scholarly journals Single particle cryo-EM structure of the outer hair cell motor protein prestin

2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Carmen Butan ◽  
Qiang Song ◽  
Jun-Ping Bai ◽  
Winston J. T. Tan ◽  
Dhasakumar Navaratnam ◽  
...  
Keyword(s):  
Hair Cell ◽  
Outer Hair Cell ◽  
Sulfate Transporter ◽  
Transmembrane Segments ◽  
Cryo Electron Microscopy ◽  
Anion Transporter ◽  
Cochlear Amplification ◽  
Displacement Currents ◽  
Factor Antagonist ◽  
Putative Mechanism

AbstractThe mammalian outer hair cell (OHC) protein prestin (Slc26a5) differs from other Slc26 family members due to its unique piezoelectric-like property that drives OHC electromotility, the putative mechanism for cochlear amplification. Here, we use cryo-electron microscopy to determine prestin’s structure at 3.6 Å resolution. Prestin is structurally similar to the anion transporter Slc26a9. It is captured in an inward-open state which may reflect prestin’s contracted state. Two well-separated transmembrane (TM) domains and two cytoplasmic sulfate transporter and anti-sigma factor antagonist (STAS) domains form a swapped dimer. The transmembrane domains consist of 14 transmembrane segments organized in two 7+7 inverted repeats, an architecture first observed in the bacterial symporter UraA. Mutation of prestin’s chloride binding site removes salicylate competition with anions while retaining the prestin characteristic displacement currents (Nonlinear Capacitance), undermining the extrinsic voltage sensor hypothesis for prestin function.

scholarly journals Single particle cryo-EM structure of the outer hair cell motor protein prestin

2021 ◽  
Author(s):  
Carmen BUtan ◽  
Qiang Song ◽  
Jun-ping Bai ◽  
Winston Tan ◽  
Dhasakumar S Navaratnam ◽  
...  
Keyword(s):  
Hair Cell ◽  
Binding Site ◽  
Outer Hair Cell ◽  
Three Dimensional ◽  
Structural Features ◽  
Meriones Unguiculatus ◽  
Dimensional Structure ◽  
Transmembrane Segments ◽  
Anion Transporter ◽  
Mechanistic Basis

The mammalian outer hair cell (OHC) protein prestin (Slc26a5), a member of the solute carrier 26 (Slc26) family of membrane proteins, differs from other members of the family owing to its unique piezoelectric-like property that drives OHC electromotility. Prestin is required by OHCs for cochlear amplification, a process that enhances mammalian hearing. Despite substantial biophysical characterization, the mechanistic basis for the prestins electro-mechanical behavior is not fully understood. To gain insight into such behavior, we have used cryo-electron microscopy at subnanometer resolution (overall resolution of 4.0 Å) to investigate the three-dimensional structure of prestin from gerbil (Meriones unguiculatus). Our studies show that prestin dimerizes with a 3D architecture strikingly similar to the dimeric conformation observed in the Slc26a9 anion transporter in an inside open/intermediate state, which we infer, based on patch clamp recordings, to reflect the contracted state of prestin. The structure shows two well separated transmembrane (TM) subunits and two cytoplasmic sulfate transporter and anti-sigma factor antagonist (STAS) domains forming a swapped dimer. The dimerization interface is defined by interactions between the domain-swapped STAS dimer and the transmembrane domains of the opposing half unit, further strengthened by an antiparallel beta strand at its N terminus. The structure also shows that each one of its two transmembrane subunits consists of 14 transmembrane segments organized in two inverted 7-segment repeats with a topology that was first observed in the structure of the bacterial symporter UraA (Lu F, et al., Nature 472, 2011). Finally, the solved anion binding site structural features of prestin are quite similar to that of SLC26a9 and other family members. Despite this similarity, we find that SLC26a9 lacks the characteristic displacement currents (or NonLinear Capacitance(NLC)) found with prestin, and we show that mutation of prestins Cl- binding site removes salicylate competition with anions in the face of normal NLC, thus refuting the yet accepted extrinsic voltage sensor hypothesis and any associated transport-like requirements for voltage-driven electromotility.

scholarly journals Single-particle cryo-EM structure of the outer hair cell motor protein prestin.

2021 ◽  
Author(s):  
Dhasakumar Navaratnam ◽  
Carmen Butan ◽  
Qiang Song ◽  
Jun-Ping Bai ◽  
Winston Tan ◽  
...  
Keyword(s):  
Hair Cell ◽  
Binding Site ◽  
Outer Hair Cell ◽  
Three Dimensional ◽  
Structural Features ◽  
Meriones Unguiculatus ◽  
Dimensional Structure ◽  
Transmembrane Segments ◽  
Anion Transporter ◽  
Mechanistic Basis

