Alzheimer's: Researchers determine the structural basis for interactions between apolipoprotein E and amyloid beta

A new biophysical study from researchers at Boston University Chobanian & Avedisian School of Medicine explains why apoE and other apolipoproteins co-deposit with amyloids and provides a structural basis for understanding how apolipoproteins modulate amyloid growth and proliferation in the body.

"Our analysis of four different amyloid fibrils shows that apoE-amyloid interactions depend on the exact amyloid structure, termed polymorph. Amyloid polymorphs are disease- and tissue-specific and can be different in different experiments, which explains discrepancies among prior studies. Understanding such disease-specific factors is essential for harnessing apoE-Aβ interactions for therapeutic targeting," explains first author Emily Lewkowicz, a PhD candidate in biophysics at the school.

The researchers used four different structures of Aβ fibrils from brains of patients with Alzheimer's and other neurodegenerative diseases. To build models of apoE in complexes with different fibrils, they performed protein docking (the prediction of the structure of the complex, based on the structures of the individual proteins) using computer modeling, followed by molecular dynamics simulations to test the stability of the complex. The computational results, taken together with prior experimental data, revealed the driving forces and the molecular mechanisms for apolipoprotein binding to amyloid fibrils.

According to the researchers, apolipoproteins such as apoE are "amyloid signature proteins" that are found in amyloid deposits and probably influence their formation. "Our work shows how these proteins can interact directly with various amyloids and thereby promote or block their growth and proliferation by binding alongside fibrils or at their ends" adds corresponding author Olga Gursky, PhD, professor of pharmacology, physiology & biophysics at the school.

Besides Aβ, nearly 40 other proteins form pathologic amyloids in various human diseases, including Parkinson's disease, chronic traumatic encephalopathy, light chain amyloidosis, and many other life-threatening disorders. Apolipoproteins such as apoE are found in all these amyloid deposits. This work shows how these proteins can interact directly with amyloids and thereby influence their physical and biological properties.

Also involved in this study were Michael J. Rynkiewicz, PhD, instructor of pharmacology, physiology & biophysics at the school, and Mari N. Nakamura, an undergraduate summer student from Middlebury College.

These findings appear online in Cellular and Molecular Life Sciences.

Funding for this study was provided by the National Institutes of Health grants RO1 GM067260 (OG), GM135158 (OG), T32 DK007201 (EL); and R01 HL036153 (MJR).