Cathepsin-L influences the expression of extracellular matrix in lymphoid organs and plays a role in the regulation of thymic output and of peripheral T cell number

Characterization of a Novel Cysteine Protease Inhibitor from Poultry Red Mites: Potential Vaccine for Chickens

Poultry red mite (PRM; Dermanyssus gallinae) is a hazardous, blood-sucking ectoparasite of birds that constitutes a threat to poultry farming worldwide. Acaricides, commonly used in poultry farms to prevent PRMs, are not effective because of the rapid emergence of acaricide-resistant PRMs. However, vaccination may be a promising strategy to control PRM. We identified a novel cystatin-like molecule in PRMs: Dg-Cys. Dg-Cys mRNA expression was detected in the midgut and ovaries, in all stages of life. The PRM nymphs that were artificially fed with the plasma from chickens that were immunized with Dg-Cys in vitro had a significantly reduced reproductive capacity and survival rate. Moreover, combination of Dg-Cys with other antigen candidates, like copper transporter 1 or adipocyte plasma membrane-associated protein, enhanced vaccine efficacies. vaccination and its application as an antigen for cocktail vaccines could be an effective strategy to reduce the damage caused by PRMs in poultry farming.

Proteomic changes in the extracellular environment of sea bass thymocytes exposed to 17α-ethinylestradiol in vitro

The thymus is an important immune organ providing the necessary microenvironment for the development of a diverse, self-tolerant T cell repertoire, which is selected to allow for the recognition of foreign antigens while avoiding self-reactivity. Thymus function and activity are known to be regulated by sex steroid hormones, such as oestrogen, leading to sexual dimorphisms in immunocompetence between males and females. The oestrogenic modulation of the thymic function provides a potential target for environmental oestrogens, such as 17α-ethynylestradiol (EE2), to interfere with the cross-talk between the endocrine and the immune system. Oestrogen receptors have been identified on thymocytes and the thymic microenvironment, but it is unclear how oestrogens regulate thymic epithelial and T cell communication including paracrine signalling. Much less is known regarding intrathymic signalling in fish. Secretomics allows for the analysis of complex mixtures of immunomodulatory signalling factors secreted by T cells. Thus, in the present study, isolated thymocytes of the European sea bass, Dicentrarchus labrax, were exposed in vitro to 30 nM EE2 for 4 h and the T cell-secretome (i.e., extracellular proteome) was analysed by quantitative label-free mass-spectrometry. Progenesis revealed a total of 111 proteins differentially displayed between EE2-treated and control thymocytes at an α-level of 5% and a 1.3-fold change cut off (n = 5-6). The EE2-treatment significantly decreased the level of 90 proteins. Gene ontology revealed the proteasome to be the most impacted pathway. In contrast, the abundance of 21 proteins was significantly increased, with cathepsins showing the highest level of induction. However, no particular molecular pathway was significantly altered for these upregulated proteins. To the best of our knowledge, this work represents the first study of the secretome of the fish thymus exposed to the environmental oestrogen EE2, highlighting the impact on putative signalling pathways linked to immune surveillance, which may be of crucial importance for fish health and defence against pathogens.

The Role of Cysteine Peptidases in Hematopoietic Stem Cell Differentiation and Modulation of Immune System Function

Cysteine cathepsins are primarily involved in the degradation and recycling of proteins in endo-lysosomal compartments but are also gaining recognition as pivotal proteolytic contributors to various immune functions. Through their extracellular proteolytic activities within the hematopoietic stem cell niche, they are involved in progenitor cell mobilization and differentiation. Cysteine cathepsins, such as cathepsins L and S contribute to antigen-induced adaptive immunity through major histocompatibility complex class II antigen presentation whereas cathepsin X regulates T-cell migration. By regulating toll-like receptor signaling and cytokine secretion cysteine cathepsins activate innate immune cells and affect their functional differentiation. Cathepsins C and H are expressed in cytotoxic T lymphocytes and natural killer cells and are involved in processing of pro-granzymes into proteolytically active forms. Cytoplasmic activities of cathepsins B and L contribute to the maintenance of homeostasis of the adaptive immune response by regulating cell death of T and B lymphocytes. The expression pattern, localization, and activity of cysteine cathepsins is tightly connected to their function in immune cells. Furthermore, cysteine cathepsins together with their endogenous inhibitors, serve as mediators in the interplay between cancer and immune cells that results in immune cell anergy. The aim of the present article is to review the mechanisms of dysregulation of cysteine cathepsins and their inhibitors in relation to immune dysfunction to address new possibilities for regulation of their function.

Interfering with Host Proteases in SARS-CoV-2 Entry as a Promising Therapeutic Strategy

Due to its fast international spread and substantial mortality, the coronavirus disease COVID-19 evolved to a global threat. Since currently, there is no causative drug against this viral infection available, science is striving for new drugs and approaches to treat the new disease. Studies have shown that the cell entry of coronaviruses into host cells takes place through the binding of the viral spike (S) protein to cell receptors. Priming of the S protein occurs via hydrolysis by different host proteases. The inhibition of these proteases could impair the processing of the S protein, thereby affecting the interaction with the host-cell receptors and preventing virus cell entry. Hence, inhibition of these proteases could be a promising strategy for treatment against SARS-CoV-2. In this review, we discuss the current state of the art of developing inhibitors against the entry proteases furin, the transmembrane serine protease type-II (TMPRSS2), trypsin, and cathepsin L.

Extracellular Matrix Injury of Kidney Allografts in Antibody-Mediated Rejection: A Proteomics Study

BACKGROUND

Antibody-mediated rejection (AMR) accounts for >50% of kidney allograft loss. Donor-specific antibodies (DSA) against HLA and non-HLA antigens in the glomeruli and the tubulointerstitium cause AMR while inflammatory cytokines such as TNFα trigger graft injury. The mechanisms governing cell-specific injury in AMR remain unclear.

METHODS

Unbiased proteomic analysis of laser-captured and microdissected glomeruli and tubulointerstitium was performed on 30 for-cause kidney biopsy specimens with early AMR, acute cellular rejection (ACR), or acute tubular necrosis (ATN).

RESULTS

A total of 107 of 2026 glomerular and 112 of 2399 tubulointerstitial proteins was significantly differentially expressed in AMR versus ACR; 112 of 2026 glomerular and 181 of 2399 tubulointerstitial proteins were significantly dysregulated in AMR versus ATN (P<0.05). Basement membrane and extracellular matrix (ECM) proteins were significantly decreased in both AMR compartments. Glomerular and tubulointerstitial laminin subunit γ-1 (LAMC1) expression decreased in AMR, as did glomerular nephrin (NPHS1) and receptor-type tyrosine-phosphatase O (PTPRO). The proteomic analysis revealed upregulated galectin-1, which is an immunomodulatory protein linked to the ECM, in AMR glomeruli. Anti-HLA class I antibodies significantly increased cathepsin-V (CTSV) expression and galectin-1 expression and secretion in human glomerular endothelial cells. CTSV had been predicted to cleave ECM proteins in the AMR glomeruli. Glutathione S-transferase ω-1, an ECM-modifying enzyme, was significantly increased in the AMR tubulointerstitium and in TNFα-treated proximal tubular epithelial cells.

