SLC22A5

The SLC22A5 gene provides instructions for making a protein, called OCTN2, that facilitates the uptake of carnitine into certain tissues in the body. Carnitine, a naturally occurring substance obtained mainly from the diet, is necessary for cells to break down fats for energy. This system depends on the OCTN2 protein being positioned in the cell membrane so it can transport carnitine from the bloodstream into the appropriate cells. The OCTN2 protein is found primarily in skeletal muscle, and in heart, kidney, brain, and several other body tissues.

primary carnitine deficiency - caused by mutations in the SLC22A5 gene

More than 50 SLC22A5 mutations have been identified in people with primary carnitine deficiency. Most of these mutations create a premature stop signal in the instructions for making OCTN2. As a result, no protein is produced. The remaining mutations change a single amino acid (a building block of proteins) in the OCTN2 protein. As a result, SLC22A5 mutations greatly reduce or prevent carnitine transport. With reduced transport, cells are not supplied with an adequate amount of carnitine, and it is excreted by the kidneys in urine.

Without adequate carnitine, fats cannot be processed correctly and are not converted into energy, which can lead to characteristic signs and symptoms of this disorder. Severe symptoms of carnitine deficiency become apparent when energy from fats is in demand, such as periods without food (fasting) or during events that increase the body's need for energy (such as infections).