Helix-strand interaction regulates stability and aggregation of the human mitochondrial membrane protein channel VDAC3.

Ankit Gupta,Radhakrishnan Mahalakshmi

doi:10.1085/jgp.201812272

Abstract

Voltage-dependent anion channels (VDACs) are β-sheet-rich transmembrane β-barrels that are vital for metabolite transport across the mitochondrial membrane. Under cellular stress, human VDACs hetero-oligomerize and coaggregate with proteins that can form amyloidogenic and neurodegenerative deposits, implicating a role for VDACs in proteotoxicity. However, whether VDACs possess intrinsic interaction sites that can lead to protein aggregation is not known. Here, we couple a systematic thiol replacement strategy with far-UV circular dichroism spectropolarimetry and UV scattering spectroscopy to map aggregation-prone regions of human VDACs, using isoform 3 as our model VDAC. We show that the region comprising strands β7-β9 is highly aggregation prone. Further, we find that an α1-β7-β9 interaction (involving the hVDAC3 N-terminal α1 helix) can lower protein aggregation, whereas perturbations of this interaction promote VDAC aggregation. We also show that hVDAC3 aggregation proceeds via a partially unfolded structure. Our findings allow us to propose a plausible mechanism for the role of human VDACs in forming proteotoxic aggregates in the cell. The key target sites on VDACs-strands β7-β9-may be useful for developing VDAC aggregation inhibitors.

Highlights

Neurodegenerative diseases such as Alzheimer’s disease (AD) and Parkinson’s disease (PD) involve the progressive and destructive association of proteins intracellularly as plaques (Gorbenko and Trusova, 2011; Betaneli et al, 2012; Boulbrima et al, 2016; Iadanza et al, 2018)
On the basis of our findings, we propose that the α1–β7–β9 interaction can serve as a promising therapeutic target for stabilizing Voltage-dependent anion channels (VDACs) and lowering their aggregation in the membrane
Cysteines respond to mitochondrial oxidative stress through oxidative modifications of their side chain (Guardiani et al, 2016; Reina et al, 2016a,b; Saletti et al, 2017, 2018; Sorrentino et al, 2017; Iadanza et al, 2018)

Summary

Introduction

Neurodegenerative diseases such as Alzheimer’s disease (AD) and Parkinson’s disease (PD) involve the progressive and destructive association of proteins intracellularly as plaques (Gorbenko and Trusova, 2011; Betaneli et al, 2012; Boulbrima et al, 2016; Iadanza et al, 2018). A suggested cure is to inhibit protein aggregation (Cuadrado-Tejedor et al, 2011; Smilansky et al, 2015; Boulbrima et al, 2016; Magrì et al, 2016; Saletti et al, 2018). VDACs are known binding partners for α-synuclein, tau, and superoxide dismutase (SOD); the latter are implicated in PD, AD, and other neurodegenerative disorders (Cuadrado-Tejedor et al, 2011; Rostovtseva et al, 2015; Smilansky et al, 2015; Magri and Messina, 2017; Sorrentino et al, 2017; Iadanza et al, 2018). We have no direct information on whether molecular elements of VDAC sequence and structure can lead to proteopathies and neurodegeneration

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Conclusion