Biomechanics in the Inner Ear

The elongation and contraction of outer hair cells (OHCs) greatly contribute to the high sensitivity and frequency selectivity of the mammalian inner ear. The motility of OHCs is believed to be based on the conformational changes of the motor protein prestin in the plasma membrane of OHCs. In the present study, four lines of research on the inner ear were conducted. First, the mechanism by which the inner ear is protected from acoustic trauma by heat stress was investigated, results showing that such conditioning makes OHCs stiffer, thus enabling them to withstand traumatic noise exposure. Second, imaging of prestin in the plasma membrane of Chinese hamster ovary (CHO) cells was performed by atomic force microscopy (AFM). Results showed that particle-like structures with a diameter of 8–12 nm observed in the CHO plasma membranes were possibly prestin. Third, mutational analysis of prestin was conducted. Consequently, the GTSRH sequence at position 127131 of the amino acid sequence of prestin was shown to be important for glycosylation and the anion transport function of prestin. Fourth, purification of prestin from prestin-expressing CHO cells was attempted. Results indicate that 120 μg of purified prestin can be obtained from 2 10 CHO cells.