Ultrasonic modulation of cellular electrical signaling - Ultrasound (US) neuromodulation (NM) utilizes mechanical energy from sound to modulate the physiology of excitable cells through mechanosensitive ion channels (MSIC). Its uninvasive bone-penetrating nature combined with a unique focusing capability provides advantages over optogenetics and chemogenetics. Recently, the FDA has approved transcranial USNM. There is a lack of a molecular understanding on how US modulates cellular excitability. Furthermore, not all cells express channels that respond to US. To address these issues, novel experimental systems and techniques will be implemented to extract mechanistic biophysical information and engineer sonogenetic tools for robust transgenic expression. The biophysical effects of US on TRAAK K+ channels were recently characterized because of its potential to serve as a sonogenetic silencer of neurons. The endogenous expression of TRAAK at the nodes of Ranvier also makes it an attractive candidate for inhibitory NM when targeting native myelinated axons in the white matter. During the mentored phase (Aim 1, K99), the fundamental biophysical effects of US will continue to be characterized on TRAAK and other channels. This includes experiments to calculate tension and surveying optimal US parameters to maximize channel stimulation. Preliminary data suggests that the CFTR Cl- channel is sensitive to US. Other MSIC will also be screened to identify those sensitive to US. The next aim (Aim 2, K99/R00) looks to optimize TRAAK and other MSIC into sonogenetic tools. To transform TRAAK into a US-hypersensitive action potential generator, structure guided mutagenesis will be used to increase its sensitivity to ultrasound and permeability to Na+. Aim 3 (R00 phase) looks to implement NM by stimulating endogenous MSIC and transgenically expressed sonogenetic tools. They will be activated in vitro in mouse brain slices and cultured neurons, and in vivo in live mice. In summary, this proposal looks to screen for and optimize the activation of endogenous MSIC with US, and also engineer novel sonogenetic tools. In a short period of time, this work will advance our understanding of the effects of US on MSIC and NM. The long-term goal is to implement these tools for clinical use in minimally invasive NM. This research program will generate a platform of complementary techniques and applicable knowledge that can also be applied by others for further studies in sonogenetics and USNM. Dr. Sorum's mentors, Profs. Brohawn and Adesnik, have expertise that spans many areas of neuroscience including mechanobiology, MSIC structure/function, optogenetics, NM, neural circuits, and behavior. Two additional years of training will allow him to fully develop skills in molecular, cellular and systems neuroscience and merge them with USNM and sonogenetics.
