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In vivo recognition of ovalbumin expressed by transgenic Leishmania is determined by its subcellular localization.

ABSTRACT: The importance of the site of Ag localization within microbial pathogens for the effective generation of CD8+ T cells has been studied extensively, generally supporting the view that Ag secretion within infected target cells is required for optimal MHC class I-restricted Ag presentation. In contrast, relatively little is known about the importance of pathogen Ag localization for the activation of MHC class II-restricted CD4+ T cells, despite their clear importance for host protection. We have used the N-terminal targeting sequence of Leishmania major hydrophilic acylated surface protein B to generate stable transgenic lines expressing physiologically relevant levels of full-length OVA on the surface of metacyclic promastigotes and amastigotes. In addition, we have mutated the hydrophilic acylated surface protein B N-terminal acylation sequence to generate control transgenic lines in which OVA expression is restricted to the parasite cytosol. In vitro, splenic dendritic cells are able to present membrane-localized, but not cytosolic, OVA to OVA-specific DO.11 T cells. Strikingly and unexpectedly, surface localization of OVA is also a strict requirement for recognition by OVA-specific T cells (DO.11 and OT-II) and for the development of OVA-specific Ab responses in vivo. However, recognition of cytosolic OVA could be observed with increasing doses of infection. These data suggest that, even under in vivo conditions, where varied pathways of Ag processing are likely to operate, the site of Leishmania Ag localization is an important determinant of immunogenicity and hence an important factor when considering the likely candidacy of vaccine Ags for inducing CD4+ T cell-dependent immunity.

SUBMITTER: Prickett S

PROVIDER: S-EPMC2695601 | biostudies-literature | 2006 Apr

REPOSITORIES: biostudies-literature

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In vivo recognition of ovalbumin expressed by transgenic Leishmania is determined by its subcellular localization.

Prickett Sara S Gray Peter M PM Colpitts Sara L SL Scott Phillip P Kaye Paul M PM Smith Deborah F DF

Journal of immunology (Baltimore, Md. : 1950) 20060401 8

The importance of the site of Ag localization within microbial pathogens for the effective generation of CD8+ T cells has been studied extensively, generally supporting the view that Ag secretion within infected target cells is required for optimal MHC class I-restricted Ag presentation. In contrast, relatively little is known about the importance of pathogen Ag localization for the activation of MHC class II-restricted CD4+ T cells, despite their clear importance for host protection. We have us ...[more]

PMID: 16585577

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Project description:Alba-domain proteins are RNA-binding proteins found in archaea and eukaryotes and recently studied in protozoan parasites where they play a role in the regulation of virulence factors and stage-specific proteins. This work describes in silico structural characterization, cellular localization and biochemical analyses of Alba-domain proteins in Leishmania infantum. We show that in contrast to other protozoa, Leishmania have two Alba-domain proteins, LiAlba1 and LiAlba3, representative of the Rpp20- and the Rpp25-like eukaryotic subfamilies, respectively, which share several sequence and structural similarities but also important differences with orthologs in other protozoa, especially in sequences targeted for post-translational modifications. LiAlba1 and LiAlba3 proteins form a complex interacting with other RNA-binding proteins, ribosomal subunits, and translation factors as supported by co-immunoprecipitation and sucrose gradient sedimentation analysis. A higher co-sedimentation of Alba proteins with ribosomal subunits was seen upon conditions of decreased translation, suggesting a role of these proteins in translational repression. The Leishmania Alba-domain proteins display differential cellular localization throughout the parasite development. In the insect promastigote stage, Alba proteins co-localize predominantly to the cytoplasm but they translocate to the nucleolus and the flagellum upon amastigote differentiation in the mammalian host and are found back to the cytoplasm once amastigote differentiation is completed. Heat-shock, a major signal of amastigote differentiation, triggers Alba translocation to the nucleolus and the flagellum. Purification of the Leishmania flagellum confirmed LiAlba3 enrichment in this organelle during amastigote differentiation. Moreover, partial characterization of the Leishmania flagellum proteome of promastigotes and differentiating amastigotes revealed the presence of other RNA-binding proteins, as well as differences in the flagellum composition between these two parasite lifestages. Shuttling of Alba-domain proteins between the cytoplasm and the nucleolus or the flagellum throughout the parasite life cycle suggests that these RNA-binding proteins participate in several distinct regulatory pathways controlling developmental gene expression in Leishmania.

