Nuclear cathepsin L activity is required for cell cycle progression of colorectal carcinoma cells

A Novel Cystatin Gene from Sea Cucumber (Apostichopus japonicus): Characterization and Comparative Expression with Cathepsin L During Early Stage of Hypoxic Exposure-Induced Autolysis

Autolysis in sea cucumber has long been a threat to raw material storage and product processing. The involvement of endogenous cysteine protease in sea cucumber autolysis has been proved extendedly. However, as an essential part of the mechanism of autolysis, the role of its endogenous inhibitor has seldom been reported. To investigate the role of cysteine protease inhibitors in the early stage of hypoxic exposure-induced autolysis, a novel cystatin gene (SjCyt) belonging to the subfamily of cystatin C was cloned from Apostichopus japonicus by homology cloning and rapid amplification of cDNA ends. The affinity of SjCyt to cysteine protease (cathepsin L and cathepsin B) was investigated by molecular dynamics simulations. Pertinent metrics, including the root mean square deviation, radius of gyration, Gibbs free energy, binding free energy, and bond-forming frequency, showed that the conformation of SjCyt-SjCL was more stable and confirmed a stronger interaction of SjCyt with cathepsin L than with cathepsin B. Thus, cathepsin L (SjCL) was selected to further study its co-expression with SjCyt over a period of 9 h at an early stage of hypoxic exposure. Quantitative RT-qPCR revealed a ubiquitous transcriptional profile of SjCyt and SjCL in all the tested tissues, with the highest abundance in the dorsal epidermis, tube feet, and coelomocytes. Temporal transcription of them showed an overall up-regulated co-expression in the dorsal epidermis and tube feet. However, up-regulated SjCyt and down-regulated SjCL were observed at the protein level. Further immunofluorescence double labeling also found increased staining of SjCyt and SjCyt-SjCL complexes and decreased SjCL. Additionally, recombinant SjCyt was prepared and demonstrated an evident autolysis-inhibiting effect. The results of this study indicated that the anti-autolytic regulation of SjCyt functions at the very early stage of hypoxic exposure, exerting effects at both the transcriptional and translational levels. The above finding offers new insights into the mechanisms of sea cucumber autolysis.

Novel Nucleus-Oriented Quenched Activity-Based Probes Link Cathepsin Nuclear Localization with Mitosis

Cysteine cathepsins are important proteases that are highly upregulated in cancers and other diseases. While their reported location is mostly endolysosomal, some evidence shows their nuclear localization and involvement in the cell cycle. We aim to generate tools to investigate the involvement of cathepsins in the cell cycle progression. To investigate nuclear cathepsin activity, we designed nucleus-directed quenched activity-based probes (qABPs) by attaching cell-penetrating peptides (CPPs). qABPs are active-site-directed compounds that enable direct real-time monitoring of enzyme activity by the covalent linkage between the probe and the enzyme's active site. Biochemical evaluation of the CPP-qABPs showed potent and selective probes; cell fractionation, multimodal flow cytometry-imaging, and time-lapse movies demonstrated nuclear cathepsin activity in living cells. Interestingly, these probes reveal a spatiotemporal pattern, a surge of nuclear cathepsin just before mitosis, suggesting yet unrevealed roles of cathepsin in cell division. In summary, these nuclear-directed qABPs serve as unique scientific tools to unlock the hidden features of cysteine proteases and to understand their involvement in cell division and cancer.

