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dictyNews Volume 43 Number 11
dictyNews
Electronic Edition
Volume 43, number 11
May 19, 2017
Please submit abstracts of your papers as soon as they have been
accepted for publication by sending them to dicty@northwestern.edu
or by using the form at
http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit.
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Abstracts
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A Tripeptidyl peptidase 1 is a binding partner of GPHR (Golgi pH regulator)
in Dictyostelium
Maria Stumpf1, Rolf Müller1, Berthold Gaßen1, Regina Wehrstedt1, Petra Fey2,
Malte A. Karow1, Ludwig Eichinger1, Gernot Glöckner1, Angelika A. Noegel1
1Institute of Biochemistry I, Medical Faculty, University Hospital Cologne,
University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Köln, Germany;
2dictyBase, Northwestern University, Biomedical Informatics Center and
Center for Genetic Medicine, Chicago, Illinois, USA
Disease Models & Mechanisms, in press
Mutations in tripeptidyl peptidase 1 (TPP1) have been associated with late
infantile neuronal ceroid lipofuscinosis (NCL2), a neurodegenerative disorder.
TPP1 is a lysosomal serine protease, which removes tripeptides from the
amino terminus of proteins and is composed of an N-terminal prodomain and
a catalytic domain. It is conserved in mammals, amphibians, fish and the
amoeba Dictyostelium discoideum. D. discoideum harbors at least six genes
encoding tripeptidyl peptidase 1, tpp1A to tpp1F. We identified TPP1F as
binding partner of Dictyostelium GPHR (Golgi pH regulator), which is an
evolutionary highly conserved intracellular transmembrane protein. For the
interaction, a region encompassing the DUF3735 (GPHR_N) domain of GPHR
was responsible. In TPP1F the binding site was located in the prodomain. The
Tpp1F gene is transcribed throughout development and translated into a
polypeptide of approximately 65 kDa. TPP1 activity was demonstrated for
TPP1F-GFP immunoprecipitated from D. discoideum cells. Its activity could be
inhibited by addition of the recombinant DUF3735 domain of GPHR. Knockout
tpp1F mutants did not display a particular phenotype and TPP1 activity was not
abrogated, which is presumably due to expression of Tpp1B showing the highest
expression levels of all Tpp1 genes during growth. The GPHR interaction was
not restricted to TPP1F but occurred also with TPP1B. Based on previous reports
showing that the majority of the TPP1 mutations in NCL2 resulted in reduction or
loss of enzyme activity, our findings may help to create new reagents with which
one can affect the activity of the protein and ameliorate the disease.
submitted by: Ludwig Eichinger [ludwig.eichinger@uni-koeln.de]
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Multiple Dictyostelid Species Destroy Biofilms of Klebsiella oxytoca and Other
Gram Negative Species
Dean Sanders1, Katarzyna D. Borys2, Fikrullah Kisa3, Sheryl A. Rakowski4,
Marcela Lozano, Marcin Filutowicz5
https://doi.org/10.1016/j.protis.2017.04.001
Dictyostelids are free-living phagocytes that feed on bacteria in diverse habitats.
When bacterial prey is in short supply or depleted, they undergo multicellular
development culminating in the formation of dormant spores. In this work, we
tested isolates representing four dictyostelid species from two genera (Dictyostelium
and Polysphondylium) for the potential to feed on biofilms preformed on glass and
polycarbonate surfaces. The abilities of dictyostelids were monitored for three
hallmarks of activity: 1) spore germination on biofilms, 2) predation on biofilm
enmeshed bacteria by phagocytic cells and 3) characteristic stages of multicellular
development (streaming and fructification). We found that all dictyostelid isolates
tested could feed on biofilm enmeshed bacteria produced by human and plant
pathogens: Klebsiella oxytoca, Pseudomonas aeruginosa, Pseudomonas syringae,
Erwinia amylovora 1189 (biofilm former) and E. amylovora 1189 Δams (biofilm
deficient mutant). However, when dictyostelids were fed planktonic E. amylovora
Δams the bacterial cells exhibited an increased susceptibility to predation by one
of the two dictyostelid strains they were tested against. Taken together, the
qualitative and quantitative data presented here suggest that dictyostelids have
preferences in bacterial prey which affects their efficiency of feeding on bacterial
biofilms.
submitted by: Marcin Filutowicz [msfiluto@wisc.edu]
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[End dictyNews, volume 43, number 11]