CONCLUSIONS

Basement membranes are often remodeled in chronic AMR. Proteomic analysis performed on laser-captured and microdissected glomeruli and tubulointerstitium identified early ECM remodeling, which may represent a new therapeutic opportunity.

Rhipicephalus microplus cystatin as a potential cross-protective tick vaccine against Rhipicephalus appendiculatus

Rhipicephalus appendiculatus, the brown ear tick, is an important disease vector of livestock in eastern, central and southern Africa. Rhipicephalus appendiculatus acaricide resistance requires the search for alternative methods for its control. Cystatins constitute a superfamily of cysteine peptidase inhibitors vital for tick blood feeding and development. These inhibitors were proposed as antigens in anti-tick vaccines. In this work, we applied structural and biochemical approaches to characterize a new cystatin named R. appendiculatus cystatin 2a (Racys2a). Structural modeling showed that this new protein possesses characteristic type 2 cystatin motifs, besides conservation of other structural patterns along the protein. Peptidase inhibitory assays with recombinant Racys2a showed modulation of tick and host cathepsins involved in blood digestion and immune system responses, respectively. A heterologous tick challenge with R. appendiculatus in rabbits immunized with recombinant Rhipicephalus microplus cystatin 2c (rBmcys2c) was performed to determine cross-reactivity. Histological staining showed that rBmcys2c vaccination caused damage to the gut, salivary gland and ovary tissues in R. appendiculatus. Furthermore, cystatin vaccine reduced the number of fully engorged adult females in 11.5 %. Consequently, strategies to increase the protection rate are necessary, including the selection of two or more antigens to compose a vaccine cocktail.

Immunosuppressive effects of sialostatin L1 and L2 isolated from the taiga tick Ixodes persulcatus Schulze

Tick saliva contains immunosuppressants which are important to obtain a blood meal and enhance the infectivity of tick-borne pathogens. In Japan, Ixodes persulcatus is a major vector for Lyme borreliosis pathogens, such as Borrelia garinii, as well as for those causing relapsing fever, such as B. miyamotoi. To date, little information is available on bioactive salivary molecules, produced by this tick. Thus, in this study, we identified two proteins, I. persulcatus derived sialostatin L1 (Ip-sL1) and sL2 (Ip-sL2), as orthologs of I. scapularis derived sL1 and sL2. cDNA clones of Ip-sL1 and Ip-sL2 shared a high identity with sequences of sL1 and sL2 isolated from the salivary glands of I. scapularis. Semi-quantitative PCR revealed that Ip-sL1 and Ip-sL2 were expressed in the salivary glands throughout the life of the tick. In addition, Ip-sL1 and Ip-sL2 were expressed even before the ticks started feeding, and their expression continued during blood feeding. Recombinant Ip-sL1 and Ip-sL2 were developed to characterize the proteins via biological and immunological analyses. These analyses revealed that both Ip-sL1 and Ip-sL2 had inhibitory effects on cathepsins L and S. Ip-sL1 and Ip-sL2 inhibited the production of IP-10, TNFα, and IL-6 by LPS-stimulated bone-marrow-derived dendritic cells (BMDCs). Additionally, Ip-sL1 significantly impaired BMDC maturation. Taken together, these results suggest that Ip-sL1 and Ip-sL2 confer immunosuppressive functions and appear to be involved in the transmission of pathogens by suppressing host immune responses, such as cytokine production and dendritic cell maturation. Therefore, further studies are warranted to investigate the immunosuppressive functions of Ip-sL1 and Ip-sL2 in detail to clarify their involvement in pathogen transmission via I. persulcatus.

Cell penetrable, clickable and tagless activity-based probe of human cathepsin L

Human cathepsin L is a ubiquitously expressed endopeptidase and is known to play critical roles in a wide variety of cellular signaling events. Its overexpression has been implicated in numerous human diseases, including highly invasive forms of cancer. Inhibition of cathepsin L is therefore considered a viable therapeutic strategy. Unfortunately, several redundant and even opposing roles of cathepsin L have recently emerged. Selective cathepsin L probes are therefore needed to dissect its function in context-specific manner before significant resources are directed into drug discovery efforts. Herein, the development of a clickable and tagless activity-based probe of cathepsin L is reported. The probe is highly efficient, active-site directed and activity-dependent, selective, cell penetrable, and non-toxic to human cells. Using zebrafish model, we demonstrate that the probe can inhibit cathepsin L function in vivo during the hatching process. It is anticipated that the probe will be a highly effective tool in dissecting cathepsin L biology at the proteome levels in both normal physiology and human diseases, thereby facilitating drug-discovery efforts targeting cathepsin L.

Identification of immune-related genes in gills of Chinese mitten crabs (Eriocheir sinensis) during adaptation to air exposure stress

The Chinese mitten crab, Eriocheir sinensis, is the most important crab in China. Air exposure is regarded as one of the crucial restriction factors in the crab cultivation and transportation process. Numerous studies have shown that air exposure stress can cause many negative effects on aquatic farming animals. However, the molecular mechanisms of drying on Chinese mitten crabs are still poorly studied. In this study, gill reference transcriptome was assembled and differentially expressed gene (DGE) analysis was conducted between air exposure 16 h and normal dissolved oxygen of Chinese mitten crab. A total of 76075 transcripts were generated and 50800 unigenes with a mean length of 1090 bp and N50 length of 1584 bp were observed. Transcriptomic comparison revealed 352 DEGs between air exposure 16 h group and control group, including 122 up-regulated genes and 230 down-regulated genes. Gene ontology (GO) analysis revealed that these DEGs involved in 16 biological process subcategories, 8 cellular component subcategories and 6 molecular function subcategories. Further Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis annotated 352 DEGs to 85 pathways, and some pathways were regarded as related with immune system and diseases, such as phagosome, systemic lupus erythematosus, and alcoholism. Eight genes involved in multiple KEGG signaling pathways were validated by qRT-PCR. This study demonstrates the first gill transcriptomic analysis challenged with air exposure stress in Chinese mitten crab and provides valuable gene resources for understanding the crab gill immunity, which can provides insight into the immune response of crab against air exposure stress.

