The role of PIPP in cell polarization and proliferation.

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Normally cells only divide when they receive a stimulus such as from a hormone or growth factor. Upon stimulation, a series of signals are generated inside the cell which lead to cell division and development. One of the signaling pathways which responds to growth factor stimulation is the PI3-kinase pathway. This pathway has been implicated in many different human cancers which occur when cells divide uncontrollably and invade into the surrounding tissues. Following growth factor stimulation, PI3-kinase generates a molecule known as PtdIns(3,4,5)P3 which leads to the activation of many proteins in the signaling pathway. All cells which have PI3-kinase also have enzymes which act to switch off the signals generated by PI3-kinase and thus may play a role in preventing cancer and regulating cell development. We have identified a new enzyme known as PIPP and have shown that it acts to switch off the signals generated by PI3-kinase. We plan to investigate the role of PIPP by increasing or decreasing the amount of PIPP in cells and analysing the effects on cell growth and development. We have also identified a number of proteins which bind to PIPP and we will investigate the role these proteins play in regulating cell signaling. In addition, we plan to characterize the function of PIPP in a whole animal by generating mice which lack PIPP (knockout mice) and assessing the effects on development and cancer.