Problems in Cochlear Micromechanics

National Institute Of Biomedical Imaging And Bioengineering, Bethesda

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Abstract

The motor protein prestin is presumed to densely populate the plasma membrane of the outer hair cells in the mammalian cochlea. Older electron microscopy (EM) studies indicated the presence of a dense array of particles with uniform size of about 10nm in diameter. It was presumed that these must be the motor proteins, but no identification was ever performed. Here, a novel cell-free protocol for imaging outer hair cell native plasma membranes was developed. We used an atomic force microscope (AFM) to image the intracellular domain of a plasma membrane that was attached to a mica substrate under physiological conditions. Imaging revealed the presence of a dense array of particles whose size was consistent with those observed by EM. In addition, the particles were organized in a specific pattern, rather than a random distribution. The pattern allowed speculation as to the oligomeric state of the protein in-situ. The particles were unambiguously identified by the introduction of anti-prestin antibodies that bound to the protein particles while maintaining their organizational patterns.