Mitochondrial lipid metabolism and regulation of cell function
Our research work will be carried out at the Faculty of Biochemistry and Molecular Medicine and Biocenter Oulu, University of Oulu, and it is the basic research in lipid biology and biochemistry with the tight link to biomedicine and nutrition. The work includes two interlinked focus areas:
- Mitochondrial lipid metabolism and regulation
- Physiological role of mitochondrial fatty acid synthesis
The subprojects require a deep understanding of lipid- and protein biochemistry, and address the regulatory interplay between cells and intracellular organelles and metabolic compartmentalization in a physiological context. Different model organisms (yeast, mouse, rat and human) and technical approaches (e.g. protein chemistry, molecular genetics, molecular biology, membrane electrophysiology and structural biology) will be used to address particular biological questions.
Background and Significance
Cell organelles are key players in maintaining of physiological homeostasis of cells and organs. The scope how we gather interplay of metabolic control mechanism in cellular setting has undergone a major revision during the last years. In reference to human health, several inherited diseases are known that are caused by malfunction of cell organelles and they contribute also to pathophysiology of almost all acquired human diseases.
A large number of studies have demonstrated significance of the polyunsaturated fatty acids (PUFAs) for human health. In spite of international research and progress many key aspects on molecular mechanisms translating PUFA sensing into changes in gene expression have remained largely enigmatic. As one approach to shed light on the responses of animals to PUFAs, we have generated a mouse line defective in mitochondrial dienoyl-CoA reductase (Decr), which is a key enzyme required for mitochondrial break-down of PUFAs, with an outcome of accumulation of PUFAs in these mice. The Decr null mutant mice are asymptomatic until exposed to fasting, during which they switch on ketogenesis, but simultaneously develop hypoglycemia and the mice do not tolerate cold. These observations highlight the necessity of Decr and the breakdown of unsaturated fatty acids in the transition of intermediary metabolism from the fed to the fasted state.
Major recent discoveries on many previously unknown or neglected aspects of mitochondrial physiology and biochemistry have brought these organelles into the spotlight of research interest in the field of life sciences. These discoveries include mechanisms of mitochondrial fusion and fission events, linkage of mitochondrial fusion events to the progression of the cell cycle, mitochondrial-nuclear crosstalk, mitochondrial DNA replication, transcription and translation, iron-sulfur cluster biogenesis, aging, mitophagy, the role of mitochondria in apoptosis and mitochondrial inheritance as a tool for the tracking of maternal lineages. Among the recently recognized features of mitochondrial functions is their ability to synthesize fatty acids in an acyl carrier protein (ACP)-dependent manner. The failure in mitochondrial fatty acid synthesis (mtFAS) in yeast leads to loss of mitochondrial respiratory function and to defective mitochondrial RNA processing and there is mounting evidence pointing to an essential function of mtFAS for well-being of mammals. Recently pieces of evidences have been emerging which link the mtFAS pathway to diseases in mammals. Our report on the development of cardiomyopathy in mice overexpressing Etr1 established a possible connection between mtFAS and heart disease. It has been recently demonstrated that compromised mtFAS results in dysfunction of mitochondrial respiration and accelerated aging in genetically modified mice. Furthermore, compromising protein lipoylation and respiratory complex I result in cell death in cultured human embryonic kidney 293T cells upon shutdown of ACP. The expression of 17βHSD8, encoding a subunit in 3-ketoacyl reductase (KAR1), was severely repressed in kidney and liver.
Figure 1. Mitochondrial fatty acid synthesis and its interaction with mitochondrial functions
The research will focus on mitochondrial fatty acid synthesis (mtFAS), that has very recently recognized to participate in many ways to mitochondrial cellular function including cellular lipoic acid metabolism, mitochondrial RNA processing, protein synthesis in mitochondrial ribosomes, respiratory chain complex assembly and Fe-S-cluster synthesis. The proposed work knits together an unexpected triangle of mitochondrial lipids, flow of information on cellular metabolic state to the mitochondrial genome and maintenance of respiratory-competent mitochondrial populations in mammals. The driving forces of the work are open fundamental questions and very recent identification of diseases in humans due to dysfunction of this pathway.. Specifically, our research will address the following subprojects:
- Organization of mitochondrial fatty acid synthesis systems
- Pathophysiology of inborn errors of mitochondrial fatty acid synthesis
- Mitochondrial fatty acid synthesis as regulator of intermediary metabolism and mitochondrial biogenesis
Depending on the scientific questions, we used as model mice, yeast strains with perturbations in mitochondrial lipid metabolism, in vitro reconstituted systems, protein engineering and analysis mtFAS defective human cell lines, and employ genetic, physiological, biochemical, biophysical and bioimaging approaches to characterize signaling pathways that respond to lipid metabolic cues.
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Masud, A.J., Kastaniotis, A.J., Rahman, M.T., Autio, K.J. & Hiltunen, J.K. (2019) Mitochondrial acyl carrier protein (ACP) at the interface of metabolic state sensing and mitochondrial function. BBA-Mol. Cell Research. 1866, 118540. doi: 10.1016/j.bbamcr.2019.118540
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Last updated: 30.4.2021