Types Of Protease Inhibitors Research Articles

Overview on Cysteine Protease Inhibitors as Chemotherapy for Schistosomiasis mansoni in Mice and also its Effect on the Parasitological and Immunological Profile

The present study evaluated the use of 3 types of Cysteine Protease Inhibitors (CPIs) with praziquantel (PZQ) as chemotherapy against schistosomiasis mansoni in mice. All groups were going to assessment of fluromethylketone (FMK), Vinyl Sulfone (VS) and Sodium Nitro Prussid (SNP) by measurement of parasitological, immunological and histological parameters. In our study, The ova count/gm liver or intestine on with PZQ treatment showed 99.1 and 95.2% Percent Reduction (PR), respectively compared to control group. The most effective CPI was FMK when combined with PZQ recording 99.8 and 99.6% PR for liver and intestine, respectively. Regarding to the oogram pattern, FMK, VS and SNP treatment either at 3 or 5 wk PI revealed marked decrease in the immature and mature ova counts and an increase of the dead ova percentages. The effect of CPIs was studied on the PR of Mean Granuloma Diameter (MGD) and Mean Granuloma Number (MGN) of infected treated groups compared to infected control and PZQ treated groups. FMK treatment proved to be highly was effective against S. mansoni in mice disintegrating ova and reduction in granulomatous size and numbers. The microscopic examination of liver sections of infected mice showed a large cellular granuloma with living central ova. sections of Infected mice liver treated with FMK or VS alone or combined with PZQ showed a great reduction in granuloma size as small cellular granuloma with central degenerated ova. We observed that these CPIs alone or combined with PZQ could effectively block schistosomal activity and prevented its growth and differentiation. Briefly, the best schistosomicidal effect of CPIs, that gained by drug administration orally in a dose of 50 mg kg(-1) mouse, was observed with FMK. This was followed by VS and lastly with SNP. These results gave evidence that CPIs can selectively arrest parasite replication without untoward toxicity to the host.

Homology modeling and structural validation of tissue factor pathway inhibitor

Blood coagulation is a cascade of complex enzymatic reactions which involves specific proteins and cellular components to interact and prevent blood loss. The coagulation process begins by either “Tissue Dependent Pathway” (also known as extrinsic pathway) or by “contact activation pathway” (also known as intrinsic pathway). TFPI is an endogenous multivalent Kunitz type protease inhibitor which inhibits Tissue factor dependent pathway by inhibiting Tissue Factor:Factor VIIa (TF:FVIIa) complex and Factor Xa. TFPI is one of the most studied coagulation pathway inhibitor which has various clinical and potential therapeutic applications, however, its exact mechanism of inhibition is still unknown. Structure based mechanism elucidation is commonly employed technique in such cases. Therefore, in the current study the generated a complete TFPI structural model so as to understand the mechanistic details of it's functioning. The model was checked for stereochemical quality by PROCHECK-NMR, WHATIF, ProSA, and QMEAN servers. The model was selected, energy minimized and simulated for 1.5ns. The result of the study may be a guiding point for further investigations on TFPI and its role in coagulation mechanism.

Group A Streptococcal Cysteine Protease Cleaves Epithelial Junctions and Contributes to Bacterial Translocation

