Secreting and Sensing the Same Molecule Allows Cells to Achieve Versatile Social Behaviors

Abstract

The Message in the Medium: What is the point of autocrine signaling in which a cell produces a signal that activates receptors on its own cell surface? An internal signal seems simpler, unless there is value to allowing neighboring cells to know what other cells are up to. Youk and Lim (p. 10.1126/science.1242782 ; see the Perspective by Lee and You ) explored the broad range of signaling outcomes that can result in a system in which some yeast cells could secrete and sense a signal whereas others could only sense signals from their neighbors. The cells were engineered so that the response of the two cell types could be distinguished from one another. Experiments and mathematical modeling showed that depending on how circuits were constructed—for example, how much receptor was present, how the signal molecule was degraded, the presence of feedback, the density of the cell culture, and so on—a range of behaviors was possible: Some conditions favored activation of one type of cell over another. Others altered the timing or consistency of the response within a population. The principles revealed could also be used in other biological contexts or in the design of synthetic biological cell systems with desired regulatory properties.