Project description:This data was generated by ENCODE. If you have questions about the data, contact the submitting laboratory directly (Piero Carninci mailto:carninci@riken.jp). If you have questions about the Genome Browser track associated with this data, contact ENCODE (mailto:genome@soe.ucsc.edu). This track shows 5' cap analysis gene expression (CAGE) tags and clusters in RNA extracts (http://hgwdev.cse.ucsc.edu/cgi-bin/hgEncodeVocab?type=rnaExtract) from different sub-cellular localizations (http://hgwdev.cse.ucsc.edu/cgi-bin/hgEncodeVocab?type=localization) in multiple cell lines (http://hgwdev.cse.ucsc.edu/cgi-bin/hgEncodeVocab?type=cellType). A CAGE cluster is a region of overlapping tags with an assigned value that represents the expression level. The data in this track were produced as part of the ENCODE Transcriptome Project. Release 2 has three new downloads only files per experiment (Clusters, TSS Gencode 7 and TSS HMM) and four new cell lines (A459, AG04450, BJ and SK-N-SH_RA). Release 1 on hg19 contained the original data on hg18 (http://hgwdev.cse.ucsc.edu/cgi-bin/hgTrackUi?db=hg18&g=wgEncodeRikenCage) that was remapped and indicated in this release as Generation 0 since that data had no replicates. If there is both old and new generation data available for a particular experiment, only the new generation data is displayed and the older data is available for download. The new data for this track was done with a different process and has standard replicate numbers. The replicate labeling in the genome browser view is a counter indicating the total number of replicates submitted. The producing lab has replicate numbers that correspond to their internal bio-replicate numbering. Where these two numbering systems conflict, both are listed in the long label of the specific track. For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf Cells were grown according to the approved ENCODE cell culture protocols (http://hgwdev.cse.ucsc.edu/ENCODE/protocols/cell). RNA molecules longer than 200 nt were isolated from each subcellular compartment and then were fractionated into polyA+ and polyA- fractions as described in these protocols (http://hgwdev.cse.ucsc.edu/ENCODE/protocols/general/rnaExtracts.txt). The CAGE tags were sequenced from the 5' ends of cap-trapped cDNAs produced using RIKEN CAGE technology (Kodzius et al. 2006; Valen et al. 2009). To create the tag, a linker was attached to the 5' end of polyA+ or polyA- reverse-transcribed cDNAs which were selected by cap trapping (Carninci et al. 1996). The first 27 bp of the cDNA were cleaved using class II restriction enzymes. A linker was then attached to the 3' end of the cDNA. After PCR amplification, the tags were sequenced (36 bp single reads) using Illumina's Genome analyzer. Tags were mapped to the human genome (hg19) using the program delve (T. Lassmann manuscript in preparation). Delve is a new probabilistic aligner focused on giving the best possible alignment of reads to a genome rather than focusing on speed. It calculates the mapping accuracy (probability of each alignment being true or not) for each alignment. There is no set limit on the number of errors allowed and therefore the mapping rate is commonly 100%. However, for analysis it is recommended to discard alignments with low mapping qualities. Exceptions to the above protocol are the polyA- RNA samples from K562 cytosol, K562 nucleus, and prostate whole cell which were sequenced using ABI SOLiD (http://www.appliedbiosystems.com/absite/us/en/home/applications-technologies/solid-next-generation-sequencing.html) technology. These reads were mapped using Bowtie using default parameters. Clusters were defined as regions of overlapping CAGE reads. The expression level was computed as the number of reads making up the cluster, divided by the total number of reads sequenced, times 1 million.

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In vivo recognition of ovalbumin expressed by transgenic Leishmania is determined by its subcellular localization.

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In vivo recognition of ovalbumin expressed by transgenic Leishmania is determined by its subcellular localization.

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