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 [[log in to unmask]]
覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧
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 [[log in to unmask]]
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[End dictyNews, volume 41, number 25]
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