Role of drug induced nuclear CTSL (nCTSL) in DNA damage response in cancer- therapeutic implications

In our efforts to enhance sensitivity to PARP inhibitors, we identified clofarabine (CLF) as a potential therapy for drug-resistant ovarian cancer and nuclear trafficking of Cathepsin L (CTSL) as a treatment- responsive biomarker. Using PARP inhibitor-sensitive and -resistant OC cell lines, ex vivo cultures of patient-derived ovarian ascites (OVA), primary ovarian tumors, and xenografts (PDX), we found that CLF monotherapy induces nuclear CTSL (nCTSL) in CLF-responsive cells (CLF-r) and sensitizes them to PARP inhibitors olaparib and rucaparib. In CLF non-responsive cells (CLF-nr), a combination of CLF with olaparib is necessary for nCTSL trafficking and synergy. CLF+olaparib synergy was observed in 47% of CLF-r and 24% of CLF-nr OVA samples. Drug-induced nCTSL is crucial for DNA damage response, including cell cycle arrest and apoptosis. Knockdown of CTSL in both CLF-r and CLF-nr cells conferred resistance to the CLF+olaparib combination, emphasizing nCTSL's role in the DNA damage response pathway (DDR). Mechanistically, CLF facilitates CTSL nuclear import via KPNB1 in CLF-r cells. In CLF-nr cells, both olaparib and CLF are needed to facilitate CTSL nuclear import. Additionally, CLF downregulates the nuclear export protein CRM1 (XPO1) in both cohorts. Interestingly, CLF does not downregulate CRM1 in a subset of OVAs (29%), and they were classified as CLF-resistant (CLF- Res). In these samples, inhibiting CRM1 with KPT8602 restored synergy between CLF and PARP inhibitors. In vivo, CLF-r and CLF-nr PDX models exhibited enhanced DDR, reduced tumor burden, and prolonged survival with the CLF+olaparib combination. These findings suggest the CLF+olaparib combination is a promising therapeutic strategy for drug-resistant OC by inducing DDR through CTSL nuclear localization.

Non-Canonical, Extralysosomal Activities of Lysosomal Peptidases in Physiological and Pathological Conditions: New Clinical Opportunities for Cancer Therapy

Lysosomes are subcellular compartments characterised by an acidic pH, containing an ample variety of acid hydrolases involved in the recycling of biopolymers. Among these hydrolases, lysosomal proteases have merely been considered as end-destination proteases responsible for the digestion of waste proteins, trafficked to the lysosomal compartment through autophagy and endocytosis. However, recent reports have started to unravel specific roles for these proteases in the regulation of initially unexpected biological processes, both under physiological and pathological conditions. Furthermore, some lysosomal proteases are no longer restricted to the lysosomal compartment, as more novel non-canonical, extralysosomal targets are being identified. Currently, lysosomal proteases are accepted to play key functions in the extracellular milieu, attached to the plasma membrane and even in the cytosolic and nuclear compartments of the cell. Under physiological conditions, lysosomal proteases, through non-canonical, extralysosomal activities, have been linked to cell differentiation, regulation of gene expression, and cell division. Under pathological conditions, these proteases have been linked to cancer, mostly through their extralysosomal activities in the cytosol and nuclei of cells. In this review, we aim to provide a comprehensive summary of our current knowledge about the extralysosomal, non-canonical functions of lysosomal proteases, both under physiological and pathological conditions, with a particular interest in cancer, that could potentially offer new opportunities for clinical intervention.

Cytoskeletal β-tubulin and cysteine cathepsin L deregulation by SARS-CoV-2 spike protein interaction with the neuronal model cell line SH-SY5Y

SARS-CoV-2 mainly infects the respiratory tract but can also target other organs, including the central nervous system. While it was recently shown that cells of the blood-brain-barrier are permissive to SARS-CoV-2 infection in vitro, it remains debated whether neurons can be infected. In this study, we demonstrate that vesicular stomatitis virus particles pseudotyped with the spike protein of SARS-CoV-2 variants WT, Alpha, Delta and Omicron enter the neuronal model cell line SH-SY5Y. Cell biological analyses of the pseudo-virus treated cultures showed marked alterations in microtubules of SH-SY5Y cells. Because the changes in β-tubulin occurred in most cells, but only few were infected, we further asked whether interaction of the cells with spike protein might be sufficient to cause molecular and structural changes. For this, SH-SY5Y cells were incubated with trimeric spike proteins for time intervals of up to 24 h. CellProfiler™-based image analyses revealed changes in the intensities of microtubule staining in spike protein-incubated cells. Furthermore, expression of the spike protein-processing protease cathepsin L was found to be up-regulated by wild type, Alpha and Delta spike protein pseudotypes and cathepsin L was found to be secreted from spike protein-treated cells. We conclude that the mere interaction of the SARS-CoV-2 with neuronal cells can affect cellular architecture and proteolytic capacities. The molecular mechanisms underlying SARS-CoV-2 spike protein induced cytoskeletal changes in neuronal cells remain elusive and require future studies.

