The role of sarcolipin in thermogenesis. (360G-Wellcome-086171_Z_08_Z)

We have shown that, in vitro, sarcolipin, a small transmembrane peptide found in skeletal muscles of larger mammals (e.g. rabbits humans) but absent from the muscles of smaller animals such as mice, uncouples calcium transport by skeletal-muscle sarcoplasmic-reticulum calcium pumps, leading to a significant increase in thermogenesis. Thermogenesis plays a major role in maintaining body temperature as well as moderating the effects of excess dietary calories thereby reducing obesity. The contri bution to overall thermogenesis played by sarcolipin in vivo has not been assessed and is the subject of this proposal. We will produce a transgenic mouse, in which sarcolipin is over-expressed. These transgenic animals will be characterized in terms of their body weight, energy expenditure and responses to different dietary regimes and ambient temperatures to measure the outcomes of the thermogenic effects of sarcolipin in a whole animal. Sarcolipin and calcium pump levels will be measured in h uman skeletal muscle to estimate the level of thermogenesis resulting from the presence of sarcolipin in human skeletal muscle. In addition, we will examine the mechanism by which sarcolipin causes the uncoupling calcium transport, using mutagenesis to alter key residues thought to interact with the calcium pump.