The Journey of a Message-Carrying Hormone Inside the Cell

When a messenger molecule reaches a cell, it attaches to an antenna on the cell's membrane. While it is attached, it relays its message to the antenna. The message passes to the tail of the antenna that is inside the cell. After this, the antennae parts that were previously single come together in groups of two. The enzymes in the body section pair up and add phosphates on each other's tails, thereby changing the shape of the tail section. These operations are like a call to the messenger modules inside the cell.

A computer simulation showing the union between a growth hormone and a receptor.

When a messenger molecule reaches the cell, it attaches to the antenna on the cell's membrane. In the course of this attachment, the message is relayed to the antenna. The message received by the antenna is then transmitted to the tail located in the inner section of the cell. The body of the microscopic communications antenna enters the fluid (cytoplasm) between the nucleus of the cell and its membrane. The connection established between the hormone and the antenna initiates a chemical reaction. This reaction causes the antennae, which were individual units, to form into groups of two, and brings about a change in the shape of the tail sections. This operation, called "phosphorilation," is a change that occurs when the enzymes in the body section add phosphate to the tail.

A base station

Several molecules and proteins add technical support to this system. For example, the GTP molecule and the proteins called "G" for short, have an important effect at this stage; they supply the phosphorous for the phosphorilation. For the system to function, it is necessary that many factors come into play at the right moment.

This operation carried out by the enzymes has an important role in the relay of information. This operation within the cell is intended to be a call to the proteins known to be communication modules in the cytoplasm. As a result of a number of complex operations, the SH2 communication module is activated, and a connection is established with the tyrosine kinase antenna, which stimulates the relay of this message within the cell.

Until recently, no one had any idea of how the messages carried by hormones reached the nucleus so speedily and with such precision. How is it that no error is made in the course of the transmission of the message? Indeed, the slightest error made in the process of the transmission of a message would cause, for example, a faulty protein production in the cells and the collapse of a marvelous physical system. The latest research has shown the existence of communication modules in cells. The SH2 module is only one of an estimated hundreds of different communication modules.

Within the cells, these modules function as communication stations. Thanks to the wonderful system that they have established, messages are carried from the membrane of the cell to its nucleus. From one point of view, these fantastic modules can be compared to base stations that establish communication with cell telephones. In this way, enzymes that work in an ordered fashion deep in the nucleus of a cell take measures to ensure that production occurs according to "ideal standards."

Because of the marvelous system created by the modules, the message is sent from the cell membrane to the nucleus. These wonderful modules can be compared to base stations that make communication possible between cell phones.

Modular Communication Stations

In this picture you can see the passage channels on the membrane of a cell. These channels are made of protein and carefully supervise entrance and exit in and out of the cell.

Research done on these communication stations has surprised scientists. The structure of the modules is composed of proteins, each made up of 100 amino acids. Each one of these has a particular three-dimensional structure. As a result of this marvelous design, every protein can establish a connection with a certain module. That is, just as every radio station broadcasts on a different frequency, different messages are relayed by different cell communication modules.

The idea of a "module" used here to describe the bits of protein that form the communication pathways in the cells is really an insufficient comparison. This analogy explains that these three-dimensional molecules fit into each other as do separately manufactured parts of a pre-fabricated house. What amazes scientists is the structure that emerges as a result of adding phosphate onto the receptors is a shape with which the SH2 module can bond completely. Thanks to this, the SH2 module and the receptor can fit into one another as if they were designed for that very purpose.

With the help of an electron microscope capable of enlarging an object one million times, some stages have been observed which enable us to understand the microscopic communication stations, but scientists inform that there are still hundreds of communication modules whose structures are not yet understood.45 These cohere closely with one another and form an inerrable system of signals within the cell. If one of these modules were not in place, or if it were faulty, communication within the cell would be completely paralyzed; this shows how extraordinary this system is.

The reason why we use the term "module" to describe the protein particles that make up the communication pathways in cells is to explain that these three-dimensional molecules fit into one another like the separately manufactured pieces of a pre-fabricated house.

This marvelous communication system in the cells has a few "expert modules" that take the message they have received from receptor on the membrane directly to the relevant gene in the cell's nucleus. That is, these modules have such a flawless design that they find the section of that information contained in the DNA molecule relevant to the message they are carrying (enough information in a human to fill a million encyclopedia pages). In this way, they ensure that the amount of protein required by the cell is produced without error. That a piece of protein one millionth of a millimeter in size can be so clever and aware is a wonder.

All of these investigations show that the cytoplasm of the cell is full of various organelles and proteins, and, once again, that the cell is the most complex structure in the universe. The internal communication system of the cell is an example of this. Certainly, the splendid order in the world of cells is the order of God, the Lord of all the worlds.

A computer simulation of the SH3 module	A computer simulation of the SH2 module.

45 J.Schultz, R.R.Copley, T.Doerks, C.P.Ponting, P. Bork, "SMART: a web-based tool for the study of genetically mobile domains," Nucleic Acids Research, Vol.28, No.1, 2000, pp. 231-234