Modulation of goat monocyte function by HCcyst-2, a secreted cystatin from Haemonchus contortus

Modulation and suppression of the host immune response by nematode parasites have been reported extensively and the cysteine protease inhibitor (cystatin) is identified as one of the major immunomodulator. In the present study, we cloned and produced recombinant cystatin protein from nematode parasite Haemonchus contortus (rHCcyst-2) and investigated its immunomodulatory effects on goat monocyte. rHCcyst-2 protein is biologically functional as shown by its ability to inhibit the protease activity of cathepsin L, cathepsin B and papain. Immunohistochemical test demonstrated that the native HCcyst-2 protein was predominantly localized at the body surface and internal surface of the worm's gut. We demonstrated that rHCcyst-2 could be distinguished by antisera from goats experimentally infected with H. contortus and could uptake by goat monocytes. The immunomodulatory effects of HCcyst-2 on cytokine secretion, MHC molecule expression, NO production and phagocytosis were observed by co-incubation of rHCcyst-2 with goat monocytes. The results showed that the interaction of rHCcyst-2 decreased the production of TNF-α, IL-1β and IL-12p40. However, it significantly increased the secretion of IL-10 in goat monocytes. After rHCcyst-2 exposure, the expression of MHC-II on goat monocytes was inhibited. Moreover, rHCcyst-2 could up-regulate the LPS induced NO production of goat monocytes. Phagocytotic assay by FITC-dextran internalization showed that rHCcyst-2 inhibited the phagocytosis of goat monocytes. Our findings provided potential target as immunoregulator, and will be helpful to illustrate the molecular basis of host–parasite interactions and search for new potential molecule as vaccine and drug target candidate.

Differential Expression of miRNAs in the Respiratory Tree of the Sea Cucumber Apostichopus japonicus Under Hypoxia Stress

The sea cucumber, an important economic species, has encountered high mortality since 2013 in northern China because of seasonal environmental stress such as hypoxia, high temperature, and low salinity. MicroRNAs (miRNAs) are important in regulating gene expression in marine organisms in response to environmental change. In this study, high-throughput sequencing was used to investigate alterations in miRNA expression in the sea cucumber under different levels of dissolved oxygen (DO). Nine small RNA libraries were constructed from the sea cucumber respiratory trees. A total of 26 differentially expressed miRNAs, including 12 upregulated and 14 downregulated miRNAs, were observed in severe hypoxia (DO 2 mg/L) compared with mild hypoxia (DO 4 mg/L) and normoxic conditions (DO 8 mg/L). Twelve differentially expressed miRNAs were clustered in severe hypoxia. In addition, real-time PCR revealed that 14 randomly selected differentially expressed miRNAs showed significantly increased expressions in severe hypoxia and the expressions of nine miRNAs, including key miRNAs such as Aja-miR-1, Aja-miR-2008, and Aja-miR-184, were consistent with the sequencing results. Moreover, gene ontology and pathway analyses of putative target genes suggest that these miRNAs are important in redox, transport, transcription, and hydrolysis under hypoxia stress. Notably, novel-miR-1, novel-miR-2, and novel-miR-3 were specifically clustered and upregulated in severe hypoxia, which may provide new insights into novel “hypoxamiR” identification. These results will provide a basis for future studies of miRNA regulation and molecular adaptive mechanisms in sea cucumbers under hypoxia stress.

Characterization of a secreted cystatin of the parasitic nematode Haemonchus contortus and its immune-modulatory effect on goat monocytes

BACKGROUND

Haemonchosis is a disease of the small ruminant caused by a nematode parasite Haemonchus contortus, and it is most important and alarming challenges to the small ruminant's production. The infection of the H. contortus could cause high economic losses worldwide. H. contortus is a blood feeding parasite which penetrates into the abomasal mucosa to feed the blood of the host and causing the anemia and decreased total plasma protein. Modulation and suppression of the immune response of the host by nematode parasites have been reported extensively, and the cysteine protease inhibitor (cystatin) is identified as one of the major immunomodulators.

METHODS

The recombinant protein of HCcyst-3 was expressed in a histidine-tagged fusion soluble form in Escherichia coli, and its inhibitory activity against cathepsin L, B, as well as papain, were identified by fluorogenic substrate analysis. Native HCcyst-3 protein was localized by an Immunohistochemical test. The immunomodulatory effects of HCcyst-3 on cytokine secretion, MHC molecule expression, NO production and phagocytosis were observed by co-incubation of rHCcyst-3 with goat monocytes.

RESULTS

We cloned and produced recombinant cystatin protein from H. contortus (rHCcyst-3) and investigated its immunomodulatory effects on goat monocyte. The rHCcyst-3 protein is biologically functional as shown by its ability to inhibit the protease activity of cathepsin L, cathepsin B, and papain. The immunohistochemical test demonstrated that the native HCcyst-3 protein was predominantly localized at the body surface and internal surface of the worm's gut. We demonstrated that rHCcyst-3 could be distinguished by antisera from goat experimentally infected with H. contortus and could uptake by goat monocytes. The results showed that the engagement of rHCcyst-3 decreased the production of TNF-α, IL-1β and IL-12p40. However, it significantly increased the secretion of IL-10 and TGF-β1 in goat monocytes. After rHCcyst-3 exposure, the expression of MHC-II on goat monocytes was restricted. Moreover, rHCcyst-3 could upregulate LPS induced NO production of goat monocytes. Phagocytotic assay by FITC-dextran internalization showed that rHCcyst-3 inhibited the phagocytosis of goat monocytes.

CONCLUSIONS

Our results suggested that the recombinant cystatin from H. contortus (rHCcyst-3) significantly modulated goat monocyte function in multiple aspects.

Molecular and structural characterization of novel cystatins from the taiga tick Ixodes persulcatus

Cystatins are cysteine peptidase inhibitors that in ticks mediate processes such as blood feeding and digestion. The ixodid tick Ixodes persulcatus is endemic to the Eurasia, where it is the principal vector of Lyme borreliosis. To date, no I. persulcatus cystatin has been characterized. In the present work, we describe three novel cystatins from I. persulcatus, named JpIpcys2a, JpIpcys2b and JpIpcys2c. In addition, the potential of tick cystatins as cross-protective antigens was evaluated by vaccination of hamsters using BrBmcys2c, a cystatin from Rhipicephalus microplus, against I. persulcatus infestation. Sequence analysis showed that motifs that are characteristic of cystatins type 2 are fully conserved in JpIpcys2b, while mutations are present in both JpIpcys2a and JpIpcys2c. Protein-protein docking simulations further revealed that JpIpcys2a, JpIpcys2b and JpIpcys2c showed conserved binding sites to human cathepsins L, all of them covering the active site cleft. Cystatin transcripts were detected in different I. persulcatus tissues and instars, showing their ubiquitous expression during I. persulcatus development. Serological analysis showed that although hamsters immunized with BrBmcys2c developed a humoral immune response, this response was not adequate to protect against a heterologous challenge with I. persulcatus adult ticks. The lack of cross-protection provided by BrBmcys2c immunization is perhaps linked to the fact that cystatins cluster into multigene protein families that are expressed differentially and exhibit functional redundancy. How to target such small proteins that are secreted in low quantities remains a challenge in the development of suitable anti-tick vaccine antigens.

Extreme genomic erosion after recurrent demographic bottlenecks in the highly endangered Iberian lynx

BACKGROUND

Genomic studies of endangered species provide insights into their evolution and demographic history, reveal patterns of genomic erosion that might limit their viability, and offer tools for their effective conservation. The Iberian lynx (Lynx pardinus) is the most endangered felid and a unique example of a species on the brink of extinction.

