Calcium domain in Orai1 regulates NFAT dependent genes

Calcium is a main trigger for the immune system due to its regulation of gene expression. This signaling process controls both the proliferation of immune cells and the defense against bacteria. To mediate these cellular processes, calcium influx occurs via special pores, termed the Orai1 ion channel. Orai1 acts like a trigger that can be oscillatory or sustained opened by an immune cell. Mutations within Orai1 can result in severe immune diseases. Within this project, Dr. Rainer Schindl and his team aim to resolve which molecular structures are required for the calcium transport into immune cells and subsequent gene regulation. In preliminary experiments, we used super computers to simulate the binding of calcium with the ion channel Orai1. We hypothesize that this calcium binding domain is crucial for gene regulation. Hence the calcium binding structure will be genetically modified and compared experimentally with the function of the original Orai1 ion channel. We will record the influx of calcium into the cell, the activation of genes and the production of proteins. These methods allow to mechanistically link the molecular Orai1 structures, with calcium transport pathways and the production of proteins. The characterization of Orai1 calcium binding structure aims to provide fundamental insight into calcium transport in immune cells. Regulation of calcium influx will determine how genes are activated efficiently.

Calcium transport as a target point to prevent an overreaction of the immune system If bacteria or viruses, such as the corona virus, find their way into the body, the immune system acts to protect us from a serious illness. In order that cells of the immune system are able to get activated and subsequently act against this invasion, requires a small charged atom - calcium. In a project funded by the Austrian Science Fund FWF, the laboratory of associate professor Rainer Schindl, Medical University of Graz, investigates how transient calcium uptake into immune cells manages to switch on immune responses. Within every cell of the immune system, specific proteins are located at the cell membrane that control the flow of calcium into cell. Instead, if these proteins are inactive, these channels are closed for the calcium transport and prevent activation of the immune cell. Together with computer scientists from the Czech Academy of Sciences and biophysicists from the University Linz, this transport route of calcium in immune cells was investigated. While the Austrian research teams were able to measure the calcium influx in single individual immune cells in live-cell recordings, the Czech scientists analyzed the molecular structures of these transport proteins. A number of new findings about the transport of calcium into the cell emerged from their joint studies. The scientists discovered a charged structure within the transport proteins that calcium attracts electrically. The computer results showed which protein structures are important for calcium docking. The Austrian researchers were able to genetically modify the proteins and measure calcium transport, thus confirming the computer prediction experimentally. Without this docking structure, however, very little calcium would reach the immune cells. This protein structure is not only important for calcium transport, but also an important docking point for novel drugs to stop or suppress the calcium flow. These discoveries are of great medical importance: when the immune system is overactive, the body and its organs can be damaged. With the corona virus, as an example, many intensive care patients experience an overreaction of the immune system and, as a result, their lungs are damaged massively. Using drugs to counter the influx of calcium into immune cells is a promising approach to stop the overreaction of the immune system. The first drugs that specifically target the calcium transport of overactive immune cells are now being tested by pharmaceutical companies in clinical studies for their effectiveness against Covid19. With the help of the knowledge gained in this project, the transport path of calcium in immune cells could be deciphered. In addition, it was experimentally clarified how this calcium transport can be stopped with medication in order to prevent an overreaction of the immune system.