dictyNews
Electronic Edition
Volume 44, number 5
February 9, 2018

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=========
Abstracts
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The physiological regulation of macropinocytosis during Dictyostelium 
growth and development

Thomas D. Williams and Robert R. Kay

MRC-Laboratory of Molecular Biology, Francis Crick Avenue, 
Cambridge, CB2 0QH, UK


J. Cell Science, in press

Macropinocytosis is a conserved endocytic process used by 
Dictyostelium amoebae for feeding on liquid medium. To further 
Dictyostelium as a model for macropinocytosis, we developed a high-
throughput flow cytometry assay to measure macropinocytosis, and 
used it to identify inhibitors and investigate the physiological regulation 
of macropinocytosis. Dictyostelium has two feeding states: phagocytic 
and macropinocytic. When cells are switched from phagocytic growth 
on bacteria to liquid media, the rate of macropinocytosis slowly 
increases, due to increased size and frequency of macropinosomes. 
Upregulation is triggered by a minimal medium of 3 amino acids plus
glucose and likely depends on macropinocytosis itself. The presence 
of bacteria suppresses macropinocytosis while their product, folate, 
partially suppresses upregulation of macropinocytosis.  Starvation, 
which initiates development, does not of itself suppress 
macropinocytosis: this can continue in isolated cells, but is shut down
by a conditioned-medium factor or activation of PKA signalling.  Thus 
macropinocytosis is a facultative ability of Dictyostelium cells, regulated 
by environmental conditions that are identified here.


submitted by: Rob Kay  [[log in to unmask]]
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[End dictyNews, volume 44, number 5]