RESULTS

We generate the first annotated draft of the Iberian lynx genome and carry out genome-based analyses of lynx demography, evolution, and population genetics. We identify a series of severe population bottlenecks in the history of the Iberian lynx that predate its known demographic decline during the 20th century and have greatly impacted its genome evolution. We observe drastically reduced rates of weak-to-strong substitutions associated with GC-biased gene conversion and increased rates of fixation of transposable elements. We also find multiple signatures of genetic erosion in the two remnant Iberian lynx populations, including a high frequency of potentially deleterious variants and substitutions, as well as the lowest genome-wide genetic diversity reported so far in any species.

CONCLUSIONS

The genomic features observed in the Iberian lynx genome may hamper short- and long-term viability through reduced fitness and adaptive potential. The knowledge and resources developed in this study will boost the research on felid evolution and conservation genomics and will benefit the ongoing conservation and management of this emblematic species.

Characterization of a secreted cystatin from the tick Rhipicephalus haemaphysaloides

A novel cystatin, designated RHcyst-2, was isolated from the tick Rhipicephalus haemaphysaloides. The full-length cDNA of RHcyst-2 is 773 bp, including an intact open reading frame encoding an expected protein of 139 amino acids and consisting of a 23 amino acids signal peptide. Predicted RHcyst-2 mature protein molecular weight is about 13 kDa, isoelectric point is 4.96. A sequence analysis showed that it has significant homology with the known type 2 cystatins. The recombinant protein of RHcyst-2 was expressed in a glutathione S-transferase-fused soluble form in Escherichia coli, and its inhibitory activity against cathepsin L, B, C, H, and S, as well as papain, was identified by fluorogenic substrate analysis. The results showed that rRHcyst-2 can effectively inhibit the six cysteine proteases' enzyme activities. An investigation of the RHcyst-2 genes' expression profile by quantitative reverse transcription-PCR demonstrated that it was more richly transcribed in the embryo (egg) stage and mainly distributed in the mid-gut of adult ticks. Western blot analysis confirmed that RHcyst-2 was secreted into tick saliva.

Functional characterization of a cystatin from the tick Rhipicephalus haemaphysaloides

Background

Ticks and tick-borne diseases affect animal and human health worldwide and cause significant economic losses in the animal industry. Functional molecular research is important to understand the biological characteristics of ticks at the molecular level. Enzymes and enzyme inhibitory molecules play very important roles in tick physiology, and the cystatins are tight-binding inhibitors of papain-like cysteine proteases. To this end, a novel cystatin, designated RHcyst-1, was isolated from the tick Rhipicephalus haemaphysaloides.

Methods

The full-length gene of RHcyst-1 was cloning by RACE. The recombinant protein of RHcyst-1 was expressed in a glutathione S-transferase (GST)-fused soluble form in Escherichia coli, and its inhibitory activity against cathepsin L, B, C, H, and S, as well as papain, was identified by fluorogenic substrate analysis. Expression analysis of RHcyst-1 at different tick stages was performed by quantitative reverse transcription - PCR (qRT-PCR). An RNAi experiment for RHcyst-1 was performed to determine its function for tick physiology.

Results

The full-length cDNA of RHcyst-1 is 471 bp, including an intact open reading frame encoding an expected protein of 98 amino acids, without a signal peptide, having a predicted molecular weight of ~11 kDa and an isoelectric point of 5.66. A sequence analysis showed that it has significant homology with the known type 1 cystatins. The results of proteinase inhibition assays showed that rRHcyst-1 can effectively inhibit the six cysteine proteases’ enzyme activities. An investigation of the RHcyst-1 genes’ expression profile showed that it was more richly transcribed in the embryo (egg) stage. A disruption of the RHcyst-1 gene showed a significant decrease in the rate of tick hatching.

Conclusions

Our results suggested that RHcyst-1 may be involved in the early embryonic development of ticks.

Knockdown of the AKT3 (PKBγ), PI3KCA, and VEGFR2 genes by RNA interference suppresses glioblastoma multiforme T98G cells invasiveness in vitro

Glioblastoma multiforme (GBM) is the most common primary brain malignancy, having a very poor prognosis and is characterized by extensive brain invasion as well as resistance to the therapy. The phosphoinositide 3-kinase (PI3K)/Akt/PTEN signaling pathway is deregulated in GBM. Besides, florid vascularization and aberrantly elevated vascular endothelial growth factor (VEGF) occur very often. The present study was designed to examine the inhibitory effect of AKT3, PI3KCA, and VEGFR2 small interfering RNAs (siRNAs) on GBM cell invasiveness. T98G cells were transfected with AKT3, PI3KCA, and/or VEGFR2 siRNAs. VEGFR2 protein-positive cells were identified by flow cytometry using specific monoclonal anti-VEGFR2 antibodies. Alterations in messenger RNA (mRNA) expression of VEGF, VEGFR2, matrix metalloproteinases (MMPs) (MMP-2, MMP-9, MMP-13, MMP-14), tissue inhibitors of metalloproteinases (TIMPs) (TIMP-1, TIMP-3), c-Fos, c-Jun, hypoxia-inducible factor-1α (HIF-1α), ObRa, and cathepsin D genes were analyzed by qRT-PCR. Cells treated with specific siRNA were also analyzed for invasion using the Matrigel invasion assay. We have found significantly lower mRNA levels of MMPs, cathepsin D, VEGF, VEGFR2, HIF-1α, and c-Fos/c-Jun ratio, as well as significantly higher mRNA level of TIMPs in AKT3 and PI3KCA siRNA transfected cells compared to untransfected cells, while significantly lower mRNA levels of MMPs (MMP-2, MMP-9, MMP-14) and TIMP-1, as well as significantly higher mRNA level of TIMP-3, were shown only in cells transfected with VEGFR2 siRNA. The positive correlation between MMP-13 and ObRa mRNA copy number has been found. Summarizing, transfection of T98G cells with AKT3, PI3KCA, or VEGFR2 siRNAs leads to a significant reduction in cell invasiveness. The siRNA-induced AKT3, PI3KCA, and VEGFR2 mRNA knockdown may offer a novel therapeutic strategy to reduce the invasiveness of GBM cells.

Proteomic analysis of cattle tick Rhipicephalus (Boophilus) microplus saliva: a comparison between partially and fully engorged females

The cattle tick Rhipicephalus (Boophilus) microplus is one of the most harmful parasites affecting bovines. Similarly to other hematophagous ectoparasites, R. microplus saliva contains a collection of bioactive compounds that inhibit host defenses against tick feeding activity. Thus, the study of tick salivary components offers opportunities for the development of immunological based tick control methods and medicinal applications. So far, only a few proteins have been identified in cattle tick saliva. The aim of this work was to identify proteins present in R. microplus female tick saliva at different feeding stages. Proteomic analysis of R. microplus saliva allowed identifying peptides corresponding to 187 and 68 tick and bovine proteins, respectively. Our data confirm that (i) R. microplus saliva is complex, and (ii) that there are remarkable differences in saliva composition between partially engorged and fully engorged female ticks. R. microplus saliva is rich mainly in (i) hemelipoproteins and other transporter proteins, (ii) secreted cross-tick species conserved proteins, (iii) lipocalins, (iv) peptidase inhibitors, (v) antimicrobial peptides, (vii) glycine-rich proteins, (viii) housekeeping proteins and (ix) host proteins. This investigation represents the first proteomic study about R. microplus saliva, and reports the most comprehensive Ixodidae tick saliva proteome published to date. Our results improve the understanding of tick salivary modulators of host defense to tick feeding, and provide novel information on the tick-host relationship.