Compensational role between cathepsins

Cathepsins, a family of lysosomal peptidases, play a crucial role in maintaining cellular homeostasis by regulating protein turnover and degradation as well as many specific regulatory actions that are important for proper cell function and human health. Alterations in the activity and expression of cathepsins have been observed in many diseases such as cancer, inflammation, neurodegenerative disorders, bone remodelling-related conditions and others. These changes are not exclusively harmful, but rather appear to be a compensatory response on the lack of one cathepsin in order to maintain tissue integrity. The upregulation of specific cathepsins in response to the inhibition or dysfunction of other cathepsins suggests a fine-tuned system of proteolytic balance and understanding the compensatory role of cathepsins may improve therapeutic potential of cathepsin's inhibitors. Selectively targeting one cathepsin or modulating their activity could offer new treatment strategies for a number of diseases. This review emphasises the need for comprehensive research into cathepsin biology in the context of disease. The identification of the specific cathepsins involved in compensatory responses, the elucidation of the underlying molecular mechanisms and the development of targeted interventions could lead to innovative therapeutic approaches.

Cysteine cathepsins: From diagnosis to targeted therapy of cancer

Cysteine cathepsins are a fascinating group of proteolytic enzymes that play diverse and crucial roles in numerous biological processes, both in health and disease. Understanding these proteases is essential for uncovering novel insights into the underlying mechanisms of a wide range of disorders, such as cancer. Cysteine cathepsins influence cancer biology by participating in processes such as extracellular matrix degradation, angiogenesis, immune evasion, and apoptosis. In this comprehensive review, we explore foundational research that illuminates the diverse and intricate roles of cysteine cathepsins as diagnostic markers and therapeutic targets for cancer. This review aims to provide valuable insights into the clinical relevance of cysteine cathepsins and explore their capacity to advance personalised and targeted medical interventions in oncology.

Cathepsin B Nuclear Flux in a DNA-Guided "Antinuclear Missile" Cancer Therapy

Some antinuclear antibodies (ANAs) bind extracellular nucleic acids released into tumor environments and are pulled into the nuclei of live cancer cells through nucleoside salvage pathways, independent of tumor-specific surface antigens. Here we show that ANA nuclear penetration induces nuclear flux by the lysosomal protease cathepsin B and leverage this mechanism to design an antinuclear antibody-drug conjugate (ANADC) with cathepsin B-labile drug linker. The ANADC targets nucleic acid exhaust from necrotic tumors and crosses membrane barriers through nucleoside salvage as a DNA-seeking and tumor agnostic "antinuclear missile" cancer therapy.

YY2/BUB3 Axis promotes SAC Hyperactivation and Inhibits Colorectal Cancer Progression via Regulating Chromosomal Instability

