We aim to better understand the function of an enzyme called PP2A. PP2A is a tumor suppressor, and is also implicated in Alzheimer disease. PP2A relays information from the outside to the inside of cells by removing phosphate groups on other proteins. Because of this activity, it is called a phosphatase. Phosphatases such as PP2A oppose the action of another enzyme family called kinases. Deregulation of the phosphatase versus kinase balance is detrimental to the cells and often leads to cancer and other diseases. We aim to identify the protein targets for PP2A as a first step to understanding its physiological role. We have already identified many proteins that can associate with PP2A by using mass spectrometry, a technique that measures with great precision the patterns that can uniquely identify a protein, in a manner similar to how fingerprints can uniquely identify an individual. One group of proteins binding to PP2A is associated to a disease called cerebral cavernous malformations, which is linked to an array of problems, including headaches, seizures, dizziness and strokes. Our central hypothesis is that PP2A may remove phosphate groups on some of the proteins implicated in the disease, and that this phosphate removal changes the activity of the proteins. We will continue our analysis regarding the biological functions of PP2A, and in particular, we will determine whether the proteins that we have identified as associating with PP2A are directly targeted by the activity of the enzyme. We will also investigate further the role of PP2A on key processes involved implicated in cerebral cavernous malformations. This study may lead to better therapeutic avenues for patients afflicted with this disease.