Mammalian outer hair cells (OHCs) can change length at acoustic frequencies when they are electrically stimulated. Recently we have suggested that these length changes are driven by a novel force generator mechanism embedded in the lateral plasma membrane. Using microbeads attached to the surface of electrically stimulated OHCs we have demonstrated that the force generated in the OHC vary along the cell body and that the motor elements are organized in patches with different orientations. Relative movements between domains could allow substantial changes of cell shape without disrupting the unit structure of the motor, thus allowing the plasma membrane to retain its elastic responses to high- frequency deformations. Using immunocytochemical techniques we have determined that in addition to the anion exchanger protein (AE), which is present in the outer hair cell lateral plasma membrane, the actin binding protein 4.1 is associated with the actin-spectrin cortical lattice. We are proposing that the plasma membrane may be connected to the cortical actin-spectrin lattice of the outer hair cell through protein """"""""pillars"""""""" formed by anion exchanger and 4.1 proteins. A near full length complementary DNA encoding a protein that is related to the AEs has been isolated from a guinea pig organ of Corti cDNA library. The organ of Corti AE clone encodes for 1130 amino acids and exhibits a 86% amino acid identity with rat AE2. A distinctive feature of this clone is a missing portion of 28 amino acids at position 643 of the organ of Corti AE sequence. The absence of these amino acids creates a different hydropathy pattern, and may reduce the number of transmembrane domains by one. This finding constitutes the initial effort towards understanding the possible role that AEs play as intramembranous structural proteins in the outer hair cells and their potential involvement in the fast electromotile process.
Showing the most recent 10 out of 74 publications
