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Cadherin and Catenin: The Nut and Bolt System of Cells
Jul 1, 2013
The human body is a great system made up of complex materials and tools. The molecular systems keep cells, tissues, organs, thus the entire system glued together. Just as we would not have been able to develop complex machines and build our civilization today without screws and screwdrivers, bolts and nuts, in the absence of molecular systems and their components, cells would not be able to stay together and tissues and organs would not develop. Cells sometimes form a loose linkage to some tissues, other times form a tight or very tight connections in other places. For instance, connections in the blood-brain barrier and bladder line should be very secure, preventing leaks, whereas the connections need to be loosely structured in secretive tissues to permit transport of ions and molecules in between cells.

Cellular joints are called “intercellular junctions.” There are thousands of molecules (proteins) in charge of these regions. As members of such molecules, the Cadherin and Catenin linkage system holds two cells together just like a secured nut and bolt. Thus unity of tissues and organs is ensured.

Masayuki Ozawa, a Japanese scientist, was the first to call these proteins “catenin” in 1989, derived form the word “catena” in Latin which means “chain.” Catenin links cells to each other like a chain. As you construct your buildings, you place cement or similar adhesive materials in between bricks and stones. In a similar fashion, when your body is developing, cellular cement is put in between cells, linking them via bolts of cadherin and nuts of catenin.

The catenin family has three members: alpha catenin, beta catenin and gamma catenin, classified according to our weight and length. Cadherin is a Calcium (Ca) dependent adhesion molecule (to bond and stick) that was discovered in 1961. Cadherin refers to a calcium dependent adhesion molecule. As Cadherin enables linkage between the two cells, catenin in the meantime sticks to the ends just like a nut on a bolt. This way a connection is properly secured. Structural cadherin deformities have been found in some stomach cancers. Cells without a properly secured anchor leave the flock like lost sheep. It relocates to other places and new proteins are synthesized there. Researchers have stumbled upon catenin while investigating the Cadherin molecule.

Catenin carries a special motif called “Armadillo” named as such because of its resemblance to this insectivorous mammalian which means “armor” in Spanish. Together with Cadherin, Catenin fulfills very important tasks in many places from the embryologic development in the mothers’ womb to the salivary glands through the skin. A body without Catenin would look like a building without nails, cement, hinges, and screws. Catenin operates like the anchor of a ship, thus it is also named as “anchoring junction molecule.”

While Cadherin molecule links two cells to each other, Catenin secures the Cadherin ends, and then connects Cadherin to the Actin as the main molecule of cellular framework. Catenin does other jobs in addition to the role of fastening. This multitasking is observed in many structures and molecules in the body. With the principle of maximum saving, these molecules are created to take care of many jobs in a limited space. For instance, Catenin works in a communication system called “WNT.” The WNT system relays signals that arrive at the cell to Catenin so that it can transfer the signal to the cell nucleus. In recent years errors in this system have been reported in breast and intestinal cancers. Furthermore, Catenin helps Cadherin as it functions like an orchestral conductor in the organization of intestinal cells. Catenin undertakes active tasks for the maintenance of intestinal cellular homeostasis, and it becomes hyperactive in Hirschsprung disease. This disease is a state of neural network absence that is in charge of intestinal (bowel) movements and supposed to be present through the intestines. In such parts of the intestines, bowel movements cannot be monitored and excretion cannot take place properly.

The diseases associated with cadherin have been reported in many cancer cases. Both cadherin and catenin are made to function flawlessly as best as possible. But just in every other blessing, we tend to appreciate their presence in times of sickness and disease – we seem to realize in such times the fact that nothing is insignificant in nature. When cadherin and catenin fail to work properly, embryonic lethality happens, and the baby may die even before he or she is born.

Cells cannot completely come together to arrange tissues and systems without these molecules. If these molecules in the salivary glands suffer from a problem, abnormal cellular structures may form, and cellular specialization is put at risk, and again death may happen in the womb. Unwanted situations arise from brain and face cartilage if these molecules do not function well during prenatal development. Miscarriages might happen because of flaws regarding establishment of fertilized egg in the womb. Zygote may have trouble transforming into an eight-celled blastocyst.

Mechanisms and systems that are built in our body are mind-blowing and put to service for many purposes only some of which we have been able to uncover. These molecules fulfill quite a number of those purposes assigned to them by the Creator, the One who acts with absolute subtlety, wisdom, and generosity.

Kadir Can is a science teacher in Ankara, Turkey.