Biochemical Cell Signals Quantified For First Time

Just as cell phones and computers transmit data through electronic networks, the cells of your body send and receive chemical messages through molecular pathways. The term "cell signaling" was coined more than 30 years ago to describe this process. Now, for the first time, scientists have quantified the data capacity of a biochemical signaling pathway and found a surprise -- it's way lower than even an old-fashioned, dial-up modem.

"This key biochemical pathway is involved in complex functions but can transmit less than one bit -- the smallest unit of information in computing," says Ilya Nemenman, an associate professor of physics and biology at Emory University. "It's a simple result, but it changes our view of how cells access chemical data."

The journal Science is publishing the discovery by Nemenman and colleagues from Johns Hopkins University, including Andre Levchenko, Raymond Cheong, Alex Rhee and Chiaochun Joanne Wang.

During the 1980s, cell biologists began identifying key signaling pathways such as nuclear factor kappa B (NF-kB), known to control the expression of genes in response to everything from invading pathogens to cancer. But the amount of information carried by chemical messengers along these pathways has remained a mystery.

"Without quantifying the signal, using math and computer analysis to attach a number to how much information is getting transmitted, you have a drastically incomplete picture of what's going on," says Nemenman, a theoretical biophysicist.

He and Levchenko, a biomedical engineer, began discussing the problem back in 2007 after they met at a conference.