Lonomia obliqua bristle extract modulates Rac1 activation, membrane dynamics and cell adhesion properties

Lonomia obliqua is a caterpillar of potential therapeutic interest whose venom is able to induce severe blood leakage and modulate leukocyte migration. Since both phenotypes are associated with changes in cytoskeleton dynamics and cell adhesion properties, the aim of this study was to analyze the effects of Lonomia obliqua bristle extract (LOBE) in cell adhesion and migration signaling. Proteomic analysis revealed that epithelial cells (CHO-K1) exposed to LOBE (30 μg/mL, 30 min) exhibited changes in levels of actin regulatory proteins, including RhoGTPases. These changes correlated with an increase in the activity of the RhoGTPase family member Rac as measured by Förster resonance energy transfer (FRET). When plated in migration promoting conditions, CHO-K1 cells exposed to LOBE (10 μg/mL) showed an increase in membrane ruffling after short (30 min) period of incubation that was accompanied by changes in the distribution of the adhesion markers paxillin, vinculin and an increase of focal adhesion kinase autophosphorylation levels (Y397), suggesting changes in cell-extracellular matrix (ECM) adhesion properties and signaling. These data suggest that LOBE possesses bioactive molecules that are capable to modulated cell migration signaling, cytoskeletal dynamics and cell-ECM properties of several cell types.

Expression profile of Rhipicephalus microplus vitellogenin receptor during oogenesis

The vitellogenin receptor (VgR), which belongs to the low-density lipoprotein receptors (LDLR) family, regulates the absorption of yolk protein accumulated in developing oocytes during oogenesis. In the present study, the full sequence of Rhipicephalus microplus VgR (RmVgR) and the partial sequence of Rhipicephalus appendiculatus VgR (RaVgR) ORF were determined and cloned. The RmVgR amino acid sequence contains the five highly conserved structural motifs characteristic of LDLR superfamily members, the same overall structure as observed in other species. Phylogenetic analysis separated VgRs in two major groups, corresponding to receptors from acarines and insects. Consistent with observations from other arthropods, RmVgR was specifically expressed in the ovarian tissue and its peak of expression occurs in females that are detaching from the host. Silencing with RmVgR dsRNA reduced VgR expression, which resulted in reduced fertility, evidenced by a decrease in the number of larvae. The present study confirms RmVgR is a specific receptor involved in yolk protein uptake and oocyte maturation in R. microplus, playing an important role in tick reproduction.

Validation of Mycobacterium tuberculosis dihydroneopterin aldolase as a molecular target for anti-tuberculosis drug development

An early step of target validation in antimicrobial drug discovery is to prove that a gene coding for a putative target is essential for pathogen's viability. However, little attention has been paid to demonstrate the causal links between gene essentiality and a particular protein function that will be the focus of a drug discovery effort. This should be considered an important step in target validation since a growing number of proteins are found to exhibit multiple and unrelated tasks. Here, we show that the Mycobacterium tuberculosis (Mtb) folB gene is essential and that this essentiality depends on the dihydroneopterin aldolase/epimerase activities of its protein product, the FolB protein from the folate biosynthesis pathway. The wild-type (WT) MtFolB and point mutants K99A and Y54F were cloned, expressed, purified and monitored for the aldolase, epimerase and oxygenase activities using HPLC. In contrast to the WT MtFolB, both mutants have neither aldolase nor epimerase activities in the conditions assayed. We then performed gene knockout experiments and showed that folB gene is essential for Mtb survival under the conditions tested. Moreover, only the WT folB sequence could be used as a rescue copy in gene complementation studies. When the sequences of mutants K99A or Y54F were used for complementation, no viable colonies were obtained, indicating that aldolase and/or epimerase activities are crucial for Mtb survival. These results provide a solid basis for further work aiming to develop new anti-TB agents acting as inhibitors of the aldolase/epimerase activities of MtFolB.

Thermodynamics, functional and structural characterization of inosine–uridine nucleoside hydrolase from Leishmania braziliensis

Inosine–uridine nucleoside hydrolase fromLeishmania braziliensisis a nonspecific enzyme that contains a disulfide bond not needed for tetramer stabilization.

Biochemical, thermodynamic and structural studies of recombinant homotetrameric adenylosuccinate lyase fromLeishmania braziliensis

Functional and structural data suggested that His¹⁹⁷and Ser³²²residues play a role inLbASL catalysis.

Gene replacement and quantitative mass spectrometry approaches validate guanosine monophosphate synthetase as essential for Mycobacterium tuberculosis growth

Guanosine monophosphate synthetase (GMPS), encoded by guaA gene, is a key enzyme for guanine nucleotide biosynthesis in Mycobacterium tuberculosis. The guaA gene from several bacterial pathogens has been shown to be involved in virulence; however, no information about the physiological effect of direct guaA deletion in M. tuberculosis has been described so far. Here, we demonstrated that the guaA gene is essential for M. tuberculosis H37Rv growth. The lethal phenotype of guaA gene disruption was avoided by insertion of a copy of the ortholog gene from Mycobacterium smegmatis, indicating that this GMPS protein is functional in M. tuberculosis. Protein validation of the guaA essentiality observed by PCR was approached by shotgun proteomic analysis. A quantitative method was performed to evaluate protein expression levels, and to check the origin of common and unique peptides from M. tuberculosis and M. smegmatis GMPS proteins. These results validate GMPS as a molecular target for drug design against M. tuberculosis, and GMPS inhibitors might prove to be useful for future development of new drugs to treat human tuberculosis.

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The guaA gene is essential for M. tuberculosis H37Rv growth.

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The lethal phenotype of guaA gene disruption was avoided by the ortholog gene from M. smegmatis.

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Multiplexed LC–MS/MS analysis was performed to validate protein expression levels.

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The guaA essentiality was confirmed by gene replacement and quantitative mass spectrometry.

Use of SILAC for exploring sheddase and matrix degradation of fibroblasts in culture by the PIII SVMP atrolysin A: Identification of two novel substrates with functional relevance

Snake venom metalloproteinases (SVMPs) in Viperid venoms primarily function to give rise to local and systemic hemorrhage following snake envenomation. Years of research on these toxins, both in vitro and in vivo, indicate that they function by disrupting capillary basement membranes, stromal matrix and cell-cell and cell-matrix contacts to allow escape of capillary contents under pressure. However, most of these studies used either defined substrates in vitro or were limited by relevant antibodies for detection of sites of action in vivo. In this investigation we use stable isotope-labeled amino acids in culture (SILAC) to determine novel proteolytic activities for exogenously added atrolysin A, a hemorrhagic PIII SVMP isolated from Crotalus atrox venom. When comparing the solubilized products of SILAC-labeled cultured human fibroblasts treated with atrolysin A to that of untreated fibroblasts using LC/MS/MS, several proteins were identified as being released into the culture media specifically due to atrolysin A proteolytic activity. These included collagen VI, fibronectin, fibulin 2 and annexin V. Of particular interest was the observation of collagen VI and annexin V in that the release of these substrates could play a role in altering hemostasis and promote hemorrhage caused by the more typical actions of atrolysin A. In summary, this study demonstrates the utility of SILAC for exploring sheddase activity with cells in culture and suggests the presence of two novel substrates for SVMPs that may play a pathological role in altering host hemostasis during envenomation.