Title: Role of mitochondrial Complex I in cellular response to hypoxia
Funder: Medical Research Council

Abstract: Mitochondrial complex I plays a critical role in regulating energy generation in cell and it is involved in a number of clinical conditions such as neurodegeneration (Parkinson?s disease, Leber?s optic neuropathy), muscular pathologies and processes of ageing. At the same time ischaemia/reperfusion injury mediated by mitochondria is a major cause of heart diseases, as well as stroke; these two are the leading causes of death in the UK, ranking before cancer and cause more than 30% of deaths. This proposal is aimed at unraveling the role of mitochondrial complex I in such pathological conditions translating new findings to clinical medicine. Complex I has a high control over the respiration rate and therefore it is likely that the moderate changes in its activity would make a strong effects on the overall rate of oxidative phosphorylation. In addition Complex I is also a source of detrimental free radicals, as well as a target for oxidative damage by them. I intend to clarify the role of Complex I in cellular response to hypoxia and identify possible key points of control of the enzyme my physiological and pharmacological modulators. I propose to investigate Complex I behaviour in detail using classical biochemical as well as novel non-invasive cell-imaging approaches. Firstly, I will identify structural differences between two Complex I states in isolated mitochondrial membranes from brain and heart, characterise them by cross-linking and amino acid specific covalent reagents. Further I will study Complex I activity and factors influencing it in several cultured cell lines including myocytes and neurons during processes of hypoxia and reoxigenation. I plan to use biochemical and live cell imaging techniques to carry out functional studies of effect of pharmacological agents on Complex I and how they influence cell viability in hypoxia/reoxygenation. The proposed line of research will clarify the physiological and pathophysiological consequences of complex I activity changes and ROS production during hypoxia/reoxygenation and nitric oxide exposure. Prolonged hypoxia initiates a sequence of cellular responses via the hypoxia-inducible transcription factors (HIFs). It has been proposed that mitochondrial ROS, oxygen redistribution and other transcriptional pathways are involved in HIF-1alpha stabilisation at low oxygen concentrations, but the relative contribution of these mechanisms in hypoxia is not clear. I will therefore also study the involvement of cellular components in accumulation of HIF-1alpha via ROS-dependent and independent mechanisms In the proposed project I am going to bring together two essential aspects of hypoxic studies important for development of cardio- and neuroprotective therapy and anticancer interventions. Understanding how and why Complex I activity is modulated in cells will elucidate the role of mitochondria in ischaemic/reoxygenation injury, muscular- and neurodegeneration as well as age-related loss of muscle function. Such understanding could lead to the development of new clinical diagnostic tools and presents opportunities for therapeutic intervention. At the same time unravelling of involvement of respiratory chain in HIF-1alpha stabilisation will help to design strategies for anticancer treatment.


Research activity codes: 1.1 NORMAL BIOLOGICAL DEVELOPMENT AND FUNCTIONING;2.1 BIOLOGICAL AND ENDOGENOUS FACTORS
Health categories: STROKE;MUSCULOSKELETAL;NEUROLOGICAL;CANCER AND NEOPLASMS;CARDIOVASCULAR