An important component of signaling pathways is the recruitment of key proteins from the cytosol to a specific subcellular membrane where they can exert their function. This process is driven by small, phosphoinositide-binding modules within the “host” protein called the pleckstrin homology (PH) domains. Recent biochemical and biophysical analyses performed in our lab suggest that PH domains may fall into one of three functional categories based on their phosphoinositide binding: (1) a high affinity, high specificity class;  (2) a high affinity, reduced specificity class ; (3) a low affinity, promiscuous class in which lipid binding is probably too weak to account for an in vivo response.  I propose to study the latter two classes of PH domain using the following approaches:  examine the regiospecificity of PH domain binding to lipids, examine phosphoinositide binding to 66 representative human PH domains, find interacting protein partners of representative human PH domains.

My current focus in the lab is to develop a protein complementation assay to assess homo- and hetero-dimerization of erbB receptors in a cellular context.  Systems utilizing EYFP and mDHFR are under development and the preliminary results are encouraging.  In concert with the biophysical/structural studies ongoing in the laboratory, we hope to parse out the discrete regions of these receptors that make specific contacts in receptor dimers induced by exposure to erbB ligands.