Joao Luis Carvalho De Souza
Research Assistant Professor
Research Assistant Professor, Ophthalmology
Research Assistant Professor, Physiology
My lab is investigating noncanonical mechanisms involved in the modulation (activation, inactivation, and deactivation) of the activity of voltage-gated ion channels by the membrane electric potential. This aspect of ion channels is key to understand many diseases caused by defective ion channels expressed in neurons and muscular cells. My lab is also interested in developing a technique that enables light sensitivity to the membrane potential of genetically unmodified cells. With that technique one can control neuronal activity with pulses of light, an experimental and/or therapeutic capability always desired in neuroscience. We are currently applying this technique in mice with the goal to restore useful vision when the photoreceptors in the retina are not functional.
The goal of research in the De Souza lab is to study in detail the mechanisms involved in voltage sensing, in voltage-gated ion channels. Ion channels are the membrane proteins that ultimately determine the membrane potential. Voltage-gated ion channels provide ways to ensure the membrane will not stay depolarized for too long and they also provide ways to rapidly depolarize and repolarize the membrane, as action potentials, as means of making a “bit” of information in neuronal circuits. To that end, different voltage-gated ion channels must work in concert. They also must be precisely modulated by intramolecular mechanisms that couples the voltage-sensing part of the protein (the voltage sensor domain) with its ion-conducting pathway (the pore domain). These mechanisms are controlled by voltage, time, and environment. With classic and modern electrophysiological techniques including voltage- and current-clamp using patch clamp, two-electrode voltage clamp and cut-open oocyte techniques, optical tools, and mutagenesis, the De Souza lab is committed to unveil those mechanistic aspects that are still unknown. It is also of interest in the De Souza lab to re-enable useful vision when photoreceptors in the retina are no longer functional. With a non-genetic technique developed by Dr. De Souza and colleagues, named optocapacitance, neurons in the retina can be labeled with gold nanoparticles to behave like photoreceptors and relay light-generated electric signals from the retina to the visual cortex in the brain where vision is perceived. In the De Souza lab transgenic mice (with retinas irresponsive to light) are used for testing the effectiveness of this technique as an enabler of useful vision. Visual evoked potentials are recorded from the visual cortex of anesthetized mice to probe retina activation by light. Behavior tests measures light avoidance in freely moving mice as means of accessing vision in those mice. We fully analyze the technique potential to damage the retina with immunofluorescence by using specific antibodies against certain proteins whose expression levels serve to report cell damage. Keywords: voltage-sensing, ion channels, electrophysiology, light sensitivity, optocapacitance, retina, vision