Unitary Recordings of TRP and TRPL Channels From Isolated Drosophila Retinal Photoreceptor Rhabdomeres: Activation by Light and Lipids

Delgado R, Bacigalupo J. Unitary recordings of TRP and TRPL channels from isolated Drosophila retinal photoreceptor rhabdomeres: activation by light and lipids. J Neurophysiol 101: 2372-2379, 2009. First published March 4, 2009; doi:10.1152/jn.90578.2008. Transient receptor potential (TRP) channels play key roles in sensory transduction. The TRP family founding members, the Drosophila light-dependent channels, were previously studied under voltage clamp, but had not been characterized in intact rhabdomeres at single-channel level. We report patch-clamp recordings from intact isolated photo-receptors of wt and mutant flies lacking TRP (trp(343)), TRPL (trpl(302)), or both channels (trp(313); trpl(302)). Unitary currents were activated by light in rhabdomere-attached patches. In excised rhabdomeral patches, the channels were directly activated by molecules implicated in phototransduction, such as diacylglycerol and polyunsaturated fatty acids. Currents recorded from trpl photoreceptors are blocked by external Ca2+, Mg2+ (1 mM), and La3+ (20 mu M), whereas those from trp photoreceptors are not. Rhabdomeric patches lacked voltage-dependent activity. Patches from trp; trpl mutants were devoid of channels. These characteristics match the macroscopic conductances, suggesting that the unitary currents from Drosophila trpl and trp photoreceptors correspond to TRP and TRPL.