Prion Protein as Copper-Binding Protein at the Synapse

Various approaches have been taken to study the function of prion proteins. Biochemical methods were applied to search for a binding partner of PrPC which is attached to the cell surface by a glycosylphosphatidylinositol GPI anchor (1 ). The glial fibrillary acidic protein was one of the first possible binding partners to be described (2 ) followed by Bcl-2 (3 ,4 ), molecular chaperones (5) , amyloid precursor-like protein 1 (6 ), the 37-kDa laminin receptor (7 ) and a 66-kDa membrane protein which has not been characterized in more detail (8 ). However, it has not been possible to show any biological significance for PrPC binding of these proteins. Based on biochemical analyses of chicken PrPC, Harris et al. (9 ) hypothesized that PrPC may play a role in the regulation of the expression of cholinergic receptors at the neuromuscular endplate.