The cells of each organism are constantly engaged in communicating with each other to maintain the necessary balance. For the first time, a general map of the types of communication between cells that affect the 144 most important cell types of the human body has been created. The cell is the fundamental unit for life; a single-celled organism (i.e., composed of a single cell) is, therefore, able to perform all the functions essential for survival. It takes on nutrients from the outside, moves around the environment, is home to metabolic reactions that provide it with energy for the synthesis of new molecules. In organisms composed of several cells, the situation is considerably more complex. The various functions are distributed among distinct populations of cells, tissues, and organs, which can also be very distant from each other.
A complex network of mechanisms is needed, through which single cells or groups of cells are enabled to communicate with each other to coordinate all these functions. The coordination of growth, differentiation, and metabolism of the multitude of cells in the various tissues and organs allows organisms to regulate their activity to adapt it to both internal needs and those of the environment in which they live and operate. Also, within the same cell, the received signal also has its own transmission pathways, to ensure that the cell responds adequately to the stimulus.
It is due to the electromagnetic energy produced by the cells of our body. It is necessary to make the various parts of the cell, the cells of the same organ, and, therefore, the various organs of the same living system function well. The cells of the same organ, by the very fact, that they have identical molecular composition, communicate and interact using all the same electromagnetic signal that propagates making them "vibrate" with the same type of frequency, which causes them to resonate with each other.
All living systems would have a very weak emission of "energy quanta" that affects their vital phenomena and therefore called "biophotons," which propagate with the speed of light. Their existence allows us to understand the high passage of information within the cell itself and between cell and cell, which are essential for initiating cellular metabolism, growth, and differentiation.
The biophotons thus represent, in the context of cells and intercellular relationships, a real language for the transmission of coded information. Even the enzymatic processes, essential for the dynamics of the good functioning of the cell, would be guided by electromagnetic signals. Last but not least genetic information, which regulates the formation of specialized cells to perform certain functions, would be determined, among other things, by electromagnetic factors.
Much of the cellular communication occurs through the release of small proteins, which bind to other proteins - called receptors - that are found on the membrane of the other cells. This communication coordinates activities between multiple cell types making complex processes such as immune response, growth, and homeostasis possible. On the other hand, cell-to-cell communication defects are implicated in the development of cancer and autoimmune and metabolic diseases. However, despite the importance of this process, studies on intercellular communication between specialized cells in higher organisms are generally limited to communication between a few cell types and a small number of ligand-receptor pairs.
Jordan A. Ramilowski and colleagues reviewed the literature data relating to 642 ligands and 589 human cell receptors that give rise to 1894 ligand-receptor pairs that allow communication between 144 different types of human cells. The analysis showed that most cells express from a minimum of a few tens of ligands and receptors to a maximum of a few hundred. The resulting signaling network is therefore highly connected and very complex and allows the various types of cells to communicate through a multiplicity of different paths.
As the authors point out, the availability of these data can help researchers discover receptors that can become targets for new drugs. But the map has already allowed the discovery of more general theoretical interest.
The development of a wide possibility of communication between cells is, in fact, a prerequisite for one of the decisive events in the history of life on Earth, which is the evolution of highly organized multicellular organisms. In particular, Ramilowski and colleagues found that the proteins that form the receptors evolved in general long before ligands, which are, on average, also much smaller. Although it is only a small piece in the reconstruction of the genesis of multicellular organisms, it can help to narrow the spectrum of hypotheses on the birth of cellular communication. There are two types of cell communication i.e.
- cell communication
- internal cell communication
Signaling between cells has two different modalities i.e. between cells distant from each other; the signals must be exchanged indirectly, through the secretion of substances. When, on the other hand, the cells are closed, the communication takes place directly, through structures that closely communicate adjacent cells.
Intercellular communication usually takes place due to the interaction of a molecule (called ligand) produced by a cell with another molecule (called receptor) placed on the membrane of another cell. All the signals that arrive in the cell from the outside are captured by the special "molecular antennas" (the receptors). But, as for television electromagnetic waves, signal transport and conversion system (television) are needed to have an organized response, so the cell has also developed a system to convert signals from outside.
The transport, conversion, and amplification of the received signal will allow the cell or cells of the tissue to respond adequately. Some signals manage to penetrate the cell (steroid hormones), where the receptors are located; in this case, the signal is direct. In the case of information that cannot overcome the cell membrane (water-soluble hormones), more complicated mechanisms are needed. The internal signals are carried by a series of small molecules called second messengers. In molecular terms, the transmission process of this signal depends on a series of proteins contained in the cell membrane. These each transmit information that induces an alteration of the form, and therefore of the function of the contiguous protein. At some point, the information reaches small molecules or even inorganic ions present in the cytoplasm. These are the second messengers, whose diffusion causes the signal to spread and amplify rapidly throughout the cell.
The number of second messengers is limited- this means that the pathways inside the cell for the transmission of signals are universal, yet capable of regulating a great variety of different physiological and biochemical processes. Two main ways are known for the transmission of the signals. One of these uses a nucleotide, the cyclic AMP, as its second messenger; the other uses a combination of second messengers, which includes ions calcium (Ca2 +) and two other substances derived from the components of the cell membrane (phospholipids). The two routes have parts in common. In both, the initial component, i.e., the receptor molecule present on the cell surface transmits the information through the plasma membrane and inside the cell itself, by means of a family of proteins that act as transducers, called G proteins.