Trained as a protein chemist and molecular biologist, I am interested in understanding how proteins respond to voltage. The ultimate goal is to convert the voltage response of a cell into an optical signal allowing simultaneous monitoring of neuronal activity from individual neurons or entire neuronal circuits. We therefore study a broad range of projects spanning from the molecular aspects of voltage-sensitivity and the photophysics of fluorescent proteins to neuronal activity mapping in the hippocampus and motor cortex.
Background
Microbiology and Enzymology
I received a Bachelor of Science in Microbiology degree from Indiana University and a Ph.D. in Biochemistry from the Ohio State University. During my undergraduate studies I was extremely fortunate to work as an intern in an enzymology lab at Eli Lilly and Co. Thanks to the expertise of that lab (and a significant amount of luck), that experience led to my first publication regarding the purification of an enzyme involved in the synthesis of the antibiotic Cephalosporin (Baker et al, 1991).
Molecular Genetics
I really enjoyed purifying proteins from native sources, but the ability to clone genes into microbes for large scale production made me realize that I should focus on molecular biology during my Ph.D. I began a study of primate genetics that even today I find absolutely fascinating. I looked at the evolution of an endogenous retrovirus residing in a region of the genome that deals with immuno-compatibility. Retroviruses are RNA viruses that insert a DNA copy of their genome into the host genome that under certain circumstances can be inherited by the host’s offspring. Over time, the viral genes mutate and no longer function. We have thousands of these ancient viral genomes in our DNA. Seeing a viral genome at the some location in the DNA from Orangutan and human means that the original infection took place millions of years ago. It was an archeology study on a molecular level.
G-Coupled Protein Receptors
During my Ph.D. studies, I had the opportunity to collaborate with Cesar Milstein who won the Noble Prize for monoclonal antibodies. The goal was to crystalize the first Cluster of Differentiation antigen identified by a monoclonal antibody, CD1. During the purification process, we discovered that an alternative splicing event lead to a secreted form of this membrane bound protein. CD1 was shown to present lipid to T-cells which got me curious as to what the secreted form of CD1 was capable of. This led to a postdoc at Yale University to study G-Coupled Protein Receptors and heterotrimeric G-proteins.
Cation/Chloride Cotransporters
Despite my protein purification background, that project was challenging. The most important thing I learned during that postdoc was how important the research environment is. It was not the environment for me. I lasted a little over a year. Fortunately, I was able to transition to another lab studying cation/chloride cotransporters. That environment was a better fit for me, but I was not good at studying transporters.
Genetically Encoded Voltage Indicators (GEVIs)
My third postdoc gave me the opportunity to study how fluorescent proteins could change their fluorescence in response to voltage. Neurons exhibit a fluctuating voltage across the plasma membrane. By fusing fluorescent proteins with proteins that respond to voltage, neuronal activity can be converted into an optical output. My lab has made several significant advancements in the understanding of how the voltage-induced conformational change affects the fluorescent output. As these insights lead to better GEVIs, we have started imaging activation and inhibition of neuronal circuits in the hippocampus and motor cortex.