Characterization of the genetic interactome of prohibitins in S. cerevisiae

Prohibitins comprise an evolutionary conserved and ubiquitously expressed family of membrane proteins that is essential for development in higher eukaryotes. Large ring complexes formed in the inner mitochondrial membrane by prohibitins regulate mitochondrial dynamics and function. Roles of prohibitins in cell signaling events across the plasma membrane and transcriptional regulation in the nucleus have been proposed as well. The molecular mechanism of prohibitin function, however, remains elusive. In contrast to higher eukaryotes, prohibitin-deficient yeast cells are viable and exhibit a reduced replicative life-span. To investigate the functional role of prohibitins in yeast and to identify redundant processes that fulfill the functions of prohibitins in their absence, an unbiased genetic approach was chosen. Synthetic genetic arrays were applied to identify genes showing synthetic lethal interactions with prohibitins. This approach revealed 35 genes required for cell survival in the absence of prohibitins. The assembly of the FO-particle of the F1FO-ATP synthase was identified as one process essential in prohibitin-deficient cells. Atp23 was characterized as a novel processing peptidase with a dual function in maturation of the mitochondrially encoded subunit Atp6 and its assembly into the functional F1FO-ATP synthase. ~50% of the genes required in prohibitin-deficient cells, including the strongest genetic interactions, are demonstrated for the first time to be required for mitochondrial phospholipid homeostasis. Evidence is provided that members of a conserved protein family, Ups1 and Gep1, coordinately regulate the levels of the non-bilayer forming phospholipids cardiolipin and phosphatidyl-ethanolamine in mitochondria. Additionally, an uncharacterized putative phosphatase was identified that is required for cardiolipin biosynthesis and might represent the last missing enzyme in the biosynthesis pathway of cardiolipin in yeast. The genetic interactome of prohibitins defined in this thesis suggests that prohibitins serve scaffolding functions in the inner mitochondrial membrane and define functional microdomains composed of proteins and non-bilayer forming lipids. This function becomes essential, when levels of cardiolipin and phosphatidylethanolamine are limiting in mitochondria. In the absence of prohibitins and decreased levels of non-bilayer forming lipids, essential processes dependent on these microdomains are compromised

Making heads or tails of phospholipids in mitochondria

Mitochondria are dynamic organelles whose functional integrity requires a coordinated supply of proteins and phospholipids. Defined functions of specific phospholipids, like the mitochondrial signature lipid cardiolipin, are emerging in diverse processes, ranging from protein biogenesis and energy production to membrane fusion and apoptosis. The accumulation of phospholipids within mitochondria depends on interorganellar lipid transport between the endoplasmic reticulum (ER) and mitochondria as well as intramitochondrial lipid trafficking. The discovery of proteins that regulate mitochondrial membrane lipid composition and of a multiprotein complex tethering ER to mitochondrial membranes has unveiled novel mechanisms of mitochondrial membrane biogenesis

LEGaTO: first steps towards energy-efficient toolset for heterogeneous computing

LEGaTO is a three-year EU H2020 project which started in December 2017. The LEGaTO project will leverage task-based programming models to provide a software ecosystem for Made-in-Europe heterogeneous hardware composed of CPUs, GPUs, FPGAs and dataflow engines. The aim is to attain one order of magnitude energy savings from the edge to the converged cloud/HPC.Peer ReviewedPostprint (author's final draft

The genetic interactome of prohibitins: coordinated control of cardiolipin and phosphatidylethanolamine by conserved regulators in mitochondria

Prohibitin ring complexes in the mitochondrial inner membrane regulate cell proliferation as well as the dynamics and function of mitochondria. Although prohibitins are essential in higher eukaryotes, prohibitin-deficient yeast cells are viable and exhibit a reduced replicative life span. Here, we define the genetic interactome of prohibitins in yeast using synthetic genetic arrays, and identify 35 genetic interactors of prohibitins (GEP genes) required for cell survival in the absence of prohibitins. Proteins encoded by these genes include members of a conserved protein family, Ups1 and Gep1, which affect the processing of the dynamin-like GTPase Mgm1 and thereby modulate cristae morphogenesis. We show that Ups1 and Gep1 regulate the levels of cardiolipin and phosphatidylethanolamine in mitochondria in a lipid-specific but coordinated manner. Lipid profiling by mass spectrometry of GEP-deficient mitochondria reveals a critical role of cardiolipin and phosphatidylethanolamine for survival of prohibitin-deficient cells. We propose that prohibitins control inner membrane organization and integrity by acting as protein and lipid scaffolds

LEGaTO: towards energy-efficient, secure, fault-tolerant toolset for heterogeneous computing

LEGaTO is a three-year EU H2020 project which started in December 2017. The LEGaTO project will leverage task-based programming models to provide a software ecosystem for Made-in-Europe heterogeneous hardware composed of CPUs, GPUs, FPGAs and dataflow engines. The aim is to attain one order of magnitude energy savings from the edge to the converged cloud/HPC.Peer ReviewedPostprint (author's final draft

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries