Distribution of protein motors along the lateral wall of the outer hair cell

The outer hair cell (OHC) plays an important role in the normal functioning of the cochlea, and cochlear amplification is believed to be based on OHC electromotility. This electromotility putatively arises from a conformation al change of molecules, i.e., 'protein motors', which would be distributed along the plasma membrane. Although it has been assumed that protein motors are distributed in a restricted area of the plasma membrane, details of su ch distribution remain unclarified. In this study, first, in order to under stand the difference in the stiffness along the cell axis, the local deform ation of the OHC in response to hypotonic stimulation is analyzed by measur ing the displacement of microspheres attached randomly to the lateral wall of the cell. As a result, the stiffness is expected to be constant througho ut the region except in the apical part of the cell, and the stiffness of t he apical part is expected to be higher than that of the other regions. The n, the local elongation and contraction of the OHC in response to sinusoida l voltage stimulation are analyzed by measuring the displacement of the mic rospheres in the same way as in the case of the hypotonic stimulation. From the two measurements mentioned above, it is concluded that there are no mo tors in the apical and basal parts of the cell, and that the motors are equ ally distributed along the cell lateral wall in the middle part of the cell . (C) 2001 Published by Elsevier Science B.V.