Constitutes a major selenium pool in the brain and may play an important role in developing and/or modulating the morphology of neurons and/or glial cells. Passes from plasma into the glomerular filtrate where it is removed by endocytosis mediated by LRP2 in the proximal tubule epithelium. Brain and kidney. Most prominently expressed in the cerebellar cortex, hippocampus and olfactory bulb. The C-terminus is not required for endocytic uptake in the proximal tubule epithelium. Phosphorylation sites are present in the extracellular medium. Belongs to the selenoprotein P family.