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Amyloid-[beta] interrupts canonical Sonic hedgehog signaling by distorting primary cilia structure
Journal article   Open access   Peer reviewed

Amyloid-[beta] interrupts canonical Sonic hedgehog signaling by distorting primary cilia structure

Anna G Vorobyeva and Aleister J Saunders
Cilia (London), v 7(1)
17 Aug 2018
DOI: https://doi.org/10.1186/s13630-018-0059-y
url
https://doi.org/10.1186/s13630-018-0059-yView
Published, Version of Record (VoR) Open

Abstract

Cell organelles Cilia and ciliary motion Microtubules
Background Primary cilia are small non-motile microtubule and cell membrane protrusions expressed on most vertebrate cells, including cortical and hippocampal neurons. These small organelles serve as sensory structures sampling the extracellular environment and reprogramming the transcriptional machinery in response to environmental change. Primary cilia are decorated with a variety of receptor proteins and are necessary for specific signaling cascades such as the Sonic hedgehog (Shh) pathway. Disrupting cilia structure or function results in a spectrum of diseases collectively referred to as ciliopathies. Common to human ciliopathies is cognitive impairment, a symptom also observed in Alzheimer's disease (AD). One hallmark of AD is accumulation of senile plaques composed of neurotoxic Amyloid-[beta] (A[beta]) peptide. The A[beta] peptide is generated by the proteolytic cleavage of the amyloid precursor protein (APP). We set out to determine if A[beta] affects primary cilia structure and the Shh signaling cascade. Methods We utilized in vitro cell-based assays in combination with fluorescent confocal microscopy to address our study goals. Shh signaling and cilia structure was studied using two different cell lines, mouse NIH3T3 and human HeLa cells. To investigate how A[beta] levels affect Shh signaling and cilia structure in these cells, we utilized naturally secreted A[beta] as well as synthetic A[beta]. Effects on Shh signaling were assessed by luciferase activity while cilia structure was analyzed by fluorescent microscopy. Results Here, we report that APP localizes to primary cilia and A[beta] treatment results in distorted primary cilia structure. In addition, we demonstrate that A[beta] treatment interrupts canonical Shh signal transduction. Conclusions Overall, our study illustrates that A[beta] can alter primary cilia structure suggesting that elevated A[beta] levels, like those observed in AD patients, could have similar effects on neuronal primary cilia in the brain. Additionally, our study suggests that A[beta] impairs the Shh signaling pathway. Together our findings shed light on two novel targets for future AD therapeutics. Keywords: Alzheimer's disease (AD), Amyloid precursor protein (APP), Amyloid-[beta] (A[beta]), Sonic hedgehog (Shh), Primary cilia

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