Helical Structure of Hair Cell Stereocilia Tip Links In the Chinchilla Cochlea

Abstract

Outer-hair-cell stereocilia tip-link structure in the chinchilla cochlea was studied by transmission electron microscopy using tannic acid and Ruthenium red/ Alcian blue histochemical procedures. Tannic acid and Ruthenium red/Alcian blue treatments showed the tip link as a compact strand of filaments 9-12 nm thick. Fourier analysis of tip-link images showed that the strand is a three-start helical bundle of fine, coiled filaments which had an axial period of 22.5+/-1.5 nm. Each of three coiled filaments in the strand showed globular structures, 4.3+/-0.3 nm in diameter. The globular structures may correspond to individual protein subunits or they may be repeating identical domains of one polypeptide. The three filaments of the helical array may provide a rigidity to the tip link during stereocilia deflections. Alternatively, changes in the subunit or domain structure of each filament may result in a lengthening or shortening of the tip-link strand.

Three-dimensional Architecture of Hair-bundle Linkages Revealed by Electron-microscopic Tomography

“…This behavior suggests a well-defined, rather stiff conformation of the basal-link protein. twisted around each other (Tsuprun et al 2004), threedimensional analysis showed that the filaments are separated. Filaments appear to be grouped and insert into only the thicker membrane portions of the kinociliary bulb (Fig.…”

“…Connections of the second type, kinociliary links, then transmit these stimuli to the five longest stereocilia (Hillman and Lewis 1971). Fourier analysis of electron-microscopic images suggests that kinociliary links constitute an array of several dozen fine strands that are arranged in a coiled-coil conformation (Csukas et al 1987;Tsuprun et al 2004).…”

“…When analyzed by high-resolution scanning electron microscopy, each tip link appears to comprise two filaments arranged in a right-handed, coiled-coil configuration (Kachar et al 2000). Fourier analysis of projection images suggests instead a double-or triple-helical structure (Tsuprun and Santi 2000;Tsuprun et al 2004). A tip link may branch 10-50 nm below its upper insertion and may contact the membrane at two or three sites at its lower end (Furness and Hackney 1985;Kachar et al 2000).…”

“…A tip link may branch 10-50 nm below its upper insertion and may contact the membrane at two or three sites at its lower end (Furness and Hackney 1985;Kachar et al 2000). The tip link may consist of glycosylated protein, for polycationic compounds label it (Neugebauer and Thurm 1987;Tsuprun and Santi 2000), and in avian preparations, it is severed by proteases only after deglycosylation (Kachar et al 2000). Genetic and immunological evidence localizes cadherin 23 to the tip link Sollner et al 2004), where it evidently constitutes the structure's upper two thirds (Kazmierczak et al 2007).…”

Structure of Outer Hair Cell Stereocilia Side and Attachment Links in the Chinchilla Cochlea

“…In the tip-link model for transduction, the tip links act as gating springs for mechanically sensitive ion channels (Hudspeth 1989;Pickles and Corey 1992). Results from electron microscopy recently showed that the tip link consists of many globular protein structures periodically arranged into two or three filaments with a helical symmetry (Kachar et al 2000;Tsuprun and Santi 2000). These globular structures may correspond to individual protein subunits or may represent repeating identical domains of one polypeptide (Tsuprun and Santi 2000).…”