News Release

Not only did researchers at UCSD and UCI visualize a mechanically induced signal traverse human cells, but they also showed that actin filaments and microtubules are involved in the process.

San Diego, CA, April 20, 2005 --Researchers at UCSD and UC Irvine have captured on video for the first time chemical signals that traverse human cells in response to tiny mechanical jabs, like waves spreading from pebbles tossed into a pond. The scientists released the videos and technical details that explain how the visualization effect was created as part of a paper published in the April 21 issue of Nature.

The researchers working at the UCSD Jacobs School of Engineering’s Department of Bioengineering developed a novel molecular “reporter” system, which allowed the dynamic visualization of the activation of an important protein called Src. Peter Yingxiao Wang, lead author of the paper and a post-doctoral researcher in UCSD’s Jacobs School of Engineering spent two years designing the reporter molecules to light up selectively only when Src was activated, and not other proteins.

Wang and his co-workers first demonstrated that the novel system was effective in

A narrated video explains how human cells reacted to prodding by a laser "tweezer." Length: 3:14

The team of researchers included Michael W. Berns (left), Shu Chien, Elliot L. Botvinick, and Peter Yingxiao Wang.

Src is one of a large group of enzymes called kinases that attach a phosphate molecule to one or more target proteins in the cell. This phosphorylation reaction typically switches the target protein from inactive to active status. Many diseases can result either when a kinase gene is mutated and can’t properly phosphorylate its targets, or when a normal kinase becomes overactive or not sufficiently active. Indeed, Src has been shown to play a key role in cell growth and development, and in the genesis of cancer, atherosclerosis, and many other disease conditions.

“This study amounts to a proof of principle that if we can visualize the activation of one kinase, we can do the same for many others using the same approach,” said Chien, the senior author of the paper. Not only are those additional studies expected to reveal temporal and spatial patterns of kinase activation, but Chien also predicted that there will be practical spin offs.

For example, cells usually tightly control the activity of Src, but in certain cancers its activity is abnormality high. “We think that our ability to measure Src activity with this new visualization technique would be useful as a diagnostic test for many cancers,” said Chien. The William J. von Liebig Center for Entrepreneurism and Technology Advancement at UCSD’s Jacobs School has provided Chien and Wang with funding to commercialize the new visualization technology as a cancer-detection tool.

The researchers showed that actin filaments and microtubules, structural elements that traverse cells like the ribs of an umbrella, could function as conduits for the spread of biochemical signals. Indeed, when Wang disrupted either actin filaments or microtubules in his test cells, the activation signal no longer spread across the cell. These results suggest that the activation of Src traverses these filamentous structures.

In addition to Chien, Wang, Tsien, Berns, and Botvinick, the other authors of the paper are Yihua Zhao and Shunichi Usami of the UCSD Department of Bioengineering. The research was supported by grants from the National Institutes of Health, the Howard Hughes Medical Institute, the Air Force Office of Scientific Research, the Arnold and Mabel Beckman Foundation, the Alliance for Cellular Signaling, and the Whitaker Foundation.

Yingxiao Wang, Elliot L. Botvinick, Yihua Zhao, Michael W. Berns, Shunichi Usami, Roger Y. Tsien and Shu Chien, “Visualizing the mechanical activation of Src” (2005). Nature. 434 (7036), pp 941-1052.