Group A Streptococcus (GAS) translocates across the host epithelial barrier. Streptococcal pyrogenic exotoxin B (SpeB) directly cleaves junctional proteins. The proteolytic efficacy of SpeB allows GAS to translocate across the epithelial barrier. SpeB-mediated dysfunction of the epithelial barrier may have important implications for not only bacterial invasion but also dissemination of other virulence factors throughout intercellular spaces. Group A Streptococcus (GAS) is an important human pathogen that possesses an ability to translocate across the epithelial barrier. In this study, culture supernatants of tested GAS strains showed proteolytic activity against human occludin and E-cadherin. Utilizing various types of protease inhibitors and amino acid sequence analysis, we identified SpeB (streptococcal pyrogenic exotoxin B) as the proteolytic factor that cleaves E-cadherin in the region neighboring the calcium-binding sites within the extracellular domain. The cleaving activities of culture supernatants from several GAS isolates were correlated with the amount of active SpeB, whereas culture supernatants from an speB mutant showed no such activities. Of note, the wild type strain efficiently translocated across the epithelial monolayer along with cleavage of occludin and E-cadherin, whereas deletion of the speB gene compromised those activities. Moreover, destabilization of the junctional proteins was apparently relieved in cells infected with the speB mutant, as compared with those infected with the wild type. Taken together, our findings indicate that the proteolytic efficacy of SpeB in junctional degradation allows GAS to invade deeper into tissues.

Plasticity of protease gene expression in Helicoverpa armigera upon exposure to multi-domain Capsicum annuum protease inhibitor

BackgroundA multi-domain Pin-II type protease inhibitor from Capsicum annuum (CanPI-7) is known to be effective against the insect pest, Helicoverpa armigera. The present study is an attempt to investigate the optimal dose of recombinant CanPI-7 (rCanPI-7) for effective antibiosis to H. armigera and further to characterize the responses of digestive proteases upon rCanPI-7 ingestion. MethodsThe gut protease activity was assessed biochemically and transcript accumulation pattern for selected trypsin and chymotrypsin genes was analyzed by quantitative Real-Time PCR. ResultsThe growth retardation upon exposure to rCanPI-7 was more prominent in neonates as compared to third instar larvae. Influence of stage and dosage of rCanPI-7 was conspicuous on the expression and regulation of candidate trypsin and chymotrypsin genes in H. armigera. The transcript accumulation pattern correlated with the protease activity in rCanPI-7 exposed larvae. ConclusionsWe conclude that early exposure and specific dose of protease inhibitor are essential for effective antibiosis despite the large diversity and plasticity in the expression of protease genes in H. armigera. Moreover, it is also evident that the regulation and expression of H. armigera gut proteases are specific to the stage of PI exposure. General significanceThese results highlight the requirement of optimal PI concentration for effective growth retardation and for inhibiting the major gut proteases of H. armigera.

SjAPI, the First Functionally Characterized Ascaris-Type Protease Inhibitor from Animal Venoms

BackgroundSerine protease inhibitors act as modulators of serine proteases, playing important roles in protecting animal toxin peptides from degradation. However, all known serine protease inhibitors discovered thus far from animal venom belong to the Kunitz-type subfamily, and whether there are other novel types of protease inhibitors in animal venom remains unclear.Principal FindingsHere, by screening scorpion venom gland cDNA libraries, we identified the first Ascaris-type animal toxin family, which contains four members: Scorpiops jendeki Ascaris-type protease inhibitor (SjAPI), Scorpiops jendeki Ascaris-type protease inhibitor 2 (SjAPI-2), Chaerilus tricostatus Ascaris-type protease inhibitor (CtAPI), and Buthus martensii Ascaris-type protease inhibitor (BmAPI). The detailed characterization of Ascaris-type peptide SjAPI from the venom gland of scorpion Scorpiops jendeki was carried out. The mature peptide of SjAPI contains 64 residues and possesses a classical Ascaris-type cysteine framework reticulated by five disulfide bridges, different from all known protease inhibitors from venomous animals. Enzyme and inhibitor reaction kinetics experiments showed that recombinant SjAPI was a dual function peptide with α-chymotrypsin- and elastase-inhibiting properties. Recombinant SjAPI inhibited α-chymotrypsin with a Ki of 97.1 nM and elastase with a Ki of 3.7 μM, respectively. Bioinformatics analyses and chimera experiments indicated that SjAPI contained the unique short side chain functional residues “AAV” and might be a useful template to produce new serine protease inhibitors.Conclusions/SignificanceTo our knowledge, SjAPI is the first functionally characterized animal toxin peptide with an Ascaris-type fold. The structural and functional diversity of animal toxins with protease-inhibiting properties suggested that bioactive peptides from animal venom glands might be a new source of protease inhibitors, which will accelerate the development of diagnostic and therapeutic agents for human diseases that target diverse proteases.