Cathepsin L protects mice from mycoplasmal infection and is essential for airway lymphangiogenesis

Cathepsin L (Ctsl) is a proposed therapeutic target to control inflammatory responses in a number of disease states. However, Ctsl is thought to support host defense via its involvement in antigen presentation pathways. Hypothesizing that Ctsl helps combat bacterial infection, we investigated its role in Mycoplasma pulmonis-infected mice as a model of acute and chronic infectious airway inflammation. Responses to the airway inoculation of mycoplasma were compared in Ctsl(-/-) and Ctsl(+/+) mice. After infection, Ctsl(-/-) mice demonstrated more body weight loss, greater mortality (22% versus 0%, respectively), and heavier lungs than Ctsl(+/+) mice, but had smaller bronchial lymph nodes. The burden of live mycoplasma in lungs was 247-fold greater in Ctsl(-/-) mice than in Ctsl(+/+) mice after infection for 3 days. Ctsl(-/-) mice exhibited more severe pneumonia and neutrophil-rich, airway-occlusive exudates, which developed more rapidly than in Ctsl(+/+) mice. Compared with the conspicuous remodeling of lymphatics after infection in Ctsl(+/+) mice, little lymphangiogenesis occurred in Ctsl(-/-) mice, but blood vessel remodeling and tissue inflammation were similarly severe. Titers of mycoplasma-reactive IgM, IgA, and IgG in blood in response to live and heat-killed organisms were similar to those in Ctsl(+/+) mice. However, enzyme-linked immunosorbent spot assays revealed profound reductions in the cellular IFN-γ response to mycoplasma antigen. These findings suggest that Ctsl helps contain mycoplasma infection by supporting lymphangiogenesis and cellular immune responses to infection, and our findings predict that the therapeutic inhibition of Ctsl could increase the severity of mycoplasmal infections.

Proteolytic characteristics of cathepsin D related to the recognition and cleavage of its target proteins

Cathepsin D (CD) plays an important role in both biological and pathological processes, although the cleavage characteristics and substrate selection of CD have yet to be fully explored. We employed liquid chromatography-tandem mass spectrometry (LC-MS/MS) to identify the CD cleavage sites in bovine serum albumin (BSA). We found that the hydrophobic residues at P1 were not only a preferential factor for CD cleavage but that the hydrophobicity at P1’ also contributed to CD recognition. The concept of hydrophobic scores of neighbors (HSN) was proposed to describe the hydrophobic microenvironment of CD recognition sites. The survey of CD cleavage characteristics in several proteins suggested that the HSN was a sensitive indicator for judging the favorable sites in peptides for CD cleavage, with HSN values of 0.5–1.0 representing a likely threshold. Ovalbumin (OVA), a protein resistant to CD cleavage in its native state, was easily cleaved by CD after denaturation, and the features of the cleaved peptides were quite similar to those found in BSA, where a higher HSN value indicated greater cleavability. We further conducted two-dimensional gel electrophoresis (2DE) to find more proteins that were insensitive to CD cleavage in CD-knockdown cells. Based on an analysis of secondary and three-dimensional structures, we postulated that intact proteins with a structure consisting of all α-helices would be relatively accessible to CD cleavage.

B-cell lymphopoiesis is regulated by cathepsin L

Cathepsin L (CTSL) is a ubiquitously expressed lysosomal cysteine peptidase with diverse and highly specific functions. The involvement of CTSL in thymic CD4+ T-cell positive selection has been well documented. Using CTSL^nkt/nkt mice that lack CTSL activity, we have previously demonstrated that the absence of CTSL activity affects the homeostasis of the T-cell pool by decreasing CD4+ cell thymic production and increasing CD8+ thymocyte production. Herein we investigated the influence of CTSL activity on the homeostasis of peripheral B-cell populations and bone marrow (BM) B-cell maturation. B-cell numbers were increased in lymph nodes (LN), spleen and blood from CTSL^nkt/nkt mice. Increases in splenic B-cell numbers were restricted to transitional T1 and T2 cells and to the marginal zone (MZ) cell subpopulation. No alterations in the proliferative or apoptosis levels were detected in peripheral B-cell populations from CTSL^nkt/nkt mice. In the BM, the percentage and the absolute number of pre-pro-B, pro-B, pre-B, immature and mature B cells were not altered. However, in vitro and in vivo experiments showed that BM B-cell production was markedly increased in CTSL^nkt/nkt mice. Besides, BM B-cell emigration to the spleen was increased in CTSL^nkt/nkt mice. Colony-forming unit pre-B (CFU pre-B) assays in the presence of BM stromal cells (SC) and reciprocal BM chimeras revealed that both BM B-cell precursors and SC would contribute to sustain the increased B-cell hematopoiesis in CTSL^nkt/nkt mice. Overall, our data clearly demonstrate that CTSL negatively regulates BM B-cell production and output therefore influencing the homeostasis of peripheral B cells.

The role of cystatins in tick physiology and blood feeding

Ticks, as obligate hematophagous ectoparasites, impact greatly on animal and human health because they transmit various pathogens worldwide. Over the last decade, several cystatins from different hard and soft ticks were identified and biochemically analyzed for their role in the physiology and blood feeding lifestyle of ticks. All these cystatins are potent inhibitors of papain-like cysteine proteases, but not of legumain. Tick cystatins were either detected in the salivary glands and/or the midgut, key tick organs responsible for blood digestion and the expression of pharmacologically potent salivary proteins for blood feeding. For example, the transcription of two cystatins named HlSC-1 and Sialostatin L2 was highly upregulated in these tick tissues during feeding. Vaccinating hosts against Sialostatin L2 and Om-cystatin 2 as well as silencing of a cystatin gene from Amblyomma americanum significantly inhibited the feeding ability of ticks. Additionally, Om-cystatin 2 and Sialostatin L possessed strong host immunosuppressive properties by inhibiting dendritic cell maturation due to their interaction with cathepsin S. These two cystatins, together with Sialostatin L2 are the first tick cystatins with resolved three-dimensional structure. Sialostatin L, furthermore, showed preventive properties against autoimmune diseases. In the case of the cystatin Hlcyst-2, experimental evidence showed its role in tick innate immunity, since increased Hlcyst-2 transcript levels were detected in Babesia gibsoni-infected larval ticks and the protein inhibited Babesia growth. Other cystatins, such as Hlcyst-1 or Om-cystatin 2 are assumed to be involved in regulating blood digestion. Only for Bmcystatin was a role in tick embryogenesis suggested. Finally, all the biochemically analyzed tick cystatins are powerful protease inhibitors, and some may be novel antigens for developing anti-tick vaccines and drugs of medical importance due to their stringent target specificity.

