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Cell Signal. 2014 Feb;26(2):453-9. doi: 10.1016/j.cellsig.2013.10.008. Epub 2013 Oct 31.

The cyclic AMP phosphodiesterase RegA critically regulates encystation in social and pathogenic amoebas.

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College of Life Sciences, University of Dundee, Dundee DD15EH, UK.
College of Life Sciences, University of Dundee, Dundee DD15EH, UK. Electronic address:


Amoebas survive environmental stress by differentiating into encapsulated cysts. As cysts, pathogenic amoebas resist antibiotics, which particularly counteracts treatment of vision-destroying Acanthamoeba keratitis. Limited genetic tractability of amoeba pathogens has left their encystation mechanisms unexplored. The social amoeba Dictyostelium discoideum forms spores in multicellular fruiting bodies to survive starvation, while other dictyostelids, such as Polysphondylium pallidum can additionally encyst as single cells. Sporulation is induced by cAMP acting on PKA, with the cAMP phosphodiesterase RegA critically regulating cAMP levels. We show here that RegA is deeply conserved in social and pathogenic amoebas and that deletion of the RegA gene in P. pallidum causes precocious encystation and prevents cyst germination. We heterologously expressed and characterized Acanthamoeba RegA and performed a compound screen to identify RegA inhibitors. Two effective inhibitors increased cAMP levels and triggered Acanthamoeba encystation. Our results show that RegA critically regulates Amoebozoan encystation and that components of the cAMP signalling pathway could be effective targets for therapeutic intervention with encystation.


3′5′-adenosine monophosphate; ACG; Acanthamoeba castellani; Acanthamoeba keratitis; Acas; AcrA; Ddis; Dictyostelium discoideum; Encystation; KO; MRSA; PDE; PKA; Polysphondylium pallidum; Ppal; RI; Sensor histidine kinase; Stress signalling; adenylate cyclase G; adenylate cyclase R; cAMP; cAMP dependent protein kinase; cAMP-phosphodiesterase; knock-out; methicillin resistant Streptococcus aureus; phosphodiesterase; random integrant

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