Publication Date:
2012-01-17
Description:
Hair cells of the inner ear are not normally replaced during an animal's life, and must continually renew components of their various organelles. Among these are the stereocilia, each with a core of several hundred actin filaments that arise from their apical surfaces and that bear the mechanotransduction apparatus at their tips. Actin turnover in stereocilia has previously been studied by transfecting neonatal rat hair cells in culture with a beta-actin-GFP fusion, and evidence was found that actin is replaced, from the top down, in 2-3 days. Overexpression of the actin-binding protein espin causes elongation of stereocilia within 12-24 hours, also suggesting rapid regulation of stereocilia lengths. Similarly, the mechanosensory 'tip links' are replaced in 5-10 hours after cleavage in chicken and mammalian hair cells. In contrast, turnover in chick stereocilia in vivo is much slower. It might be that only certain components of stereocilia turn over quickly, that rapid turnover occurs only in neonatal animals, only in culture, or only in response to a challenge like breakage or actin overexpression. Here we quantify protein turnover by feeding animals with a (15)N-labelled precursor amino acid and using multi-isotope imaging mass spectrometry to measure appearance of new protein. Surprisingly, in adult frogs and mice and in neonatal mice, in vivo and in vitro, the stereocilia were remarkably stable, incorporating newly synthesized protein at 〈10% per day. Only stereocilia tips had rapid turnover and no treadmilling was observed. Other methods confirmed this: in hair cells expressing beta-actin-GFP we bleached fiducial lines across hair bundles, but they did not move in 6 days. When we stopped expression of beta- or gamma-actin with tamoxifen-inducible recombination, neither actin isoform left the stereocilia, except at the tips. Thus, rapid turnover in stereocilia occurs only at the tips and not by a treadmilling process.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3267870/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉 〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3267870/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zhang, Duan-Sun -- Piazza, Valeria -- Perrin, Benjamin J -- Rzadzinska, Agnieszka K -- Poczatek, J Collin -- Wang, Mei -- Prosser, Haydn M -- Ervasti, James M -- Corey, David P -- Lechene, Claude P -- 2P41RR0112553-12/RR/NCRR NIH HHS/ -- F32DC009539/DC/NIDCD NIH HHS/ -- P41EB001974/EB/NIBIB NIH HHS/ -- P41RR14579/RR/NCRR NIH HHS/ -- R01 AR042423/AR/NIAMS NIH HHS/ -- R01 AR042423-08/AR/NIAMS NIH HHS/ -- R01 AR049899/AR/NIAMS NIH HHS/ -- R01 DC000033/DC/NIDCD NIH HHS/ -- R01 DC002281/DC/NIDCD NIH HHS/ -- R01AR049899/AR/NIAMS NIH HHS/ -- R01D K58762/PHS HHS/ -- R01DC00033/DC/NIDCD NIH HHS/ -- R01DC02281/DC/NIDCD NIH HHS/ -- R01DC03463/DC/NIDCD NIH HHS/ -- R01DC04179/DC/NIDCD NIH HHS/ -- R01EY12963/EY/NEI NIH HHS/ -- R01GM47214/GM/NIGMS NIH HHS/ -- R37DK39773/DK/NIDDK NIH HHS/ -- WT079643/Wellcome Trust/United Kingdom -- Howard Hughes Medical Institute/ -- England -- Nature. 2012 Jan 15;481(7382):520-4. doi: 10.1038/nature10745.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Neurobiology, Harvard Medical School and Howard Hughes Medical Institute, Boston, Massachusetts 02115, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22246323" target="_blank"〉PubMed〈/a〉
Keywords:
Actins/metabolism
;
Animals
;
Animals, Newborn
;
Bleaching Agents
;
Chickens
;
Epithelium/drug effects/metabolism
;
Fiducial Markers
;
Hair Cells, Auditory, Inner/*cytology
;
Homologous Recombination/drug effects
;
Mass Spectrometry/*methods
;
Mice
;
Mice, Inbred C57BL
;
Proteins/*metabolism
;
Rana catesbeiana
;
Stereocilia/*metabolism
;
Tamoxifen/pharmacology
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
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