Cell differentiation, adhesion and motility, proliferation and apoptosis occur in response to the extracellular environment. Membrane proteins detect environmental stimuli, and elicit molecular and genetic responses that determine cell fate. Cancer results when these membrane-protein-orchestrated processes malfunction. Despite the central roles of human membrane proteins in cancer biology, no high-resolution structures of these proteins exist. Our goal is to address this gap in the understanding of the molecular mechanisms of cancer. We will initiate a comprehensive study of the structural biology of cancer-related membrane proteins (CRIMPs). We selected membrane protein targets involved in signaling pathways, cell-cell interactions, and transport that are integral to cancer biology. The goal of the proposed research is not to solve the structures of all of the target CRIMPs. However, the combination of our proposed methods and the large, diverse target set makes solving several CRIMP structures realistic. Structures of any of the targets will contribute significantly to the understanding of cancer biology. While it is difficult to predict the utility of membrane protein structures in drug design, therapeutic potential was an important factor in our target selection, and structures of CRIMPs may facilitate therapeutic drug or protocol development. We will also generate valuable data on the heterologous expression of human membrane proteins in P. pastoris. During the course of the proposed research we will complete the most comprehensive analysis to date on the expression of human membrane proteins in P. pastoris.
The specific aims of the proposed research are: 1. Identify cancer related human membrane proteins that are amenable to crystallization. We will select 60 structurally and functionally diverse membrane proteins based on cancer relevance and degree of predicted disorder. Selecting CRIMPs with limited disorder will enhance the probability of successful crystallization. 2. Evaluate the heterologous expression of sixty diverse cancer related membrane proteins in Pichia pastoris. We will use novel Gateway?1/2 vectors, 10 ml P. pastoris growths, dot-blots, and small scale detergent solubilization experiments to rapidly evaluate the heterologous expression and detergent solubility of target CRIMPs. All experiments through solubilization will be performed on batches of twelve targets. 3. Solve the structures of cancer-related membrane proteins that overexpress and form good crystals without significant modification. We will use a novel membrane protein solubility screen to determine the optimal concentrations of targets for crystallization. We will use a crystallization robot to set up 1024 conditions with 120 microliters of protein (~100 nl per experiment). We will use lab-written software and a fluid-handling robot to optimize crystallization. We will use an automated plate imager to view and document crystallization experiments. We will solve the structures of CRIMPs that form high quality crystals. ? ? ?
