Our topic this week was the MAPK pathways. Quite simply, the MAPK pathways are a series of signalling molecules that carry messages from outside sources into the cell’s nucleus. This signal is carried from a receptor on the surface of the cell activating a signalling molecule. After that signalling molecule is activated, a signal cascade occurs. That is to say that a series of molecules whose purpose is to activate the next molecule in a chain of events are all activated. This carries the signal to the nucleus where it can have diverse effects from killing the cell to making the cell divide.
One apparent problem with these pathways is that the same molecule can occur in several pathways that lead to very dissimilar results. One can only imagine how disastrous it would be to promote cell death whenever the cell was supposed to divide and vice versa. Within our cells, however, there is little to no crosstalk between the pathways in spite of the same molecules being used. The reason for this is that in many cases, the signalling molecules are bound to scaffold proteins that keep them localized in one area and direct their signal to specific other molecules.
Although scaffold proteins do not play an active role in carrying the cell signal, by coordinating which molecules receive it next and where in the cell that signal goes next, they are one of the most important parts. They are analogous to the designer who decides how an assembly line is to be set up: although the designer doesn’t actually put any of the pieces together, they in effect decide what is going to be made through their organization.