title: The tip-link antigen, a protein associated with the transduction complex of sensory hair cells, is protocadherin-15.
abstract: Sound and acceleration are detected by hair bundles, mechanosensory structures located at the apical pole of hair cells in the inner ear. The different elements of the hair bundle, the stereocilia and a kinocilium, are interconnected by a variety of link types. One of these links, the tip link, connects the top of a shorter stereocilium with the lateral membrane of an adjacent taller stereocilium and may gate the mechanotransducer channel of the hair cell. Mass spectrometric and Western blot analyses identify the tip-link antigen, a hitherto unidentified antigen specifically associated with the tip and kinocilial links of sensory hair bundles in the inner ear and the ciliary calyx of photoreceptors in the eye, as an avian ortholog of human protocadherin-15, a product of the gene for the deaf/blindness Usher syndrome type 1F/DFNB23 locus. Multiple protocadherin-15 transcripts are shown to be expressed in the mouse inner ear, and these define four major isoform classes, two with entirely novel, previously unidentified cytoplasmic domains. Antibodies to the three cytoplasmic domain-containing isoform classes reveal that each has a different spatiotemporal expression pattern in the developing and mature inner ear. Two isoforms are distributed in a manner compatible for association with the tip-link complex. An isoform located at the tips of stereocilia is sensitive to calcium chelation and proteolysis with subtilisin and reappears at the tips of stereocilia as transduction recovers after the removal of calcium chelators. Protocadherin-15 is therefore associated with the tip-link complex and may be an integral component of this structure and/or required for its formation.
authors.affiliation: Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, Maryland 20850, USA.
authors.forename: Zubair M
authors.initials: ZM
authors.lastname: Ahmed
authors.forename: Richard
authors.initials: R
authors.lastname: Goodyear
authors.forename: Saima
authors.initials: S
authors.lastname: Riazuddin
authors.forename: Ayala
authors.initials: A
authors.lastname: Lagziel
authors.forename: P Kevin
authors.initials: PK
authors.lastname: Legan
authors.forename: Martine
authors.initials: M
authors.lastname: Behra
authors.forename: Shawn M
authors.initials: SM
authors.lastname: Burgess
authors.forename: Kathryn S
authors.initials: KS
authors.lastname: Lilley
authors.forename: Edward R
authors.initials: ER
authors.lastname: Wilcox
authors.forename: Sheikh
authors.initials: S
authors.lastname: Riazuddin
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Griffith
authors.forename: Gregory I
authors.initials: GI
authors.lastname: Frolenkov
authors.forename: Inna A
authors.initials: IA
authors.lastname: Belyantseva
authors.forename: Guy P
authors.initials: GP
authors.lastname: Richardson
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Friedman
mesh_terms: D000818:Animals; D000070585:Cadherin Related Proteins; D015820:Cadherins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002614:Chelating Agents / Q000494:pharmacology; D002645:Chickens; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D006199:Hair Cells, Auditory, Inner / Q000378:metabolism / Q000502:physiology*; D013058:Mass Spectrometry; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D051379:Mice; D020033:Protein Isoforms / Q000378:metabolism; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017434:Protein Structure, Tertiary; D020539:Sequence Analysis, Protein; D013997:Time Factors; D046509:Tissue Culture Techniques; D014018:Tissue Distribution
chemical_list: C418976:CDHR15 protein, mouse; D000070585:Cadherin Related Proteins; D015820:Cadherins; D002614:Chelating Agents; D020033:Protein Isoforms; D011498:Protein Precursors; D004533:Egtazic Acid; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid