Research article

Upregulation of CRABP1 in human neuroblastoma cells overproducing the Alzheimer-typical Aβ₄₂ reduces their differentiation potential

Markus Uhrig^1,2 , Peter Brechlin^3,4 , Olaf Jahn^4,5 , Yuri Knyazev⁶ , Annette Weninger⁶ , Laura Busia¹ , Kamran Honarnejad¹ , Markus Otto⁷ and Tobias Hartmann^1,2

¹Center for Molecular Biology of the University of Heidelberg (ZMBH), D-69120 Heidelberg, Germany

²Institute for Neurodegeneration and Neurobiology, Neurology, Saarland University, D-66421 Homburg/Saar, Germany

³Department of Neurodegeneration and Restorative Research, Center for Neurological Medicine, University of Göttingen, D-37073 Göttingen, Germany

⁴DFG Research Center for Molecular Physiology of the Brain (CMPB), D-37073 Göttingen, Germany

⁵Max Planck Institute for Experimental Medicine, Proteomics, D-37075 Göttingen, Germany

⁶German Cancer Research Center (DKFZ), D-69120 Heidelberg, Germany

⁷Department of Neurology, D-89075 Ulm, Germany

author email corresponding author email

BMC Medicine 2008, 6:38doi:10.1186/1741-7015-6-38

Published:	16 December 2008

Abstract

Background

Alzheimer's disease (AD) is characterized by neurodegeneration and changes in cellular processes, including neurogenesis. Proteolytic processing of the amyloid precursor protein (APP) plays a central role in AD. Owing to varying APP processing, several β-amyloid peptides (Aβ) are generated. In contrast to the form with 40 amino acids (Aβ₄₀), the variant with 42 amino acids (Aβ₄₂) is thought to be the pathogenic form triggering the pathological cascade in AD. While total-Aβ effects have been studied extensively, little is known about specific genome-wide effects triggered by Aβ₄₂ or Aβ₄₀ derived from their direct precursor C99.

Methods

A combined transcriptomics/proteomics analysis was performed to measure the effects of intracellularly generated Aβ peptides in human neuroblastoma cells. Data was validated by real-time polymerase chain reaction (real-time PCR) and a functional validation was carried out using RNA interference.

Results

Here we studied the transcriptomic and proteomic responses to increased or decreased Aβ₄₂ and Aβ₄₀ levels generated in human neuroblastoma cells. Genome-wide expression profiles (Affymetrix) and proteomic approaches were combined to analyze the cellular response to the changed Aβ₄₂- and Aβ₄₀-levels. The cells responded to this challenge with significant changes in their expression pattern. We identified several dysregulated genes and proteins, but only the cellular retinoic acid binding protein 1 (CRABP1) was up-regulated exclusively in cells expressing an increased Aβ₄₂/Aβ₄₀ ratio. This consequently reduced all-trans retinoic acid (RA)-induced differentiation, validated by CRABP1 knock down, which led to recovery of the cellular response to RA treatment and cellular sprouting under physiological RA concentrations. Importantly, this effect was specific to the AD typical increase in the Aβ₄₂/Aβ₄₀ ratio, whereas a decreased ratio did not result in up-regulation of CRABP1.

Conclusion

We conclude that increasing the Aβ₄₂/Aβ₄₀ ratio up-regulates CRABP1, which in turn reduces the differentiation potential of the human neuroblastoma cell line SH-SY5Y, but increases cell proliferation. This work might contribute to the better understanding of AD neurogenesis, currently a controversial topic.