Prion diseases are infectious neurodegenerative disorders linked to the accumulation in the central nervous system of the abnormally folded prion protein (PrP) scrapie (PrPsc), which is thought to be the infectious agent. Once present, PrPsc catalyzes the conversion of naturally occurring cellular PrP (PrPc) to PrPsc. Prion infection is usually initiated in peripheral organs, but the mechanisms involved in infectious spread to the brain are unclear. We found that both PrPc and PrPsc were actively released into the extracellular environment by PrP-expressing cells before and after infection with sheep prions, respectively. Based on Western blot with specific markers, MS, and morphological analysis, our data revealed that PrPc and PrPsc in the medium are associated with exosomes, membranous vesicles that are secreted upon fusion of multivesicular endosomes with the plasma membrane. Furthermore, we found that exosomes bearing PrPsc are infectious. Our data suggest that exosomes may contribute to intercellular membrane exchange and the spread of prions throughout the organism. Infectious prion diseases include Kuru and variant CreutzfeldtJakob disease in humans, scrapie in sheep, and bovine spongiform encephalopathy in cattle (1, 2). In these diseases, infectious prions enter the host through the gastrointestinal tract and migrate to the spleen, after which they cause pathology in the central nervous system (3). Different cell types, including immune cells, contribute to the replication and transfer of infectious prions from peripheral sites of replication to the brain (4). The mechanisms underlying this intercellular transfer are not elucidated (2), but close cell contact may be involved (5). Nevertheless, cell-free conversion data (6) indicate that additional pathways involving non-cell-associated forms of infectious agent may participate in the propagation of prions. Consistent with this notion, the culture medium of scrapie-infected GT1 cells was infectious (7), suggesting that PrPsc may be released from cells and induce transconformation of PrPc in neighboring cells. Noninfected PrP-expressing cells may also have the ability to release PrPc, given that PrPc has been shown to be transferred between cells (8). Thus, release of PrPc and PrPsc by PrP-expressing cells may provide for a potential cellular mechanism underlying propagation and replication of prions. In this study, we further explored the possibility that PrPsc and PrPc may occur in a non-cell-associated form and analyzed their nature in the culture medium of infected and noninfected cell cultures. Our studies indicate that PrPsc and PrPc are associated with exosomes, secreted intralumenal contents of multivesicular bodies (MVB). These findings open the possibility that exosomes may provide for intercellular carriers of both PrPc and PrPsc. Materials and MethodsCells, Reagents, and Antibodies. Rov cells are derived from the RK13 cell line and express the ovine VRQ allele of PrP in a doxycyclinedependent manner (9). Mov cells are immortalized neuroglial ...

SummaryMultiple sclerosis is an autoimmune disease that is caused by the interplay of genetic, particularly the HLA-DR15 haplotype, and environmental risk factors. How these etiologic factors contribute to generating an autoreactive CD4+ T cell repertoire is not clear. Here, we demonstrate that self-reactivity, defined as “autoproliferation” of peripheral Th1 cells, is elevated in patients carrying the HLA-DR15 haplotype. Autoproliferation is mediated by memory B cells in a HLA-DR-dependent manner. Depletion of B cells in vitro and therapeutically in vivo by anti-CD20 effectively reduces T cell autoproliferation. T cell receptor deep sequencing showed that in vitro autoproliferating T cells are enriched for brain-homing T cells. Using an unbiased epitope discovery approach, we identified RASGRP2 as target autoantigen that is expressed in the brain and B cells. These findings will be instrumental to address important questions regarding pathogenic B-T cell interactions in multiple sclerosis and possibly also to develop novel therapies.

Engrailed also confers in vivo protection against 6-hydroxydopamine and α-synuclein-A30P.Finally, the unilateral infusion of Engrailed into the midbrain increases striatal dopamine content resulting in contralateral amphetamine-induced turning. Therefore, Engrailed is both a

Summary The HLA-DR15 haplotype is the strongest genetic risk factor for multiple sclerosis (MS), but our understanding of how it contributes to MS is limited. Because autoreactive CD4 + T cells and B cells as antigen-presenting cells are involved in MS pathogenesis, we characterized the immunopeptidomes of the two HLA-DR15 allomorphs DR2a and DR2b of human primary B cells and monocytes, thymus, and MS brain tissue. Self-peptides from HLA-DR molecules, particularly from DR2a and DR2b themselves, are abundant on B cells and thymic antigen-presenting cells. Furthermore, we identified autoreactive CD4 + T cell clones that can cross-react with HLA-DR-derived self-peptides (HLA-DR-SPs), peptides from MS-associated foreign agents (Epstein-Barr virus and Akkermansia muciniphila ), and autoantigens presented by DR2a and DR2b. Thus, both HLA-DR15 allomorphs jointly shape an autoreactive T cell repertoire by serving as antigen-presenting structures and epitope sources and by presenting the same foreign peptides and autoantigens to autoreactive CD4 + T cells in MS.

