Structural Biochemistry/APC

Adenomatous polyposis coli (APC) or also known as deleted in polyposis 2.3 (DP2.5) is a protein found in humans that are coded by the APC gene Mutations in the APC gene may lead to colorectal cancer syndrome known as Familial Adenomatosis Polyposis (FAP). APC is also known as a tumor suppression gene that block possible cancer cells from growing uncontrollably.

Structure
The APC gene is found in the 5p21 region in the human genome and its protein is about 2843 amino acids long. It is mainly composed of ten repeated sequences The genes encoded in APC include β-catenin, which is a binding region that occupies the 1020-1169 region of the gene. APC also contains a glycogen synthase kinase (GSK-3β) binding portion that occupies 1324-2075 These sites that are found in the APC genome are also involved in glycosylation, myristylation, and phosphorylation of proteins.

Function
APC is an important role in many cellular processes in human bodies that determine if a cell may or may not develop cancer. The APC protein works in helps in tumor suppression by controlling how often a cell divides, whether it moves within a tissue or away, and how it attaches itself to other cells within a certain tissue. This protein also ensures that the correct number of chromosomes is produced during cell division. APC does this by working with other proteins, specifically the ones that are involved in cell attachment and signaling. In particular APC works with beta-catenin, which helps prevents genes that stimulate cell division from being turned on too often and inhibits cells from overgrowth

Role in Cancer
Adenomatous polyposis coli plays an important role in Wnt signaling pathway. APC is involved in cell migration by interacting with microtubules and actins which cells lead with. In 2003, Sansom et al showed that a decrease in speed of motion of mice intestinal epithelial cell is the effect of a mutation in the APC gene In addition, it has been studied that Adenomatous polyposis coli also plays an important role in apoptosis. For example the study by Morin et al in 1996 showed that the APC gene in human cells decreases the cell growth of other possible tumor genes. The most common mutation in colon cancer is caused by the inactivation of APC. When APC does not have an inactivating mutation, beta catenin, a protein that turn cell division genes on and off, is inactivated. These certain mutations found in APC and beta catenin can be inherited, or come infrequently. As a result from these mutations, other genes can be come mutated as well and lead to chromosomal instability. A mutation in APC and beta catenin is followed by other cancerous mutations. It has been seen in carriers of APC inactivating mutations have a 100% risk of colorectal cancer by 40 Familial adenomatous polyposis (FAP) is caused by mutations in the APC gene. People in Familial adenomatous polyposis have identified to have more than 800 mutations in the APC gene. These mutations produce APC proteins that are short and ultimately nonfunctional. Short proteins cannot inhibit abnormal cellular growth, which can become cancerous. The most common mutation in FAP is when five bases in APC are deleted. The mutation changes the sequence of amino acids in the APC gene. Another mutation in APC is caused by the substitution of the amino acid lysine for isoleucine at the 1307 position in the APC protein The substitution of lysine with isoleucine was first thought of to be harmless, but studies have shown that it is associated with 10-20 percent of colon cancer patients. This mutation is seen in approximately six percent of people in eastern and central Europe and that of Jewish heritage