Journal of Lipid Research, Vol 36, 1-12, Copyright © 1995 by Lipid Research, Inc.
Uptake and compartmentalization of fluorescent lipid analogs in larval Schistosoma mansoni
ST Furlong, KS Thibault, LM Morbelli, JJ Quinn and RA Rogers
Department of Medicine, Harvard Medical School, Boston, MA.
Recent studies have suggested that host lipids are both a requirement for
the human parasite Schistosoma mansoni and may play a role in evasion of
host immunity. To study lipid utilization by this organism we have followed
the uptake of fluorescent fatty acid and phospholipid analogs in two
parasite stages, cercariae and schistosomula. As determined by both
morphological and biochemical methods, a fluorescent fatty acid analog
labeled with bodipy was incorporated into both stages. In cercariae,
diffuse fluorescence was present throughout the organism and discrete lipid
droplets were observed in the tail and in the anterior structures. In
contrast, fluorescence distribution in cercariae transformed to
schistosomula was restricted to cytoplasmic lipid droplets throughout the
organism. Biochemical analysis demonstrated that the fatty acid analog was
biosynthetically incorporated primarily into neutral lipids but also
somewhat into phospholipids. The percentage of free label decreased with
time. Similar results were obtained when organisms were labeled directly in
vitro or indirectly by labeling the intermediate snail host. Compared to
the fatty acid analogs, localization of fluorescent phospholipid analogs by
schistosomula was considerably different. Phosphatidylcholine labeled on
short acyl chains with either bodipy or NBD localized primarily to a
network of cells beneath the organism's surface. A longer chain
bodipy-labeled phosphatidylcholine localized to the parasite surface, gut
and acetabulum. These studies show specificity in the transport of lipid
analogs by this important human parasite, elucidate the compartments within
the organism in which specific lipids preferentially accumulate, and
demonstrate stage- dependent differences in the utilization of exogenous
lipids by this organism.