Oxidized phospholipid ionic transduction mechanism of human vascular cells

At least half of the European population dies from cardiovascular disease, often prematurely and following prolonged periods of disability. There is compelling evidence that this type of disease and several related diseases are caused, or accelerated, by unwanted inflammation, excessive oxidative stress, inactivity, and high fat load. Seminal studies over the past decade have identified special types of fat (lipid) in the disease conditions that are collectively referred to as oxidized phospholipids. There is excellent evidence that oxidized phospholipids play pivotal roles in cardiovascular disease but there is little fundamental understanding of how cells sense or respond to the lipids; or defend against them. In our new studies of vascular cells from patients with cardiovascular disease we have identified a striking initial reception mechanism for the lipids and so propose investigation of how the mechanism works as well as identification of genes that encode the mechanism. Through this work we will provide new insight into an important and poorly understood area of human biology and lay the foundations for valuable therapeutic interventions with high relevance to major human diseases.

New data generated by our group have revealed a previously unrecognized monovalent cation-selective membrane current that depends on Orai1 and is triggered by oxidized phospholipids without store-depletion. A similar ionic current can be triggered by store-depletion but we suggest the oxidized phospholipids are the physiological or pathological factors that activate the mechanism. The mechanism may have widespread importance for survival of human cells and be a key element in oxidized phospholipid signaling in inflammation and related cardiovascular diseases. We propose a project that will define molecular components of the mechanism and reveal distinguishing features and tools that will enable investigation of the mechanism in vivo. Using combinations of electrophysiology, calcium measurement and molecular techniques the study will: Characterise the monovalent cationic current and its activation mechanism; Identify molecular tools that specifically manipulate the monovalent cationic current; Investigate RNA editing of Orai1-3 and STIM1-2 because preliminary data suggest that RNA-editing is necessary for the monovalent mechanism but not Orai1-dependent Ca2+-entry; and Identify monovalent cation channel subunits coupled to Orai1. The study will provide important fundamental information about Orai1 and oxidized phospholipid signaling in human cells and may reveal new targets for therapeutic intervention.