Prestin is expressed on the whole outer hair cell basolateral surface

Prestin has been identified as a motor protein responsible for outer hair cell (OHC) electromotility. Previous experiments revealed that OHC electromotility and its associated nonlinear capacitance resided in the OHC lateral wall and was not detected at the apical cuticular plate and basal region. In this experiment, the distribution of prestin in adult mouse, rat, and guinea pig OHCs was re-examined by use of immunofluorescent staining and confocal microscopy. We found that prestin labeling was located at the whole OHC basolateral wall, including the basal plasma membrane. However, staining at the basal membrane was weak. As compared with the intensity at the lateral wall, the intensities of prestin labeling at the membrane at the nuclear level and basal pole were 80.5% and 61.1%, respectively. Prestin labeling was not found at the cuticular plate and stereocilia. The prestin labeling was also absent in the cytoplasm and nuclei. The OHC lateral wall above the nuclear level is composed of the plasma membrane, cortical lattice, and subsurface cisternae. By co-staining with di-8-ANEPPS, prestin labeling was found at the outer layer of the OHC lateral wall, which was further evidenced by use of a hypotonic challenge to separate the plasma membrane from the underlying subsurface cisternae. The data revealed that prestin is expressed at the whole OHC basolateral membrane. Prestin in the basal plasma membrane may provide a reservoir on the OHC surface for prestin-recycling and may also facilitate performing its hypothesized transporter function.