Shark class II invariant chain reveals ancient conserved relationships with cathepsins and MHC class II

The invariant chain (Ii) is the critical third chain required for the MHC class II heterodimer to be properly guided through the cell, loaded with peptide, and expressed on the surface of antigen presenting cells. Here, we report the isolation of the nurse shark Ii gene, and the comparative analysis of Ii splice variants, expression, genomic organization, predicted structure, and function throughout vertebrate evolution. Alternative splicing to yield Ii with and without the putative protease-protective, thyroglobulin-like domain is as ancient as the MHC-based adaptive immune system, as our analyses in shark and lizard further show conservation of this mechanism in all vertebrate classes except bony fish. Remarkable coordinate expression of Ii and class II was found in shark tissues. Conserved Ii residues and cathepsin L orthologs suggest their long co-evolution in the antigen presentation pathway, and genomic analyses suggest 450 million years of conserved Ii exon/intron structure. Other than an extended linker preceding the thyroglobulin-like domain in cartilaginous fish, the Ii gene and protein are predicted to have largely similar physiology from shark to man. Duplicated Ii genes found only in teleosts appear to have become sub-functionalized, as one form is predicted to play the same role as that mediated by Ii mRNA alternative splicing in all other vertebrate classes. No Ii homologs or potential ancestors of any of the functional Ii domains were found in the jawless fish or lower chordates.

Radical reversal of vasoactive intestinal peptide (VIP) receptors during early lymphopoiesis

Successful thymocyte maturation is essential for normal, peripheral T cell function. Vasoactive intestinal peptide (VIP) is a neuropeptide which is highly expressed in the thymus that has been shown to modulate thymocyte development. VIP predominantly binds two G protein coupled receptors, termed vasoactive intestinal peptide receptor 1 (VPAC1) and VPAC2, but their expression profiles in CD4(-)/CD8(-) (double negative, DN) thymocyte subsets, termed DN1-4, have yet to be identified. We hypothesized that a high VPAC1:VPAC2 ratio in the earliest thymocyte progenitors (ETP cells) would be reversed during early lymphopoiesis as observed in activated, peripheral Th(2) cells, as the thymus is rich in Th(2) cytokines. In support of this hypothesis, high VPAC1 mRNA levels decreased 1000-fold, accompanied with a simultaneous increase in VPAC2 mRNA expression during early thymocyte progenitor (ETP/DN1)→DN3 differentiation. Moreover, arrested DN3 cells derived from an Ikaros null mouse (JE-131 cells) failed to completely reverse the VIP receptor ratio compared to wild type DN3 thymocytes. Surprisingly, VPAC2(-/-) mice did not show significant changes in relative thymocyte subset numbers. These data support the notion that both VPAC1 and VPAC2 receptors are dynamically regulated by Ikaros, a master transcriptional regulator for thymocyte differentiation, during early thymic development. Moreover, high VPAC1 mRNA is a novel marker for the ETP population making it enticing to speculate that the chemotactic VIP/VPAC1 signaling axis may play a role in thymocyte movement. Also, despite the results that VPAC2 deficiency did not affect thymic subset numbers, future studies are necessary to determine whether downstream T cell phenotypic changes manifest themselves, such as a propensity for a Th(1) versus Th(2) polarization.

Cytotoxic T lymphocyte antigen-2 alpha induces apoptosis of murine T-lymphoma cells and cardiac fibroblasts and is regulated by cAMP/PKA

The mechanism of cAMP-promoted apoptosis is not well defined. In wild-type (WT) murine S49 lymphoma cells, cAMP promotes apoptosis in a protein kinase A (PKA)-dependent manner. We find that treatment of WT S49 cells with 8-CPT-cAMP prominently increases the expression (as determined by DNA microarray analysis, real-time PCR and immunblotting) of cytotoxic T lymphocyte antigen-2α (CTLA-2α), a cathepsin L-like cysteine protease inhibitor. By contrast, CTLA-2α expression is only slightly increased by 8-CPT-cAMP treatment of D-S49 cells, which lack cAMP/PKA-promoted apoptosis. Raising endogenous cAMP (by use of forskolin or inhibition of phosphodiesterase [PDE] 4) or a PKA-selective, but not an Epac-selective, cAMP analogue, increases CTLA-2α mRNA expression; PKA, and not Epac, thus mediates the increase in CTLA-2α expression. An adenoviral CLTA-2α (Ad-CTLA-2α) construct induces apoptosis and enhances cAMP-promoted apoptosis in WT S49 cells but such cells do not have an increase in cathepsin L activity nor does a cathepsin L inhibitor alter cAMP-promoted apoptosis. 8-CPT-cAMP also increases CTLA-2α expression and induces apoptosis in murine cardiac fibroblasts; knockdown of CTLA-2α expression by siRNA blocks 8-CPT-cAMP-promoted apoptosis. Thus, cAMP increases CTLA-2α expression in murine lymphoma and cardiac fibroblasts and this increase in CTLA-2α contributes to cAMP/PKA-promoted apoptosis by mechanisms that are independent of the ability of CTLA-2α to inhibit cathepsin L.

Cathepsin K deficiency reduces elastase perfusion-induced abdominal aortic aneurysms in mice

OBJECTIVE

Cathepsin K (CatK) is one of the most potent mammalian elastases. We have previously shown increased expression of CatK in human abdominal aortic aneurysm (AAA) lesions. Whether this protease participates directly in AAA formation, however, remains unknown.

METHODS AND RESULTS

Mouse experimental AAA was induced with aortic perfusion of a porcine pancreatic elastase. Using this experimental model, we demonstrated that absence of CatK prevented AAA formation in mice 14 days postperfusion. CatK deficiency significantly reduced lesion CD4(+) T-cell content, total lesion and medial cell proliferation and apoptosis, medial smooth muscle cell (SMC) loss, elastinolytic CatL and CatS expression, and elastin fragmentation, but it did not affect AAA lesion Mac-3(+) macrophage accumulation or CD31(+) microvessel numbers. In vitro studies revealed that CatK contributed importantly to CD4(+) T-cell proliferation, SMC apoptosis, and other cysteinyl cathepsin and matrix metalloproteinase expression and activities in SMCs and endothelial cells but played negligible roles in microvessel growth and monocyte migration. AAA lesions from CatK-deficient mice showed reduced elastinolytic cathepsin activities compared with those from wild-type control mice.

CONCLUSIONS

This study demonstrates that CatK plays an essential role in AAA formation by promoting T-cell proliferation, vascular SMC apoptosis, and elastin degradation and by affecting vascular cell protease expression and activities.

