On the temperature and tension dependence of the outer hair cell lateral membrane conductance G_metL and its relation to prestin

Recently, we identified an outer hair cell (OHC) lateral membrane conductance, G_metL, that colocalizes with prestin and passes Cl ^-, thereby influencing prestin's (SLC26A5) electromechanical activity. In this study, we report on a comparison of the temperature and tension dependence of G_metL and prestin. Though we find significant temperature and tension dependence of each, substantial differences exist which indicate their independent identity. The following data support this conclusion: (1) The voltage dependence of G_metL does not follow that of prestin's nonlinear capacitance (NLC) function when the latter is shifted by either temperature or membrane tension; (2) Unlike native OHCs whose NLC can be modulated by influx of extracellular Cl^-, prestin-transfected Chinese hamster ovary (CHO) cells do not show this phenomenon; (3) Stretch-sensitive, single channel currents are not evidenced after prestin transfection in CHO cells; and (4) There is no correlation between prestin expression level (gauged via NLC) and transmembrane current through G_metL. Thus, G _metL must result from the activity of another molecular species within the lateral membrane of the OHC. A clue to its identity is the conductance's nonlinear temperature dependence in contrast to prestin and other OHC conductances' linear dependence. Whereas K⁺ conductances in OHCs present a uniform Q₁₀ close to 1.2, G_metL shows a bimodal Q₁₀, with a Q₁₀ of 1.5 below 34°C and a Q₁₀ of greater than 4 and above. The dissociation of SLC26A5 (prestin) and G _metL theoretically provides for a modifiable anionic feedback to prestin via the degree of spatial separation between these interacting partners within the OHC lateral membrane.