Thermodynamic destabilization and aggregation propensity as the mechanism behind the association of apoE3 mutants and lipoprotein glomerulopathy

Maria Katsarou,Efstratios Stratikos,Angeliki Chroni

doi:10.1194/jlr.m088732

Maria Katsarou, Efstratios Stratikos + Show 1 more

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https://doi.org/10.1194/jlr.m088732

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Abstract

Lipoprotein glomerulopathy (LPG) is a rare renal disease, characterized by lipoprotein thrombi in glomerular capillaries. A series of apoE mutations have been associated with LPG development. We previously showed that three mutants based on apoE3 sequence, in which an arginine was substituted by proline, are thermodynamically destabilized and aggregation-prone. To examine whether other LPG-associated apoE3 mutations induce similar effects, we characterized three nonproline LPG-associated apoE3 mutations, namely, R25C (apoEKyoto), R114C (apoETsukuba), and A152D (apoELasVegas). All three apoE3 variants are found to have significantly reduced helical content and to be thermodynamically destabilized, both in lipid-free and lipoprotein-associated form, and to expose a larger portion of hydrophobic surface to the solvent compared with WT apoE3. Furthermore, all three apoE3 variants are aggregation-prone, as shown by dynamic light-scattering measurements and by their enhanced capacity to bind the amyloid probe thioflavin T. Overall, our data suggest that the LPG-associated apoE3 mutations R25C, R114C, and A152D induce protein misfolding, which may contribute to protein aggregation in glomerular capillaries. The similar effects of both LPG-associated proline and nonproline mutations on apoE3 structure suggest that the thermodynamic destabilization and enhanced aggregation of apoE3 may constitute a common underlying mechanism behind the pathogenesis of LPG.

Highlights

Lipoprotein glomerulopathy (LPG) is a rare renal disease, characterized by lipoprotein thrombi in glomerular capillaries
Our analysis showed that enhanced capacity for Thioflavin T (ThT) binding displayed, at all incubation times, the LPG-associated apoE3 mutants R145P and R158P (Fig. 9), which had been analyzed in a previous study by Dynamic light-scattering (DLS) and were likewise found to be oligomerized following their incubation at 37°C for 24 h [18]
We had suggested that apoE3 variants where a proline residue substituted another residue led to secondary content alterations, thermodynamic destabilization, hydrophobic surface exposure, and aggregation of apoE3 due to secondary structure destabilization resulting from the incompatibility of proline in helical regions [18]

Summary

Introduction

Lipoprotein glomerulopathy (LPG) is a rare renal disease, characterized by lipoprotein thrombi in glomerular capillaries. Our data suggest that the LPG-associated apoE3 mutations R25C, R114C, and A152D induce protein misfolding, which may contribute to protein aggregation in glomerular capillaries. The similar effects of both LPG-associated proline and nonproline mutations on apoE3 structure suggest that the thermodynamic destabilization and enhanced aggregation of apoE3 may constitute a common underlying mechanism behind the pathogenesis of LPG.—Katsarou, M., E. Thermodynamic destabilization and aggregation propensity as the mechanism behind the association of apoE3 mutants and lipoprotein glomerulopathy. Lipid-free apoE is folded into two structural domains, an N-terminal and a carboxyl-terminal, connected with a hinge region [10, 13,14,15,16].

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