Spindle assembly checkpoint (SAC) is a crucial safeguard mechanism of mitosis fidelity that ensures equal division of duplicated chromosomes to the two progeny cells. Impaired SAC can lead to chromosomal instability (CIN), a well-recognized hallmark of cancer that facilitates tumor progression; paradoxically, high CIN levels are associated with better therapeutic response and prognosis. However, the mechanism by which CIN determines tumor cell survival and therapeutic response remains poorly understood. Here, using a cross-omics approach, YY2 is identified as a mitotic regulator that promotes SAC activity by activating the transcription of budding uninhibited by benzimidazole 3 (BUB3), a component of SAC. While both conditions induce CIN, a defect in YY2/SAC activity enhances mitosis and tumor growth. Meanwhile, hyperactivation of SAC mediated by YY2/BUB3 triggers a delay in mitosis and suppresses growth. Furthermore, it is revealed that YY2/BUB3-mediated excessive CIN causes higher cell death rates and drug sensitivity, whereas residual tumor cells that survived DNA damage-based therapy have moderate CIN and increased drug resistance. These results provide insights into the role of SAC activity and CIN levels in influencing tumor cell survival and drug response, as well as suggest a novel anti-tumor therapeutic strategy that combines SAC activity modulators and DNA-damage agents.

Cathepsin X deficiency alters the processing and localisation of cathepsin L and impairs cleavage of a nuclear cathepsin L substrate

Proteases function within sophisticated networks. Altering the activity of one protease can have sweeping effects on other proteases, leading to changes in their activity, structure, specificity, localisation, stability, and expression. Using a suite of chemical tools, we investigated the impact of cathepsin X, a lysosomal cysteine protease, on the activity and expression of other cysteine proteases and their inhibitors in dendritic cells. Among all proteases examined, cathepsin X gene deletion specifically altered cathepsin L levels; pro-cathepsin L and its single chain accumulated while the two-chain form was unchanged. This effect was recapitulated by chemical inhibition of cathepsin X, suggesting a dependence on its catalytic activity. We demonstrated that accumulation of pro- and single chain cathepsin L was not due to a lack of direct cleavage by cathepsin X or altered glycosylation, secretion, or mRNA expression but may result from changes in lysosomal oxidative stress or pH. In the absence of active cathepsin X, nuclear cathepsin L and cleavage of the known nuclear cathepsin L substrate, Lamin B1, were diminished. Thus, cathepsin X activity selectively regulates cathepsin L, which has the potential to impact the degree of cathepsin L proteolysis, the nature of substrates that it cleaves, and the location of cleavage.

Unravelling the role of cathepsins in cardiovascular diseases

Lysosomal cathepsins as a regulatory medium have been assessed as potential therapeutic targets for the treatment of various cardiac diseases such as abdominal aortic aneurysm, hypertension, cardiomyopathy, coronary heart disease, atherosclerosis, etc. They are ubiquitous lysosomal proteases with papain-like folded protein structures that are involved in a variety of physiological processes, such as the digestion of proteins, activation of pro-inflammatory molecules, degradation of extracellular matrix components, and maturation of peptide hormones. Cathepsins are classified into three major groups: cysteine cathepsins, aspartic cathepsins, and serine-threonine cathepsins. Each of these groups is further divided into subgroups based on their substrate specificity, structural characteristics, and biochemical properties. Several studies suggest that cathepsins control the degradation of ECM components such as collagen and elastin fibres. These enzymes are highly expressed in macrophages and inflammatory cells, and their upregulation has been demonstrated to be critical in the progression of atherosclerotic lesions. Additionally, increased cathepsin activity has been linked to increased vascular inflammation and oxidative stress, both of which are associated with CVDs. Specifically, the inhibition of cathepsins may reduce the release of pro-apoptotic mediators such as caspase-3 and PARP-1, which are thought to contribute to plaque instability. The potential of cathepsins as biomarkers and therapeutic targets has also been supported by the identification of potential cathepsin inhibitors, which could be used to modulate the activities of cathepsins in a range of diseases. This review shall familiarise the readers with the role of cysteinyl cathepsins and their inhibitors in the pathogenesis of cardiovascular diseases.

