A team of researchers from Penn State University has developed a new way of evaluating drug safety which they say is faster than conventional methods.
Scientists typically rely on detecting cell death when evaluating drug safety. The method developed by the team uses a fluorescent sensor that is turned on in the cell when proteins aggregate – which is an early sign of cellular stress. This new method has the potential to be used in detecting protein aggregates caused by toxins and disease such as Alzheimer’s and Parkinson’s, according to a report filed by Sam Sholtis from Penn States Eberly College of Science.
The new system was described in a paper published in the journal Angewandte Chemie International Edition.
This is the first time that researchers used a fluorescent sensor that is not turned on until the misfolded proteins begin to aggregate, according to Xin Zhang, assistant professor of chemistry and of biochemistry and molecular biology at Penn State and the senior author of the paper.
Protein stress can be caused by heat, toxins, bacterial infections, cancer, and even aging can cause proteins to misfold and form aggregates in cells.
“Drug-induced protein stress in cells is a key factor in determining drug safety,” he said. “Drugs can cause proteins — which are long strings of amino acids that need to be precisely folded to function properly — to misfold and clump together into aggregates that can eventually kill the cell.”
The new method allows researchers to quantitatively detect protein stress in cells at much earlier stages. This means researchers can begin to study the mechanisms that cells use to combat this stress and develop compounds that can enhance the cell’s ability to handle protein stress, said Zhang.
The team developed a system that can detect these aggregates at very early stages.
The researchers designed an unstable protein — called AgHalo.
The protein is tagged with a special fluorescent dye which becomes active in a hydrophobic environment. Hydrophobic portions of proteins are usually buried deep in the structure of a properly-folded protein since the cell is mostly in water.
When the protein begins to misfold and aggregate the dye can interact with the hydrophobic portions of the protein and begin to fluoresce.
Conventional systems used sensors that were always on. They could only detect protein stress when misfolded proteins aggregated and formed brighter spots of fluorescence that could be detected under a microscope.
The level of fluorescence detected by the new method correlates with the amount of protein aggregation in the cell, according to Yu Liu, a postdoctoral researcher at Penn State and the first author of the paper. She said this enables researchers to quantify the level of cellular stress.
“…because our method measures the level of fluorescence, rather than having to identify the fluorescence under a microscope, it can be done using more accessible technology, like plate readers, and it is much more high-throughput,” she said.
Aside from Zhang and Liu, the research team includes Matthew Fares, Noah P. Dunham, Zi Gao, Kun Miao, Xuenyuan Jiang, Samuel S. Bollinger, and Amie K Boal at Penn State. Their research was funded by the Burroughs Wellcome Fund Career Award at the Scientific Interface, the Paul Berg Early Career Professorship, the Lloyd and Dottie Huck Early Career Award, the U.S. National Institutes of Health, and the Searle Scholars Program. Additional support was provided by the Huck Institutes of the Life Sciences at Penn State.