Coordinated gating of TRP-dependent channels in rhabdomeral membranes from Drosophila retinas.
Using a newly developed dissociation procedure, we isolated the specialized rhabdomeral membranes from Drosophila retinal photoreceptors. From these membranes, we have recorded spontaneous active currents in excised patch, voltage-clamp recordings. We observed rapid opening events that closely resembled those ascribed to one class of light-activated channels, TRP. All activity exhibited Ba(2+) permeability, little voltage dependence, and sensitivity to La(3+) block. Mutational analysis indicated that the spontaneous activity present in these membranes was TRP-dependent. Excised patches from wild-type 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 La(3+) 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.
Haab
J E
JE
Institute of Neuroscience and Department of Biology, University of Oregon, Eugene, Oregon 97403, USA.
Vergara
C
C
Bacigalupo
J
J
O'Day
P M
PM
D000818:Animals; D001464:Barium / Q000378:metabolism / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D021961:Cell Membrane Structures / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004330:Drosophila; D029721:Drosophila Proteins; D019476:Insect Proteins / Q000378:metabolism*; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D007811:Lanthanum / Q000494:pharmacology; D018408:Patch-Clamp Techniques / Q000379:methods; D017956:Photoreceptor Cells, Invertebrate / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D012160:Retina / Q000737:chemistry / Q000378:metabolism*; D050051:Transient Receptor Potential Channels
D015220:Calcium Channels; D029721:Drosophila Proteins; D019476:Insect Proteins; D050051:Transient Receptor Potential Channels; C063169:trp protein, Drosophila; D001464:Barium; D007811:Lanthanum