An investigation into the role and regulation of BACE1.

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The cell is the basic unit of all known living organisms, and humans consist of many different and highly specialised types of cells. To function properly cells, need to communicate with both their environment and neighbouring cells. This requires the passing of information across the cell membrane, which separates the interior of the cell from the outside environment. One main mechanism by which this is achieved is though activation of proteins located in the cell surface, so called receptors. Attaching of a ligand (key) switches on the receptor (lock) which causes a signalling cascade resulting in a cellular response, including growth, differentiation and death. For example, the insulin receptor recognises and responds to the hormone ligand, insulin. It is crucial for cells to be able to control the signals it receives. One way this is achieved is via the actions of molecular scissors. These proteins cut off sections of the receptor, meaning the ligand cannot attach. This is a normal cellular process and results in switching off the signal, providing an appropriate amount and duration of signal to the cell. However, too much or too little cutting leads to mis-communication resulting in developmental abnormalities and diseases including cancer, dementia and heart disease.Therefore, understanding how these molecular scissors work and how they are regulated is fundamental to understanding how cells communicate with each other and how this can be distorted leading to disease.In this project we will study one of these molecular scissors, BACE1. BACE1 was first identified as being responsible for the production of beta-amyloid proteins, which combine, leading to the development of Alzheimer's disease. However, recent studies have identified more than 70 different proteins in the brain which are cut by BACE1. So, it is becoming apparent that the BACE1 protein could play a major role in the regulation of a range of cell signals and therefore responses.Despite BACE1 protein being found in most of the cells in the body, researchers have up until now have focused on the brain. So, we plan to examine the role of BACE1 in endothelial cells, an important cell type found throughout the body. These cells are responsible for regulating blood flow, nutrient and oxygen delivery to tissues and preventing infections.In this project we aim to understand what basic cellular functions BACE1 is involved with. To do this we plan to explore the following aspects:1) We will identify what proteins come in close proximity of BACE1 and of those which are cut, using a technique known as mass spectrometry. 2) We will also investigate how physiological stimuli such as hormones, blood flow and low oxygen regulate BACE1 activity and how this affects which proteins it selects to cut.3) Finally, we have shown that reducing the activity of BACE1 can have major effects on endothelial cells. Therefore, we will further examine what effect the regulation of BACE1 has on endothelial cell functions including growth, formation of blood vessels and sensing the environment.The results will provide fundamental information on how cells are able to regulate communication with each other. These findings could have wide ranging impact for the understanding of many cell processes in a range of cell types. Furthermore, this study has the capacity to uncover important understanding for diseases where cell communication is disrupted. This is potentially important knowledge which could lead to manipulation of BACE1 actions being a way to restore cell homeostasis.