The Control Mechanism in the Communication Within Cells

The insulin hormone.

Different hormones have their own particular effects on their target cells; this is necessary if the human body is to function in an orderly way. For example, the messages carried by insulin and glucagon-the hormones that adjust the level of sugar in the blood-are completely opposite in structure to one another. For this reason, these two hormones stimulate different communication pathways in the cell. The receptors that function like a communications station inerrably find the communication module to relay the message.

If a wrong choice were made at this stage, the communication network would fail and the person may die. But the receptors on the cell's membrane work like experts, ensuring that communication continues without interruption.

How do receptors that are stimulated by different hormones select without error the messenger proteins with which they must unite? How do the receptors successfully perform their functions without making a fatal error? Recent scientific research has helped us to find the answer to these questions. The flawless communication within the cells comes from their perfect design.

Let us consider the SH2 module about which we know most. This small piece of protein is composed of two main parts. One section of SH2 is the part that attaches firmly to the tail of the receptor. The second section of SH2, the section that gives it its basic characteristic, operates like a code reading device.

The number and arrangement of amino acids in the tail section of the receptor forms the code of the message being brought to the cell. This code is only deciphered by a certain kind of SH2 module. It is this same module that unites with it. Another section of this module unites with a different module. In this way, a special line of communication is established between the membrane and the cell nucleus. In short, all these complicated operations do not happen at random; they are organized according to a definite system. This arrangement is another demonstration that everything has been created in a measured and harmonious way.

The communication system in cells is much more highly advanced than the communication network between the branches of an international company with production and marketing centers throughout the world.

Now, in order to observe an example of this harmony, let us examine the communication mechanism that goes into action to repair the area where a person has cut his hand. In this situation, a messenger molecule called "platelet derived growth factor" (PDGF) unites with the receptor of the smooth muscle cell in the blood vessel that has received the damage. As a result of this union, the tail of the receptor inside the cell binds to a protein called Grb2. Grb2 is a messenger protein formed from the union of SH2 and SH3 particles; in order to establish communication among the proteins, it takes on the function of an adaptor. Next, Grb2 assimilates a messenger protein called "sos" which is in the cytoplasm that contains enzymes. Sos then activates another protein named "ras." In this way, at the end of a number of operations, it sends instructions to the relevant genes in the cell. Then the cells begin to multiply in order to heal the wound.46

Scientists make the following evaluation based on their research: in the communication system of the cells are mechanisms that automatically prevent a malfunction. These mechanisms are the product of superb design much more advanced than the control systems employed by modern high technology. So it is that, ever since the creation of human beings, hormones, receptors, adaptors, proteins and microscopic elements have been operating in perfectly harmonious cooperation.

It is impossible to conclude that such a complex order has come to be by evolution. The complexity of this system is extraordinary and more advanced than a communications system established by an international company, with branches, production and marketing centers all over the world. Above all, it is not conscious, informed, educated and intelligent human beings who operate this wonderfully integrated communications web, but tiny molecules too small for the eye to see. Certainly it cannot be expected that molecules establish such a system among themselves. The One Who established this system and controls it is God.

Special Messengers in the Cells

Internet technology is one of the most important developments in human history. But, the speed and capacity of the information transfer provided by the Internet is quite simple compared to the transfer of information in cells.

If you asked your friends what was the most important communications event of our time, "the Internet" would most probably rank first. Then, ask them why they think this. They will tell you that internet technology has made it possible for a great amount of information to be transmitted from one end of the world to the other within a short time. Internet technology is one of the most important developments in the history of humanity, but it is also true that the speed and capacity of information transmission afforded by the Internet is slow compared to the transfer of information among cells.

The nerve cells in the brain cells (neurons) or eye cells actually have the fastest known capacity for the transfer of information.

In these cells are systems functioning at every moment to make the transfer of information fast and without error. The latest research on the communication web of nerve cells has shown that some proteins in neuronal pathways have an "incredibly large number of linker domains."47 Therefore, these proteins are able to hold groups of messenger proteins together permanently. The very rapid communication in nerve cells is the result of this special design.

As an example of the special proteins that have a role in the communications mechanism in the world of cells, we will consider PSD-95. This messenger protein is thought to be an agent in the neurons related to learning.

PDZ is one of the various linker modules of the PSD-95 protein. In the first picture, you can see the structure of the PDZ module. In the picture on the right, the red areas are the PSD-95 protein.

In the linker modules of the PSD-95 protein are three PDZ domains. The first of these attaches to the tail of the receptor in the cytoplasm; the second controls the ion channel in the membrane of the cell; the third grasps the messenger proteins in the cytoplasm. In other words, the linker modules in the structure of PSD-95 makes it possible for it to coordinate several elements of communication at the same time.

This wonderful communication system is not limited to the nerve cells; a similar system exists in our eyes. You are reading this book due in large measure to the rapid communication system in the cells in your eyes. This marvelous mechanism is also found in the eyes of animals. Research on fruit flies has demonstrated that in this creature's compound eye containing many smaller eyes, special communication modules exist. The operation model of the special "InaD" messenger protein that causes the transfer of visual messages from the eye to the brain of a fruit fly is outlined below.

How did proteins establish such intelligent and particular communication systems? And how is it that proteins have constructed communication networks to respond immediately to the different needs of 100 trillion cells? And again, how did the wonderfully designed module system agree among themselves and formulate plans to form complex structures?

The eye of a fruit fly contains many smaller eyes and research has shown that there are special communication modules within this mass of eyes. Above you can see a simplified diagram of the operation of the special communication protein called InaD, which affects the transfer of visual messages from the eye of a fruit fly to its brain.

The modular system in the world of cells can be compared to the International Space Station. This station, built on the modular system, is recognized as one of the greatest engineering achievements in human history. No one can claim that this space station came to be by the chance combination of atoms, molecules, wind, lightening, or solar energy. The fact is, this space vehicle was built as a result of highly intricate engineering calculations, based on a pool of knowledge built up over the years by scientists from many countries.

The nearest thing to the modular system in the world of the cells is the International Space Station that is still being constructed according to a modular system.

Who made this communication system working inside cells whose technology is so advanced those scientists cannot completely unlock its secrets?

The messenger proteins and the wonderful communication systems formed by them are created and ordered by God, "He created all things" (Qur'an, 6: 101) and "directs the whole affair from heaven to Earth." (Qur'an, 32: 5).

46 J.D. Scott, T. Pawson, "Cell Communication," Scientific American, June 2000, p. 76
47 Scientific American, June 2000, p. 76