Model to explain cellular sensor organization
August 15, 2014 § Leave a comment
Cell-surface receptors are like radiowave antennae: They pick up signals to send them forward to the appropriate cellular equipment that process the information in the signals. But how do cells know where to best position receptors to cleanly and efficiently pick up the numerous signals coming at them?
In a paper recently published in the Proceedings in the National Academy of Sciences, Garud Iyengar at the Columbia University and Madan Rao at the Raman Research Institute and the National Centre for Biological Sciences in India came up with a theoretical model inspired by observations made in cell biology. They noted that different kinds of cell-surface molecules involved in sensing, such as receptors, share a common organizational motif. Sensors are either organized as dynamic clusters or as monomers. What was the organizing principle?
Iyengar and Rao used information theory to model how cells come up with an organizing principle for cell-surface receptors. In their model, cells must balance two contradictory needs. They must cluster some types of receptors at a given location to reduce the statistical `reading’ error but spread out other types of receptors across the cell surface. To figure out which ones to cluster and which ones to keep as monomers, cells assess the number of receptors they have at their disposal, how well the receptors function as sensors and how long it takes for the receptors to pick up signals in space and time.
The model by Iyengar and Rao predicts that receptors that bind to more than one ligand, and therefore are more susceptible to inadvertently picking up wrong ligands, are more likely to be clustered; receptors that selectively bind to one or two ligands roam freely on the cell surface.
Rao and Iyengar explains that the model doesn’t apply to just cellular organization of receptors. Rao says, “This research may have implications for many different contexts, from ad-hoc sensor networks to immunology.” The investigators point out that the distributions of integrins and E-cadherins in mammalian cells or the organization of receptors on bacteria for chemosensing may follow this model.