Prolonged treatment with boosted protease inhibitor monotherapy is not associated with a higher rate of neurocognitive impairment than triple drug ART

Purpose of the studyTo investigate if boosted protease inhibitor monotherapy is associated with a higher risk of neurocognitive impairment (NCI).MethodsHIV‐infected patients from two hospitals in Madrid (Spain) without concomitant major neurocognitive confounders, currently receiving for ≥1 year lopinavir/ritonavir (LPV) or darunavir/ritonavir (DRV) as monotherapy or with two N(t)RTIs were included if they had prolonged (≥1 year) plasma viral suppression (<50 c/mL, single blip allowed). Patients underwent full neurocognitive assessment (7 domains) by two psychologists blinded to the treatment group. NCI was defined as per 2007 Frascati criteria using demographically adjusted normative scores. Rates of NCI and the association between NCI and boosted protease inhibitor monotherapy, adjusted by significant confounders, were analyzed. Two categories of monotherapy duration were considered: short‐term (1–2 years) and long‐term (2–9 years). We evaluated as potential confounding variables: demographics, HIV risk factor, AIDS, CD4 (nadir/current), smoking, alcohol/illicit drug use, prior medical, neurological and psychiatric disease, HCV coinfection, years of ART, prior blips, time with HIV viral suppression, type of protease inhibitor, lipids and HOMA index.Summary of results191 patients (89.5% Caucasian) were included (Table 1). Triple therapy (n=95) Monotherapy (n=96) p value Male. n (%) 70 (73.7) 70 (72.9) 0.91 Former IVDU. n (%) 30 (31.6) 34 (35.4) 0.85 MSM. n (%) 29 (30.5) 30 (31.3) 0.85 Age. Median (IQR) 44.7 (40.6–48.4) 47.4 (44.8–51.4) <0.01 Years of education. Mean (SD) 11.3 (4.1) 10.4 (4.4) 0.13 Prior neurologic disease. N (%) 12 (12.6) 10 (10.4) 0.63 Prior psychiatric disease. n (%) 19 (20.0) 24 (25.0) 0.44 Current or past use of illicit drugs. n (%) 49 (53.6) 46 (47.9) 0.66 HCV coinfection (past or active) 43 (47.3) 43 (45.3) 0.54 Years of ART. Median (IQR) 10.7 (4.8–15.7) 14.1 (10.7–15.9) 0.01 Years of monotherapy. Median (IQR) Not applicable 2.3 (1.7–3.2) Not applicable Years suppressed (<50 c/mL). Median (IQR) 4.8 (2.9–8.9) 7.5 (4.5–10.0) <0.01 No prior blip 63 (66.3) 61 (63.5) 0.17 Currently on LPV. n (%) 70 (73.7) 53 (55.2) <0.01 Currently on DRV. n (%) 25 (26.3) 43 (44.8) <0.01 CPE score (2010). Median (IQR) 7 (7–7) 3 (3–3) Not applicable CD4 cell nadir. Median (IQR) 153 (49–255) 182 (76–288) 0.11 CD4 cell current. Median (IQR) 560 (440–754) 629.5 (476–845.5) <0.05 Proportion (95% CI) with NCI: Overall: 27.2% (20.9–33.6, all asymptomatic or mild). Triple therapy: 31.6 (22.1–41.0). 1–2 years of monotherapy (n=40): 25.0 (11.3–38.7). 2–9 years of monotherapy (n=56): 21.4 (10.5–32.3) No differences in rates of NCI were found by treatment group (p=0.38). In our regression model confounding variables for NCI were years on ART, ethnicity, years of education, transmission category and the HOMA index. Adjusted by those variables the odds ratio (95% CI) for NCI of patients receiving boosted protease inhibitor monotherapy monotherapy during 1–2 years was 0.85 (0.29–2.50) and for 2–9 years was 0.40 (0.14–1.15).ConclusionsBoosted protease inhibitor monotherapy, regardless of duration, was not associated with a higher rate of neurocognitive impairment than triple drug ART. These results call into question the ability of neuropenetrance scores to predict the neuroefficacy of antiretroviral regimens in HIV‐infected patients with adequate blood viral suppression.

