Date of Award

January 2014

Document Type

Open Access Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

Joseph Santos-Sacchi

Subject Area(s)

Acoustics, Physiology

Abstract

IR LASER-INDUCED PERTURBATIONS OF THE VOLTAGE-DEPENDENT SOLUTE CARRIER PROTEIN, SLC26A5. Oluwarotimi S. Nettey and Joseph Santos-Sacchi. Sections of Otolaryngology and Neurobiology, Department of Surgery, Yale University, School of Medicine, New Haven, CT.

Alterations in membrane capacitance can arise from linear and nonlinear sources. For example, changes in membrane surface area or dielectric properties can modify capacitance linearly, whereas sensor residues of voltage-dependent proteins can modify capacitance nonlinearly. Here, we examined the effects of fast temperature jumps induced by an IR laser in control and prestin (SLC26a5)-transfected HEK cells under whole cell voltage clamp. Prestin's voltage sensor imparts a characteristic bell- shaped, voltage-dependent nonlinear capacitance (NLC). Temperature jumps in control HEK cells cause a monophasic increase in membrane capacitance (Cm) regardless of holding voltage due to double layer effects. Prestin-transfected HEK cells, however, additionally show a biphasic increase/decrease in Cm with a reversal potential corresponding to the voltage at peak NLC of prestin (Vh), attributable to a rapid temperature-following shift in Vh, with shift rates up to 14 V/s over the course of a 5 ms IR pulse. Treatment with salicylate, a known inhibitor of NLC, re-establishes control cell behavior. A simple kinetic model recapitulates our biophysical observations. These results verify a voltage-dependent protein's ability to respond to fast temperature perturbations on par with double layer susceptibility, likely arising from prestin's unique ability to move sensor charge at kilohertz rates, a requirement for the OHC's role as cochlear amplifier.

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