The Chediak-Higashi syndrome (CHS) is a human recessive autosomal disease caused by mutations in a single gene encoding a protein of unknown function, called lysosomal-trafficking regulator. All cells in CHS patients bear enlarged lysosomes. In addition, T- and natural killer cell cytotoxicity is defective in these patients, causing severe immunodeficiencies. We have analyzed major histocompatibility complex class II functions and intracellular transport in Epstein Barr Virus–transformed B cells from CHS patients. Peptide loading onto major histocompatibility complex class II molecules and antigen presentation are strongly delayed these cells. A detailed electron microscopy analysis of endocytic compartments revealed that only lysosomal multilaminar compartments are enlarged (reaching 1–2 μm), whereas late multivesicular endosomes have normal size and morphology. In contrast to giant multilaminar compartments that bear most of the usual lysosomal markers in these cells (HLA-DR, HLA-DM, Lamp-1, CD63, etc.), multivesicular late endosomes displayed reduced levels of all these molecules, suggesting a defect in transport from the trans-Golgi network and/or early endosomes into late multivesicular endosomes. Further insight into a possible mechanism of this transport defect came from immunolocalizing the lysosomal trafficking regulator protein, as antibodies directed to a peptide from its COOH terminal domain decorated punctated structures partially aligned along microtubules. These results suggest that the product of the Lyst gene is required for sorting endosomal resident proteins into late multivesicular endosomes by a mechanism involving microtubules.

The use of grafted trypsin magnetic beads in a microchip for performing protein digestion is described. The PDMS device uses strong magnets to create a magnetic field parallel to the flow with a strong gradient pointing through the center of the chip channel. This allows for the formation of a low-hydrodynamic resistance plug of magnetic trypsin beads that serves as a matrix for protein digestion. This device represents an inexpensive way of fabricating a multi open-tubular-like column with an appropriate pore size for proteins. Kinetics studies of the hydrolysis of a model peptide show a 100-fold increase in digestion speed obtained by the microsystem when compared to a batch wise system. This system also offers the great advantage of easy replacement, as the bead matrix is easily washed out and replaced. High performance and reproducibility for digesting recombinant human growth hormone are confirmed by analysing the digest products in both CE and MALDI-TOF MS. Similar sequence coverage (of about 44%) is obtained from MS analysis of products after 10 minutes on-chip and 4 h with soluble trypsin in bulk.

Multiple sclerosis is an immune-mediated autoimmune disease of the central nervous system that develops in genetically susceptible individuals and likely requires environmental triggers. The autoantigens and molecular mimics triggering the autoimmune response in multiple sclerosis remain incompletely understood. By using a brain-infiltrating CD4+ T cell clone that is clonally expanded in multiple sclerosis brain lesions and a systematic approach for the identification of its target antigens, positional scanning peptide libraries in combination with biometrical analysis, we have identified guanosine diphosphate (GDP)–l-fucose synthase as an autoantigen that is recognized by cerebrospinal fluid–infiltrating CD4+ T cells from HLA-DRB3*–positive patients. Significant associations were found between reactivity to GDP-l-fucose synthase peptides and DRB3*02:02 expression, along with reactivity against an immunodominant myelin basic protein peptide. These results, coupled with the cross-recognition of homologous peptides from gut microbiota, suggest a possible role of this antigen as an inducer or driver of pathogenic autoimmune responses in multiple sclerosis.

We have characterized Schizosaccharomyces pombe open reading frames encoding potential orthologues of constituents of the evolutionarily conserved Saccharomyces cerevisiae Nup84 vertebrate Nup107-160 nuclear pore subcomplex, namely Nup133a, Nup133b, Nup120, Nup107, Nup85, and Seh1. In spite of rather weak sequence conservation, in vivo analyses demonstrated that these S. pombe proteins are localized at the nuclear envelope. Biochemical data confirmed the organization of these nucleoporins within conserved complexes. Although examination of the S. cerevisiae and S. pombe deletion mutants revealed different viability phenotypes, functional studies indicated that the involvement of this complex in nuclear pore distribution and mRNA export has been conserved between these highly divergent yeasts. Unexpectedly, microscopic analyses of some of the S. pombe mutants revealed cell division defects at the restrictive temperature (abnormal septa and mitotic spindles and chromosome missegregation) that were reminiscent of defects occurring in several S. pombe GTPase Ran (Ran Sp )/Spi1 cycle mutants. Furthermore, deletion of nup120 moderately altered the nuclear location of Ran Sp /Spi1, whereas overexpression of a nonfunctional Ran Sp /Spi1-GFP allele was specifically toxic in the ⌬nup120 and ⌬nup133b mutant strains, indicating a functional and genetic link between constituents of the S. pombe Nup107-120 complex and of the Ran Sp /Spi1 pathway.