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

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.

Pan-Cancer Analysis of Voltage-Dependent Anion Channel (VDAC1) as a Cancer Therapeutic Target or Diagnostic Biomarker

“…Recent studies have demonstrated that some tumor-related signaling pathways alter the phosphorylation level of VDAC1, leading to cell metabolism rearrangement and affecting apoptosis and cell cycle regulation [ 38 , 39 ]. Our results showed VDAC1 protein expression and phosphorylation level at the S104 were elevated in breast cancer, colon cancer, lung adenocarcinoma, ovarian cancer, and uterine corpus endometrial carcinoma except for clear cell renal cell carcinoma.…”

PHDs/CPT1B/VDAC1 axis regulates long-chain fatty acid oxidation in cardiomyocytes

“…In this case, VDAC1 binding would just act as an OOM anchoring/docking protein. Noteworthy, very recent data from the literature ( Haloi et al, 2021 ) suggest that VDAC1/Hexokinase-II binding promotes HK-II anchorage to the OOM, and more interestingly that this binary complex formation decreases VDAC1 conductance. In other words, favoring glycolysis decreases VDAC1 opening range, which might be in accordance with our working model suggesting VDAC1 as a part of LCFA mitochondrial uptake.…”

How Do Hexokinases Inhibit Receptor-Mediated Apoptosis?

“…The structural basis of complex formation between VDAC and hexokinases is yet to be elucidated. It has been suggested that hexokinase first inserts into the OMM and then interacts with VDAC on the outer leaflet of OMM [92]. Complex formation between both proteins seems to be mediated by their N-terminal domains [93,94].…”

“…Thus, hexokinase-dependent VDAC closure has been speculated to be an anti-apoptotic event by preventing cyt c release [95]. These discrepancies may be explained by the assumption that VDACs, besides an open and closed state, can adopt a partially closed conformation through their interaction with hexokinases [92]. This conformation would still allow some flux of low molecular weight substances while preventing the release of apoptotic factors.…”