Study reveals workings of promising Copper deficiency drug

We think of copper as the stuff of pennies and fancy kitchen pans, but it’s also an essential nutrient. Most healthy people get enough of it from foods like nuts, meats and fish. But when the body is unable to absorb copper because of rare genetic disorders like Menkes disease, the consequences can be devastating. Most babies born with Menkes, for example, do not survive more than three to four years.

A new study offers insights on a promising drug for treating copper deficiency with help from the bright X-ray beams at the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science user facility at DOE’s Argonne National Laboratory. Vishal M. Gohil, an associate professor in the Department of Biochemistry and Biophysics at Texas A&M University, led the work, which was conducted in part by scientists at Argonne. Researchers at the University of Houston, University of Missouri, and Oregon Health and Sciences University also contributed.

“Right now, there is no effective drug for copper deficiency diseases. We know that elesclomol binds with copper very tightly outside the cell. Before this paper, we did not know how copper is released from the drug once inside the cell.” — Mohammad Zulkifli, Texas A&M University 

People need just the right balance of copper to thrive. Too little compromises cells’ ability to make energy, transport iron and perform other life-supporting functions. Too much can be toxic. The drug elesclomol was initially developed to treat cancer by killing rogue cells with an excess of copper. It failed clinical trials for that purpose, but the drug offers the tantalizing prospect of being repurposed to feed cells that cannot absorb copper on their own.

“Right now, there is no effective drug for copper deficiency diseases,” said Mohammad Zulkifli, a research scientist at Texas A&M University and the first author of the paper, which was published in the Proceedings of the National Academy of Sciences. ​“We know that elesclomol binds with copper very tightly outside the cell. Before this paper, we did not know how copper is released from the drug once inside the cell.”

Gohil Lab at Texas A&M University had shown in earlier work that elesclomol could carry copper into cells and deliver it to copper-dependent enzymes. But to adapt the drug to copper deficiency disorders, they needed a better understanding of how it worked.

At the APS, researchers used a technique called X-ray fluorescence microscopy, which detects the ​“glow” given off by copper and other metals when they are exposed to X-rays. As the sample is hit by the X-ray beam, it emits photons, or particles of light, with energies that are distinct to the elements present in the sample.

“These immediate X-ray photons are the fingerprints of elements,” said Luxi Li, an Argonne physicist and study co-author. ​“If we measure the energy and intensity of the emitted photons, then we’re able to quantify how much of a specific element is inside the sample.”

Without X-ray fluorescence microscopy, researchers need to inject additives that serve as ​“labels” within cells to create a visible contrast that highlights different molecules, said Si Chen, an Argonne physicist and study coauthor. This can lead to damage within the cell that makes it harder to study. 

“The big difference with X-ray fluorescence is that it is a label-free technique,” Chen said. ​“We can look at the cell directly and without any harsh chemical treatment, then map the natural distributions of elements inside.”

The new study found that a protein called ferredoxin 1 (FDX1) offers the key to unlock the copper from elesclomol. The protein resides inside mitochondria, which are the energy-generating powerhouses of human cells.

The researchers examined cell samples at two APS beamlines — locations where the X-rays are tuned for specific purposes. The microprobe at beamline 2-ID-D offered the ability to see samples at a resolution of 300 nanometers. (For comparison, a sheet of paper is about 100,000 nanometers thick.) Using the Bionanoprobe at beamline 2-ID-D, they were able to examine a selection of samples in even finer detail at 80 nanometers.

The imaging offered a second, unexpected revelation. While FDX1 proved to be a key protein in releasing copper to mitochondria in cells, the copper glow could be seen outside mitochondria, suggesting that elesclomol was delivering copper to other parts of the cells. That’s a welcome prospect, since the need for copper isn’t confined to mitochondria.

“The APS X-rays helped us to see copper accumulating all over the cells,” Zulkifli said. ​“However, what releases copper outside the mitochondria? We do not know. So we’ll be focusing on what is causing that release in future work.”

The APS is currently undergoing an upgrade that will lend studies like this one with even more speed and detail. ​“Data that took one hour to collect at the current APS will take only a few minutes to finish after the upgrade,” Li said.

The Bionanoprobe at the future APS will also see a dramatic improvement in resolution, zooming from 80 nanometers down to 10 nanometers, a scale only about as big as a few dozen molecules of water. That will allow scientists to examine mitochondria, for example, even more closely.

“For research like this on the inner workings of cells, that kind of improvement in resolution will revolutionize the study,” Chen said.

The study was supported by the National Institutes of Health, the National Cancer Institute, the National Institute of Diabetes and Digestive and Kidney Diseases, and DOE’s Office of Basic Energy Sciences.

About the Advanced Photon Source

The U. S. Department of Energy Office of Science’s Advanced Photon Source (APS) at Argonne National Laboratory is one of the world’s most productive X-ray light source facilities. The APS provides high-brightness X-ray beams to a diverse community of researchers in materials science, chemistry, condensed matter physics, the life and environmental sciences, and applied research. These X-rays are ideally suited for explorations of materials and biological structures; elemental distribution; chemical, magnetic, electronic states; and a wide range of technologically important engineering systems from batteries to fuel injector sprays, all of which are the foundations of our nation’s economic, technological, and physical well-being. Each year, more than 5,000 researchers use the APS to produce over 2,000 publications detailing impactful discoveries, and solve more vital biological protein structures than users of any other X-ray light source research facility. APS scientists and engineers innovate technology that is at the heart of advancing accelerator and light-source operations. This includes the insertion devices that produce extreme-brightness X-rays prized by researchers, lenses that focus the X-rays down to a few nanometers, instrumentation that maximizes the way the X-rays interact with samples being studied, and software that gathers and manages the massive quantity of data resulting from discovery research at the APS.

This research used resources of the Advanced Photon Source, a U.S. DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science.

The U.S. Department of Energy’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit https://​ener​gy​.gov/​s​c​ience.