Director of Biophysics Graduate Program
Department of Physiology and Biophysics
Jacobs School of Medicine & Biomedical Sciences
Ion channel kinetics and structure; Membrane Transport (Ion Transport); Molecular and Cellular Biology; Molecular Basis of Disease; Neurobiology; Pain Management; Protein Function and Structure; Signal Transduction
We study structural functions of ion channels involved in pain and temperature sensation. Nearly 1/3rd of the population suffers from some form of pain each year, yet less than 30% experience adequate relief with painkillers. Modern pain medications are not only ineffective, but also extremely outdated, with little to no progress having been made in the past 60 years. As a result, patients routinely turn to opioids for relief, spurring a culture of addiction and abuse in what is currently known as the opioid epidemic. The development of new painkillers is badly needed to combat this ongoing crisis. A promising drug target lies in a family of ion channels known as TRP (transient receptor potential) channels. These channels are located in sensory neurons of the peripheral nervous system and are responsible for registering pain-inducing stimuli.
TRP channels are sensitive to extreme temperatures. Unlike ligand- or voltage-dependent gating, the mechanism behind temperature activation is unknown. Our lab studies two subgroups of thermosensitive TRP channels including TRPV1, which is activated by extreme heat (>42°C) and TRPM8, which is activated by cold and menthol.
Most pain stems from tissue damage caused by physical injury or disease (i.e. cancer). Damaged tissues trigger the release of inflammatory markers and chemicals, which cause nociceptors to overreact, producing sensations of pain. TRP channels can interact directly, or indirectly with these compounds, contributing to these sensations. We are interested in how TRP channels detect and combine signals from different types of these compounds.
Capsaicin (hot ingredient in chili peppers) evokes an unpleasant burning sensation by activating TRPV1. Ironically, capsaicin is also used in topical creams as a way to relieve pain. The therapeutic benefits of capsaicin are believed to originate from its ability to switch the channel into a refractory or desensitized state. We are interested in the signaling pathway responsible for bringing about this functional desensitization as well as potential ways of exploiting it for pain relief.
We employ a variety of techniques spanning multiple disciplines including electrophysiology, molecular biology, biophysics, biochemistry and structural & computational biology. We study these ion channels both in vitro in living cells and in situ by purifying and inserting them into artificially made liposomes. We see these channels as miniature machines, with each part posing a distinct function. Our bread and butter consists of using patch clamp (which lets us monitor ion channel functioning) with mutagenesis to pinpoint the functional role behind each structural part. We are also using cryo-EM to visualize the different structural forms these channels adopt under different temperatures. We then map these distinct conformations to their respective functions by using luminescence energy transfer (LRET), an optical technique capable of discerning individual moving parts of the protein, in conjunction with molecular dynamics (MD) simulations. At the cellular level we are interested in the signaling cascade that regulates channel activity. An example of this is an experiment we performed where we used fluorescence microscopy (TIRF) in conjunction with patch clamp. TIRF microscopy allowed us to monitor fluctuating PIP2 levels within the plasma membrane whereas the patch clamp allowed us to monitor TRPV1 functionality. The experiment allowed us to observe a causal relationship, wherein a decrease in PIP2 concentration led to TRPV1 desensitization.
Our lab places a strong focus on building new tools. For example, we recently developed a fast temperature clamp using infrared laser diodes. This contraption permits ultra-fast local heating of single cells and has proven vital to our study of thermal channels. We also possess a custom-built microscopy-based LRET detection system (with a pulsed ND:YAG laser) for spectroscopic studies. We have also developed a suite of algorithms for interpreting data from single-channel recording, a type of measurement that supplies rich information regarding channel functioning. This software, known as QuB, is world-renowned and used by ion channel researchers worldwide. Students will not only have the opportunity to use state-of-the-art equipment to conduct cutting-edge biomedical research, but will also have the opportunity to gain deeper insight as to the technical aspects behind the tools they use.