Coordinated gating of TRP-dependent channels in rhabdomeral membranes fromDrosophila retinas

Using a newly developed dissociation procedure, we isolated the specialized rhabdomeral membranes from Drosophila retinal photoreceptors. From these m embranes, we have recorded spontaneous active currents in excised patch, vo ltage-clamp recordings. We observed rapid opening events that closely resem bled those ascribed to one class of light-activated channels, TRP. All acti vity exhibited Ba2+ permeability, little voltage dependence, and sensitivit y to La3+ block. Mutational analysis indicated that the spontaneous activit y present in these membranes was TRP-dependent. Excised patches from wild-t ype rhabdomeral membranes exhibited a wide range of conductance amplitudes. In addition, large conductance events exhibited many conductance levels in the open state. Block of activity by La3+ both developed and recovered in a stepwise manner. Our results indicate that TRP-dependent channels have a small unitary conductance and that many channels can be gated coordinately.