Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Making Blood-Sucking Deadly for Mosquitoes

19.07.2011
Inhibiting a molecular process cells use to direct proteins to their proper destinations causes more than 90 percent of affected mosquitoes to die within 48 hours of blood feeding, a UA team of biochemists found.

Mosquitoes die soon after a blood meal if certain protein components are experimentally disrupted, a team of biochemists at the University of Arizona has discovered.

The approach could be used as an additional strategy in the worldwide effort to curb mosquito-borne diseases like dengue fever, yellow fever and malaria.

When the researchers blocked a cellular process known as vesicle transport, on which the mosquitoes rely to release digestive enzymes into the gut among other functions, it caused the affected animals to die within two days of blood feeding.

"The idea behind our research is this: If we can kill the mosquito after she bites the first person, she won't be able to bite and infect a second," said Roger Miesfeld, a professor in the UA's department of chemistry and biochemistry, who led the research project.

"We do this by blocking the mosquito's ability to digest its blood meal," said Miesfeld, also a member of the UA's BIO5 Institute.

The research team's findings were recently published in Proceedings of the National Academy of Sciences, or PNAS.

"During a blood meal, a mosquito ingests its body weight in blood. It's the equivalent of a 125-pound human consuming a 12-gallon smoothie made from 25 pounds of hamburger meat plus a half pound of butter and two tablespoons of sugar," Miesfeld said.

Miesfeld and the research team had previously shown that the blood feeding process poses a huge metabolic challenge to the female mosquito.

"By disrupting any number of biochemical processes needed to fully utilize the blood meal, the mosquito has a very difficult time completing the egg production cycle," he added.

To maintain their bodily needs, the insects rely on sugary nectar from flowers, but when the time to make eggs comes, they need large amounts of protein. Only female mosquitoes bite and feed on the blood of humans or warm-blooded animals.

If a mosquito finds enough victims to bite and avoids being squashed, it can live as long as three weeks. During that time, it may lay up to five clutches of more than 100 eggs each.

For their studies, the team used mosquitoes of the species Aedes aegypti, which originally hails from the sub-tropical and tropical regions of Africa. These mosquitoes are now found in many parts of the world and are particularly abundant in towns and cities where the climate is warm and water is plentiful. A. aegypti mosquitoes buzz about at dawn and dusk in search of their next blood meal, preferably from people's ankles.

A. aegypti mosquitoes are the main vector for dengue fever, now the most common viral disease transmitted by mosquitoes. Dengue fever has made a comeback especially in subtropical and tropical regions due to the geographical spread of the mosquitoes and the virus. Four strains, or serotypes, of disease-causing dengue viruses are known.

When infected for the first time, most people suffer through a bout of high and painful fever, but usually the illness is not life threatening and renders them immune to that particular strain of dengue virus. However, a subsequent infection with any of the other dengue virus strains often triggers an all-out immune response that leads to a much more severe form, called dengue hemorrhagic fever, which can be fatal.

Miesfeld said most mosquito-borne pathogens are not passed down from the female mosquito to her offspring, but instead picked up by the mosquitoes when they bite an infected human.

In the case of A. aegypti mosquitoes, the pathogen is often dengue or yellow fever viruses, whereas the Anopheles gambiae mosquito, which is found in many parts of Africa, transmits the more deadly malaria parasite. Miesfeld further explained that malaria and dengue pathogens take about 10 to 12 days to complete their life cycle within the mosquito before they can be transmitted to humans through blood feeding.

"The most dangerous mosquitoes are the older ones," Miesfeld said.

His team used a technique called RNAi to specifically target genes that are required for the digestion process. The researchers homed in on a protein complex called COPI, which stands for coatomer protein 1.

COPI consists of several subunits that together make up the envelope of the vesicles on which the cell relies for internal transport and for secretion of enzymes into the gut.

When a female mosquito takes a blood meal, the cells lining its gut secrete enzymes to break down the blood proteins. The secretion process involves packaging the enzymes in small droplets called vesicles that the cells then release into the gut.

"We thought, 'Why don't we knock out the whole process that allows the proteases to be secreted?' That's where we got this amazing result," Miesfeld said. "Not only did we eliminate her ability to secrete anything, we were surprised to find that about 90 percent of those mosquitoes died within two days after feeding on blood."

The COPI RNAi does not have an adverse effect on the female mosquitoes for 10 days – unless they decide to take a blood meal.

"When she does, all hell starts breaking loose, biochemically and anatomically speaking," Miesfeld said.

"What we think is happening is that if there is protein in her gut, it induces the secretory machinery. It initiates this huge secretion process but it's defective and causes cells to disintegrate," he added. "The whole lining of the gut starts to fall apart, allowing the blood to seep into her body."

In looking at the potential causes, Miesfeld said his team found that removing any one of the COPI subunits causes the whole complex to fall apart.

"Based on what we know about the COPI system, it shouldn't have that strong of an effect," he said.

"As scientists have been knocking out COPI to learn more about its function over the past couple of years, they have achieved some interesting results," Miesfeld added. "Together with our findings they suggest that COPI does a lot more than what people thought."

Miesfeld envisions that the ultimate goal of this research is to develop a small molecule that works in place of injected RNAi and acts as a specific inhibitor of the secretion process.

For this to be an effective mosquito-selective insecticide, it must not have any effect on humans.

The simplest use would be to soak it into mosquito nets like currently available insecticides that target the mosquito's nervous system. A slightly more complex strategy would be to include it in a pill that humans take, so the mosquitoes pick up the inhibitor drug when they bite. As part of this strategy, the researchers are looking for genes that are unique to the mosquito and could serve as targets without affecting human health.

To explain, Miesfeld said to imagine a village in the tropics during a rainy season.

"As the mosquitoes hatch in large numbers, the whole population of villagers is ready," he explained. "As soon as the insects start biting, they take up the inhibitor and before they can bite again, they die in large numbers. Over a few seasons, that can make a difference."

Miesfeld added it is unlikely there would ever be a silver bullet eliminating mosquito-transmitted diseases like malaria and dengue fever altogether.

"One potential issue with our strategy is genetic changes rendering the mosquitoes immune over time," Miesfeld said. "Many approaches from different angles will be necessary, and ours could be another tool in the toolbox."

LINKS:

The PNAS paper, Defects in coatomer protein I (COPI) transport cause blood feeding-induced mortality in Yellow Fever mosquitoes, can be viewed at http://www.pnas.org/content/108/24/E211/1.full

CONTACTS:

Roger L. Miesfeld
Department of Chemistry & Biochemistry
The University of Arizona
520-626-2343
rlm@email.arizona.edu
Daniel Stolte
University Communications
The University of Arizona
520-626-4402
stolte@email.arizona.edu

Daniel Stolte | The University of Arizona
Further information:
http://www..arizona.edu

More articles from Life Sciences:

nachricht Cryo-electron microscopy achieves unprecedented resolution using new computational methods
24.03.2017 | DOE/Lawrence Berkeley National Laboratory

nachricht How cheetahs stay fit and healthy
24.03.2017 | Forschungsverbund Berlin e.V.

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>