Prestin forms oligomer with four mechanically independent subunits

Area of Science:

• Molecular and Cellular Biology
• Bioacoustics
• Biophysics

Background:

• Prestin is the key motor protein responsible for the electromechanical properties of cochlear outer hair cells (OHCs).
• The precise oligomeric structure of prestin within OHC membranes and its functional implications remain incompletely understood.
• Previous studies suggest prestin forms homo-oligomers, likely tetramers, but direct evidence in OHCs is lacking.

Purpose of the Study:

• To elucidate the oligomeric structure of prestin in gerbil OHCs.
• To investigate the functional coupling between prestin's charge movement and OHC somatic motility.
• To determine how individual prestin subunits contribute to the overall electromechanical response.

Main Methods:

• Nonlinear capacitance (NLC) measurements were used to determine prestin charge density in OHCs.
• Simultaneous measurements of NLC and OHC somatic motility were performed on the same cells.
• Analysis focused on comparing the voltage dependency and slope factors of NLC and motility.

Main Results:

• The measured charge density of prestin was significantly higher than intramembrane particle (IMP) density, suggesting each IMP contains multiple prestin molecules (estimated four).
• Voltage dependency and slope factors of NLC and somatic motility were statistically indistinguishable.
• This indicates full functional coupling between prestin's charge movement and OHC mechanical activity.

Conclusions:

• The findings support a model where prestin forms functional tetramers in OHCs, with each monomer operating in parallel.
• Each prestin monomer within the tetramer interacts independently to facilitate the electromechanical response.
• This independent subunit function is crucial for the rapid and precise mechanical tuning of the cochlea.