ISSN:
1432-1351
Keywords:
Phototransductive membrane turnover
;
Crab retinas
;
Diacylglycerol lipase inhibitor
;
Protein kinases
;
Regulation of turnover
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract 1. Arthropod phototransduction cascades release diacylglycerols (DAGs). We have suggested that DAGs may activate protein kinase Cs (PKCs) to induce phosphorylations of proteins that regulate nuclear transcriptions of rhabdomeral membrane precursors during circadian phototransductive membrane turnover. 2. When retinas of a crab, Leptograpsus, held in vitro after illumination at dawn were treated with an inhibitor of diacylglycerol lipases, U-57908, endomembranes proliferated from nuclear envelopes and differentiated to renew rhabdomeral microvilli, following the pathways described by Stowe (1980). 3. When retinas were treated with exogenous, 1,2-dioctanoyl-sn-glycerol alone rhabdomeres were rapidly stripped of microvilli. 4. A combination of 1,2-dioctanoyl-sn-glycerol and U-57908 induced an initial endocytosis of rhabdomeral membrane, followed by proliferation of endomembranes from nuclear envelopes and reassembly of rhabdoms. 5. Two hypothetical processes are implied: (i) PKCs activated peripherally by DAGs released by phototransduction are translocated to photoreceptor nuclei where they induce the phosphorylation of proteins that regulate transcriptions, (ii) Peripherally, activated PKCs may determine phosphorylation of the cytoplasmic domains of integral rhabdomeral membrane proteins to create signals that initiate endocytosis. The latter process, however, may not occur in vivo. 6. The model for the regulation of phototransductive membrane turnover rests upon assumptions about the intracellular compartmentalisation of arthropod photo-receptors. They have not been critically examined. Crab R1-7 nuclear envelopes seem to possess a high population of nuclear pores. It may be mandatory for the transfer of peripheral signals to intra-nuclear sites.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00209618
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