Transcripts of sulphur metabolic genes are co-ordinately regulated in developing seeds of common bean lacking phaseolin and major lectins

The lack of phaseolin and phytohaemagglutinin in common bean (dry bean, Phaseolus vulgaris) is associated with an increase in total cysteine and methionine concentrations by 70% and 10%, respectively, mainly at the expense of an abundant non-protein amino acid, S-methyl-cysteine. Transcripts were profiled between two genetically related lines differing for this trait at four stages of seed development using a high density microarray designed for common bean. Transcripts of multiple sulphur-rich proteins were elevated, several previously identified by proteomics, including legumin, basic 7S globulin, albumin-2, defensin, albumin-1, the Bowman–Birk type proteinase inhibitor, the double-headed trypsin inhibitor, and the Kunitz trypsin inhibitor. A co-ordinated regulation of transcripts coding for sulphate transporters, sulphate assimilatory enzymes, serine acetyltransferases, cystathionine β-lyase, homocysteine S-methyltransferase and methionine gamma-lyase was associated with changes in cysteine and methionine concentrations. Differential gene expression of sulphur-rich proteins preceded that of sulphur metabolic enzymes, suggesting a regulation by demand from the protein sink. Up-regulation of SERAT1;1 and -1;2 expression revealed an activation of cytosolic O-acetylserine biosynthesis. Down-regulation of SERAT2;1 suggested that cysteine and S-methyl-cysteine biosynthesis may be spatially separated in different subcellular compartments. Analysis of free amino acid profiles indicated that enhanced cysteine biosynthesis was correlated with a depletion of O-acetylserine. These results contribute to our understanding of the regulation of sulphur metabolism in developing seed in response to a change in the composition of endogenous proteins.

TLS-CHOP represses miR-486 expression, inducing upregulation of a metastasis regulator PAI-1 in human myxoid liposarcoma

Myxoid liposarcomas (MLSs) are characterized by t(12;16)(q13;p11) translocation and expression of TLS-CHOP chimeric oncoprotein. However, the molecular functions of TLS-CHOP have not been fully understood. On the other hand, microRNAs (miRNAs) comprise an abundant class of endogenous small non-coding RNAs that negatively regulate the expression of their target genes, and are involved in many biological processes. It is now evident that dysregulation of miRNAs is an important step in the development of many cancers. To our knowledge, however, there have been no reports of the miRNAs involved in MLS tumorigenesis and development. In this study, we have found that miR-486 expression was repressed in TLS-CHOP-expressed NIH3T3 fibroblasts and MLS tissues, and exogenous overexpression of miR-486 repressed growth of MLS cells. Thus, downregulation of miR-486 may be an important process for MLS. In addition, we have identified plasminogen activator inhibitor-1 (PAI-1) as a novel target gene of miR-486. PAI-1 is a unique type of serine protease inhibitor and is known to be one of the key regulators of tumor invasion and metastasis. Furthermore, knockdown of PAI-1 by a specific small interfering RNA (siRNA) inhibited growth of MLS cells, suggesting that increased expression of PAI-1 by miR-486 repression is critical for survival of MLS cells. Collectively, these results suggest a novel essential molecular mechanism that TLS-CHOP activates PAI-1 expression by repression of miR-486 expression in MLS tumorigenesis and development.

