Communication Within The Cell
Up to this point, we have examined how cells communicate among themselves and the means by which one cell sends its message to another. We touched on the functions of these messages (hormones) and the effects they have on cells. In this section we will examine how the message carried to the cell by a hormone is transferred from the cell's membrane to its nucleus. In other words, we will examine the communication system inside the cell.
The Communications Center in a Cell and Its Stations
Most of us are familiar with high communications towers, and many of us have seen television news reports of the opening of such installations. The first impression that these images leave on our minds is probably the image of a structure full of antennas and complicated electrical devices. This idea is not mistaken because, in order to understand the technological devices used in these installations, one must have a certain engineering expertise in electronics and communications. Besides this, almost all of us believe that these facilities are now indispensable in enabling us to establish communication with people in every part of the world. Just think of this: What would happen if all the communications towers, with their centers and stations, were to shut down for a short time? There is no doubt that this situation would cause great chaos and anxiety. But, no matter how much material damage might result, it could still be repaired.
However, if the communication between our hundred trillion cells, or the communication within one cell, were to shut down for just an instant, and the cellular messages were not to reach their destination, the result would be death. Modern communication systems are established using electronic and mechanical devices with the most advanced technology. However, the advanced technology of the inner communications systems of cells, which is too advanced for human beings to fathom, is constructed with the use of devices structured from protein. Inside protein there are no electrical circuits (or even semi-conductors) as exist in modern devices; in their place are atoms of carbon, hydrogen, oxygen and nitrogen. There are an estimated 30,000 different proteins in our body and of these, the function of only two percent is completely understood.44 The function performed for human beings by many proteins is still largely unknown.
The communications system among cells in some ways resembles systems used by human beings. For example, on the membranes of the cells there are "antennae" that allow them to sense the messages that come to them. Immediately under these antennae are "power stations" which decode the message sent to the cell.
These antennae are located on the one hundred thousandth of a millimeter thick cell membrane that surrounds the cell. This receptor, which is known as "tyrosine kinase," is composed of three basic sections: the antenna, the body and the tail. The shape of the part of the antenna that projects out from the cell membrane resembles a dish antenna used to collect satellite transmissions. Just as each dish antenna is designed to receive certain satellite transmissions, there are different receptors that understand the language of the messages carried by various hormone molecules.
The messages coming from different cells/hormones come into contact with the antennae on the cell membrane, but each antenna is designed to sense only one single message. This is a very special instance of design and because of this, a message cannot be sent in error to another cell.
The great harmony in which hormones and antennae are created in relation to one another can be compared to the lock-and-key relation observed in almost all biological activity. Only the right key can open the lock; that is, only the right cell will have anything to do with the message sent, this message being without meaning for other cells.
In order to understand just how wonderful this operation is, think about an ordinary occurrence that everyone can encounter in their daily life. Information is sent via the Internet to a personal computer connected to a network of other computers.
The information sent to the computer is transmitted to another unit, for example, to a printer, and the printer puts the information on paper. People have been using computers since the 1980's; they are used at home and in the workplace and, since the mid 90's, the Internet has become a part of people's lives. If you read in a newspaper one day that a computer has been built that was too small for the eye to see, and that this computer was communicating with other computers, your reaction would be quite different. Perhaps you would not believe that this technology could be compacted to such a small size. However, in real life there is a communications system with a technology much more highly developed that this, working in an area too small for the eye to see.
The fact that a message coming to a cell's antennae is transmitted at great speed to the nucleus of the cell, and that a highly advanced technology is employed in the process of this communication, is a much greater wonder than a microscopically small computer. This is because a cell is a piece of flesh and your whole body, from your eyes with which you are reading this book to your hands you are holding it with, is formed by cells working together.
In the body of each one of us, there are 100 trillion small organisms possessed of a highly advanced communications system. Now let us examine the system by which the message reaching the cell is transmitted inside the cell, and let us see the wonder of creation manifested in a piece of flesh one percent of a millimeter in size.
The Journey of a Message-Carrying Hormone Inside the Cell
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.
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.
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."
Modular Communication Stations
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.
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.
The Control Mechanism in the Communication Within Cells
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.
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.46Scientists 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
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."47Therefore, 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.
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 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.
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).
The Scientific World and Cellular Communication
In the last part of the twentieth century there were enormous scientific advances in the field of cellular communication. Huge steps were taken towards an understanding of the communication networks in the depths of our bodies. For example, if we look at the awarding of the Nobel prizes over the past twelve years, six of the awards given in this period in the field of medicine were to research done in the field of cellular communication. The systems we have described so far are a part of the wonders discovered as a result of this research.
n the year 2003? How much farther does the scientific world have to go? The answer to this question is very important because the answers we give will help us to understand that this cell communication system is a great wonder of creation.
In various countries of the world are many organizations, with a total budget of millions of dollars that are researching this matter. Towards the end of the year 2000, the Alliance for Cellular Signaling (AFCS) was established. Twenty universities and hundreds of scientists belong to this organization, and its founder, Alfred Gilman, was awarded the Nobel Prize in 1994 for his work in cellular communication. Professor Gilman had this to say about this subject:
If the brain needs sugar, the liver has got to put it out. If the muscles need more blood, the heart has got to beat faster. Hundreds of different chemical signals flow around the body, released from one cell to influence the activities of other cells. Cells are constantly being bombarded with very large numbers of chemical signals that tell them what to do and how to perform…The bigger problem, and the one that is most difficult to figure out, is how all of these modules interact together.48
And the AFCS, beginning its work towards this goal, explained their enterprise using this comparison;
The Alliance will launch voyages of discovery aimed at two continents (cardiac myocytes, B lymphocytes). We know a little about the coastline of each continent—a few harbors and mountain ranges near the coast (receptors, ligands, and crudely sketched signaling pathways). We will thus concentrate first on exploring the coast more thoroughly, at the outset with more attention to the harbors that we know best (e.g., G protein-coupled receptors and heterotrimeric G proteins) but not neglecting many we know less well (receptor tyrosine kinases, cytokine receptors, etc.). Mapping the interior of the continent begins with expeditions to inland areas nearest the coast (cytosol), following rivers and trade routes (critical nodes of signaling pathways already known). Further exploration will radiate out from these nodes, and later expeditions will push further into the interior (cytoplasm to nucleus)…49
The fact is, as the paragraph above shows, the information that we have at our disposal regarding cellular communication is quite limited and that, in the years ahead, microorganisms will increase our knowledge or other systems.
There are scientists who speak clearly and sincerely on this subject. One of these is the 1999 winner of the Nobel Prize in medicine, Günter Blobel who did research on the "zip code" system in cells. This world-renowned professor said the following in an interview on this subject:
It's shocking how little we know about how a cell works . . . And that will take a long, long time to figure out.50
The twenty-first century will, as science advances, allow us to learn more incomparable wonders of communication within our cells. For a person of understanding, every system that is being discovered is a demonstration of God's eternal wisdom and power, and a sign that reminds us that the only Being worthy of praise is God.
It is He Who created the heavens and the Earth with truth.
49. Alliance for Cellular Signaling (AFCS), "I.Program Summary, D.Experimental Strategies, 2.Definition of Our Initial Sphere of Interest", 2000, http://afcs.swmed.edu/afcs/Program_Summary/ID2.%20DEFINITION%20OF%20OUR%20INITIAL%20SPHERE%20OF%20INTEREST.htm.