Human Mitochondrial Cytochrome b Variants Studied in Yeast: Not All Are Silent Polymorphisms.

Zehua Song,Anaïs Laleve,Rhiannon E Lloyd,Brigitte Meunier,Cindy Vallières,John E Mcgeehan

doi:10.1002/humu.23024

Zehua Song, Anaïs Laleve + Show 4 more

Open Access

https://doi.org/10.1002/humu.23024

Copy DOI

Abstract

ABSTRACTVariations in mitochondrial DNA (mtDNA) cytochrome b (mt‐cyb) are frequently found within the healthy population, but also occur within a spectrum of mitochondrial and common diseases. mt‐cyb encodes the core subunit (MT‐CYB) of complex III, a central component of the oxidative phosphorylation system that drives cellular energy production and homeostasis. Despite significant efforts, most mt‐cyb variations identified are not matched with corresponding biochemical data, so their functional and pathogenic consequences in humans remain elusive. While human mtDNA is recalcitrant to genetic manipulation, it is possible to introduce human‐associated point mutations into yeast mtDNA. Using this system, we reveal direct links between human mt‐cyb variations in key catalytic domains of MT‐CYB and significant changes to complex III activity or drug sensitivity. Strikingly, m.15257G>A (p.Asp171Asn) increased the sensitivity of yeast to the antimalarial drug atovaquone, and m.14798T>C (p.Phe18Leu) enhanced the sensitivity of yeast to the antidepressant drug clomipramine. We demonstrate that while a small number of mt‐cyb variations had no functional effect, others have the capacity to alter complex III properties, suggesting they could play a wider role in human health and disease than previously thought. This compendium of new mt‐cyb‐biochemical relationships in yeast provides a resource for future investigations in humans.

Highlights

Complex III of the mitochondrial respiratory chain is central to the cellular energy production process
All of the subunits are encoded by the nuclear genome, except cytochrome b (MT-CYB; MIM# 516020), which is encoded by mitochondrial DNA
M.15257G>A that causes a D to N substitution at position 171 (p.Asp171Asn) of the mt-cyb encodes the core subunit (MT-CYB) polypeptide [Heher and Johns, 1993; Johns and Neufeld, 1993; Johns et al, 1993] is associated with Leber hereditary optic neuropathy (LHON) and a number of different disease cohorts, whereas m.14798T>C that causes a phenylalanine to leucine amino acid substitution in MT-CYB (p.Phe18Leu) is frequently found in patient-derived glioblastoma biopsy cells [Kirches et al, 2001; Larman et al, 2012; Lloyd et al, 2015], but biochemical data are often lacking

Summary

Introduction

Complex III (or bc complex) of the mitochondrial respiratory chain is central to the cellular energy production process. M.15257G>A that causes a D to N substitution at position 171 (p.Asp171Asn) of the MT-CYB polypeptide [Heher and Johns, 1993; Johns and Neufeld, 1993; Johns et al, 1993] is associated with Leber hereditary optic neuropathy (LHON) and a number of different disease cohorts, whereas m.14798T>C that causes a phenylalanine to leucine amino acid substitution in MT-CYB (p.Phe18Leu) is frequently found in patient-derived glioblastoma biopsy cells [Kirches et al, 2001; Larman et al, 2012; Lloyd et al, 2015], but biochemical data are often lacking Obtaining such biochemical data is experimentally challenging due to the absence of tools for introducing single variations into mammalian mtDNA. We show that some variants previously reported as “silent” mutations, including some frequent polymorphisms, significantly modify the properties of the yeast complex III, suggesting they may play a greater role in human health and disease than previously thought

Materials and Methods

Results and Discussion