Comprehensive proteomics analysis of glycosomes from Leishmania donovani.

Leishmania donovani is a kinetoplastid protozoan that causes a severe and fatal disease kala-azar, or visceral leishmaniasis. L. donovani infects human host after the phlebotomine sandfly takes a blood meal and resides within the phagolysosome of infected macrophages. Previous studies on host-parasite interactions have not focused on Leishmania organelles and the role that they play in the survival of this parasite within macrophages. Leishmania possess glycosomes that are unique and specialized subcellular microbody organelles. Glycosomes are known to harbor most peroxisomal enzymes and, in addition, they also possess nine glycolytic enzymes. In the present study, we have carried out proteomic profiling using high resolution mass spectrometry of a sucrose density gradient-enriched glycosomal fraction isolated from L. donovani promastigotes. This study resulted in the identification of 4022 unique peptides, leading to the identification of 1355 unique proteins from a preparation enriched in L. donovani glycosomes. Based on protein annotation, 566 (41.8%) were identified as hypothetical proteins with no known function. A majority of the identified proteins are involved in metabolic processes such as carbohydrate, lipid, and nucleic acid metabolism. Our present proteomic analysis is the most comprehensive study to date to map the proteome of L. donovani glycosomes.

A bioinformatics approach to reanalyze the genome annotation of kinetoplastid protozoan parasite Leishmania donovani.

Leishmania donovani is a kinetoplastid protozoan parasite which causes the fatal disease visceral leishmaniasis in humans. Genome sequencing of L. donovani revealed information about the arrangement of genes and genome architecture. After curation of the genome sequence, many genes in L. donovani were assigned as truncated or "partial" genes by the genome sequencing group. In the present study, we have carried out an extensive analysis and attempted to improve the gene models of these partial genes. Our analysis resulted in the identification of 308 partial genes in L. donovani, which were further categorized as C-terminal extensions, joining of genes, tandemly repeated paralogs and wrong chromosomal assignments. We have analyzed each of these genes from these categories and have improved the annotation of existing gene models in L. donovani. Some of these corrections have been confirmed by mass spectrometry derived peptide data from our previous comparative proteogenomics study in L. donovani.

Neglected tropical diseases and omics science: proteogenomics analysis of the promastigote stage of Leishmania major parasite.

Among the neglected tropical diseases, leishmaniasis is one of the most devastating, resulting in significant mortality and contributing to nearly 2 million disability-adjusted life years. Cutaneous leishmaniasis is a debilitating disorder caused by the kinetoplastid protozoan parasite Leishmania major, which results in disfiguration and scars. L. major genome was the first to be sequenced within the genus Leishmania. Use of proteomic data for annotating genomes is a complementary approach to conventional genome annotation approaches and is referred to as proteogenomics. We have used a proteogenomics-based approach to map the proteome of L. major and also annotate its genome. In this study, we searched L. major promastigote proteomic data against the annotated L. major protein database. Additionally, we searched the proteomic data against six-frame translated L. major genome. In all, we identified 3613 proteins in L. major promastigotes, which covered 43% of its proteome. We also identified 26 genome search-specific peptides, which led to the identification of three novel genes previously not identified in L. major. We also corrected the annotation of N-termini of 15 genes, which resulted in extension of their protein products. We have validated our proteogenomics findings by RT-PCR and sequencing. In addition, our study resulted in identification of 266 N-terminally acetylated peptides in L. major, one of the largest acetylated peptide datasets thus far in Leishmania. This dataset should be a valuable resource to researchers focusing on neglected tropical diseases.