Sarcolipin
# Sarcolipin

Sarcolipin is a micropeptide protein that in humans is encoded by the SLN gene.

## Function

Sarcoplasmic reticulum $Ca^{2+}-ATPases$ are transmembrane proteins that catalyze the ATP-dependent transport of $Ca^{2+}$ from the cytosol into the lumen of the sarcoplasmic reticulum in muscle cells. The SLN gene encodes a small transmembrane proteolipid that regulates several sarcoplasmic reticulum $Ca^{2+}-ATPases$ by reducing the accumulation of $Ca^{2+}$ in the sarcoplasmic reticulum without affecting the rate of ATP hydrolysis.

Ablation of sarcolipin increases atrial $Ca^{2+}$ transient amplitudes and enhanced atrial contractility. Furthermore, atria from sarcolipin-null mice have blunted response to isoproterenol stimulation, implicating sarcolipin as a mediator of beta-adrenergic responses in atria.

Sarcolipin is an important mediator of muscle based non shivering thermogenesis (NST). It causes the sarcoplasmic reticulum $Ca^{2+}-ATPases$ to stop pumping $Ca^{2+}$ ions but continue futilely hydrolysing ATP, thus releasing the energy as heat. Sarcolipin mediated heat production is very important for many organisms to maintain a warm body. In mammals thermogenesis by skeletal muscles is complemented by thermogenesis in the brown adipose tissue and beige adipose tissue. Sarcolipin mediated heat production in contractile muscles helps endothermic fish like the opah heat its body. Some fishes like the billfishes have a specialised brain heater tissue that is derived from muscles that cannot contract but specialise in producing heat using sarcolipin.

## Interactions

SLN (gene) has been shown to interact with PLN and ATP2A1.

