Abstract
Phototransduction in Drosophila
Highlights
Vision throughout the animal kingdom is based on rhodopsins, at least three subfamilies of which arose before the deuterostome and protostome invertebrate lineages diverged over 550 Mya [1,2]
Protons and bilayer mechanics phospholipase C (PLC) activity has at least two further consequences: PIP2 depletion and proton release (Figure 2). The latter is usually ignored; a proton is released for each PIP2 hydrolysed and Huang et al [*35] measured a rapid light-induced and PLC-dependent acidification in the rhabdomeres
Recent evidence suggests that the channels may be activated by the combination of two neglected consequences of PLC activity: the physical effects of PIP2 depletion on the membrane, and acidification
Summary
Vision throughout the animal kingdom is based on rhodopsins, at least three subfamilies of which arose before the deuterostome (chordate and vertebrate) and protostome invertebrate lineages diverged over 550 Mya [1,2]. The latter is usually ignored; a proton is released for each PIP2 hydrolysed and Huang et al [*35] measured a rapid light-induced and PLC-dependent acidification in the rhabdomeres They found that the strict combination of PIP2 depletion and acidification achieved by protonophores, rapidly and reversibly activated both TRP and TRPL channels in photoreceptors (Figure 3). During light-adaptation, accumulation of Ca2+ entering via many microvilli raises steady-state Ca2+ throughout the cell to maximally ~10 M; this inhibits both TRP and TRPL channels, progressively reducing quantum bump currents, whilst depolarization of the cell and activation of voltage-activated K channels results in further global reduction in voltage gain This conceptual model of quantum bump generation [21] has been combined with experimentally determined parameters to generate molecularly explicit computational models that accurately predict quantum bump waveforms and their latency distribution (Figure 4) [8,51,52,**53]. This strategy enables perceptually consistent estimates of real-world light contrast patterns over a large illumination range, in an energy efficient manner [54]
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