MyosinVIIa interacts with Twinfilin-2 at the tips of mechanosensory stereocilia in the inner ear.
In vertebrates hearing is dependent upon the microvilli-like mechanosensory stereocilia and their length gradation. The staircase-like organization of the stereocilia bundle is dynamically maintained by variable actin turnover rates. Two unconventional myosins were previously implicated in stereocilia length regulation but the mechanisms of their action remain unknown. MyosinXVa is expressed in stereocilia tips at levels proportional to stereocilia length and its absence produces staircase-like bundles of very short stereocilia. MyosinVIIa localizes to the tips of the shorter stereocilia within bundles, and when absent, the stereocilia are abnormally long. We show here that myosinVIIa interacts with twinfilin-2, an actin binding protein, which inhibits actin polymerization at the barbed end of the filament, and that twinfilin localization in stereocilia overlaps with myosinVIIa. Exogenous expression of myosinVIIa in fibroblasts results in a reduced number of filopodia and promotes accumulation of twinfilin-2 at the filopodia tips. We hypothesize that the newly described interaction between myosinVIIa and twinfilin-2 is responsible for the establishment and maintenance of slower rates of actin turnover in shorter stereocilia, and that interplay between complexes of myosinVIIa/twinfilin-2 and myosinXVa/whirlin is responsible for stereocilia length gradation within the bundle staircase.
Rzadzinska
Agnieszka K
AK
The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom. akr@sanger.ac.uk
Nevalainen
Elisa M
EM
Prosser
Haydn M
HM
Lappalainen
Pekka
P
Steel
Karen P
KP
D000818:Animals; D002460:Cell Line; D002923:Cilia / Q000378:metabolism*; D006224:Cricetinae; D007758:Ear, Inner / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism*; D005786:Gene Expression Regulation; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008647:Mesocricetus; D051379:Mice; D008809:Mice, Inbred C3H; D008840:Microfilament Proteins / Q000378:metabolism*; D008856:Microscopy, Fluorescence / Q000379:methods; D008954:Models, Biological; D000081412:Myosin VIIa; D009218:Myosins / Q000378:metabolism*
D008840:Microfilament Proteins; C000631456:Myo7a protein, mouse; D000081412:Myosin VIIa; C485645:TWF2 protein, mouse; D049452:Green Fluorescent Proteins; D009218:Myosins