Projects

The availability of fluorescent sensors for mapping mitochondrial and cytosolic concentrations of ATP and [ATP]/[ADP] ratio and also for quantifying the activity of related pathways such as AMPK, pyruvate, glucose uptake, along with metabolic flux studies and measurements of oxygen consumption and lactate release, allows us to address basic questions about how cells match changes in energy provision with changes in demand.

These questions raise fundamental questions about the energetic costs of different activities of the cell and the specific roles of different regulatory pathways (e.g. of mitochondrial calcium uptake, regulation of mitochondrial carriers, the TCA cycle and costs of the calcium signal itself).

Blockade of the Adenine Nucleotide Translocase allows dissection of changes in individual compartments and is revealing fascinating comparative cell biology. Benchmarking basic rules in different tissues then allows us to explore the energetic consequences of impaired mitochondrial function in disease models. This is coupled with a potential for mathematical modeling in collaboration with a group in Belgium.

Mutations of glucocerebrosidase (GBA) in relation to Parkinson’s disease: Homoplasmic mutations of the lysosomal protein GBA cause Gaucher’s Disease. However heteroplasmic mutations are the major known genetic factor known to increase risk of Parkinson’s Disease. These cause impaired mitochondrial quality control pathways and mitochondrial dysfunction. We wish to understand the pathways that couple impaired lysosomal function to dysfunctional mitochondria, to understand whether these are general features of all (or many) lysosomal storage disorders, and to understand the contribution of impaired mitochondrial function to the underlying disease and as potential therapeutic targets (Osellame et al, Cell Metabolism, 2013;17(6):941-53; Plotegher N, Duchen MR. Trends Mol Med. 2017;23(2):116-134 and Cell Death and Differentiation in press.). We have fibroblasts and have made iPS cells and neurons from patients with PD related to GBA mutations in which we are characterising mitochondrial function and exploring the therapeutic potential of modulators of autophagy pathways. Impaired autophagy and mechanisms of mitochondrial dysfunction in Vici syndrome. In a related project, we are exploring the pathophysiology of Vivi syndrome, a devastating multi-system childhood disorder. This is caused by mutations of a protein EPG5 which is thought to be important in regulating lysosomal-autophagosome fusion. We have identified mitochondrial dysfunction in fibroblasts from patients and now have access to a mouse model and to patient derived iPS cells.

 

Alessia Fischer

There is a substantial literature describing altered NADH fluorescence lifetimes in cancer but the biochemical basis for the observations are not understood. We are trying to systematically explore the basis for altered lifetimes in cancer models so that we can interpret such data in relation to the underlying biochemical phenotype of the cancer.

Blacker et al., Nature Comms  2014;5:3936. Nickel et al., Cell Metabolism, 2015 Sep 1;22(3):472-84; Blacker TS, Duchen MR. Free Radic Biol Med. 2016 Nov;100:53-65.

In particular we wish to understand the roles of various cell signalling/nutrient sensing pathways that determine levels of mitochondrial heteroplasmy – the proportion of mitochondria carrying WT or mutant mtDNA – and also the role of downstream nutrient sensing pathways (mTOR/HIF/Akt/PI3K) in driving the pathological phenotypes in patients with mtDNA mutations.

Abramov et al., Brain, 134(Pt 6):1658-72.

Almost all people with Down syndrome will develop a dementia with age that is patjologicall indistinguishable from Alzheimer’s. The gene for APP is on Chromosome 21 and is therefore triplicated, the possible basis for increased Abeta generation. We have generated iPS cells from Down subjects, differentiated these into neurons and have evidence for significant mitochondrial and redox abnormalities in these cells which we wish to explore further - to characterise the defect and understand the pathways responsible as potential therapeutic targets that may be transferrable to AD.

  

Sigma1 receptors are present at mitochondrial associated membranes between mitochondria and the ER, and are thought to play a role in regulating the transfer of calcium from ER to mitochondria. Sigma1R antagonists are potent analgesics especially for chronic pain. We don’t understand how these relate to each other. We are studying ER mitochondrial calcium signalling and the downstream bioenergetic consequences in isolated sensory neurons and to identify the specific role of the Sigma1 R in this signalling pathway using antagonists and a Sigma1R knockout mouse.

Sepsis and septic shock syndrome are major causes of morbidity and mortality. Death from sepsis is associated with severe multiorgan failure. There is accumulating evidence that mitochondrial dysfunction plays a major role in defining the progression of organ dysfunction. This underpins a long standing collaboration between our lab and that of Prof Mervyn Singer Professor of Intensive care medicine at UCLH with a number of collaborative grants and jointly supervised PhD students. Current projects include an exploration of mechanisms of sepsis induced cardiomyopathy (Giacomo Stanzani) and understanding the mechanisms and role of fever in sepsis (Robert Tidswell). As the management and outcomes of sepsis remain disappointing, our overarching goal is to define new candidate therapeutic targets associated with mitochondrial related pathways.

Mervyn Singer