Cloning, characterization and expression analysis of a novel gene encoding Kunitz-type protease inhibitor from Dolichos biflorus

This paper reports the presence of a Kunitz-type protease inhibitor (HGPI) gene in Dolichos biflorus for the first time. A full-length protease inhibitor gene with complete open reading frame of 669 bp encoding 222 amino acids was cloned from D. biflorus using a PCR-based method. BlastN search showed that the HGPI gene shared 100% homology with Cicer arietinum trypsin inhibitor mRNA and 97% with Cajanus cajan protease inhibitor. The deduced amino acid sequence exhibited homology with Kunitz-type trypsin inhibitor from chickpea, pigeon pea and soybean. The deduced amino acid sequence contained N-terminal signal sequence of 18 amino acids and had a molecular weight of 24 kDa. The phylogenetic tree also showed close relationship with Cicer arietinum and Cajanus cajan. Southern blotting revealed the presence of only one copy of HGPI gene in the D. biflorus genome. Homology modeling was employed to predict secondary structure and 3D-structural models for the protease inhibitor. The gene was found to be constitutively expressed in different tissues as determined by semi-quantitative RT-PCR. The novel HGPI gene has been submitted to the GenBank with Accession No. FN666416. The isolated novel HGPI gene will broaden the pool of plant defense genes and might be an ideal choice for developing transgenic crops resistant to insect pests, as well as pathogens. In addition, it could be used as a probe for selection of insect- and pathogen-resistant genotypes.

Sanger sequencing solved a cryptic case of severe alpha1-antitrypsin deficiency

Alpha(1)-antitrypsin deficiency (AATD) is a clinically under-diagnosed genetic disorder that originates from deleterious mutations in the alpha(1)-antitrypsin (AAT) gene, SERPINA1. Severe deficiency is associated with significant pulmonary and hepatic malfunctions. Conventional clinical diagnosis involves the evaluation of serum AAT level and detection of diseased protein isoforms. In this communication, we describe the investigations of a case of severe AATD in which the AAT levels were well below those expected from the MZ phenotype determined by isoelectric focusing for protease inhibitor type (IEF PI-typing). In addition to the traditional diagnostic method that combines the assessment of serum AAT concentration and IEF PI-typing, we investigated the SERPINA1 gene of the proband and participating family members for mutations using Sanger sequencing. We identified a novel mutation (M409T) in the proband, initially missed by the standard diagnostic approach. The novel mutation was present in 4 out of 8 family members who participated in the study. This report illustrates the diagnostic value of incorporating exon sequencing of the AAT gene into the algorithm for evaluating AATD, particularly when the AAT serum level is significantly lower than expected from IEF PI-typing.

Netherton syndrome in one Chinese adult with a novel mutation in the SPINK5 gene and immunohistochemical studies of LEKTI

Background:Netherton syndrome (NS) is a severe autosomal recessive ichthyosis. It is characterized by congenital ichthyosiform erythroderma, trichorrhexis invaginata, ichthyosis linearis circumflexa, atopic diathesis, and frequent bacterial infections. The disease is caused by mutations in the SPINK5 (serine protease inhibitor Kazal-type 5) gene, a new type of serine protease inhibitor involved in the regulation of skin barrier formation and immunity. We report one Chinese adult with NS. The patient had typical manifestation of NS except for trichorrhexis invaginata with an atopic diathesis and recurrent staphylococcal infections since birth.Aims:To evaluate the gene mutation and of its product activity of SPINK5 gene in confirmation of the diagnosis of one Chinese adult with NS.Materials and Methods:To screen mutations in the SPINK5 gene, 33 exons and flanking intron boundaries of SPINK5 were amplified with polymerase chain reaction (PCR) and used for direct sequencing. In addition, immunohistochemical staining of LEKTI (lymphoepithelial Kazal-type-related inhibitor) with specific antibody was used to confirm the diagnosis of NS. The results were compared with that of healthy individuals (twenty-five blood samples).Results:A G318A mutation was found at exon 5 of patient's SPINK5 gene which is a novel missense mutation. The PCR amplification products with mutation-specific primer were obtained only from the DNA of the patients and their mother, but not from their father and 25 healthy individuals. Immunohistochemical studies indicated there was no LEKTI expression in NS patient's skin and there was a strong LEKTI expression in the normal human skin.Conclusion:In this report, we describe heterozygous mutation in the SPINK5 gene and expression of LEKTI in one Chinese with NS. The results indicate that defective expression of LEKTI in the epidermis and mutations of SPINK5 gene are reliable for diagnostic feature of NS with atypical clinical symptoms.

