o identify proteins that might exist in an equimolar complex with PrPC. Such PrPmycinteracting proteins would display an ICAT ratio of specific/ unspecific signals similar to that of PrPC. Based on this mass spectrometric approach, we found a small number of protein candidates equimolarly associated with PrPmyc in native brain homogenates. There are some caveats to the equimolarity filter described above. Supramolecular complexes encompassing PrPC may contain superstoichiometric amounts of accompanying molecules, in which case the ICAT ratios may be skewed. Conversely, if PrPC exists in a free form as well as in a complex, or in several different complexes, the partner proteins may appear to be substoichiometric in an immunoprecipitate. Therefore, even if the 11741928 seven proteins identified here represent promising candidates, the Interactome of Myc-Tagged PrP the tropism of prions, the interactome of PrPC and PrPSc in lymphoid organs will also be of interest. 
The inoculation of wildtype animals with myc-tagged prions may help elucidating the initial events that occur during infection of an animal with prions. Finally, the successful conversion of PrPmyc into a protease-resistant moiety may allow for the purification of native PrPSc-containing complexes using the techniques described above for PrPC. The latter studies may lead to the identification of the elusive chaperones involved in prion propagation, strain barriers and strain adaptation, as well as the crossing of prion species barriers. Materials and Methods Generation of myc-tagged PrPC PCRs were performed in 50 ml volumes containing 10 ng of template DNA WP 1130 phgPrP, 200 mM of each dNTP, 20 pmol of Interactome of Myc-Tagged PrP UniProt accession number P16330 Q62059 Protein name and cICAT peptide sequences 29,39-cyclic-nucleotide 39-phosphodiesterase, Chondroitin sulfate proteoglycan core protein 2, Neuronal membrane glycoprotein M6-a, Neurofascin, Gene Cnp Cspg2 Function/localization Associated with membrane structures of brain white matter May play a role in intercellular signaling and in connecting cells with the extracellular matrix. May take part in the regulation of cell motility, growth and differentiation. Multi-pass membrane protein. Enriched in the granule cell layer of the cerebellum but not in the molecular layer or white matter. Belongs to the myelin proteolipid protein family. Single-pass type I membrane protein. Cell adhesion, ankyrin-binding protein which may be involved in neurite extension, axonal guidance, synaptogenesis, myelination and neuron-glial cell interactions Cellular prion protein. Coated pits. Necessary for the fragmentation of Golgi stacks 23964788 during mitosis and for their reassembly after mitosis P35802 Gpm6a Q810U3 Nfasc P04925 Q80U89 Q01853 Major prion protein, Prnp MKIAA0034 protein ), Cltc Valosin containing protein, transitional endoplasmic reticulum ATPase, Vcp doi:10.1371/journal.pone.0004446.t001 each primer, 1 ml of ”Advantage IIpolymerase, 10 ml of 106 reaction buffer supplied by the manufacturer. Reaction mixtures were kept at 94uC for 5 min in a thermocycler to inactivate the blocking antibody,,and cycled 30 times. The two PCR products of PrP cDNA were cleaved with ClaI and ligated into the pGEM-T easy vector system, generating plasmid pGEM-PrP; ClaI. The final insert of pGEMPrP; ClaI consists of a mutated PrP cDNA fragment extending from the XmaI restriction site of the PrP ORF to the Pmli restriction site located 39 of the PrP coding region. The my
