dictyNews
Electronic Edition
Volume 41, number 25
November 20, 2015

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=========
Abstracts
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Isolation and characterisation of various amoebophageous fungi and 
evaluation of their prey spectrum

Rolf Michel, Julia Walochnik, Patrick Scheid 


Experimental Parasitology 145 (2014) S131-S136

This article gives an overview on the isolation and characterisation 
of endoparasitic fungi invading freeliving amoebae (FLA), including 
the ones forming thalli inside their hosts such as Cochlonema 
euryblastum and also the predatory fungi which capture amoebae by 
adhesive hyphae. Acaulopage spp. and Stylopage spp. trap, intrude, 
and exploit amoebal trophozoites. Previous phylogenetic studies 
proved Cochlonema to be a member of the Zoopagales. The genetic 
investigation of Acaulopage tetraceros demonstrated its close 
relationship to Cochlonema. Co-cultivation of A. tetraceros with a 
number of FLA revealed a great prey spectrum of this amoebophageous 
fungus. In addition it was shown that solitary amoebal stages of 
slime moulds such as Dictyostelium sp. and Physarum sp. are also 
suited as welcome prey amoebae.


Submitted by Rolf Michel [r.michel1@gmx.de]  
————————————————————————————————————


PP2A/B56 and GSK3/Ras suppress PKB activity during Dictyostelium 
chemotaxis

Marbelys Rodriguez Pino, Boris Castillo, Bohye Kim, and Lou W. Kim
 
Department of Biological Sciences, Biochemistry PhD Program, 
and Biomolecular Sciences Institutes, Florida International University, 
Miami, FL 33199


MBoC, In Press

We have previously shown that the Dictyostelium protein phosphatase 
2A regulatory subunit B56, encoded by psrA, modulates Dictyostelium 
cell differentiation through negatively affecting glycogen synthase 
kinase 3 (GSK3) function. Our follow-up research uncovered that B56 
preferentially associated with GDP forms of RasC and RasD, but not 
with RasG in vitro, and psrA- cells displayed inefficient activation of 
multiple Ras species, decreased random motility, and inefficient 
chemotaxis toward cAMP and folic acid gradient. Surprisingly, psrA- 
cells displayed aberrantly high basal and poststimulus phosphorylation 
of Dictyostelium protein kinase B (PKB) kinase family member PKBR1 
and PKB substrates. Expression of constitutively active Ras mutants or 
inhibition of GSK3 in psrA- cells increased activities of both PKBR1 
and PKBA, but only the PKBR1 activity was increased in wild-type 
cells under the equivalent conditions, indicating that either B56- or 
GSK3-mediated suppressive mechanism is sufficient to maintain low 
PKBA activity, but both mechanisms are necessary for suppressing 
PKBR1. Finally, cells lacking RasD or RasC displayed normal PKBR1 
regulation under GSK3-inhibiting conditions, indicating that RasC or 
RasD proteins are essential for GSK3-mediated PKBR1 inhibition. In 
summary, B56 constitutes inhibitory circuits for PKBA and PKBR1 and 
thus heavily affects Dictyostelium chemotaxis.


submitted by: Lou W. Kim [kiml@FIU.EDU]
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[End dictyNews, volume 41, number 25]