Usher type 1G protein sans is a critical component of the tip-link complex, a structure controlling actin polymerization in stereocilia. Article - Avril 2011

Elisa Caberlotto, Michel Vittot, Isabelle Foucher, Amel Bahloul, Richard J Goodyear, Elise Pepermans, Nicolas Michalski, Isabelle Perfettini, O. Alegria-Prevot, Sébastien Chardenoux, Marcio Do Cruzeiro, P. Hardelin, P. Richardson, Paul Avan, Dominique Weil, Christine Petit

Elisa Caberlotto, Michel Vittot, Isabelle Foucher, Amel Bahloul, Richard J Goodyear, Elise Pepermans, Nicolas Michalski, Isabelle Perfettini, O. Alegria-Prevot, Sébastien Chardenoux, Marcio Do Cruzeiro, P. Hardelin, P. Richardson, Paul Avan, Dominique Weil, Christine Petit, « Usher type 1G protein sans is a critical component of the tip-link complex, a structure controlling actin polymerization in stereocilia.  », Proceedings of the National Academy of Sciences of the United States of America, avril 2011, pp. 5825-30. ISSN 0027-8424

Abstract

The mechanotransducer channels of auditory hair cells are gated by tip-links, oblique filaments that interconnect the stereocilia of the hair bundle. Tip-links stretch from the tips of stereocilia in the short and middle rows to the sides of neighboring, taller stereocilia. They are made of cadherin-23 and protocadherin-15, products of the Usher syndrome type 1 genes USH1D and USH1F, respectively. In this study we address the role of sans, a putative scaffold protein and product of the USH1G gene. In Ush1g(-/-) mice, the cohesion of stereocilia is disrupted, and both the amplitude and the sensitivity of the transduction currents are reduced. In Ush1g(fl/fl)Myo15-cre(+/-) mice, the loss of sans occurs postnatally and the stereocilia remain cohesive. In these mice, there is a decrease in the amplitude of the total transducer current with no loss in sensitivity, and the tips of the stereocilia in the short and middle rows lose their prolate shape, features that can be attributed to the loss of tip-links. Furthermore, stereocilia from these rows undergo a dramatic reduction in length, suggesting that the mechanotransduction machinery has a positive effect on F-actin polymerization. Sans interacts with the cytoplasmic domains of cadherin-23 and protocadherin-15 in vitro and is absent from the hair bundle in mice defective for either of the two cadherins. Because sans localizes mainly to the tips of short- and middle-row stereocilia in vivo, we conclude that it belongs to a molecular complex at the lower end of the tip-link and plays a critical role in the maintenance of this link.

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