Actin-bundling protein TRIOBP forms resilient rootlets of hair cell stereocilia essential for hearing
- PMID: 20510926
- PMCID: PMC2879707
- DOI: 10.1016/j.cell.2010.03.049
Actin-bundling protein TRIOBP forms resilient rootlets of hair cell stereocilia essential for hearing
Abstract
Inner ear hair cells detect sound through deflection of mechanosensory stereocilia. Each stereocilium is supported by a paracrystalline array of parallel actin filaments that are packed more densely at the base, forming a rootlet extending into the cell body. The function of rootlets and the molecules responsible for their formation are unknown. We found that TRIOBP, a cytoskeleton-associated protein mutated in human hereditary deafness DFNB28, is localized to rootlets. In vitro, purified TRIOBP isoform 4 protein organizes actin filaments into uniquely dense bundles reminiscent of rootlets but distinct from bundles formed by espin, an actin crosslinker in stereocilia. We generated mutant Triobp mice (Triobp(Deltaex8/Deltaex8)) that are profoundly deaf. Stereocilia of Triobp(Deltaex8/Deltaex8) mice develop normally but fail to form rootlets and are easier to deflect and damage. Thus, F-actin bundling by TRIOBP provides durability and rigidity for normal mechanosensitivity of stereocilia and may contribute to resilient cytoskeletal structures elsewhere.
Copyright 2010 Elsevier Inc. All rights reserved.
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Comment in
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Wrapping up stereocilia rootlets.Cell. 2010 May 28;141(5):748-50. doi: 10.1016/j.cell.2010.05.022. Cell. 2010. PMID: 20510920
References
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- Belyantseva IA, Boger ET, Naz S, Frolenkov GI, Sellers JR, Ahmed ZM, Griffith AJ, Friedman TB. Myosin-XVa is required for tip localization of whirlin and differential elongation of hair-cell stereocilia. Nat Cell Biol. 2005;7:148–156. - PubMed
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