Photomechanical Responses in Drosophila Photoreceptors

Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3EG, UK.
Science (Impact Factor: 33.61). 10/2012; 338(6104):260-3. DOI: 10.1126/science.1222376
Source: PubMed


Phototransduction in Drosophila microvillar photoreceptor cells is mediated by a G protein-activated phospholipase C (PLC). PLC hydrolyzes the minor membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP(2)), leading by an unknown mechanism to activation of the prototypical transient receptor potential (TRP) and TRP-like (TRPL) channels. We found that light exposure evoked rapid PLC-mediated contractions of the photoreceptor cells and modulated the activity of mechanosensitive channels introduced into photoreceptor cells. Furthermore, photoreceptor light responses were facilitated by membrane stretch and were inhibited by amphipaths, which alter lipid bilayer properties. These results indicate that, by cleaving PIP(2), PLC generates rapid physical changes in the lipid bilayer that lead to contractions of the microvilli, and suggest that the resultant mechanical forces contribute to gating the light-sensitive channels.

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    • "Physical properties of PR membranes are important as structural parameters, but they are also important for signaling. In Drosophila, upon light exposure, the cleavage of the minor lipid membrane phosphatidylinositol 4,5-bisphosphate (PIP2) by the NORPA phospholipase C (PLC) leads to a contraction of the rhabdomere, which is able to activate mechanosensitive channels [76]. Lipid composition of PR membrane is therefore essential to anchor and regulate the activity of proteins involved in phototransduction. "
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    • "In Drosophila, photon absorption by rhodopsin causes photoisomerization to metarhodopsin, which activates a heterotrimeric Gq-protein, initiating a cascade leading to activation of IP 3 and diacylglycerol. Linkages from this cascade to opening of transient receptor potential (dTRP) and TRP-like (dTRPL) ion channels that carry the receptor current are still debated, and both chemical (Chyb et al., 1999; Huang et al., 2010) and mechanical (Hardie and Franze, 2012) intermediate steps have been proposed. In Drosophila, dTRP and dTRPL channels are thought to carry approximately equal parts of light-activated current under physiological conditions (Reuss et al., 1997). "
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    • "light-induced activation of a known MSC, gramicidin, introduced in photoreceptor cells in place of TRP and TRPL [48]. "
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