The conformational cycle of prestin underlies outer-hair cell electromotility

Abstract

The voltage-dependent motor protein Prestin (SLC26A5) is responsible for the electromotive behavior of outer hair cells (OHCs) and underlies the cochlear amplifier 1 . Knock out or impairment of Prestin causes severe hearing loss [2][3][4][5] . Despite Prestin's key physiological role in hearing, the mechanism by which mammalian Prestin senses voltage and transduces it into cellular-scale movements (electromotility) is poorly understood. Here, we determined the structure of dolphin Prestin in six distinct states using single particle cryo-electron microscopy. Our structural and functional data suggest that Prestin adopts a unique and complex set of states, tunable by the identity of bound anions (Clor SO4 = ). Salicylate, a drug that can cause reversible hearing loss, competes for the anion-binding site of Prestin, inhibits its function by immobilizing locking in a novel conformation. This suggests that the anion together with its coordinating fixed charges act as a dynamic voltage sensor. Analysis of all aniondependent conformations reveals how structural rearrangements in the voltage sensor are coupled to conformational transitions at the protein-membrane interface, suggesting a novel mechanism of area expansion. Visualization of Prestin's electromotility cycle distinguishes Prestin from closely related SLC26 anion transporters, highlighting the basis for evolutionary specialization of the mammalian cochlear amplifier at high resolution. Perozo lab for a healthy exchange of ideas and comments on the manuscript. We thank Dr. Peng Shi for sharing Tursiops Prestin plasmid. James Fuller, Joe Austin II, and Tera Lavoie at the University of Chicago Advanced Electron Microscopy Facility for microscope maintenance and training. N.B. would like to acknowledge the Biology of Inner ear course (BIE2019) and Gordon Conference (Auditory System Gordon Research Conference) for inspiring him to study hearing and Prestin.

Cryo-EM structures of thermostabilized prestin provide mechanistic insights underlying outer hair cell electromotility

“…Salicylate inhibits the motor activity of prestin 9 , which accounts for the reversible hearing loss caused by aspirin overdosage 12 . Previous structures of bacterial SLC26 13 , mouse SLC26A9 14 , and human SLC26A9 15 have allowed homology modeling of prestin with high confidence, and in addition, very recent structures of prestin from human 16 and dolphin 17 have revealed its molecular structure and Clinduced conformational change, which advanced our understanding of the voltage-driven motor mechanism of prestin. However, many questions still remain regarding the anion-induced conformational changes.…”

Analysis of outer hair cell electromechanics reveals power delivery at the upper-frequency limits of hearing

“…Over the frequency range of human hearing, voltage-driven electro-motility is imparted by expression of the transmembrane protein prestin [2,3] through a mechanism that couples electrical charge displacement in the prestin-membrane motor complex to changes in cell length. The structure of prestin [4][5][6] suggests OHC piezoelectricity arises on the whole-cell level from a large number of prestin molecules undergoing conformational changes on the nanoscale, with each conformational change involving an electrical charge displacement and a change in membrane area. But this mechanism might not extend beyond the range of human hearing to species with ultrasonic hearing.…”

Ion Channel Thermodynamics Studied With Temperature Jumps Measured at the Cell Membrane

“…The Hilbert transform provides a key advantage: time resolution is higher than the carrier wave frequency. We believe this approach can be employed in other settings where capacitance measurements are routinely used, such as the study of vesicular fusion (29), and the movement of gating charges (30)(31)(32). The CTM method provides a compelling advantage: an accurate readout of the temperature at the membrane level without needing of external probes.…”