N-glycans of Human Protein C Inhibitor: Tissue-Specific Expression and Function

Protein C inhibitor (PCI) is a serpin type of serine protease inhibitor that is found in many tissues and fluids in human, including blood plasma, seminal plasma and urine. This inhibitor displays an unusually broad protease specificity compared with other serpins. Previous studies have shown that the N-glycan(s) and the NH2-terminus affect some blood-related functions of PCI. In this study, we have for the first time determined the N-glycan profile of seminal plasma PCI, by mass spectrometry. The N-glycan structures differed markedly compared with those of both blood-derived and urinary PCI, providing evidence that the N-glycans of PCI are expressed in a tissue-specific manner. The most abundant structure (m/z 2592.9) had a composition of Fuc3Hex5HexNAc4, consistent with a core fucosylated bi-antennary glycan with terminal Lewisx. A major serine protease in semen, prostate specific antigen (PSA), was used to evaluate the effects of N-glycans and the NH2-terminus on a PCI function related to the reproductive tract. Second-order rate constants for PSA inhibition by PCI were 4.3±0.2 and 4.1±0.5 M−1s−1 for the natural full-length PCI and a form lacking six amino acids at the NH2-terminus, respectively, whereas these constants were 4.8±0.1 and 29±7 M−1s−1 for the corresponding PNGase F-treated forms. The 7–8-fold higher rate constants obtained when both the N-glycans and the NH2-terminus had been removed suggest that these structures jointly affect the rate of PSA inhibition, presumably by together hindering conformational changes of PCI required to bind to the catalytic pocket of PSA.

Genes encoding WFDC- and Kunitz-type protease inhibitor domains: are they related?

We have previously demonstrated that the genes of SCPs (semen coagulum proteins) and the WFDC (whey acidic protein four-disulfide core)-type protease inhibitor elafin are homologous in spite of lacking similarity between their protein products. This led to the discovery of a locus on human chromosome 20, encompassing genes of the SCPs, SEMG1 (semenogelin I) and SEMG2, and 14 genes containing the sequence motif that is characteristic of WFDC-type protease inhibitors. We have now identified additional genes at the locus that are similarly organized, but which give rise to proteins containing the motif of Kunitz-type protease inhibitors. Here, we discuss the evolution of genes encoding SCPs and describe mechanisms by which they and genes with Kunitz motifs might have evolved from genes with WFDC motifs. We can also demonstrate an expansion of the WFDC locus with 0.6 Mb in the cow. The region, which seems to be specific to ruminants, contains several genes and pseudogenes with Kunitz motifs, one of which is the much-studied BPTI (bovine pancreatic trypsin inhibitor).

Passion fruit flowers: Kunitz trypsin inhibitors and cystatin differentially accumulate in developing buds and floral tissues