Cathepsin V regulates cell cycle progression and histone stability in the nucleus of breast cancer cells

Introduction: We previously identified that Cathepsin V (CTSV) expression is associated with poor prognosis in ER+ breast cancer, particularly within the Luminal A subtype. Examination of the molecular role of the protease within Luminal A tumours, revealed that CTSV promotes tumour cell invasion and proliferation, in addition to degradation of the luminal transcription factor, GATA3, via the proteasome. Methods: Cell line models expressing CTSV shRNA or transfected to overexpress CTSV were used to examine the impact of CTSV on cell proliferation by MTT assay and flow cytometry. Western blotting analysis was used to identify the impact of CTSV on histone and chaperone protein expression. Cell fractionation and confocal microscopy was used to illustrate the presence of CTSV in the nuclear compartment. Results: In this work we have identified that CTSV has an impact on breast cancer cell proliferation, with CTSV depleted cells exhibiting delayed progression through the G2/M phase of the cell cycle. Further investigation has revealed that CTSV can control nuclear expression levels of histones H3 and H4 via regulating protein expression of their chaperone sNASP. We have discovered that CTSV is localised to the nuclear compartment in breast tumour cells, mediated by a bipartite nuclear localisation signal (NLS) within the CTSV sequence and that nuclear CTSV is required for cell cycle progression and histone stability in breast tumour cells. Discussion: Collectively these findings support the hypothesis that targeting CTSV may have utility as a novel therapeutic target in ER+ breast cancer by impairing cell cycle progression via manipulating histone stabilisation.

COVID-19 and Gastrointestinal Tract: From Pathophysiology to Clinical Manifestations

Background: Since its first report in Wuhan, China, in December 2019, COVID-19 has become a pandemic, affecting millions of people worldwide. Although the virus primarily affects the respiratory tract, gastrointestinal symptoms are also common. The aim of this narrative review is to provide an overview of the pathophysiology and clinical manifestations of gastrointestinal COVID-19. Methods: We conducted a systematic electronic search of English literature up to January 2023 using Medline, Scopus, and the Cochrane Library, focusing on papers that analyzed the role of SARS-CoV-2 in the gastrointestinal tract. Results: Our review highlights that SARS-CoV-2 directly infects the gastrointestinal tract and can cause symptoms such as diarrhea, nausea/vomiting, abdominal pain, anorexia, loss of taste, and increased liver enzymes. These symptoms result from mucosal barrier damage, inflammation, and changes in the microbiota composition. The exact mechanism of how the virus overcomes the acid gastric environment and leads to the intestinal damage is still being studied. Conclusions: Although vaccination has increased the prevalence of less severe symptoms, the long-term interaction with SARS-CoV-2 remains a concern. Understanding the interplay between SARS-CoV-2 and the gastrointestinal tract is essential for future management of the virus.

Expression, Intracellular Localization, and Maturation of Cysteine Cathepsins in Renal Embryonic and Cancer Cell Lines

Cysteine cathepsins play an important role in tumor development and metastasis. The expression of these enzymes is often increased in many types of tumor cells. Cysteine cathepsins contribute to carcinogenesis through a number of mechanisms, including proteolysis of extracellular matrix and signaling molecules on the cell surface, as well as degradation of transcription factors and disruption of signaling cascades in the cell nucleus. Distinct oncogenic functions have been reported for several members of the cysteine cathepsin family in various types of cancer, but a comparative study of all eleven cysteine cathepsins in one experimental model is still missing. In this work, we assessed and compared the expression, localization, and maturation of all eleven cysteine cathepsins in embryonic kidney cells HEK293 and kidney cancer cell lines 769-P and A-498. We found that the expression of cathepsins V, B, Z, L, and S was 3- to 9-fold higher in kidney tumor cells than in embryonic cells. We also showed that all cysteine cathepsins were present in varying amounts in the nucleus of both embryonic and tumor cells. Notably, more than half of the cathepsin Z or K and over 88% of cathepsin F were localized in tumor cell nuclei. Moreover, mature forms of cysteine cathepsins were more prevalent in tumor cells than in embryonic cells. These results can be further used to develop novel diagnostic tools and may assist in the investigation of cysteine cathepsins as potential therapeutic targets.

