Information Cascade and Push-pull Control in cells
Apparently, we like to fit mathematical models to the nature. It is much easier for us to understand, to analyze, and to predict systems or phenomenons with a good model. In the modern days, we verify the correctness of models by running simulations. If the simulation outcome is identical, or very close to, assuming that there is no perfect model, we will adopt the model for various purposes. From Economics to Information Science, uncountable models have been set up to mimic the way human beings interact. Modelling not only applies to human interaction, but also, more interestingly, applies to cell interaction. In this post, I will use my imagination, together with a new study in cell biology, to conjure some information cascading models in the cell “community”.
In yeast, when information is transmitted through the pheromone-response cascade, each protein involved activates its downstream partner. This can be seen as a network of cells, where information cascading takes place, just like how information cascading happens for people, but through a different mechanism. It is the mechanism that is interesting.
In the past, negative feedback control was thought to be the mechanism that information cascading occurs. Negative feedback is where a system tries to adjust itself back when a disturbance is introduced. For example, when you are taking a shower and the water gets too hot, you will turn the nob to make the water cooler. When the water gets too cold, you will again turn the nob to adjust the temperature back up. In cells, it can be seen as the protein change in the different cells. In cell terms, the change in the protein of a cell will trigger other cells such that other cells will alter their chemicals to push the first cell back to where it was. In some ways, this can be seen as a control system, where the system, the protein in the cells, displays oscillating behaviour. However, negative feedback failed terribly when simulated for cells. This model does fit well with the information cascading in cell clusters.
In 2016, Fred Hutch molecular biologist Dr. Roger Brent led a study that established a new cascading mechanism in cells. It is called the push-pull control. In push-pull, the “inactive” forms of the proteins in the information cascade actively keep the steps ahead of them shut off, while the active forms turn those steps on. In other words, the inative proteins are not actually inactive. Instead, they act as switches that stops information cascading. This model was well verified with simulation result.
There are more models that will be conjured and tested as the mechanism for information cascading, but now lets use what we have to its best.
https://www.fredhutch.org/en/news/center-news/2016/10/cells-sense-respond-outside-world.html