Biography

After undergraduate studies at Reed College, Peter G. Barr-Gillespie attended graduate school at the University of Washington, working with Joe Beavo; he received his PhD in Pharmacology in 1988. From 1988 to 1993, he worked as a postdoc with Jim Hudspeth — first at the UCSF, then at the UT Southwestern Medical Center. He joined the Department of Physiology at Johns Hopkins University as an assistant professor in 1993, rising to associate professor in 1998. In 1999, he moved to the Oregon Hearing Research Center (OHRC) at OHSU as an associate professor of Otolaryngology, as well as the Vollum Institute; he was promoted to Professor of Otolaryngology in 2004 and granted tenure in 2007. In 2012, Barr-Gillespie was named director of the Hearing Health Foundation's Hearing Restoration Project (HRP), a consortium of scientists who are developing a strategy for regeneration of sensory hair cells of the inner ear. Barr-Gillespie was associate vice president for Basic Research at OHSU from 2014–2017 and interim senior vice president for Research from 2017–2018. He was named chief research officer at OHSU in 2018.

Summary of current research

We want to understand how the sensory cells of the inner ear, hair cells, detect mechanical signals like sound and head movements. These extraordinary cells mechanotransduce with their sensory organelle, the hair bundle, a beautiful and complex structure made of ~100 actin-filled stereocilia of regimented lengths and a single microtubule-based kinocilium. Our approach is molecular, and addresses two of the most important questions in our field. First, what is the molecular mechanism for mechanotransduction? And second, how does the hair cell assemble the hair bundle so that its multiple levels of organization are produced and maintained?

Being interested in what molecules make up the transduction apparatus, the collection of channels, linker molecules, and motors that mediate transduction, we take a reductionist approach. We start with physiology: when you mechanically stimulate a hair bundle, the mechanically sensitive organelle of the hair cell, what are the characteristics of the resulting receptor current? By studying these transduction currents, we learn how transduction channels open and close in response to mechanical forces, how the adaptation motor responds to sustained forces and allows channels to close, and how the cell responds to the high levels of calcium ion that enter. The transduction currents are key; they report the functional operation of the hair cell.

But we need to know the molecules that underlie the physiology, and for this we turn to proteomics. We apply mass-spectrometry techniques to every aspect of the lab's research program, determining with increasing accuracy the hair bundle's proteome and investigating how the proteome changes in response to genetic and pharmacological manipulations. When we combine the bundle proteome with the collection of proteins expressed by "deafness genes," genes which when mutated cause deafness, we can define a list of ~100 proteins that may be involved in building and operating bundle.

Nice idea, but now we have to show that these are indeed the key molecules. We therefore take a systems-level approach to studying hair cell function, with the ultimate goal of determining which of those 100 proteins are responsible for assembly and transduction. To carry out this analysis, we characterize multiple facets of hair-bundle development using modern technology for proteomics, genomics, and imaging. We are presently resolving the developmental time course of transcript and protein expression, as well as targeting to bundles. We intend to determine the matrix of protein-protein interactions for those 100 proteins — which interacts with which? — to define the bundle's interactome. Together these descriptive data will motivate formulation of models for bundle assembly and transduction. Critically, we will test these models using targeted experiments, for example gene knockout or expression of inhibitor-sensitive alleles of key proteins.

Finally, our knowledge of several proteins of the transduction complex, together with the sensitivity of mass spectrometry, allows us to take a biochemical approach to identification of the transduction channel, one of the central mysteries of the auditory system. We have developed a large-scale purification method that enriches stereocilia membranes from thousands of chick ears. Applying immunoaffinity purification methods using monoclonal antibodies for key transduction molecules, like the tip-link molecule PCDH15, molecular motor MYO7A, and transmembrane component TMC1, we will establish the composition of the complexes they reside in. We hope to use this approach to reveal the identity of the transduction channel, as well as identities of other components of the complete transduction apparatus.

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