Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Powerful drug's surprising, simple method could lead to better treatments

17.01.2012
With one simple experiment, University of Illinois chemists have debunked a widely held misconception about an often-prescribed drug.

Led by chemistry professor and Howard Hughes Medical Institute early career scientist Martin Burke, the researchers demonstrated that the top drug for treating systemic fungal infections works by simply binding to a lipid molecule essential to yeast’s physiology, a finding that could change the direction of drug development endeavors and could lead to better treatment not only for microbial infections but also for diseases caused by ion channel deficiencies.

“Dr. Burke’s elegant approach to synthesizing amphotericin B, which has been used extensively as an antifungal for more than 50 years, has now allowed him to expose its elusive mode of action,” said Miles Fabian, who oversees medicinal chemistry research at the National Institute of General Medical Sciences. The institute is part of the National Institutes of Health, which supported the work. “This work opens up avenues for improving upon current antifungals and developing novel approaches for the discovery of new agents.”

Systemic fungal infections are a problem worldwide and affect patients whose immune systems have been compromised, such as the elderly, patients treated with chemotherapy or dialysis, and those with HIV or other immune disorders. A drug called amphotericin (pronounced AM-foe-TARE-uh-sin) has been medicine’s best defense against fungal infections since its discovery in the 1950s. It effectively kills a broad spectrum of pathogenic fungi and yeast, and has eluded the resistance that has dogged other antibiotics despite its long history of use.

The downside? Amphotericin is highly toxic.
“When I was in my medical rotations, we called it ‘ampho-terrible,’ because it’s an awful medicine for patients,” said Burke, who has an M.D. in addition to a Ph.D. “But its capacity to form ion channels is fascinating. So my group asked, could we make it a better drug by making a derivative that’s less toxic but still powerful? And what could it teach us about avoiding resistance in clinical medicine and possibly even replacing missing ion channels with small molecules? All of this depends upon understanding how it works, but up until now, it’s been very enigmatic.”

While amphotericin’s efficacy is clear, the reasons for its remarkable infection-fighting ability remained uncertain. Doctors and researchers do know that amphotericin creates ion channels that permeate the cell membrane. Physicians have long assumed that this was the mechanism that killed the infection, and possibly the patient’s cells as well. This widely accepted dogma appears in many scientific publications and textbooks.

However, several studies have shown that channel formation alone may not be the killing stroke. In fact, as Burke’s group discovered, the mechanism is much simpler.

Amphotericin binds to a lipid molecule called ergosterol, prevalent in fungus and yeast cells, as the first step in forming the complexes that make ion channels. But Burke’s group found that, to kill a cell, the drug doesn’t need to create ion channels at all – it simply needs to bind up the cell’s ergosterol.

Burke’s group produced a derivative of amphotericin using a molecule synthesis method Burke pioneered called iterative cross-coupling (ICC), a way of building designer molecules using simple chemical “building blocks” called MIDA boronates joined together by one simple reaction. They created a derivative that could bind ergosterol but could not form ion channels, and tested it against the original amphotericin.

If the widely accepted model was true, and ion channel formation was the drug’s primary antifungal action, then the derivative would not be able to wipe out a yeast colony. But the ergosterol-binding, non-channel-forming derivative was almost equally potent to natural amphotericin against both of the yeast cell lines the researchers tested, once of which is highly pathogenic in humans. The researchers detailed their findings in the journal Proceedings of the National Academy of Sciences.

“The results are all consistent with the same conclusion: In contrast to half a century of prior study and the textbook-classic model, amphotericin kills yeast by simply binding ergosterol,” Burke said.

“The beauty is, because we now know this is the key mechanism, we can focus squarely on that goal. Now we can start to think about drug discovery programs targeting lipid binding.”

The researchers currently are working to synthesize a derivative that will bind to ergosterol in yeast cells, but will not bind to cholesterol in human cells, to see if that could kill an infection without harming the patient. They also hope to explore other derivatives that would target lipids in fungi, bacteria and other microbes that are not present in human cells. Attacking these lipids could be a therapeutic strategy that may defy resistance.

In addition to exploiting amphotericin’s lipid-binding properties for antimicrobial drugs, Burke and his group hope to harness its channel-creating ability to develop treatments for conditions caused by ion-channel deficiencies; for example, cystic fibrosis. These new findings suggest that the ion-channel mechanism could be decoupled from the cell-killing mechanism, thus enabling development of derivatives that could serve as “molecular prosthetics,” replacing missing proteins in cell membranes with small-molecule surrogates.

“Now we have a road map to take ampho-terrible and turn it into ampho-terrific,” Burke said.

Editor’s notes: To reach Martin Burke, call (217)244-8726; email burke@scs.illinois.edu.

The paper, “Amphotericin Primarily Kills Yeast by Simply Binding Ergosterol,” is available from the News Bureau or PNAS.

Liz Ahlberg | University of Illinois
Further information:
http://www.illinois.edu

More articles from Life Sciences:

nachricht Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery
20.01.2017 | GSI Helmholtzzentrum für Schwerionenforschung GmbH

nachricht Seeking structure with metagenome sequences
20.01.2017 | DOE/Joint Genome Institute

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

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...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | 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

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>