LRP1 shedding in human brain: roles of ADAM10 and ADAM17

Qiang Liu,Guojun Bu,Steven Estus,Juan Zhang,Marcel M Verbeek,Hien Tran,Karina Reiss

doi:10.1186/1750-1326-4-17

Abstract

BackgroundThe low-density lipoprotein receptor-related protein 1 (LRP1) plays critical roles in lipid metabolism, cell survival, and the clearance of amyloid-β (Aβ) peptide. Functional soluble LRP1 (sLRP1) has been detected in circulating human placenta; however, whether sLRP1 is also present in the central nervous system is unclear.ResultsHere we show that abundant sLRP1 capable of binding its ligands is present in human brain tissue and cerebral spinal fluid (CSF). Interestingly, the levels of sLRP1 in CSF are significantly increased in older individuals, suggesting that either LRP1 shedding is increased or sLRP1 clearance is decreased during aging. To examine potential effects of pathological ligands on LRP1 shedding, we treated MEF cells with Aβ peptide and found that LRP1 shedding was increased. ADAM10 and ADAM17 are key members of the ADAM family that process membrane-associated proteins including amyloid precursor protein and Notch. We found that LRP1 shedding was significantly decreased in MEF cells lacking ADAM10 and/or ADAM17. Furthermore, forced expression of ADAM10 increased LRP1 shedding, which was inhibited by ADAM-specific inhibitor TIMP-3.ConclusionOur results demonstrate that LRP1 is shed by ADAM10 and ADAM17 and functional sLRP1 is abundantly present in human brain and CSF. Dysregulated LRP1 shedding during aging could alter its function and may contribute to the pathogenesis of AD.

Highlights

The low-density lipoprotein receptor-related protein 1 (LRP1) plays critical roles in lipid metabolism, cell survival, and the clearance of amyloid-β (Aβ) peptide
Together our results demonstrate that LRP1 shedding is regulated by ADAM10 and ADAM17 and functional soluble LRP1 (sLRP1) is abundantly present in human brain tissues and cerebral spinal fluid (CSF)
Dysregulated LRP1 shedding during aging could alter its function and may contribute to the pathogenesis of Alzheimer's disease (AD)

Summary

Introduction

The low-density lipoprotein receptor-related protein 1 (LRP1) plays critical roles in lipid metabolism, cell survival, and the clearance of amyloid-β (Aβ) peptide. The central hypothesis of AD is the amyloid hypothesis which proposes that accumulation of amyloid-β (Aβ) peptide, a small peptide with a high propensity to form aggregates in the brain, is the primary factor driving AD pathogenesis [1,2,3]. LRP1 was shown to bind to apolipoprotein E (apoE) [6] and Aβ, both of which play important roles in the pathogenesis of AD. It has been suggested that decreased clearance of Aβ from brain and CSF is the main cause of Aβ accumulation in sporadic AD [7]. LRP1 plays critical roles in Aβ clearance and neuronal survival [8,9]. Aβ has been shown to initially form a complex with LRP1

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Conclusion