Identifying regulators of mitochondrial membrane potential
Description: Mitochondria are essential components of any eukaryotic organism, serving various functions from energy generation to cell signaling and apoptosis. Crucial to their function is the building and sustaining of an electrochemical gradient across their inner membrane. This results in the generation of a mitochondrial membrane potential (MMP), which drives ATP synthesis in exchange for the transport of protons across the inner membrane. MMP is a global indicator both for mitochondrial and cellular health. In a vast array of diseases such as muscular dystrophies and metabolic disorders, but also neurodegenerative diseases and diabetes, mitochondria show low MMP. Additionally, there is a general observation that MMP decreases with age1. Loss of MMP leads to the degradation of the respective mitochondria and often triggers cell death, indicating the tight monitoring of membrane potential for quality control2. Despite this reoccurring observation of disturbed MMP in age-related diseases, we currently have very limited knowledge on whether and how cells actively monitor and regulate mitochondrial membrane potential.Experimentally, MMP can be artificially decreased by respiratory inhibition or the use of uncouplers, which diminish the proton gradient by transporting protons across the inner membrane. However, we have very limited options to study the effects of aberrantly elevated membrane potential. One such way is the use of oligomycin, an inhibitor of oxidative phosphorylation complex V, the ATP synthase3. Since this also blocks mitochondrial ATP production, it has profound and complicated effects on cellular metabolism and ultimately viability. Some evidence for potentially beneficial effects of higher MMP was recently described in C.elegans, where the authors elevated MMP through expression of a photoactivatable proton pump4. Intriguingly, this led to an increase in life span and delayed certain age-related phenotypes. Identifying other, more physiological, mechanisms to increase membrane potential would greatly facilitate the study of MMP regulation and potentially enable the discovery of therapeutic modifiers of MMP to improve mitochondrial health in ageing and disease. The Rutter lab has recently identified such a mechanism of MMP upregulation in a study of yeast mitochondria. We found that yeast cells upregulate mitochondrial membrane potential when grown in the absence of phosphate5. The same phenomenon was observed when phosphate signaling was genetically modified to generate a continuous signal for low phosphate even in the presence of phosphate. This suggests that the response is to the perception of low phosphate rather than actual phosphate deprivation, and strongly suggests active regulation of the membrane potential rather than simply passive stoichiometric flux. Our preliminary data in Drosophila melanogaster confirms this finding in vivo and showed that blocking cellular phosphate uptake using phosphonoformic acid (PFA) increased MMP, prolonged life-span and delayed age-related phenotypesI now propose to utilize phosphate depletion to investigate how mammalian cells sense and regulate their mitochondrial membrane potential. By applying high-throughput molecular biology techniques, we now for the first time have the ability to screen thousands of genes for their involvement in upregulation of MMP. I will study cellular and mitochondrial health in the context of high MMP and combine an unbiased genetic approach (CRISPR screen) along with investigation of chosen candidate genes to identify regulators of MMP which historically has been perceived as merely as a result of metabolic activity. The components of such a regulatory network are entirely unknown and hold potential for therapeutic modulation of membrane potential as well as advancing our understanding of mitochondrial biology.
Amount: CHF 115,500
Funding type: fellowship
Funder scheme: Postdoc.Mobility
Start date: 2023-08-01
End date: 2024-02-29
Investigator: Seiler, Kristina
Institution: Institution abroad - United States of America
Subfield: Molecular Biology
Domain: Life Sciences
Funded outputs count: 0
Funder award ID: 217820
OpenAlex ID: G5552162153