Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Biogenic Insecticides decoded: Scientists from Bochum and Freiburg present their results in Science

01.03.2010
Researchers elucidate the Mechanism of Action of Tc Proteins

Infective entomopathogenic nematodes are minute worms that penetrate insect larva and serve as transport vehicles for the bacterium Photorhabdus luminescens, which lives in their alimentary tract.

After larva penetration the nematodes release these bacteria, which secrete toxins that compromise the immune system of the larvae. Thus the nematodes are used together with the bacterium as insecticide. The exact mechanism of action of the Photorhabdus luminescens had been unknown to date.

Together with colleagues from Freiburg, Prof. em. Hans Georg Mannherz (Medical Faculty of the RUB and the Max-Planck-Institute for Molecular Physiology, Dortmund) has now managed to elucidate this process. Specific subunits of the bacterial toxin complex that inhibit essential defence reactions of immune cells are of instrumental significance. Some of the bacterial infectious toxins bear resemblances to toxins of human pathogenic bacteria, e.g. the bacteria that cause pulmonary and bubonic plaque may make use of similar mechanisms. The researchers have published their findings in the current volume of SCIENCE.

Worms transport the bacteria to the target

Photorhabdus luminescens lives in symbiosis with nematodes. The minute worms penetrate insect larvae via natural openings and then more or less "regurgitate" the bacteria. Bacterial toxins produced by this light-emitting bacterium kill the insect larvae thus creating a large food reservoir for the proliferation of nematodes and bacteria.

Two subunits of the toxin complex are biologically active

Photorhabdus luminescens produces diverse toxins that generate large toxin complexes (Tc proteins). The biologically active complex consists of the three components TcA, TcB and TcC. So far the mechanism of action of these toxins has been unknown. Together with the Dow AgroSciences (USA) and Prof. em. Mannherz and research scientists in Freiburg, working under the auspices of Prof. Klaus Aktories and Prof. Gudula Schmidt, investigated the impact of the toxins on insect and mammalian cells. They were able to demonstrate that the biological activity is located in the TcC components TccC3 and TccC5. The two toxin components are enzymes that inhibit the essential defence reactions of immune cells, e.g. the phagocytosis of bacteria.

Toxins function in two ways

The toxins act on the target cells of the insect larvae in two different ways. TccC3 modifies the cytoskeletal protein actin (ADP-ribosylation) to such an extent that it is no longer controlled by the regulator protein thymosin beta 4. This results in a significant polymerisation of the actin. The second toxin, TccC5, changes so-called Rho proteins, i.e. the switch proteins responsible for the regulation of the actin cytoskeleton. Normally these regulators are switched on and off within the cell. TccC5 modifies the switch by blocking the switching-off procedure. Subsequently the permanently active Rho protein enhances the polymerisation of actin. Together the two toxins lead to a strong aggregation and even clustering of the actin cytoskeleton, which is incompatible with the normal cellular function or immune defence reaction. TcA, which forms pores in host cells, is necessary to enable the toxins TccC3 and TccC5 to enter the insect cells. The toxins probably infiltrate the interior of the cells through these pores.

Decisive knowledge for the comprehension of Tc proteins

Tc Proteins have also been identified in human pathogenic bacteria such as Yersinia pseudotuberculosis and Yersinia pestis. As Prof. Mannherz pointed out, the clarification of the molecular mechanism of prototypical Tc proteins is thus of fundamental importance for the comprehension of other Tc proteins from insecticidal and human pathogenic bacteria.

Title

Alexander E. Lang, Gudula Schmidt, Andreas Schlosser, Timothy D. Hey, Ignacio M. Larrinua, Joel J. Sheets, Hans G. Mannherz and Klaus Aktories: "Photorhabdus luminescens Toxins ADP-Ribosylate Actin and RhoA to Force Actin Clustering." In: Science 26 February 2010 327: 1139-1142 [DOI: 10.1126/science.1184557]

Further Information

Prof. em. Hans Georg Mannherz, Abteilung für Anatomie und Embryologie der Ruhr-Universität Bochum und Abteilung für Physikalische Biochemie des Max-Planck-Instituts für Molekulare Physiologie, Dortmund, Germany

E-Mail: hans.g.mannherz@rub.de

Editor: Meike Drießen

Dr. Josef König | idw
Further information:
http://www.ruhr-uni-bochum.de/

More articles from Life Sciences:

nachricht Toward a 'smart' patch that automatically delivers insulin when needed
18.01.2017 | American Chemical Society

nachricht 127 at one blow...
18.01.2017 | Stiftung Zoologisches Forschungsmuseum Alexander Koenig, Leibniz-Institut für Biodiversität der Tiere

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

A big nano boost for solar cells

18.01.2017 | Power and Electrical Engineering

Glass's off-kilter harmonies

18.01.2017 | Materials Sciences

Toward a 'smart' patch that automatically delivers insulin when needed

18.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>