In our introduction of cells a few weeks ago, we discussed how the different types of cells have specific jobs. These cells make up our entire body, but how do the cells in our kidneys know when they need to retain more water to increase blood pressure for the heart?
Cells must be able to communicate with each other for the human body to work effectively, and they can do this through many different signaling pathways. There is one type of signaling that occurs within a single cell, called intracrine signaling. You can imagine this as the intercom within the factory. An announcement is made inside of the factory over the intercom so only the workers inside hear it. An example of an internal announcement (intracrine signal) could be an order for the factory (cell) to ramp up production of a certain product (protein).
Another type of signaling within the body is autocrine signaling. Autocrine signals are produced within a cell and then bind to the same cell on the outside. Autocrine signals can be thought of as messengers. A cell sends the messenger outside to talk to the plasma membrane, or security guard. These types of signals may tell the security guard to let something in or out of the cell that may not normally be allowed. An example of cells that utilize autocrine signaling are immune cells. When an immune cell recognizes something foreign, it makes a protein (such as a cytokine) that travels to the outside of the cell and notifies the security guard that something at the front gate is not recognized. Autocrine signaling can also notify nearby immune cells (of the same cell type) of the foreign invader. This can help initiate an immune response against the virus or bacteria (tune in next week for more on the immune system).
While some signaling pathways stay within the same cell or very close by, other products need to be shipped various distances to other cells. In this case, once Factory A makes enough of the desired product, it is shipped to its neighboring cell, Factory B. This is an example of juxtacrine signaling. Juxtacrine signaling is a type of signaling that occurs when the two factories (cells) are within close contact to each other, think of next-door-neighbors.
Some factory products only need to be transmitted to direct neighbors, while other products are transmitted to factories (or cells) that are within the whole neighborhood. This type of signaling can be thought of as a railway system. Paracrine signals target cells that are in close proximity to each other. These types of signals cannot be sent worldwide (like endocrine signaling), but rather these signals remain domestic and are only delivered to factories that are on the railway.
What about products that need to be shipped worldwide? Let’s say Factory C has worked to generate a product that needs to be shipped to three command centers in different locations throughout the world (body). This product is going to be shipped via endocrine signaling, by loading it onto a cargo ship to travel through the body’s canals (blood system). An example of endocrine signaling is the movement of different hormones throughout the body, such as estrogen. Estrogen is a product of cells located within the ovary, but it has many roles in other parts of the body. To get to these different locations, estrogen travels through the blood via endocrine signaling. This way, it is able to work in larger capacities, like the development of the female body, where it plays a role in body fat, muscle growth and more.
Signaling is a critical component of biology. Making sure our cells communicate effectively with one another ultimately ensures our body functions to the best of its ability. When signaling pathways go awry, information is not processed correctly and diseases like cancer and diabetes can develop. Research in cell signaling is crucial for understanding the biology of these diseases so they can be treated at a clinical level.
Thanks for reading and make sure to check back next week for the launch of our IMMUNOLOGY introductory post! In the meantime, let us know if you have any questions, comments or feedback and don’t forget to follow/ like us.
Written by Annah & Megan
Illustrated by Rhea
Disclaimer: We are not medical professions and the above information is not meant to serve as diagnostic factors or medical advice. Further, the opinions in this post are our opinions and in no way reflect the opinions of our mentors or Medical University of South Carolina.