dictyNews
Electronic Edition
Volume 46, number 29
October 23, 2020

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=========
Abstracts
=========


Polyphosphate is an extracellular signal that can facilitate bacterial
survival in eukaryotic cells

Ramesh Rijal, Louis A. Cadena, Morgan R. Smith, Joseph F. Carr,
 and Richard H. Gomer

Department of Biology, Texas A&M University, College Station, 
TX 77843-3474 USA


PNAS, accepted

Polyphosphate is a linear chain of phosphate residues and is present 
in organisms ranging from bacteria to humans. Pathogens such as 
Mycobacterium tuberculosis accumulate polyphosphate, and reduced 
expression of the polyphosphate kinase that synthesizes polyphosphate 
decreases their survival. How polyphosphate potentiates pathogenicity 
is poorly understood. Escherichia coli K-12 do not accumulate 
detectable levels of extracellular polyphosphate, and have poor survival 
after phagocytosis by Dictyostelium discoideum or human macrophages. 
In contrast, Mycobacterium smegmatis and Mycobacterium tuberculosis 
accumulate detectable levels of extracellular polyphosphate, and have 
relatively better survival after phagocytosis by D. discoideum or 
macrophages. Adding extracellular polyphosphate increased E. coli 
survival after phagocytosis by D. discoideum and macrophages. 
Reducing expression of polyphosphate kinase 1 in M. smegmatis 
reduced  extracellular polyphosphate and reduced survival in 
D. discoideum and  macrophages, and this was reversed by the addition 
of extracellular  polyphosphate. Conversely, treatment of D. discoideum 
and macrophages  with recombinant yeast exopolyphosphatase reduced 
the survival of  phagocytosed M. smegmatis or M. tuberculosis. 
D. discoideum cells  lacking the putative polyphosphate receptor GrlD 
had reduced sensitivity  to polyphosphate, and compared to wild-type 
cells showed increased  killing  of phagocytosed E. coli and M. smegmatis. 
Polyphosphate inhibited  phagosome acidification and lysosome activity 
in D. discoideum and  macrophages, and reduced early endosomal 
markers in macrophages. Together, these results suggest that bacterial 
polyphosphate potentiates pathogenicity by acting as an extracellular 
signal that inhibits phagosome maturation.


submitted by: Ramesh Rijal [[log in to unmask]]
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[End dictyNews, volume 46, number 29]