Sarcolipin is a micropeptide protein that in humans is encoded by the SLN gene.[3][4]
Function
Sarcoplasmic reticulum Ca2+-ATPases are transmembrane proteins that catalyze the ATP-dependent transport of Ca2+ 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 Ca2+-ATPases by reducing the accumulation of Ca2+ in the sarcoplasmic reticulum without affecting the rate of ATP hydrolysis.[4]
Ablation of sarcolipin increases atrial Ca2+ 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.[5]
Sarcolipin is an important mediator of muscle based non shivering thermogenesis (NST). It causes the sarcoplasmic reticulum Ca2+-ATPases to stop pumping Ca2+ ions but continue futilely hydrolysing ATP, thus releasing the energy as heat.[6][7] 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. [8] 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[9][10] and ATP2A1.[9][10]