A protein has been identified that may help prion protein aggregate into its infectious form (PLoS Pathog., DOI: 10.1371/journal.ppat.1000666). This assisted biopathway could thus be a target for drugs against transmissible spongiform encephalopathies (TSEs) such as mad cow disease and human Creutzfeldt-Jakob disease, the family of brain disorders associated with prions. Prion protein (PrPC) is an endogenous neurological protein. In TSEs, it converts to a pathological form (PrPSc) and aggregates, but the mechanism by which this process occurs is not fully understood. Nigel M. Hooper and coworkers of the University of Leeds, in England, now find that the concentration of PrPSc in cells increases in the presence of glypican-1, a member of the heparan sulfate proteoglycan class of glycosylated proteins. When cellular expression of glypican-1 is inhibited, PrPSc formation is reduced. The researchers believe glypican-1 helps bring molecules of PrPC and PrPSc together, inducing conversion of the normal form into the infectious form. “Now that we know the identity of one of the key molecules in the disease process, we may in the future be able to design drugs that target this,” Hooper says.