How does membrane turnover relate with the turnover of the
membrane's major constituents, the phospholipids? I pursued this
question in investigations undertaken in collaboration with Prof. G. Y. Sun,
Department of Biochemistry, University of Missouri. This is especially
relevant since it also relates to visual transduction mechanisms.
In Drosophila vision, one of the oldest and best studied
mutants, norpA (no receptor potential), has a transduction
defect involving phospholipase C (PLC). Because of this, the phospholipid
and fatty acid composition of Drosophila heads was of interest.
Major phospholipids were quantified in various mutants and were
shown to turn over rapidly by labeling with radioactive phosphate,
separation using thin layer chromatography (TLC), and quantification.
Fatty acids of selected phospholipids were analyzed by gas chromatography
(GC). Perhaps our most interesting finding was that there are
no fatty acids longer than 18 carbons in fly heads. Although docosahexaenoic
acid (22:6) is high in vertebrate photoreceptors, Drosophila
heads had none. Neither is there arachidonic acid (20:4),
a precursor of signaling molecules. Using several different media
which differed in fatty acid composition, we showed that the fatty
acid composition of the heads could be readily manipulated.
Papers on phospholipids and fatty acids:
Stark, W. S., Lin, T.-N., Brackhahn, D., Christianson, J. S., Sun, G. Y. Phospholipids in Drosophila heads: Effects of visual mutants and phototransduction manipulations . Lipids, 1993A, 28, 23-28. PubMed
Stark, W. S., Lin, T.-N., Brackhahn, D., Christianson, J. S., Sun, G. Y. Fatty acids in the lipids of Drosophila heads: Effects of visual mutants, carotenoid deprivation and dietary fatty acids. Lipids 1993B, 28,345-350. PubMed
We used eyes absent (eya), shown in this SEM, to selectively eliminate compound eyes in these studies. Eya lacks compound eyes but not simple eyes (ocelli)
A gas chromatogram
showing thefatty acids (especially the lack of long chain fatty
acids) in the Drosophilahead (from Stark et al., 1993B).
A thin layer chromatogram showingthe labeling pattern of lipids in the Drosophila head (from Starket al., 1993A).
This page was last updated on June, 22, 2005
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