Tracking Protein Function in Living Cells


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A team of Stanford bioengineers led by Assistant Professor Markus Covert has invented a way to observe and report on the behavior of kinase proteins. Image: Steve Fisch / Stanford.edu

Proteins are molecules in the human body that keep our cellular functions running smoothly, which is essential for good health. When proteins are not functioning correctly, cellular reactions begin to break down and can lead to illness.

Good health relies on accurate communication among cells—delivering the right messages at the right time to the right cells. The kinase family of proteins is a critical group because kinase proteins deliver signals that regulate and orchestrate the actions of other proteins. Proper kinase activity maintains health; irregular kinase activity, over time, is linked to cancer and other diseases.

Because kinase proteins play such an important role in human health, drug-development companies want to create drugs that either boost or suppress kinase activity. The current standard approach for checking to see how a drug is affecting a kinase protein is to collect and pulverize a cell sample, extract the relevant kinase, and measure its levels. This is a time-consuming process that drives up costs.

This problem may soon be eliminated by a new technology developed by Stanford University bioengineers that allows scientists to observe the behavior of these signaling proteins as they “go about their business” inside living cells. Researchers can observe, in real time, how these kinase proteins regulate health or cause disease, with no extraction, pulverizing, or analysis required.

"We’ve been able to observe multiple kinases functioning in living cells, which is something no one else has ever seen," states Markus Covert, an associate professor of bioengineering and leader of the research team.

The circle inside each cell is its nucleus. When bioengineers stimulate the cells to activate the kinases, the nuclear circles darken. Image: Sergi Regot, Covert Lab

Signaling System

Protein signaling is a complex chemical event. The protein consists of a long chain of atoms. Upon arriving at its destination, the kinase delivers its message, instructing the protein to perform a function at a particular location within the cell. If, however, the message is scrambled, cells will function abnormally—for example, with cancer, the communication breakdown errantly instructs cells to multiply.

To track the activity of this signaling system in living cells, kinase substrates were engineered and tagged with a fluorescent protein so they could be tracked inside the cell with regular microscopy tools. Covert’s team spent more than a year perfecting this technique. So far they have successfully tracked five kinases and see no reason why the technology cannot be extended to other kinases, making it a highly useful tool in drug development that can speed up the rate of discovery.

Faster Drug Development

This new technique will likely allow researchers to observe and compare kinase activity in healthy versus diseased cells, followed by introducing an experimental drug to see how it affects the living cells.

“Currently, most of the methods used to interrogate cell physiology depend on killing the cells at a particular time, and then going through time-consuming and expensive procedures to assess protein function,” says post-doc student and team member Sergi Regot. “With our method, we can observe cells under the microscope and analyze the function of key effectors, while things are happening.”

The Stanford researchers believe their new process will speed up the development of new drugs aimed at cancers and other conditions linked to kinase irregularities. They also hope it will expand research possibilities in the field of live, single-cell signaling dynamics.

‘Hopefully researchers will now be able to analyze multiple cell parameters simultaneously and therefore generate more precise pictures of how cells operate,” adds Regot. “For pharmaceutical companies, this represents a novel, biologically relevant way to test the effects of new drugs. Over the long term, I believe this approach will be implemented to rapidly assess heterogeneity, drug sensitivity, and other parameters in patient cells that can be used to treat diseases such as cancer, in a personalized way.”

Mark Crawford is an independent writer.

We've been able to observe multiple kinases functioning in living cells, which is something no one else has ever seen.

Prof. Markus Covert,
Stanford University

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November 2014

by Mark Crawford, ASME.org