title: The Stereociliary Paracrystal Is a Dynamic Cytoskeletal Scaffold In Vivo.
abstract: Permanency of mechanosensory stereocilia may be the consequence of low protein turnover or rapid protein renewal. Here, we devise a system, using optical techniques in live zebrafish, to distinguish between these mechanisms. We demonstrate that the stereocilium's abundant actin cross-linker fascin 2b exchanges, without bias or a phosphointermediate, orders of magnitude faster (t1/2 of 76.3 s) than any other known hair bundle protein. To establish the logic of fascin 2b's exchange, we examine whether filamentous actin is dynamic and detect substantial β-actin exchange within the stereocilium's paracrystal (t1/2 of 4.08 hr). We propose that fascin 2b's behavior may enable cross-linking at fast timescales of stereocilia vibration while noninstructively facilitating the slower process of actin exchange. Furthermore, tip protein myosin XVa fully exchanges in hours (t1/2 of 11.6 hr), indicating that delivery of myosin-associated cargo occurs in mature stereocilia. These findings suggest that stereocilia permanency is underpinned by vibrant protein exchange.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA; Department of Biology, Case Western Reserve University, Cleveland, OH 44106, USA.
authors.forename: Philsang
authors.initials: P
authors.lastname: Hwang
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA; Department of Biology, Case Western Reserve University, Cleveland, OH 44106, USA.
authors.forename: Shih-Wei
authors.initials: SW
authors.lastname: Chou
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA; Department of Biology, Case Western Reserve University, Cleveland, OH 44106, USA.
authors.forename: Zongwei
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA; Department of Biology, Case Western Reserve University, Cleveland, OH 44106, USA; Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA; Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA. Electronic address: bmm30@case.edu.
authors.forename: Brian M
authors.initials: BM
authors.lastname: McDermott
mesh_terms: D000818:Animals; D003599:Cytoskeleton / Q000378:metabolism* / Q000648:ultrastructure; D005136:Eye Proteins / Q000378:metabolism; D006198:Hair Cells, Auditory / Q000378:metabolism / Q000648:ultrastructure; D008840:Microfilament Proteins / Q000378:metabolism; D009218:Myosins / Q000378:metabolism; D021381:Protein Transport; D059547:Stereocilia / Q000378:metabolism* / Q000648:ultrastructure; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000378:metabolism
chemical_list: D005136:Eye Proteins; D008840:Microfilament Proteins; D029961:Zebrafish Proteins; C518611:fscn2b protein, zebrafish; D009218:Myosins