What do tip link proteins do?

Tip links are extracellular filaments that connect stereocilia to each other or to the kinocilium in the hair cells of the inner ear. These channels are cation-selective transduction channels that allow potassium and calcium ions to enter the hair cell from the endolymph that bathes its apical end.

How do tip links function?

Tip links are tiny thread-like strands that link the tip of a shorter stereocilium to the side of the taller one behind it. When sound vibrations enter the inner ear, the stereocilia, connected by the tip links, all lean to the same side and open special channels, called mechanotransduction channels.

What happens if tip links are damaged?

Broken tip links are repaired in both regenerating and non-regenerating hair cells. Intense noise exposure damages the stereocilia F-actin core, which may be repaired by localized F-actin remodeling.

Do outer hair cells have tip links?

Hair bundles possess tip links that interconnect the mechanosensitive stereocilia and convey force to the transduction channels. A dimer of dimers, each of these links comprises two molecules of protocadherin 15 (PCDH15) joined to two of cadherin 23 (CDH23).

What is a kinocilium?

The kinocilium is an immotile primary cilium that is found at the apical surface of auditory receptor cells. Hair bundles, the mechanosensory device of the sensory hair cells, are composed of height-ranked rows of stereocilia and a single kinocilium that are interconnected by extracellular proteinaceous links.

Are hair cells Polarised?

Individual hair cells are therefore intrinsically polarized. Subsequently, this primary cilium, known as the kinocilium on hair cells, begins to migrate towards the lateral side of the apical surface, and thus becomes asymmetrically positioned. This movement is concomitant with a graded enlargement of microvilli.

What do inner and outer hair cells do?

The outer hair cells mechanically amplify low-level sound that enters the cochlea. The inner hair cells transform the sound vibrations in the fluids of the cochlea into electrical signals that are then relayed via the auditory nerve to the auditory brainstem and to the auditory cortex.

What is the difference between stereocilia and kinocilium?

Stretching of the tip link due to movement toward the tallest stereocilia causes the channels to open. There is a structural difference between a kinocilium (which is a true cilium, having a 9+2 microtubule arrangement), and stereocilia (which don’t have microtubules, instead they have actin cores).