Project Summary/Abstract This project will expand my recent inventions in directed evolution to create tools for cell-type specific photoswitchable tuning of G-protein coupled receptors. The human genome encodes >900 G-protein coupled receptors (GPCRs). Found in every cell, GPCRs contribute to every known biological process; from our sense of taste, smell, and sight to coordinating hormone, neurotransmitter, and immune functions. The past one-hundred years of biochemical research on this protein family has produced 346 structural determinations, >100,000 confirmed ligands, and a wealth of signaling assay platforms. Absent from this impressive roster are any tools for the discrete, cell-type specific tuning of endogenous receptor activity (Fig 1). Without such tools, we lack the ability to directly connect discrete GPCR signaling events to cell-type specific physiological outputs. Such tools are essential if we are to understand how GPCRs dictate human health and disease. In this NIH New Innovator proposal, I will expand my recently invented platform for mammalian directed evolution to create a production pipeline for cell-type specific, photoswitchable allosteric modulators of GPCRs. I will then develop the first of these modulators for the D1 and D2 dopamine GPCRs and use these tools to refine existing models of dopaminergic reward signaling in the murine brain. The success of this proposal will benefit every field of biomedical research, creating a pipeline to gain tunable control of not only any GPCR, but any cell signaling protein.

Project Narrative Receptors are specialized proteins in our bodies that we use to experience the world – from our sense of smell and taste to our perception of pain and our ability to learn new information. We do not possess the tools necessary to determine how and under what conditions each of the hundreds of unique receptors in our bodies promote health or disease. In this project I will apply a revolutionary new method I have developed in protein engineering to create the tools necessary to control these receptors and study how they make us who we are.