Abstract The mammalian outer hair cell (OHC) protein prestin (Slc26a5), a member of the solute carrier 26 (Slc26) family of membrane proteins, differs from other members of the family owing to its unique piezoelectric-like property that drives OHC electromotility. OHCs require prestin for cochlear amplification, a process that enhances mammalian hearing. Despite substantial biophysical characterization, the mechanistic basis for the prestin’s electro-mechanical behavior is not fully understood. To gain insight into such behavior, we have used cryo-electron microscopy at subnanometer resolution (overall resolution of 3.96Å) to investigate the three-dimensional structure of prestin from gerbil (Meriones unguiculatus). Our studies show that prestin dimerizes with a 3D architecture strikingly similar to the dimeric conformation observed in the Slc26a9 anion transporter in an inside open/intermediate state, which we infer, based on patch-clamp recordings, to reflect the contracted state of prestin. The structure shows two well-separated transmembrane (TM) subunits and two cytoplasmic sulfate transporter and anti-sigma factor antagonist (STAS) domains forming a swapped dimer. The dimerization interface is defined by interactions between the domain-swapped STAS dimer and the transmembrane domains of the opposing half unit, further strengthened by an antiparallel beta-strand at its N terminus. The structure also shows that each one of its two transmembrane subunits consists of 14 transmembrane segments organized in two inverted 7-segment repeats with a topology that was first observed in the structure of bacterial symporter UraA (Lu F, et al., Nature 472, 2011). Finally, the solved anion binding site structural features of prestin are quite similar to that of SLC26a9 and other family members. Despite this similarity, we find that SLC26a9 lacks the characteristic displacement currents (or nonlinear capacitance (NLC)) found with prestin, and we show that mutation of prestin’s Cl- binding site removes salicylate competition with anions in the face of normal NLC, thus refuting the yet accepted extrinsic voltage sensor hypothesis and any associated transport-like requirements for voltage-driven electromotility.

An outer hair cell-powered global hydromechanical mechanism for cochlear amplification

2021 ◽  
pp. 108407
Author(s):  
Wenxuan He ◽  
George Burwood ◽  
Anders Fridberger ◽  
Alfred L. Nuttall ◽  
Tianying Ren
Keyword(s):  
Hair Cell ◽  
Outer Hair Cell ◽  
Cochlear Amplification

scholarly journals A gap-junction mutation in the mouse cochlea reveals cochlear amplification is driven by outer hair cell extracellular receptor potentials

2021 ◽  
Author(s):  
Snezana Levic ◽  
Victoria A Lukashkina ◽  
Patricio Simoes ◽  
Andrei N Lukashkin ◽  
Ian J Russell
Keyword(s):  
Hair Cell ◽  
Gap Junction ◽  
High Frequency ◽  
Outer Hair Cell ◽  
Stria Vascularis ◽  
Organ Of Corti ◽  
Receptor Potential ◽  
Wild Type ◽  
Hearing Sensitivity ◽  
Cochlear Amplification

Cochlear amplification, whereby cochlear responses to low-to-moderate sound levels are 31 amplified and compressed to loud sounds, is attributed to outer hair cell (OHC) electromotility 32 driven by voltage changes across the OHC basolateral membranes due to sound-induced 33 receptor-current modulation. Cochlear operation at high acoustic frequencies is enigmatic 34 because the OHC intracellular receptor potential (RP) is severely attenuated at these 35 frequencies. Clues to understanding the voltage control of OHC electromotility at different 36 frequencies was provided by measurements from CD-1 mice with an A88V mutation of the 37 gap-junction (GJ) protein connexin 30 (Cx30), which with Cx26, form heterogeneous GJs 38 between supporting cells in the organ of Corti (OoC) and stria vascularis. The A88V mutation 39 results in a smaller GJ conductance which may explain why the resistance across the OoC in 40 CD-1Cx30A88V/A88V mutants is higher compared with wild-type mice. The endocochlear 41 potential, which drives the OHC receptor current and, consequently, the OHC RPs, is smaller 42 in CD-1Cx30A88V/A88V mutants. Even so, their high-frequency hearing sensitivity equals that of 43 wild-type mice. Preservation of high-frequency hearing correlates with similar amplitude of 44 extracellular receptor potentials (ERPs), measured immediately adjacent to the OHCs. ERPs 45 are generated through OHC receptor current flow across the OoC electrical resistance, which 46 is larger in CD-1Cx30A88V/A88V than in wild-type mice. Thus, smaller OHC receptor currents 47 flowing across a larger OoC resistance in CD-1Cx30A88V/A88V mice may explain why their ERP 48 magnitudes are similar to wild-type mice. It is proposed that the ERPs, which are not subject 49 to low-pass electrical filtering, drive high-frequency cochlear amplification.

scholarly journals Prestin-Driven Cochlear Amplification Is Not Limited by the Outer Hair Cell Membrane Time Constant

Neuron ◽  
2011 ◽  
Vol 70 (6) ◽  
pp. 1143-1154 ◽  
Author(s):  
Stuart L. Johnson ◽  
Maryline Beurg ◽  
Walter Marcotti ◽  
Robert Fettiplace
Keyword(s):  
Cell Membrane ◽  
Hair Cell ◽  
Time Constant ◽  
Outer Hair Cell ◽  
Membrane Time Constant ◽  
Cochlear Amplification
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