title: Myosin IIIa boosts elongation of stereocilia by transporting espin 1 to the plus ends of actin filaments.
abstract: Two proteins implicated in inherited deafness, myosin IIIa, a plus-end-directed motor, and espin, an actin-bundling protein containing the actin-monomer-binding motif WH2, have been shown to influence the length of mechanosensory stereocilia. Here we report that espin 1, an ankyrin repeat-containing isoform of espin, colocalizes with myosin IIIa at stereocilia tips and interacts with a unique conserved domain of myosin IIIa. We show that combined overexpression of these proteins causes greater elongation of stereocilia, compared with overexpression of either myosin IIIa alone or espin 1 alone. When these two proteins were co-expressed in the fibroblast-like COS-7 cell line they induced a tenfold elongation of filopodia. This extraordinary filopodia elongation results from the transport of espin 1 to the plus ends of F-actin by myosin IIIa and depends on espin 1 WH2 activity. This study provides the basis for understanding the role of myosin IIIa and espin 1 in regulating stereocilia length, and presents a physiological example where myosins can boost elongation of actin protrusions by transporting actin regulatory factors to the plus ends of actin filaments.
authors.forename: Felipe T
authors.initials: FT
authors.lastname: Salles
authors.forename: Raymond C
authors.initials: RC
authors.lastname: Merritt
authors.forename: Uri
authors.initials: U
authors.lastname: Manor
authors.forename: Gerard W
authors.initials: GW
authors.lastname: Dougherty
authors.forename: Aurea D
authors.initials: AD
authors.lastname: Sousa
authors.forename: Judy E
authors.initials: JE
authors.lastname: Moore
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Yengo
authors.forename: Andréa C
authors.initials: AC
authors.lastname: Dosé
authors.forename: Bechara
authors.initials: B
authors.lastname: Kachar
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D017089:Ankyrin Repeat; D019556:COS Cells; D002522:Chlorocebus aethiops; D002923:Cilia / Q000378:metabolism* / Q000648:ultrastructure; D051379:Mice; D008840:Microfilament Proteins / Q000737:chemistry / Q000378:metabolism*; D025102:Myosin Type III / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D011554:Pseudopodia / Q000378:metabolism / Q000648:ultrastructure; D051381:Rats; D014162:Transfection
chemical_list: C472022:Espn protein, rat; D008840:Microfilament Proteins; D025102:Myosin Type III