Reciprocal electromechanical properties of rat prestin: The motor molecule from rat outer hair cells

Abstract

Cochlear outer hair cells (OHCs) are responsible for the exquisite sensitivity, dynamic range, and frequency-resolving capacity of the mammalian hearing organ. These unique cells respond to an electrical stimulus with a cycle-by-cycle change in cell length that is mediated by molecular motors in the cells' basolateral membrane. Recent work identified prestin, a protein with similarity to pendrin-related anion transporters, as the OHC motor molecule. Here we show that heterologously expressed prestin from rat OHCs (rprestin) exhibits reciprocal electromechanical properties as known for the OHC motor protein. Upon electrical stimulation in the microchamber configuration, rprestin generates mechanical force with constant amplitude and phase up to a stimulus frequency of at least 20 kHz. Mechanical stimulation of rprestin in excised outside-out patches shifts the voltage dependence of the nonlinear capacitance characterizing the electrical properties of the molecule. The results indicate that rprestin is a molecular motor that displays reciprocal electromechanical properties over the entire frequency range relevant for mammalian hearing. O uter hair cells (OHCs) of the mammalian cochlea exhibit the unique property of actively changing their cell length in response to changes in the membrane potential (1-3): the cell shortens upon depolarization and lengthens when hyperpolarized. This electromotility occurs at acoustic frequencies (4, 5) and is believed to provide a basis for the cochlear amplifier, a local mechanical amplification mechanism within the organ of Corti (6), that enables the high sensitivity, dynamic range, and frequency selectivity of hearing in mammals.The mechanism underlying electromotility has been tracked down to an intrinsic property of the OHC basolateral membrane: (i) OHC motility is directly driven by the transmembrane voltage and is independent of Ca 2ϩ influx or ATP supply (7, 8); (ii) it works in a cycle-per-cycle mode at frequencies up to at least 70 kHz, faster than any other biological force generator including myosin or kinesin (4, 5, 9); (iii) it is accompanied by a charge movement (or gating current) that can be measured as a nonlinear capacitance (C nonlin ) and shares voltage dependence and a panel of antagonists with the motility itself (10-12); and (iv) changes in mechanical membrane tension cause a shift of C nonlin along the voltage axis (13-15).These findings have led to the hypothesis of an integral membrane protein, termed the motor protein, as the molecular element underlying fast OHC motility (7,16). In response to changes in the transmembrane voltage, the motor protein is thought to undergo a structural rearrangement that changes its area in the plasma membrane (17, 18). As a result of the concerted action of a large number of motor molecules supposed to be densely packed in the OHC basolateral membrane (19), the cell changes its length by up to 5%. In this concept, the voltage dependence of electromotility is brought about by a charged voltage sensor within the motor prot...

Congenital Chloride-losing Diarrhea Causing Mutations in the STAS Domain Result in Misfolding and Mistrafficking of SLC26A3

“…The experimental topology data presented here is the first to be reported for SLC26A3 and supports a model with intracellularly located N and C termini. Consistent with our results, some previous studies on SLC26A5 and SLC26A6 have indicated that the N and C termini of these proteins are located in the cytosol (7,10,13,61). The location of the N terminus is important as previous reports have reported it to be proteolytically cleaved in vivo (65,66), raising the possibility that proteolytic cleavage may regulate transporter function.…”

Expression of prestin-homologous solute carrier (SLC26) in auditory organs of nonmammalian vertebrates and insects

“…Prestin (SLC26A5) (14) is a motor protein specific to cochlear outer hair cells and thought to be responsible for active mechanical amplification in mammalian ears (6)(7)(8)(9). Beside prestin, pendrin (SLC26A4) (15) is a member of the SLC26 family, displaying a defined expression pattern in the developing cochlea different from that of prestin.…”

“…[1][2][3][4][5]. A molecular motor driving this cellular electromotility has been identified recently to be prestin, a membrane-based molecule that seems to change its conformation in a voltage-dependent way (6)(7)(8)(9).…”

Dissection of the Mechanical Impedance Components of the Outer Hair Cell Using a Chloride-Channel Blocker

“…Whole-cell patch-clamp recordings were performed to determine NLC of: 1) OHCs mechanically isolated from the adult guinea-pig cochlea, and 2) HEK293 cells transfected with plasmids encoding prestin [8]. OHCs were bathed in Hanks' balanced salt solution (HBSS, pH 7.3, osmolarity 310 mOsm/L).…”