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Fig. 1. TRPL channels display two stages of light-induced translocation. (A) Diagram of a single ommatidium and cross-sections of single wild-type ommatidia. (Left panel) Single ommatidium illustrating apical and basolateral membranes of the photoreceptor cell. Black features, apical membrane, including the rhabdomere (R) and the supporting stalk membrane (arrowheads); gray, basolateral membrane; 
, adherens junctions separating apical and basolateral membranes. (Right panels) Cross-sections of single wild-type ommatidia, immunostained for TRPL, shown to illustrate typical localization of TRPL channels in the dark, after the first or the second stage of light-induced TRPL translocation. In each ommatidium, seven photoreceptor cells are visible. The rhabdomere (R) and cell body (C) of a single photoreceptor cell are indicated in one ommatidium (Dark); the approximate boundary of the cell body is outlined. TRPL channels are exclusively localized to the rhabdomeres of dark-adapted photoreceptors; arrowheads indicate the concentration of channels at the base of rhabdomeres. After 2 hours of light-exposure (stage 1), TRPL moves into the supporting stalk membrane adjacent to each rhabdomere (arrowheads), forming an apical ring-like localization pattern for each ommatidium. With 12 hours of light-exposure (stage 2), TRPL translocates to the basolateral membrane (arrowheads); light intensity was 
244 lux. Representative ommatidia are shown here and in Figs 3, 5 and 7 from multiple wild-type retinal sections taken from 37 eyes of 35 flies (Dark), 45 eyes of 37 flies (Light, 2hrs), 28 eyes of 26 flies (Light, 12hrs). (B) Representative immunoblot analysis of retinal membrane (M) and cytosolic (C) fractions isolated from wild-type flies that were dark-adapted (DR) or light-exposed for 2 or 12 hours (Lex 2hrs or Lex 12hrs, respectively). In contrast to Gq
, which displays a light-dependent shift from membrane to cytosol as previously reported (Cronin et al., 2004), TRPL is found in the membrane fraction during each light condition examined. Rhodopsin (Rh1) was used as a loading control for the membrane fractions. An immunoblot representative for seven different experiments is shown. (C) Time course of the two stages of TRPL-channel translocation from the rhabdomere to the basolateral membrane. Shown are wild-type retinal cross-sections immunostained for TRPL after light-exposures of increasing duration. Dark-raised wild-type flies show rhabdomeric TRPL localization. Within 5 minutes of light-exposure, TRPL rapidly translocates to the stalk membrane, producing the same apical ring-like pattern as seen after 2 and 4 hours of light-exposure; we designate this translocation to the stalk membrane as stage 1. After 6 hours of light-exposure, TRPL is first found localized to the basolateral membrane in some, but not all photoreceptor cells. With 10 hours of light exposure, TRPL is consistently found localized to the basolateral membrane of all photoreceptors. TRPL localization to the basolateral membrane is designated as stage 2 of TRPL translocation. Shown are representative ommatidia from multiple retinal sections, taken from five eyes of five flies (Dark), six eyes of five flies (Light, 5min), seven eyes of six flies (Light, 2hrs), eight eyes of five flies (Light, 4hrs), six eyes of four flies (Light, 6hrs), five eyes of four flies (Light, 10hrs).
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