Cell communication (biology)

One of the way the cells can communicate with each other through a process called cell junction. Cell junction can happen in many forms, but the three main forms of cell junction are gap junctions, tight junctions, and desmosomes.[4]

Gap junctions

Gap junctions have a very crucial job that cause a tube to form between the 2 cells allowing in the transport of ions and water. Gap junction tubes help the cells to spread electrochemical signals from cell to cell. Electrochemical signals are the product of action potentials that occur in neurons and cardiac cells. Without gap junctions, we would not be able to have a beating heart or functioning nervous system.

Gap junctions showing transport of signal molecule between adjascent cells

The breakdown of cell communication result in many forms of diseases and the different types of communication breakdown produce different diseases. Multiple sclerosis (MS) is the product when a signal is lost and does not reach its target. In MS the nerve cells protective wrapping found in the brain and spinal cord, get destroyed affecting the nerve cells where they can no longer send signals from one part of the brain to another resulting in the loss of functions such as movement. When the target receptor ignores the signal completely, we end up with the diseases type 1 and type 2 diabetes. In type 1 diabetes the insulin signal is unable to be produced, while in type 2 diabetes the cells have lost the ability to respond to the signals, resulting in abnormally high and dangerous sugar levels in the blood.[6] A stroke results in the production of too much signaling, where dying brain cells release a large amount of glutamate, killing off healthy brain cells leading to widespread damage to the brain. Glutamate is the molecule responsible for many functions in the brain when produced in low concentrates, but when produced in high concentrations is extremely toxic. Excitotoxicity is the spread of highly concentrated glutamine that kill off healthy brain cells not affected by the stroke. Multiple breakdowns in cell communication result in the uncontrolled growth of cells. When one breakdown occurs, the cell gains the ability to grow and divide with out the signal telling it to do so. A cell has the ability to activate a self-destruct sequence (RNAi) to control the unregulated growth of the cell, but when multiple breakdowns occur, the cell loses the ability to self-destruct and the cell divides uncontrollably mutating and creating a tumor. Further cell communication causes blood cells to grow inside the tumor making it grow larger, while more signaling allow the cancerous cells to be spread throughout the body.[7]

In cells, DNA is housed in the nucleus and it never leaves. The DNA within the nucleus is transcribed by tRNA, and the transcriptions of the DNA become RNA. The RNA (ribonucleic acid) leaves the nucleus to float freely around the cytoplasm, and it contains the instructions of the DNA that are vital to the coding, decoding, regulation and expression of genes. The ribosomes then take the RNA messages and turn them into proteins that build cells. When a virus enters a cell and inserts its DNA code into the nucleus, it gets transcribed and released into the cell for the ribosome to make it into a protein. This is how viral infections occur. The cell then explodes with the overproduction of the virus, releasing it into the body to infect any and all other cells it finds. It is theorized that through evolution, cells developed a defense system called RNA interference (RNAi) to stop the production of the proteins that have suspicious mirror image messages of the RNA. They don’t just destroy the suspicious messages, but the correct messages as well to stop all production of that message. This is a cell’s self-destruct mechanism and every cell, plant and animal, have RNAi: a way to turn off the production of a certain gene inside the protein.[8]

Cancer cells will communicate via gap junctions most of the time, and the proteins that form these gap junctions are known as connexins. These connexins have been shown to suppress cancer cells, but this suppression is not the only thing that connexins facilitates. Connexins can also promote tumor progression; therefore, this makes connexins only conditional tumor suppressors.[10] However, this relationship that connects cells makes the spreading of drugs through a system much more effective as small molecules can pass through gap junctions and spread the drug much more quickly and efficiently.[10] The idea that increasing cell communication, or more specifically, connexins, to suppress tumors has been a long, ongoing debate[11] that is supported by the fact that so many types of cancer, including liver cancer, lack the cell communication that characterizes normal cells.