Big Ideas in Cell Communication

The article titled “Cell Communication: The Inside Story” by John D. Scott and Tony Pawson (2006) is a detailed look at both the history and a general overview of how communication occurs within the body’s cells. The transmission of signals within a cell is a process that starts with so-called messenger molecules, which can include certain enzymes and hormones, which lock into or dock onto receptor molecules on the surface of cells. When this occurs, the cell’s receptor molecule begins a reaction that activates particular responses in molecules along the receptor’s signaling pathway. For instance, this may include the activation of a particular gene, which in turn, may begin to encode a particular protein and secrete said protein. This is typically what occurs with a genetically transmitted molecular disease through an individuals' hemoglobin.

While this process may seem simple enough, it is necessary to begin with this general overview of cell communication. In actuality, very little has been known about how exactly messenger molecules seek out and determine the exact location of receptor molecules. In fact, many recent discoveries have helped to solve some of this mystery. Scott and Pawson (2006) explain that by the early 1980s, Joseph Schlessinger of New York University helped to discover that communication within the cell was helped along by the structure and function of the modular design of signaling molecules. Schlessinger discovered that this modular design meant that signaling molecules are built from smaller domains, or modules, each of which functions in a particular task (Scott and Pawson, 2006). For instance, tyrosine kinases are a type of receptor molecule that, when docked by a messenger molecule, will add additional modules onto themselves, such as phosphate groups to tyrosine or amino acids, onto their tails in the cell’s cytoplasm. From here, SH2 modules will hook onto the receptor molecule’s altered tail, which allows for the entire signaling process to pass a message along to the cell.

This modular design in the signaling process also has important payoffs in the evolution of cells. Scott and Pawson (2006) explain that the ease of forming new molecule combinations by mixing and matching the modular building blocks has been important for evolutionary development in cells. Without this ability, entirely new molecules would have to be “invented”, which would be a longer, slower process in cell evolution. Additionally, Scott and Pawson describe that when a single new module does come about via evolutionary processes, it can add a very large number of new functions to the cell, because it can be combined with existing modules in a wide variety of ways (2006).

Another important aspect of cell communication is the process of information flow and storage, which has been found to be improved significantly by so-called scaffolding proteins. The proteins act literally as construction scaffolding, in which they hold a number of other proteins together in a kind of chain. This allows more than one signaling molecule to simultaneously effect a similar change, and as such, scaffolding proteins are often found throughout the pre-frontal cortex of the brain (Scott and Pawson, 2006). Additionally, Scott and Pawson (2006) explain that a scaffolding protein called InaD is important for cell communication in the eyes of fruit flies. In this process, the InaD scaffold links together an ion channel in the cell with a nearby light receptor and an enzyme used for opening the channel. This way, when light hits the receptor, the scaffolding protein ensures that all components are in place to allow for the completion of the signaling process to occur.

As we have seen, the modular design of the structure and function of signaling proteins allow for certain evolutionary advantages in cell communication. Additionally, scaffolding proteins are responsible for aiding in the information flow and storage within the cell. The three big ideas of structure and function, evolution, and information flow and storage are thus covered.

Reference

Scott, J., & Pawson, T. (2006). Cell communication: The inside story. Evolution a Scientific American reader. (pp. 72-79). Chicago: University of Chicago Press.