease (AD) remains one of the most critical
questions in AD research. Over the past few years, we have pursued an interesting hypothesis that APOE
genotype alters normal brain neurochemistry and structure early in life, generating an environment that alters
the risk of AD with aging. Our previous studies of APOE knock-in mice have demonstrated that, even in young
control mouse brains, APOE genotype affects brain lipid biochemistry, neuronal structure, and spatial learning.
In exploring the cause of these various effects, we are now testing the hypothesis that early alterations of
brains in APOE4 individuals are due to differences in normal lipid metabolism in astrocytes and
neurons. In preliminary studies, we found that APOE isolated from the brain exists in two separate
populations: either modified and water soluble, or unmodified and membrane associated. New mass
spectrometry approaches allowed us to define that soluble APOE was glycosylated at several sites with
several types of glycans; most of the modified APOE in the CNS was not found in the plasma (particularly with
unique modification of APOE in its lipid binding domain). In vivo studies showed that APOE4 was less lipidated
in CSF lipoproteins compared to APOE2 and APOE3, and that APOE4 mice have altered brain lipid
homeostasis. Finally, we found that APOE4-associated phenotypes in mice were rescued by an AD
preventative treatment. In this work, we propose to define how brain lipid homeostasis is affected by APOE
isoforms, including the newly identified glycoforms. In Aim 1, we will define how APOE modifications alter
APOE metabolism, trafficking, and function in the CNS. For these studies, we will identify and quantify new
post-translational modifications of APOE across tissues, and develop new astrocyte culture models for
expression and modulation of human glyco-APOE isoforms. In Aim 2, we will determine whether APOE4
causes poor lipid efflux in vitro and in vivo, leading to increased activation of LXR targets in mouse and human
brains. We will use computer modeling to test the effects of glyco-APOE species on APOE tertiary structure
and on APOE binding to CNS lipoproteins. In Aim 3, we will test whether APOE4 causes poor lipid uptake in
vitro, leading to changes in neuronal APOE metabolism. We will use glial and neuronal cultures to define how
APOE modification changes as APOE travels through CNS compartments. Finally, in Aim 4, we will test
whether approaches that prevent AD in mice and humans (anti-inflammatory drugs and exercise/environmental
enrichment) affect brain lipid metabolism and brain structure/function. We will test whether our new markers
that are affected by the presence of APOE4, including the CNS-specific glycoforms, respond to conditions that
reduce AD risk. Thus, this proposal provides new mechanistic insight into the post-translational modification of
APOE in the CNS and how the complex set of APOE isofo...

## Key facts

- **NIH application ID:** 10191057
- **Project number:** 5R01NS100704-05
- **Recipient organization:** GEORGETOWN UNIVERSITY
- **Principal Investigator:** G WILLIAM REBECK
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $385,698
- **Award type:** 5
- **Project period:** 2017-08-15 → 2023-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10191057

## Citation

> US National Institutes of Health, RePORTER application 10191057, APOE isoform affects protein structure and function in normal brain (5R01NS100704-05). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10191057. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*