A phospholipase inhibitor, manoalide, and a G-protein activator, Mas-7, both affect the turnover of phototransductive membranes by crab retinas in darkness
With a model for the regulation of rhabdomeral membrane turnover |
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| Authors: | A D Blest Sally Stowe |
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| Institution: | (1) Developmental Neurobiology Group and Centre for Visual Sciences, Australian National University, GPO Box 475, Canberra ACT2601, Australia, AU;(2) Australian National University Electron Microscope Unit, GPO Box 475, Canberra ACT2601, Australia, AU |
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| Abstract: | (1) In vitro retinas of a crab, Leptograpsus, were treated with a phospholipase inhibitor, manoalide, or a G-protein activator, Mas-7. Both drugs address early stages
of the phototransduction cascade. (2) Manoalide inhibited the light-dependent reduction of rhabdoms during the `day' phase
of the light cycle, but did not induce rhabdom overgrowth. Following a period of darkness manoalide failed to affect the diminution
of illuminated rhabdoms. (3) The diminution of rhabdoms that follows photoreceptor depolarisation induced by 100 mmol · l−1 K+ in darkness was not affected by 2␣μmol · l−1 manoalide. (4) When retinas in the `night' phase were treated with Mas-7 in darkness, rhabdom diameters were augmented, concurrently
with endocytosis of photoreceptor plasma membranes. (5) The results of combining manoalide and Mas-7 with actinomycin D, U-57908
or okadaic acid, drugs used in previous studies to manipulate steps notionally lower in the transduction cascade, lead to
a hypothetical model for the regulation of phototransductive membrane turnover by arthropods.
Accepted: 3 October 1996 |
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| Keywords: | Phototransductive membrane Turnover Phospholipases G-proteins Membrane turnover regulation |
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