Description of Research Expertise

Research Interests
Signaling by growth factor receptor tyrosine kinases, and inositol phospholipid signaling - biochemical, cellular, and structural biological studies.

Key words: growth factor receptor, phosphoinositide, signaling, cancer, structure, membrane recruitment.

Description of Research

Signaling by Growth Factor Receptor Tyrosine Kinases

We are interested in understanding how growth factor receptors from the epidermal growth factor (EGF) receptor family signal across the membrane. For the EGF receptor itself, X-ray crystal structures recently determined in our lab and elsewhere have shown that EGF binding promotes conformational changes that induce receptor dimerization (which is responsible for receptor activation). It is also known that the four members of the EGF receptor family, which includes EGF receptor, ErbB2 (also known as HER2/Neu), ErbB3, and ErbB4 from hetero-oligomers. We are now trying to understand this hetero-oligomerization process using cellular, biochemical, and biophysical approaches. We are now especially interested in understanding how ErbB2/HER2/Neu is activated. This member of the family has no known ligand, yet is activated in trans by ligands for other family members – through receptor heteromerization. ErbB2 is overexpressed in some 30% of human breast cancer cases, and the value of Herceptin( TM) as a breast cancer drug has shown it to be an important therapeutic target. If we are able to understand the normal mechanism of ErbB2 regulation, we hope that this will suggest new pharmacological approaches for targeting this process that will not bring with them the disadvantages of HerceptinTM. Our approach to this is multidisciplinary, and currently draws substantially from insights gained from our recent structural studies.

Signal-Dependent Membrane Recruitment by Small Domains

The second main focus of the laboratory is on small (100 aa or so) domains in signaling, cytoskeletal, and other proteins that recognize membrane components, and target their host proteins to cellular membranes. To date we have worked primarily with pleckstrin homology (PH) domains, and have shown structurally how a subset of PH domains recognize the lipid products of agonist-dependent phosphoinositide 3-kinases, and so can drive acute recruitment of their host proteins to the plasma membrane. The PH domain is the 11th most common domain in the human proteome. We now know that, while several bind to specific phosphoinositides, many (most) PH domains do not. We have recently embarked on a genome-wide analysis of PH domains in S. cerevisiae in order to ascertain what other roles PH domains play.

In addition to PH domains, we are also interested in the roles of FYVE domains and phox homology (PX) domains, which bind to phosphatidylinositol-3-phosphate, a lipid found in endosomal compartments. We have analyzed all S. cerevisiae PX domains, and are currently assessing their physiological roles. A current focus in our work on these domains is to test the hypothesis, suggested by several observations, that PH and PX domains act as ‘coincidence’ detectors, effectively checking for the coincidence of a particular protein target and lipid target in the same cellular compartment. Our approaches again draw from biochemical, biophysical, and cell biological studies. Finally, we are studying lipid binding by some novel phosphoinositide-targeting domains.

Rotation Projects for 2006-2007
1. Investigations of natural EGF receptor inhibitors found in Drosophila, with a view to designing mammalian analogues that could be developed into anti-cancer drugs.
2. Analysis of novel yeast phosphoinositide binding proteins identified in genome-wide studies, using cellular and biophysical/biochemical approaches.
3. Biochemical, cellular, and structural studies of dual-target recognition by PH and other domains.

Lab personnel:
Diego Alvarado, Ph.D. - Damon Runyon Postdoctoral Fellow
Sung Hee Choi - Ph.D. Student, BMB
Jessica P. Dawson, Ph.D. - ACS Postdoctoral Fellow
Jon Kenniston, Ph.D. - Postdoctoral Researcher
Jeannine Mendrola, Ph.D. - Research Associate
Kartik Narayan, Ph.D. - NIH Postdoctoral Fellow
Kelley Bethoney - Ph.D. Student, BMB
David Keleti - Ph.D. Student, BMB
Daryl E. Klein - M.D./Ph.D. Student, BMB
Pamela Burgess-Jones - Research Specialist