dictyNews
Electronic Edition
Volume 30, number 17
May 30, 2008

Please submit abstracts of your papers as soon as they have been
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or by using the form at
http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit.

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Abstracts
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Giorgione, J., and Clarke, M.

Heterogeneous modes of uptake for latex beads revealed through live cell imaging of 
phagocytes expressing a probe for phosphatidylinositol (3,4,5)-trisphosphate 
and phosphatidylinositol (3,4)-bisphosphate.  


Cell Motil. Cytoskel, in press

Latex beads are the preferred phagocytic substrate in biochemical studies of 
phagosome composition and maturation.  Using living Dictyostelium cells and 
fluorescent probes, we compared the properties of phagosomes formed to ingest 
latex beads or digestible prey.  Significant differences were found during the 
initial steps of phagocytosis.  During uptake of bacteria or yeast, PHcrac-GFP, 
a probe that binds to membranes enriched in PI(3,4,5)P3 and PI(3,4)P2, always 
labeled the nascent phagosome and faded shortly after it sealed.  However, labeling 
of bead-containing phagosomes was highly variable.  Beads were engulfed by 
phagosomes either lacking or displaying the PHcrac-GFP label, and that label, 
if present, often persisted for many minutes, revealing that early trafficking 
steps for bead-containing phagosomes are quite heterogeneous.  Later stages of 
the endocytic pathway appeared more similar for phagosomes containing prey and 
latex beads.  Both types of phagosomes fused with acidic endosomes while 
undergoing transport along microtubules, both acquired the V-ATPase and lost 
it prior to exocytosis, and both bound the late endosome marker vacuolin B, 
which was transferred to the plasma membrane upon exocytosis.  We conclude that 
caution is needed in extrapolating results from latex bead phagosomes to 
phagosomes containing physiological substances, especially in early stages 
of the endocytic pathway.


Submitted by: Margaret Clarke [clarkem@omrf.org]
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