About RCN / Reticulocalbin:
Reticulocalbin refers to a family of proteins that are important to the immune system. They help trigger a response from white blood cells and serve as an initial point for other responses.
RCN is not only involved in immunity. It also plays a role in inflammation as well as neuron growth.
Reticulocalbin is one of the many small proteins that are found in all living organisms. It has many functions, including transporting nutrients to cells and food particles from inside a cell out into the gut. It also takes waste material from the gut back up through your body and removes it when you defecate or urinate.
In addition, Reticulocalbin is essential for eliminating cholesterol by breaking down bile acids in humans. Without enough RCN in our bodies, we would not break down fats efficiently, leading to health problems such as gallstones or liver disease.
Reticulocalbin's mechanism can differ depending on what type of food it is interacting with. When bacteria are present, reticulocalbin will bind to them and pull the waste material away from other cells in your body for disposal elsewhere.
In contrast, when there are no bacteria around, a different mechanism called endocytosis occurs where food particles taken up by cells on one side of the membrane use RCN as an anchor to bring them back across into another cell or part of the organism's surface area. These two mechanisms mean that without enough RCN, our bodies would not remove fat efficiently, which could cause problems such as gallstones or liver disease.
Reticulocalbin contains two domains. One that is involved in nucleotide binding and the other that binds to phospholipids. It also has an N-terminal domain for targeting, a C-terminal domain for substrate recognition, and an SBD or secondary binding site which recognizes cholesterol esters. Reticulocalbin interacts with different membrane lipids by recognizing headgroups like acyl chains of sphingomyelin through its second interaction sites. The interactions affect both structure and conformation due to conformational changes as well as lipid translocation into preformed multivesicular bodies or MVBs.
There are a few different interactions that reticulocalbin can have with other proteins. For example, it has been shown to bind and inhibit the interaction of protein phosphatase-phosphodiesterases (PDE) with both cyclin D and CDKs in vitro but not in vivo. PDE is rapidly endocytosed during cell cycle progression after being released from its inhibitor binding site on RCN.
It also increased levels of PDE expression through an unknown mechanism without any effect on p38 or ERK activation suggesting there may be another unidentified regulator controlling this process. Reticulocalbin was also found to interact directly with Hsp27 at lysine residues 114/115, resulting in increased Hsp27 protein stability.
Reticulocalbin can bind and inhibit the interaction of PDE with cyclin D and CDKs as well as increase Hsp27 expression through direct binding to it at lysine residues 114/115.