Myosin IIIa boosts elongation of stereocilia by transporting espin 1 to the plus ends of actin filaments.
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.
Salles
Felipe T
FT
Merritt
Raymond C
RC
Manor
Uri
U
Dougherty
Gerard W
GW
Sousa
Aurea D
AD
Moore
Judy E
JE
Yengo
Christopher M
CM
Dosé
Andréa C
AC
Kachar
Bechara
B
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
C472022:Espn protein, rat; D008840:Microfilament Proteins; D025102:Myosin Type III