Structural basis of complex formation between mitochondrial anion channel VDAC1 and Hexokinase-II

Nandan Haloi,Po-Chao Wen,Wai-Meng Kwok,Qunli Cheng,Gayathri Natarajan,Meiying Yang,Amadou K S Camara,Emad Tajkhorshid

doi:10.1038/s42003-021-02205-y

Nandan Haloi, Po-Chao Wen + Show 6 more

Open Access

https://doi.org/10.1038/s42003-021-02205-y

Copy DOI

Abstract

Complex formation between hexokinase-II (HKII) and the mitochondrial VDAC1 is crucial to cell growth and survival. We hypothesize that HKII first inserts into the outer membrane of mitochondria (OMM) and then interacts with VDAC1 on the cytosolic leaflet of OMM to form a binary complex. To systematically investigate this process, we devised a hybrid approach. First, we describe membrane binding of HKII with molecular dynamics (MD) simulations employing a membrane mimetic model with enhanced lipid diffusion capturing membrane insertion of its H-anchor. The insertion depth of the H-anchor was then used to derive positional restraints in subsequent millisecond-scale Brownian dynamics (BD) simulations to preserve the membrane-bound pose of HKII during the formation of the HKII/VDAC1 binary complex. Multiple BD-derived structural models for the complex were further refined and their structural stability probed with additional MD simulations, resulting in one stable complex. A major feature in the complex is the partial (not complete) blockade of VDAC1’s permeation pathway, a result supported by our comparative electrophysiological measurements of the channel in the presence and absence of HKII. We also show how VDAC1 phosphorylation disrupts HKII binding, a feature that is verified by our electrophysiology recordings and has implications in mitochondria-mediated cell death.

Highlights

Complex formation between hexokinase-II (HKII) and the mitochondrial VDAC1 is crucial to cell growth and survival
Once we established the membrane-binding mode of HKII-N using molecular dynamics (MD) simulations, we extended our study to investigate the molecular interaction between membrane-bound HKII-N with membrane-embedded VDAC1 by performing an aggregate of millisecond-scale atomicresolution Brownian dynamics (BD) simulations
Whereas BD simulation of wt-VDAC1 resulted in an HKIIbinding hot spot near S215 (Cluster 1), the probability of HKII presence at this region is substantially reduced after S215 phosphorylation (Fig. 6b), suggesting that the formation of HKII/VDAC1 complex can be inhibited when S215 is phosphorylated

Summary

Introduction

Complex formation between hexokinase-II (HKII) and the mitochondrial VDAC1 is crucial to cell growth and survival. The resulting membrane-bound HKII is used to study the formation of its complex with VDAC1 using Brownian dynamics (BD) simulations. Our results show that HKII binds to the membrane by inserting its H-anchor, independent of VDAC1.

Results

Conclusion