User:Elizabeth G. Aylesworth/Sandbox 1

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History

Dictyostelium discoideum was the first organism in which coronin was identified. Since that discovery in 1991, plants are the only eukaryotes that coronin has not been identified. There are 12 subfamilies, and half of them are found only in vertebrates (1).

Function

The function of coronin 1C can be seen in many parts of the cell. Coronin 1C helps the cell to migrate by “regulation the activation and subcellular location of RAC1” (2). Coronin 1C helps to organize the cytoskeleton, helps the proliferation of the cell, and helps form a lamellipodia. Coronin 1C is “localized to endosome membrane tubules and promotes recruitment of TMCC1, leading to recruitment of the endoplasmic reticulum to endosome tubules for fission” (2).

Disease

Coronin 1C is seen in many different cancers. The promotor of coronin 1C binds to C-myc in lymphoma cells. The levels of coronin 1C are low in normal skin cells, but high in melanoma cells. It is used as a marker for hepatocellular carcinoma (HCC), but the expression is dependent on the Erk pathway. If coronin 1C is imbalanced, it could lead to a defect in the brain growth. This could also lead to brain diseases. Coronin 1C is high at the start of development and decreases as the brain develops. Coronin 1C is also found in brain tumors, but the levels depend on where the brain tumor is in the brain (3).

Relevance

Coronin 1C uses the Arp 2/3 complex with motility and phagocytosis. A deletion of the gene coding for coronin does not cause abnormal function of endocytosis, but it does interact abnormally with other genetic mutations. For this reason, coronin is an important protein for the proper function and form of the cytoskeleton. In other organisms coronin being either deleted completely or over or under produced can prove to affect endocytosis and phagocytosis negatively or be deadly (4).

Structural highlights

Coronin 1C is a part of proteins that are approximately 474 amino acids long. Coronin 1A has Asp452 on the 3 position, whereas Coronin 1C has Ser463. This allows the protein to be phosphorylated, which interferes with Arg461’-Glu466, thus leading to the loss of a coil. Another structural difference is that Coronin 1C has a Ser450 in a hexa-peptide, which is not found in other coronin proteins. This allows for another phosphorylation site for the protein. This, however, has not been shown to impact the protein function in significant ways (5).

There are three parts of coronin 1C: the propeller, unique segment, and coiled coil domain. The propeller binds with the F-actin. The coiled coil domain helps coronin 1C bind with Arp 2/3 complex and forms trimers and dimers. The unique segment is not fully understood. Coronin 1C is different because it also has a second actin binding site. Coronin 1C lacks the phosphorylation site but can still bind the complex (6). If the Coronin 1C is phosphorylated, then the protein moves throughout the cytoplasm, not reacting with the plasma membrane. Coronin 1C is eight residues longer than 1A. If the coiled coil domain is deleted in coronin 1C, it prevents the creation of a bond to the plasma membrane (7). It is not a transmembrane protein and instead only binds to the membrane with the cytoskeleton through interaction with cholesterol (8).

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