Proteins are substances in the body that help facilitate various chemical processes. As a specific class of proteins, apoptosis proteins trigger and assist a cell’s self-destruction. These proteins may either signal a problem that necessitates a cell’s death or they may help carry out the process that ultimately destroys the cell.
The process of apoptosis facilitates cell death. When a cell is no longer functional or becomes a danger to an organism because of infection or damage, apoptosis will cause the cell to self-destruct. After a cell life ends in this way, the cell will fragment and be consumed by other cells. In cell growth diseases like cancer, this process is inhibited in some manner. Apoptosis is an essential maintenance process in most organisms; in the average human, for example, apoptosis destroys around 60 billion cells a day.
Apoptosis proteins monitor changes both inside and outside of a cell. These changes may derive from toxic substances, from hormones, or from other means. When the proteins detect an anomaly, such as DNA damage or a viral infection, they will send signals that trigger the destruction process within the cell. Some pro-apoptosis proteins also work specifically to suppress the development of tumors, such as the P53 protein.
In addition to detecting the need for apoptosis, proteins can also play an important beginning role in the actual process. For example, in the common form of apoptosis, a cell structure called the mitochondrion releases a protein known as cytochrome c. This protein then triggers protein substances called caspases that break down other proteins in the cell. A domino effect is thus created, in which more substances that disintegrate other parts of the cell are activated. The mitochondrion itself is often targeted because it is an important center of cellular respiration.
Cancers and other conditions can develop from an overabundance of anti-apoptosis proteins — known as apoptosis protein inhibitors — in one’s system. This particular protein family works to deter apoptosis and subsequent cell death by inhibiting the release of the proteins and substances that conduct cell disintegration. BCL-2 proteins and X-linked inhibitors of apoptosis (XIAP) molecules, which are found in many tumors, are two such examples. While a lack of apoptosis can be harmful, an overabundance of the process can cause normal cells and tissues in the body to waste away, or atrophy. Such a result has been implicated in the destruction of immune cells in human immunodeficiency virus (HIV)-infected individuals, as well as in other infectious conditions.