In order to better understand the physiological functions of protease inhibitors (PIs) the PI activity in buds and flower organs of passion fruit ( Passiflora edulis Sims) was investigated. Trypsin and papain inhibitory activities were analyzed in soluble protein extracts from buds at different developmental stages and floral tissues in anthesis. These analyses identified high levels of inhibitory activity against both types of enzymes at all bud stages. Intriguingly, the inhibitory activity against both proteases differed remarkably in some floral tissues. While all organs tested were very effective against trypsin, only sepal and petal tissues exhibited strong inhibitory activity against papain. The sexual reproductive tissues (ovary, stigma-style and stamen) showed either significantly lower activity against papain or practically none. Gelatin–SDS–PAGE assay established that various trypsin inhibitors (TIs) homogenously accumulated in developing buds, although some were differentially present in floral organs. The N-terminal sequence analysis of purified inhibitors from stamen demonstrated they had homology to the Kunitz family of serine PIs. Western-blot analysis established presence of a ∼60 kDa cystatin, whose levels progressively increased during bud development. A positive correlation between this protein and strong papain inhibitory activity was observed in buds and floral tissues, except for the stigma-style. Differences in temporal and spatial accumulation of both types of PIs in passion fruit flowers are thus discussed in light of their potential roles in defense and development.

Characterization of the protease activity of detergents laboratory practicals for studying the protease profile and activity of various commercial detergents

Detergent enzymes account for about 30% of the total worldwide production of enzymes and are one of the largest and most successful applications of modern industrial biotechnology. Proteases can improve the wash performance of household, industrial, and institutional laundry detergents used to remove protein-based stains such as blood, grass, body fluids, and food soils. This article describes two easy and cheap laboratory exercises to study the presence, profile, and basic enzymology of detergent proteases. These laboratory practicals are based on the determination of the detergent protease activity of various commercial detergents using the N-succinyl-L-alanyl-L-alanyl-L-prolyl-L-phenylalanine p-nitroanilide method and the bovine serum albumin degradation capacity. Students are also required to elucidate the enzymatic subtype of detergent proteases by studying the inhibitory potential of several types of protease inhibitors revealed by the same experimental methodology. Additionally, the results of the exercises can be used to provide additional insights on elementary enzymology by studying the influence of several important parameters on protease activity such as temperature (in this article) and the influence of pH and effects of surfactants and oxidizers (proposed). Students also develop laboratory skills, problem-solving capacities, and the ability to write a laboratory report. The exercises are mainly designed for an advanced undergraduate project in the biochemistry and biotechnology sciences. Globally, these laboratory practicals show students the biotechnological applications of proteases in the detergent industry and also reinforce important enzymology concepts.

The HIV reverse transcriptase inhibitor tenofovir induces cell cycle arrest in human cancer cells

Selected HIV drugs, either of the protease inhibitor type or the nucleoside antagonist type, have been shown to exert tumoricidal effects. Here, we show that the HIV reverse transcriptase inhibitor Truvada, a combination drug of the cytidine analogue emtricitabine and the adenosine analogue tenofovir, induces DNA damage and cell cycle arrest in human cancer cells. Phosphorylation of the DNA repair enzyme H2AX by emtricitabine/tenofovir indicated that it interfered with the integrity of the DNA and replication machinery in human cancer cells. Long term incubation of cancer cells with emtricitabine/tenofovir caused the formation of multi-nuclear giant cells, further indicating DNA replication problems. When tested as single agents, the anti-tumoral activity of emtricitabine/tenofovir was predominantly caused by tenofovir, although the combination with emtricitabine enhanced its effect on cancer cells. Combined with established anti-cancer drugs, emtricitabine/tenofovir was preferentially found to enhance the cytotoxic effect of doxorubicin, a promising drug for the treatment of relapsed, chemoresistant cancer. These results show that especially the adenosine analogue tenofovir could be used to interfere with the proliferation machinery of human cancer cells and to be applied for chemosensitization of cancer cells to already established DNA-interacting drugs.

HIV Protease Inhibitors: Present and Future

Antiretroviral therapy offers many options, largely based on the next-generation protease inhibitors (PIs). Early PI-based treatments involve high pill burdens and dosing schedules, and concerns of long-term toxicities are well established. In patients who have already achieved viral suppression, novel agents and strategies should be used to simplify the dosing treatment, reduce adverse events or preserve drug options. In experienced patients, drug escalation between PIs and different associations between classes allow virological suppression to be reached in the majority of patients. Therefore, there is a persistent clinical need for the discovery and development of new protease inhibitors. Several firms are trying to develop new types of PIs that will not be cross-resistant with existing drugs and will not require ritonavir boosting. This article aims to offer an overview on present drug options recommended for treatment in naive and experienced patients, new strategies currently undergoing clinical evaluation and new compounds in the pipeline.

