The chloride intracellular channel protein CLIC5 is expressed at high levels in hair cell stereocilia and is essential for normal inner ear function.
Although CLIC5 is a member of the chloride intracellular channel protein family, its association with actin-based cytoskeletal structures suggests that it may play an important role in their assembly or maintenance. Mice homozygous for a new spontaneous recessive mutation of the Clic5 gene, named jitterbug (jbg), exhibit impaired hearing and vestibular dysfunction. The jbg mutation is a 97 bp intragenic deletion that causes skipping of exon 5, which creates a translational frame shift and premature stop codon. Western blot and immunohistochemistry results confirmed the predicted absence of CLIC5 protein in tissues of jbg/jbg mutant mice. Histological analysis of mutant inner ears revealed dysmorphic stereocilia and progressive hair cell degeneration. In wild-type mice, CLIC5-specific immunofluorescence was detected in stereocilia of both cochlear and vestibular hair cells and also along the apical surface of Kolliker's organ during cochlear development. Refined immunolocalization in rat and chicken vestibular hair cells showed that CLIC5 is limited to the basal region of the hair bundle, similar to the known location of radixin. Radixin immunostaining appeared reduced in hair bundles of jbg mutant mice. By mass spectrometry and immunoblotting, CLIC5 was shown to be expressed at high levels in stereocilia of the chicken utricle, in an approximate 1:1 molar ratio with radixin. These results suggest that CLIC5 associates with radixin in hair cell stereocilia and may help form or stabilize connections between the plasma membrane and the filamentous actin core.
Gagnon
Leona H
LH
The Jackson Laboratory, Bar Harbor, Maine 04609, USA.
Longo-Guess
Chantal M
CM
Berryman
Mark
M
Shin
Jung-Bum
JB
Saylor
Katherine W
KW
Yu
Heping
H
Gillespie
Peter G
PG
Johnson
Kenneth R
KR
D000161:Acoustic Stimulation / Q000379:methods; D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002462:Cell Membrane / Q000378:metabolism; D018118:Chloride Channels / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D002923:Cilia / Q000235:genetics / Q000378:metabolism*; D007758:Ear, Inner / Q000502:physiology*; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology; D005786:Gene Expression Regulation / Q000502:physiology*; D006198:Hair Cells, Auditory / Q000378:metabolism; D051379:Mice; D008809:Mice, Inbred C3H; D008817:Mice, Mutant Strains; D008840:Microfilament Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data
D000199:Actins; C411466:CLIC5 protein, human; C514190:CLIC5 protein, mouse; D018118:Chloride Channels; D008840:Microfilament Proteins