Characterization of a protein with unknown function (LinJ.30.3360) in Leishmania amazonensis and Leishmania infantum.

Leishmaniasis is a disease caused by trypanosomatid protozoa of the genus Leishmania. In the Americas, the species Leishmania amazonensis is predominantly associated with American cutaneous leishmaniasis (ACL) while L. infantum is an agent of visceral leishmaniasis (VL). The genome sequences of Leishmania spp. have shown that each genome can contain about 8000 genes encoding proteins, more than half of which have an unknown function (''hypotheticals") at the time of publication. To understand the biology and genome of the organisms, it is important to discover the function of these "hypothetical" proteins; however, few studies have focused on their characterizations. Previously, LinJ.30.3360 (a protein with unknown function) was identified as immunogenic to canine serum with VL and a good antigen to diagnose the visceral form in dogs. Here, we show that the LinJ.30.3360 protein is conserved in L. infantum, L. tarantolae, L. donovani, L. major, L. mexicana, L. braziliensis, L. panamensis, Leptomonas pyrrhocoris, and Leptomonas seymouri. It has been annotated as a MORN (Membrane Occupation and Recognition Nexus) domain protein. However, since the function of this motif is unknown, functional inferences based on the primary sequence are not possible. The protein has a folded ß-leaf secondary structure, and phosphorylation was the only post-translational modification (PTM) found using prediction approach. Experiments have shown that it is located close to the flagellar pocket and presents similar abundance in both L. amazonensis and L. infantum. Furthermore, because it is a conserved protein in trypanosomatids but not in mammals and also because of its antigenicity, LinJ.30.3360 may constitute a potential drug target and/or vaccine for leishmaniasis.

Identification of potential biomarkers for systemic lupus erythematosus diagnosis using two-dimensional differential gel electrophoresis (2D-DIGE) and mass spectrometry.

Systemic lupus erythematosus (SLE) is an autoimmune disease of the connective tissue with a large spectrum of clinical manifestations. Immune deregulation leads to autoantibody and immune complexes overproduction, complement activation, and persistent tissue inflammation. Considering that the current diagnosis depends on the interpretation of the complex criteria established by the American College of Rheumatology and that the disease course is characterized by unpredictable activations and remissions, each patient develops different manifestations, and therefore, the discovery of specific biomarkers is urgently required. Therefore, this study aimed to identify putative biomarkers for active and inactive SLE potentially capable in distinguishing laboratorial SLE from other autoimmune diseases. The 2D-DIGE proteomics technique was used to evaluate the differential abundance of proteins between patients with active SLE, inactive SLE, patients with other autoimmune disease, and healthy individuals. Six proteins showed increased abundance in active SLE (A) and inactive SLE (I) compared to the C and O groups, but not between groups A and I. There were two transthyretin (TTR) fragments or proteins with a structure similar to TTR (accession numbers: PDB: 1GKO_A and 2PAB_A), retinol-binding protein 4 (RBP4) isoform X1 (no information in databases such as UNIPROT), and antibody fragments. Two proteins, APO-AIV and SP-40,40, were upregulated in group A than in O and C and in group I versus C, but not in group I versus O. Therefore, we suggest these proteins to be considered as candidates for the diagnosis of SLE.