Search

Abstract: Homogenous metacyclic promastigotes of Leishmania chagasi were isolated by buoyant density from in vitro heterogeneous cultures and used for biochemical characterization of isoforms of the major surface protease (MSP). Compared to stationary phase promastigotes, metacyclic cells had three times more MSP, produced 3-fold higher parasite loads in a mouse model in vivo, and were more resistant to complement-mediated lysis in vitro. These metacyclic L. chagasi expressed both the virulence-associated 59-kDa, and the constitutively expressed 63-kDa, isoforms of MSP. [Copyright &y& Elsevier]

Abstract: Trypanosomatid protozoa lack consensus promoters for RNA polymerase (RNAP) II. However, the artificial insertion of the T7 promoter (PT7) and the tetracycline repressor into Trypanosoma brucei cell lines expressing T7RNAP allows PT7-driven gene expression to be tetracycline-inducible. These cell lines provide a molecular tool to address protein function by several recombinant approaches. We describe here the development of an analogous Leishmania chagasi cell line bearing the genes for exogenous T7RNAP and the tetracycline repressor inserted in the multi-gene α-tubulin locus. A plasmid construct with PT7 and the tetracycline operator upstream of a reporter gene, when introduced into this cell line as episomal plasmids or chromosomal insertion into the non-coding strand of an 18SrRNA gene, resulted in tetracycline-inducible expression of the reporter as much as 16- and 150-fold, respectively. The reporter was under a much tighter control when chromosomally inserted than extra-chromosomally born. Furthermore, PT7 augmented the reporter’s expression 2-fold more in comparison to PT7-less constructs. This cell line is the first Leishmania spp. that allows the exogenous T7RNAP-driven gene expression to be tetracycline-inducible; and may provide a useful tool for addressing protein function by manipulating expression levels of Leishmania endogenous genes. [Copyright &y& Elsevier]

The intestine of Haemonchus contortus is hypersensitive to the effects of the anthelmintic fenbendazole (FBZ). The effects are postulated to stem from disruption of microtubules and interference with apical secretory vesicle transport, followed by release of digestive enzymes into the intestinal cell cytoplasm. Here, FBZ caused marker proteins for both apical (pepsinogen-like protease, PEP-1) and basal (cystatin-like protein) protein compartments to became homogeneously distributed in the cytoplasm of H. contortus intestinal cells. The observations with PEP-1 support the hypothesis that release of hydrolytic enzymes into the intestinal cell cytoplasm contributes to the mechanism of benzimidazole efficacy. A benzimidazole resistant isolate of H. contortus expressed type 1 and 2 intestinal β-tubulin transcripts that would encode predominately tyr200 and phe200 variants, respectively. This isolate was resistant to the known intestinal cell alterations induced by FBZ treatment in the susceptible isolate, including inhibition of apical vesicle transport. These results implicate type 1 β-tubulin in mediating apical vesicle transport in intestinal cells and suggest that the tyr200 variant is a determinant of FBZ resistance in intestinal cells. In contrast, the basal protein compartment demonstrated sensitivity to FBZ treatment in these otherwise “resistant” worms. Hence, distinct FBZ-sensitive components appear to be involved in distributing intestinal proteins into the described apical and basal compartments of normal worms. [Copyright &y& Elsevier]

In this work, a lateral flow immunoassay (LFIA) with peptide functionalized gold nanoparticles (termed as biotin- p peptide-AuNPs) has been developed for rapid, semi-quantitative detection of PTP1B activity without using any sophisticated equipment. In this method, the anti-phosphotyrosine (anti-pY) monoclonal antibody and streptavidin were used as test line and control line, respectively. The biotin- p peptide-AuNPs contain 10% biotinylated peptide ligand carry a motif SDGHEpYIYVDP with pY (phosphotyrosine) and 90% pentapeptide (CALNN) ligand, which are used as PTP1B substrates and LFIA labelling probes. The experimental results demonstrate that the as-proposed LFIA with biotin- p peptide-AuNPs exhibits a wide linear range (from 50 ng/mL to 10 μg/mL), a relatively low limit of detection (LOD, 44 ng/mL), and good specificity. In addition, the LFIA with biotin- p peptide-AuNPs has been successfully used to evaluate activity levels of PTP1B in four cell lysates and the detection results exhibit a consistent trend with that of commercial kit. A lateral flow immunoassay with peptide functionalized gold nanoparticles was developed for rapid, semi-quantitative detection of PTP1B activity. [Display omitted] • We developed a LFIA with peptide functionalized AuNPs for rapid, semi-quantitative detection of PTP1B activity. • The LFIA has been successfully used to evaluate activity levels of PTP1B in biological samples (e.g., cell lysates). • The result is in accordance with that of commercial kit. [ABSTRACT FROM AUTHOR]