Protective role of cathepsin L in mouse skin carcinogenesis

Lysosomal cysteine protease cathepsin L (CTSL) is believed to play a role in tumor progression and is considered a marker for clinically invasive tumors. Studies from our laboratory using the classical mouse skin carcinogenesis model, with 7,12-dimethyl-benz[a]anthracene (DMBA) for initiation and 12-O-tetradecanoylphorbol-13-acetate (TPA) for promotion, showed that expression of CTSL is increased in papillomas and squamous cell carcinomas (SCC). We also carried out carcinogenesis studies using Ctsl-deficient nackt (nkt) mutant mice on three different inbred backgrounds. Unexpectedly, the multiplicity of papillomas was significantly higher in Ctsl-deficient than in wild-type mice on two unrelated backgrounds. Topical applications of TPA or DMBA alone to the skin of nkt/nkt mice did not induce papillomas, and there was no increase in spontaneous tumors in nkt/nkt mice on any of the three inbred backgrounds. Reduced epidermal cell proliferation in Ctsl-deficient nkt/nkt mice after TPA treatment suggested that they are not more sensitive than wild-type mice to TPA promotion. We also showed that deficiency of CTSL delays terminal differentiation of keratinocytes, and we propose that decreased elimination of initiated cells is at least partially responsible for the increased papilloma formation in the nackt model.

Lack of cathepsin activities alter or prevent the development of lung granulomas in a mouse model of sarcoidosis

BACKGROUND

Remodeling of lung tissues during the process of granuloma formation requires significant restructuring of the extra-cellular matrix and cathepsins K, L and S are among the strongest extra-cellular matrix degrading enzymes. Cathepsin K is highly expressed in various pathological granulomatous infiltrates and all three enzymes in their active form are detected in bronchoalveolar lavage fluids from patients with sarcoidosis. Granulomatous inflammation is driven by T-cell response and cathepsins S and L are actively involved in the regulation of antigen presentation and T-cell selection. Here, we show that the disruption of the activities of cathepsins K, L, or S affects the development of lung granulomas in a mouse model of sarcoidosis.

METHODS

Apolipoprotein E-deficient mice lacking cathepsin K or L were fed Paigen diet for 16 weeks and lungs were analyzed and compared with their cathepsin-expressing littermates. The role of cathepsin S in the development of granulomas was evaluated using mice treated for 8 weeks with a potent and selective cathepsin S inhibitor.

RESULTS

When compared to wild-type litters, more cathepsin K-deficient mice had lung granulomas, but individually affected mice developed smaller granulomas that were present in lower numbers. The absence of cathepsin K increased the number of multinucleated giant cells and the collagen content in granulomas. Cathepsin L deficiency resulted in decreased size and number of lung granulomas. Apoe-/- mice treated with a selective cathepsin S inhibitor did not develop lung granulomas and only individual epithelioid cells were observed.

CONCLUSIONS

Cathepsin K deficiency affected mostly the occurrence and composition of lung granulomas, whereas cathepsin L deficiency significantly reduced their number and cathepsin S inhibition prevented the formation of granulomas.

Superantigens increase the survival of mice bearing T cell lymphomas by inducing apoptosis of neoplastic cells

Superantigens bind to major histocompatibility complex class II molecules and interact with T cells expressing a particular T cell receptor Vβ inducing a strong proliferation/deletion response of the superantigen-reactive T cells. However, there have been no attempts to investigate the ability of Sags to induce apoptosis in neoplastic T cells by signaling through the Vβ region of their TCR. In the present study we show that bacterial and MMTV-encoded superantigens induce the apoptosis of AKR/J cognate lymphoma T cells both in vitro and in vivo. The Fas-Fas-L pathway was shown to be involved in the apoptosis of lymphoma T cells induced by bacterial superantigens. In vivo exposure to bacterial superantigens was able to improve the survival of lymphoma bearing mice. Moreover, the permanent expression of a retroviral encoded superantigen induced the complete remission of an aggressive lymphoma in a high percentage of mice. The possibility of a therapeutic use of superantigens in lymphoma/leukemia T cell malignancies is discussed.

Diverse regulatory roles for lysosomal proteases in the immune response

The innate and adaptive immune system utilise endocytic protease activity to promote functional immune responses. Cysteine and aspartic proteases (cathepsins) constitute a subset of endocytic proteases, the immune function of which has been described extensively. Although historically these studies have focused on their role in processes such as antigen presentation and zymogen processing within the endocytic compartment, recent discoveries have demonstrated a critical role for these proteases in other intracellular compartments, and within the extracellular milieu. It has also become clear that their pattern of expression and substrate specificities are more diverse than was first envisaged. Here, we discuss recent advances addressing the role of lysosomal proteases in various aspects of the immune response. We pay attention to reports demonstrating cathepsin activity outside of its canonical endosome/lysosome microenvironment.

Acquisition of T regulatory function in cathepsin L-inhibited T cells by eye-derived CTLA-2alpha during inflammatory conditions

Pigment epithelium isolated from the eye possesses immunosuppressive properties such as regulatory T (Treg) cell induction; e.g., cultured retinal pigment epithelium (RPE) converts CD4(+) T cells into Treg cells in vitro. RPE constitutively expresses a novel immunosuppressive factor, CTLA-2alpha, which is a cathepsin L (CathL) inhibitor, and this molecule acts via RPE to induce Treg cells. To clarify CTLA-2alpha's role in the T cell response to RPE in ocular inflammation, we used the experimental autoimmune uveitis (EAU) animal model to examine this new immunosuppressive property of RPE. In EAU models, TGF-beta, but not IFN-gamma inflammatory cytokines, promotes the up-regulation of the expression of CTLA-2alpha in RPE. Similarly, CTLA-2alpha via RPE was able to promote TGF-beta production by the CD4(+) T cells. The RPE-exposed T cells (RPE-induced Treg cells) greatly produced TGF-beta and suppressed bystander effector T cells. There was less expression of CathL by the RPE-exposed T cells, and CathL-inhibited T cells were able to acquire the Treg phenotype. Moreover, CathL-deficient mice spontaneously produced Treg cells, with the increase in T cells potentially providing protection against ocular inflammation. More importantly, CD4(+) T cells from EAU in CathL knockout mice or rCTLA-2alpha from EAU animals were found to contain a high population of forkhead box p3(+) T cells. In both EAU models, there was significant suppression of the ocular inflammation. These results indicate that RPE secretes CTLA-2alpha, thereby enabling the bystander T cells to be converted into Treg cells via TGF-beta promotion.

