These changes are consistent with normal aging in mice. on prion replication in mice, we conclude that Sho is the first non-PrP marker specific for prion disease. Additional studies using this paradigm may provide insight into the cellular pathways and systems subverted by PrPScduring prion disease. == Author Summary == Shadoo is a protein Mouse monoclonal to CD62L.4AE56 reacts with L-selectin, an 80 kDaleukocyte-endothelial cell adhesion molecule 1 (LECAM-1).CD62L is expressed on most peripheral blood B cells, T cells,some NK cells, monocytes and granulocytes. CD62L mediates lymphocyte homing to high endothelial venules of peripheral lymphoid tissue and leukocyte rollingon activated endothelium at inflammatory sites that resembles the prion Nardosinone protein, which causes prion diseases such as Creutzfeldt-Jakob disease in humans and mad cow disease. In this paper, we demonstrate that during prion disease in animals, levels of Shadoo were reduced in the brain and correlated with levels of infectious prions. This phenomenon occurred following infection with 14 different prion strains but was not observed following the accumulation of other aggregated proteins, including those that cause Alzheimer’s disease and Parkinson’s disease. Thus, Shadoo levels in the brain are a specific indicator of prion disease status, and it may be possible to exploit this observation for diagnostic purposes. Although we show that Shadoo itself is unlikely to influence prion disease, using Shadoo as a tool to probe the biology of prions may be a useful strategy for deciphering how prions damage the brain. == Introduction == Prion diseases, such as Creutzfeldt-Jakob disease (CJD) in humans, bovine spongiform encephalopathy (BSE), and chronic wasting disease (CWD) in cervids, are invariably fatal neurodegenerative disorders caused by the accumulation of misprocessed prion protein (PrPSc) in the brain. The central pathognomonic event in prion diseases is the post-translational refolding of the cellular prion protein (PrPC) into PrPSc, a partially protease-resistant and -sheet-enriched conformation that is infectious[2],[3]. Mice lacking PrPCfail to develop prion disease and do not propagate infectious prions in their brains, indicating that PrPCexpression is required for prion replication[4],[5]. Despite a clear involvement in pathogenesis, the mechanism by which PrPSccauses neuronal dysfunction during prion disease remains obscure. Although PrPCis known to interact with or reside in close spatial proximity to numerous other proteins in the cell membrane[6],[7],[8], none of these identified proteins has been shown to be associated with prion disease pathogenesis or prion replication. The mammalian prion protein family consists of three members: PrPC; Doppel (Dpl), a testes-specific protein involved in the proper functioning of the male reproductive system[9],[10]; and Shadoo (Sho), a recently identified neuronal paralog of PrPCencoded by theSprngene[1],[11]. Unlike Dpl, which resembles the alpha-helical C-terminal domain of PrPC[12], Sho is reminiscent of the flexibly disordered N-terminal domain of PrP. In particular, the similarity between PrP and Sho is striking within the alanine/glycine-rich hydrophobic tract. This region of PrP is of particular interest because (i) it is the most-conserved region among PrP ortholog sequences; (ii) it is conformationally altered in PrPSc[13]; (iii) its deletion renders PrP toxic to cerebellar neurons[14],[15]; and (iv) deletions within this region result in a loss of PrPC-associated neuroprotective activity[1]. Like PrPC, Sho is an N-glycosylated GPI-anchored protein that is expressed in the brain and exhibits neuroprotective properties in response to various neurotoxic stimuli in cells[1],[16]. Both PrPCand Sho undergo endoproteolytic cleavage just N-terminal to the hydrophobic tract to generate a C-terminal fragment termed C1[1],[17]. PrPCis also cleaved in the vicinity of residue 88 to generate a distinct C-terminal fragment termed C2[17]. Production of the C2 fragment is greatly increased during prion disease, likely due to the inability of the cell to clear aggregated PrPScvia lysosomal degradation[18],[19]. Although the biological role of Sho in the brain is currently unknown, knockdown ofSprnin mouse embryos lacking PrP expression results in a lethal phenotype[20], arguing for an overlapping function with PrPC. However, Sho levels are unchanged in the brains of adult mice Nardosinone lacking PrPC[1], indicating that cross-regulation of protein expression does not occur between the two proteins. The influence, if any, of Sho on prion replication and pathogenesis remains to be evaluated. Analogously toPrnpencoding the prion protein, polymorphisms have been identified in the human, ovine, Nardosinone and murineSprngenes; whether these are linked to prion disease incubation time or susceptibility is.