Affinity of Avr2 for tomato cysteine protease Rcr3 correlates with the Avr2‐triggered Cf‐2‐mediated hypersensitive response

The Cladosporium fulvum Avr2 effector is a novel type of cysteine protease inhibitor with eight cysteine residues that are all involved in disulphide bonds. We have produced wild-type Avr2 protein in Pichia pastoris and determined its disulphide bond pattern. By site-directed mutagenesis of all eight cysteine residues, we show that three of the four disulphide bonds are required for Avr2 stability. The six C-terminal amino acid residues of Avr2 contain one disulphide bond that is not embedded in its overall structure. Avr2 is not processed by the tomato cysteine protease Rcr3 and is an uncompetitive inhibitor of Rcr3. We also produced mutant Avr2 proteins in which selected amino acid residues were individually replaced by alanine, and, in one mutant, all six C-terminal amino acid residues were deleted. We determined the inhibitory constant (K(i) ) of these mutants for Rcr3 and their ability to trigger a Cf-2-mediated hypersensitive response (HR) in tomato. We found that the two C-terminal cysteine residues and the six amino acid C-terminal tail of Avr2 are required for both Rcr3 inhibitory activity and the ability to trigger a Cf-2-mediated HR. Individual replacement of the lysine-17, lysine-20 or tyrosine-21 residue by alanine did not affect significantly the biological activity of Avr2. Overall, our data suggest that the affinity of the Avr2 mutants for Rcr3 correlates with their ability to trigger a Cf-2-mediated HR.

Multidrug resistance reversal properties and cytotoxic evaluation of representatives of a novel class of HIV-1 protease inhibitors

P-Glycoprotein (P-gp) plays a central role in the development of resistance against cytostatics in anticancer therapy and against human immunodeficiency virus (HIV) therapeutics of the HIV-1 protease inhibitor type. An approach to reverse the so-called multidrug resistance (MDR) phenomenon by the use of P-gp inhibiting agents is a challenge in the therapy of cancer and AIDS. Effective in-vitro inhibitors have P-gp substrate properties so that the expected in-vivo effects have been disappointing so far. Consequent higher dosages cause toxic effects. Novel HIV-1 protease inhibitors (H17, JW41, JW33 and JW46) have been evaluated in comparison with ritonavir as P-gp inhibiting agents, in the exclusively P-gp overexpressing model cell line mouse T lymphoma using flow cytometry. The cytotoxic properties against various cell lines were characterized in the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay to estimate potential toxic effects in therapeutically relevant concentrations in metabolically active HepG2 cells, drug-sensitive Jurkat cells and in gastric carcinoma cells. Concentration-dependent effective reversal properties have been discussed in context and proved to be mainly influenced by the number of potential hydrogen bond acceptor functions. The compounds showed no cytotoxic properties in P-gp inhibiting concentration ranges. Ritonavir, a known P-gp substrate, proved to be less toxic in the P-gp expressing cell line than in the nonexpressing cell line at the cell-exposed concentrations and thus showed P-gp substrate properties. Two compounds, H17 and JW41, showed no P-gp substrate properties, with higher toxicity in the P-gp expressing cell line compared with the nonexpressing cell line. The novel compounds have been shown to be prospective AIDS therapeutics, acting as effective and nontoxic P-gp inhibitors compared with ritonavir, which is a known P-gp inhibitor with unfavourable toxic and P-gp substrate properties.

CDNA cloning and expression of a novel type protease inhibitor (FPI-F) from the silkworm, Bombyx mori

cDNA cloning and expression of a novel type protease inhibitor (FPI-F) from the silkworm, Bombyx mori