Retinal pigment epithelium-derived CTLA-2alpha induces TGFbeta-producing T regulatory cells

T cells that encounter ocular pigment epithelium in vitro are inhibited from undergoing TCR-triggered activation, and instead acquire the capacity to suppress the activation of bystander T cells. Because retinal pigment epithelial (RPE) cells suppress T cell activation by releasing soluble inhibitory factors, we studied whether soluble factors also promote the generation of T regulatory (Treg) cells. We found that RPE converted CD4(+) T cells into Treg cells by producing and secreting CTLA-2alpha, a cathepsin L (CathL) inhibitor. Mouse rCTLA-2alpha converted CD4(+) T cells into Treg cells in vitro, and CTLA-2alpha small interfering RNA-transfected RPE cells failed to induce the Treg generation. RPE CTLA-2alpha induced CD4(+)CD25(+)Foxp3(+) Treg cells that produced TGFbeta in vitro. Moreover, CTLA-2alpha produced by RPE cells inhibited CathL activity in the T cells, and losing CathL activity led to differentiation to Treg cells in some populations of CD4(+) T cells. In addition, T cells in the presence of CathL inhibitor increased the expression of Foxp3. The CTLA-2alpha effect on Treg cell induction occurred through TGFbeta signaling, because CTLA-2alpha promoted activation of TGFbeta in the eye. These results show that immunosuppressive factors derived from RPE cells participate in T cell suppression. The results are compatible with the hypothesis that the eye-derived Treg cells acquire functions that participate in the establishment of immune tolerance in the posterior segment of the eye.

Cysteine protease cathepsin X modulates immune response via activation of beta2 integrins

Cathepsin X is a lysosomal, cysteine dependent carboxypeptidase. Its expression is restricted to cells of the immune system, suggesting a function related to the processes of inflammatory and immune responses. It has been shown to stimulate macrophage antigen-1 (Mac-1) receptor-dependent adhesion and phagocytosis via interaction with integrin beta2 subunit. Here its potential role in regulating lymphocyte proliferation via Mac-1 and the other beta2 integrin receptor, lymphocyte function-associated antigen-1 (LFA-1) has been investigated. Cathepsin X has been shown to suppress proliferation of human peripheral blood mononuclear cells, by activation of Mac-1, known as a suppressive factor for lymphocyte proliferation. On the other hand, co-localization of cathepsin X and LFA-1 supports the role of cathepsin X in regulating LFA-1 activity, which enhances lymphocyte proliferation. As shown by fluorescence resonance energy transfer, using U-937 and Jurkat cells transfected with alpha(L)-mCFP and beta2-mYFP, recombinant cathepsin X directly activates LFA-1. The activation was confirmed by increased binding of monoclonal antibody 24, recognizing active LFA-1. We demonstrate that cathepsin X is involved in the regulation of two beta2 integrin receptors, LFA-1 and Mac-1, which exhibit opposing roles in lymphocyte activation.

Expression of the human Cathepsin L inhibitor hurpin in mice: skin alterations and increased carcinogenesis

The serine protease inhibitor (serpin) hurpin (serpin B13) is a cross class-specific inhibitor of the cysteine protease Cathepsin (Cat) L. Cat L is involved in lysosomal protein degradation, hair follicle morphogenesis, epidermal differentiation and epitope generation of antigens. Hurpin is a 44 kDa protein which is expressed predominantly in epidermal cells. In psoriatic skin samples, hurpin was strongly overexpressed when compared with normal skin. Keratinocytes overexpressing hurpin showed increased resistance towards UVB-induced apoptosis. To further analyse the functional importance of this inhibitor, we have generated transgenic mice with deregulated Cat L activity by expressing human hurpin in addition to the endogenous mouse inhibitor. The three independent transgenic lines generated were characterized by identical effects excluding insertional phenotypes. Macroscopically, mice expressing human hurpin are characterized by abnormal abdominal fur. The number of apoptotic cells and caspase-3 positive cells was reduced after UV-irradiation in transgenic animals compared with wild-type mice. Interestingly, after chemical carcinogenesis, transgenic mice showed an increased susceptibility to develop skin cancer. Array analysis of gene expression revealed distinct differences between wild-type and hurpin-transgenic mice. Among others, differentially expressed genes are related to antigen presentation and angiogenesis. These results suggest an important role of Cat L regulation by hurpin which might be of clinical relevance in human skin diseases.

Cysteine cathepsins: regulators of antitumour immune response

Cysteine cathepsins are lysosomal cysteine proteases that are involved in a number of important biological processes, including intracellular protein turnover, propeptide and hormone processing, apoptosis, bone remodelling and reproduction. In cancer, the cathepsins have been linked to extracellular matrix remodelling and to the promotion of tumour cell motility, invasion, angiogenesis and metastasis, resulting in poor outcome of cancer patients; however, cysteine cathepsins are also involved at different levels of the innate and adaptive immune responses. Their best known role in this aspect is their contribution to major histocompatibility complex class II antigen presentation, the processing of progranzymes into proteolytically active forms, cytotoxic lymphocyte self-protection, cytokine and growth factor degradation and, finally, the induction of cytokine expression and modulation of integrin function. This review is focused on the role of cysteine cathepsins in the antitumour immune response and the evaluation of their pro- and anticancer behaviours during the regulation of these processes.

Trafficking on serpentines: molecular insight on how maturating T cells find their winding paths in the thymus

Maintenance of the peripheral T-cell pool throughout the life requires uninterrupted generation of T cells. The majority of peripheral T cells are generated in the thymus. However, the thymus does not contain hematopoietic progenitors with unlimited self-renewing potential, and continuous production of T cells requires importation of such progenitors from the bone marrow into the thymus. Thymus-homing progenitors enter the thymus and subsequently migrate throughout distinct intrathymic microenvironments while differentiating into mature T cells. At each step of this scheduled journey, developing thymocytes interact intimately with the local stroma, which allow them to proceed to the next stage of their differentiation and maturation program. Undoubtedly, thymocyte/stroma interactions are instrumental for both thymocytes and stroma, because only their ongoing interplay generates and maintains a fully operational thymus, able to guarantee unimpaired T-cell supply. Therefore, proper T-cell generation intrinsically involves polarized cell migration during both adult life and embryogenesis when the thymus primordium develops into a functional thymus. The molecular mechanisms controlling cell migration during thymus development and postnatal T-cell differentiation are beginning to be defined. This review focuses on recent data regarding the role of cell migration in both colonization of the fetal thymus and T-cell development during postnatal life in mice.

Antiinflammatory and immunosuppressive activity of sialostatin L, a salivary cystatin from the tick Ixodes scapularis

Here we report the ability of the tick Ixodes scapularis, the main vector of Lyme disease in the United States, to actively and specifically affect the host proteolytic activity in the sites of infestation through the release of a cystatin constituent of its saliva. The cystatin presence in the saliva was verified both biochemically and immunologically. We named the protein sialostatin L because of its inhibitory action against cathepsin L. We also show that the proteases it targets, although limited in number, have a prominent role in the proteolytic cascades that take place in the extracellular and intracellular environment. As a result, sialostatin L displays an antiinflammatory role and inhibits proliferation of cytotoxic T lymphocytes. Beyond unraveling another component accounting for the properties of tick saliva, contributing to feeding success and pathogen transmission, we describe a novel tool for studying the role of papain-like proteases in diverse biologic phenomena and a protein with numerous potential pharmaceutical applications.