TY  - JOUR
A1  - Beitzinger, Christoph
A1  - Bronnhuber, Annika
A1  - Duscha, Kerstin
A1  - Riedl, Zsuzsanna
A1  - Huber-Lang, Markus
A1  - Benz, Roland
A1  - Hajos, György
A1  - Barth, Holger
T1  - Designed Azolopyridinium Salts Block Protective Antigen Pores In Vitro and Protect Cells from Anthrax Toxin
JF  - PLoS ONE
N2  - Background
Several intracellular acting bacterial protein toxins of the AB-type, which are known to enter cells by endocytosis, are shown to produce channels. This holds true for protective antigen (PA), the binding component of the tripartite anthrax-toxin of Bacillus anthracis. Evidence has been presented that translocation of the enzymatic components of anthrax-toxin across the endosomal membrane of target cells and channel formation by the heptameric/octameric \(PA_{63}\) binding/translocation component are related phenomena. Chloroquine and some 4-aminoquinolones, known as potent drugs against Plasmodium falciparium infection of humans, block efficiently the \(PA_{63}\)-channel in a dose dependent way.

Methodology/Principal Findings
Here we demonstrate that related positively charged heterocyclic azolopyridinium salts block the \(PA_{63}\)-channel in the µM range, when both, inhibitor and \(PA_{63}\) are added to the same side of the membrane, the cis-side, which corresponds to the lumen of acidified endosomal vesicles of target cells. Noise-analysis allowed the study of the kinetics of the plug formation by the heterocycles. In vivo experiments using J774A.1 macrophages demonstrated that the inhibitors of \(PA_{63}\)-channel function also efficiently block intoxication of the cells by the combination lethal factor and \(PA_{63}\) in the same concentration range as they block the channels in vitro.

Conclusions/Significance
These results strongly argue in favor of a transport of lethal factor through the \(PA_{63}\)-channel and suggest that the heterocycles used in this study could represent attractive candidates for development of novel therapeutic strategies against anthrax.
KW  - intoxication
KW  - chloroquine
KW  - toxins
KW  - anthrax
KW  - cell membranes
KW  - lipid bilayer
KW  - macrophages
KW  - membrane potential
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-130097
VL  - 8
IS  - 6
ER  - 
TY  - JOUR
A1  - Graus, Dorothea
A1  - Konrad, Kai R.
A1  - Bemm, Felix
A1  - Nebioglu, Meliha Görkem Patir
A1  - Lorey, Christian
A1  - Duscha, Kerstin
A1  - Güthoff, Tilman
A1  - Herrmann, Johannes
A1  - Ferjani, Ali
A1  - Cuin, Tracey Ann
A1  - Roelfsema, M. Rob G.
A1  - Schumacher, Karin
A1  - Neuhaus, H. Ekkehard
A1  - Marten, Irene
A1  - Hedrich, Rainer
T1  - High V-PPase activity is beneficial under high salt loads, but detrimental without salinity
JF  - New Phytologist
N2  - The membrane-bound proton-pumping pyrophosphatase (V-PPase), together with the V-type H+-ATPase, generates the proton motive force that drives vacuolar membrane solute transport. Transgenic plants constitutively overexpressing V-PPases were shown to have improved salinity tolerance, but the relative impact of increasing PPi hydrolysis and proton-pumping functions has yet to be dissected.

For a better understanding of the molecular processes underlying V-PPase-dependent salt tolerance, we transiently overexpressed the pyrophosphate-driven proton pump (NbVHP) in Nicotiana benthamiana leaves and studied its functional properties in relation to salt treatment by primarily using patch-clamp, impalement electrodes and pH imaging.

NbVHP overexpression led to higher vacuolar proton currents and vacuolar acidification. After 3 d in salt-untreated conditions, V-PPase-overexpressing leaves showed a drop in photosynthetic capacity, plasma membrane depolarization and eventual leaf necrosis. Salt, however, rescued NbVHP-hyperactive cells from cell death. Furthermore, a salt-induced rise in V-PPase but not of V-ATPase pump currents was detected in nontransformed plants.

The results indicate that under normal growth conditions, plants need to regulate the V-PPase pump activity to avoid hyperactivity and its negative feedback on cell viability. Nonetheless, V-PPase proton pump function becomes increasingly important under salt stress for generating the pH gradient necessary for vacuolar proton-coupled Na+ sequestration.
KW  - cell death
KW  - plasma membrane voltage
KW  - proton pump currents
KW  - salt
KW  - vacuolar pH
KW  - vacuolar proton-ATPase (V-ATPase)
KW  - vacuolar proton-pyrophosphatase (V-PPase)
Y1  - 2018
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-227553
VL  - 219
ER  -