Surface Trafficking of APP and BACE in Live Cells

Anna Bauereiss,Teja W Groemer,Oliver Welzel,Natalia Lelental,Simon Grosse‐Holz,Eva M Wenzel,Jasmin Jung,Piotr Lewczuk,Johannes Kornhuber

doi:10.1111/tra.12270

Anna Bauereiss, Teja W Groemer + Show 7 more

Open Access

https://doi.org/10.1111/tra.12270

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Abstract

Amyloid‐β (Aβ)‐peptide, the major constituent of the plaques that develop during Alzheimer's disease, is generated via the cleavage of Aβ precursor protein (APP) by β‐site APP‐cleaving enzyme (BACE). Using live‐cell imaging of APP and BACE labeled with pH‐sensitive proteins, we could detect the release events of APP and BACE and their distinct kinetics. We provide kinetic evidence for the cleavage of APP by α‐secretase on the cellular surface after exocytosis. Furthermore, simultaneous dual‐color evanescent field illumination revealed that the two proteins are trafficked to the surface in separate compartments. Perturbing the membrane lipid composition resulted in a reduced frequency of exocytosis and affected BACE more strongly than APP. We propose that surface fusion frequency is a key factor regulating the aggregation of APP and BACE in the same membrane compartment and that this process can be modulated via pharmacological intervention.

Highlights

Alzheimer’s disease is the most common form of dementia [1]
The expression of both proteins was verified via western blot using a polyclonal green fluorescent protein (GFP) antibody (Figure 1A). pHAPP and pHBACE were only detectable via their pHluorin tags in the transfected cells
To quantify the molecular weights (MWs) of the proteins detected in the pHAPP-transfected cells, the intensities of the MW marker bands and the protein bands detected in the lysates and the media were plotted as intensity profile spectra according to the distance traveled (Figure 1B)

Summary

Introduction

The pathological correlates of this disease include neurodegeneration and the development of characteristic neurofibrillary tangles and senile plaques These plaques are predominantly composed of amyloid-β (Aβ) deposits, which are derived from Aβ precursor protein (APP). The cellular localization of this processing, the interaction between APP and BACE, has been a focus of research in recent years. Following their synthesis in the endoplasmic reticulum, APP and BACE are transported via the Golgi apparatus. Recent studies in neurons have shown recycling endosomes as sites where APP is www.traffic.dk 655 We pharmacologically modulated the frequency of these fusion events, which represents a potential strategy to inhibit Aβ-peptide generation

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Conclusion