Dancing cells at a laser show: UA scientists study membrane proteins to benefit drug manufacturing
Cells have been around since the first living organisms developed, and after many eons and advancements in scientific technology, there’s still much we don’t know about them—especially when it comes to their reactions to pharmaceutical drugs.
But Adam Smith, Ph.D. is determined to figure it out. And watching how cells react to his laser show might provide the answers.
Smith, an associate professor of chemistry at The University of Akron (UA), is analyzing special cell membrane proteins called dopamine and adenosine receptors. He’s determining how these receptors move and interact with each other and other parts of the body to produce the intended effects of pharmaceutical drugs.
The reason? Smith says there’s a structural puzzle that scientists have been working on for several years: Can dopamine and adenosine receptors pair up and form one structure? If so, then drugs can be designed that co-target the receptors, potentially leading to drugs that could even treat addiction.
“Whether or not and how these unique protein structures form will influence how future pharmaceutical drugs will be manufactured,” says Smith. “Drug design is getting trickier and trickier to do. It is getting more expensive, and the subtleties of biology make it more complicated. The findings from our research will provide drug manufacturers with actionable information.”
If it’s discovered that the proteins do not form a single structure, Smith says that’s still an achievement. “If they don’t pair, then we go in a different direction and scientists have direct evidence that they do not pair. So even a ‘no’ would be helpful in moving forward in drug development.”
Lasers illuminate the answers
To tell whether two cell membrane proteins can physically bind together requires the use of a unique form of microscopy with lasers and plenty of darkness.
Smith is using a specialized method called Pulsed Interleaved Excitation-Fluorescence Cross-Correlation Spectroscopy (PIE-FCCS), which requires lasers for illumination to show if and how different particles during molecular interactions can pair up.
“The technology is quite unique,” says Smith. “Just a handful of labs around the world have microscopes with this capability. Other techniques don’t have the required resolution, or they don’t work at typical protein levels in living cells. Our method is more physiologically relevant and can view proteins in their natural environment.”
When examining the membrane proteins, Smith and his team isolate a single microscopic cell, then use pulsed lasers to look at an even smaller region of that cell. The lasers light up proteins on the surface of the cell which enables a researcher to watch how the proteins interact with each other and, more importantly, whether they pair up.
"It’s like if you were to envision a middle school dance … and you can’t see the whole dance but if you put a spotlight in the middle of the room and monitor who is dancing with whom, and who is off on their own,” says Grant Gilmore, a fourth-year biochemistry doctoral student assisting Smith on this project.
On a typical day in the lab, Gilmore will load a petri dish on the microscope and focus on a single cell surface. Because the individual proteins are so small, they are labeled with a fluorescent dye. This allows Gilmore and Smith to track the proteins and determine if they form pairs. If two different colored proteins pair up, it’s a success. Before examining the cells, Gilmore ensures the lab area is enclosed in a large black curtain to block out any unwanted light that can disrupt the process.
Gilmore says the average-size protein he and Smith analyze is about 2 nanometers in size. To compare, a typical human hair is about 80,000 nanometers in size.
“In each cell is a bunch of proteins — thousands doing different functions,” says Gilmore.
Smith was awarded a $550,000 contract with the New York State Psychiatric Institute at Columbia University Medical College, sponsored by the National Institute of Mental Health, to conduct this fundamental research on the molecular mechanisms of dopamine receptors. The team’s next steps are to carry out the dopamine receptor measurements and then move to several other neurotransmitter receptors. Afterward, Smith and Gilmore will begin testing several new bivalent drugs, which can target receptor pairs in a systematic way.
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