Logo: University of Southern California

Current Projects

Antibody Mimetic Proteins vs. Peptides.

Within the lab, we work on two major type of polypeptide ligands—antibody mimetic proteins and peptides.

Antibody Mimetic Proteins. We use a protein scaffold we call e10FnIII, a domain from human fibronectin that is an improved version of the monobody scaffold. Most of these projects aim to use the e10FnIII as an intrabody—an antibody-like molecule that can function inside cells (where antibodies don’t fold properly). New intrabodies made in this way can be used to visualize the trafficking and localization of endogenous proteins inside living cells. This is exciting because most existing methods rely on overexpressing the protein of interest, which often perturbs the cell behavior of interest.

Peptides as Ligands. Our recent work has made clear that relatively short peptides (10-20 amino acids) can bind proteins and nucleic acids of interest, with extremely high affinity—in many cases better than existing monoclonal antibodies. This opens the door to many new and exciting areas—the ability to create antibody-free diagnostics, new imaging agents for cancer and therapy, and better fundamental understanding of protein interactions. Our current record binder is a peptide with a Kd = 8.5 pM—equal or better than the highest affinity therapeutic monoclonal antibody.

New Tools for Neurobiology. Our recent work has resulted in antibody mimetic proteins that bind the neuronal proteins PSD-95 and Gephyrin. These proteins enable labeling and visualizing these markers of excitatory and inhibitory postsynaptic density in live neurons, simultaneously. We are interested expanding this effort to map changes in neuronal structure and function with our collaborators.

New Ligands for G Proteins and GPCRs. We have isolated peptide ligands for both the G proteins Gia1 and Gs as well as the beta-2 adrenergic receptor, one of the best studied and most important G protein coupled receptors (GPCRs). We continue to be very interested in GPCR-directed reagents as a means to control, understand, and modulate receptor function.

New Tools for the MAP Kinase Signaling Axis. The MAP Kinase cascade is activated in more than 50% of human cancers. We are interested in developing new imaging agents that can detect receptor overexpression, new intrabodies that monitor key phosphorylation events, and new reagents that block protein-protein interactions involved in signal transduction. The long-term goal of this work is to improve cancer diagnosis and therapy.

RNA Recognition by Peptides and Proteins. We remain interested in developing new structure- and sequence specific peptides and proteins that can be used for high affinity and high selectivity RNA recognition.