Cathepsin L-containing exosomes from α-synuclein-activated microglia induce neurotoxicity through the P2X7 receptor

Uncontrolled microglial activation is pivotal to the pathogenesis of Parkinson's disease (PD), which can secrete Cathepsin L (CTSL) to affect the survival of neurons in the PD patients; however, the precise mechanism has yet to be determined. We demonstrated for the first time that CTSL was mostly released by exosomes derived from α-Syn-activated microglia, resulting in neuronal damage and death. The elevation of CTSL activity was blocked by GW4869, suggesting a critical role for exosomes in mediating CTSL release. Furthermore, the P2X7R/PI3K/AKT signalling pathway was identified as the underlying molecular mechanism since specific antagonists of this signalling pathway, P2X7R knockdown and exosome release inhibitors significantly reduced the injury to cultured mouse cortical neurons. Our study suggests that increased extracellular release of CTSL from α-Syn-activated microglia through exosomes amplifies and aggravates of the neurotoxic effect of microglia, implying that CTSL may be involved in a fresh mechanism of PD pathogenesis, and serve as a potential biomarker and a target for PD drug development.

Spatial localization of cathepsins: Implications in immune activation and resolution during infections

Cathepsins were first described, as endolysosomal proteolytic enzymes in reference to the organelles where they degrade the bulk of endogenous and exogenous substrates in a slightly acidic environment. These substrates include pathogens internalized via endocytosis and/or marked for destruction by autophagy. However, the role of cathepsins during infection far exceeds that of direct digestion of the pathogen. Cathepsins have been extensively investigated in the context of tumour associated immune cells and chronic inflammation. Several cathepsin-dependent immune responses develop in the endocytic pathway while others take place in the cytosol, the nucleus, or in the extracellular space. In this review we highlight the spatial localization of cathepsins and their implications in immune activation and resolution pathways during infection.

Exposure to polystyrene microplastics reduces regeneration and growth in planarians

The potential adverse effects of microplastics (MPs) on ecosystems and human health have received much attention in recent years. However, only limited data are available on the mechanisms for the uptake, distribution, and effects of MPs in freshwater organisms, especially with respect to tissue repair, regeneration and impairment of stem cell functions. To address this knowledge gap, we conducted exposure experiments in which planarians (Dugesia japonica) were exposed to polystyrene (PS)-MPs mixed in liver homogenate and examined the tissue growth and regeneration, stem cell functions, and oxidative stress. The body and blastema areas decreased upon exposure to PS-MPs, indicating that the growth and regeneration of planarians were delayed. The proliferation and differentiation processes of stem cells were inhibited, and the proportion of mitotic stem cells decreased, which may be related to the activation of the TGFβ/SMAD4 and Notch signaling pathways. The enhancement of antioxidant enzyme activities and malondialdehyde on the first day of exposure to PS-MPs confirmed the oxidative stress response of planarians to PS-MPs. The present study demonstrated the likelihood of biotoxicity induced by PS-MPs. These results will provide clues for further investigations into the potential risks of PS-MPs to human stem cells.

Low level lysosomal membrane permeabilization for limited release and sub-lethal functions of cathepsin proteases in the cytosol and nucleus

For a long time, lysosomes were purely seen as organelles in charge of garbage disposal within the cell. They destroy any cargo delivered into their lumen with a plethora of highly potent hydrolytic enzymes, including various proteases. In case of damage to their limiting membranes, the lysosomes release their soluble content with detrimental outcomes for the cell. In recent years however, this view of the lysosome changed towards acknowledging it as a platform for integration of manifold intra- and extracellular signals. Even impaired lysosomal membrane integrity is no longer considered to be a one-way street to cell death. Increasing evidence suggests that lysosomal enzymes, mainly cathepsin proteases, can be released in a spatially and temporarily restricted manner that is compatible with cellular survival. This way, cathepsins can act in the cytosol and the nucleus, where they affect important cellular processes such as cell division. Here, we review this evidence and discuss the routes and molecular mechanisms by which the cathepsins may reach their unusual destination.

Regulatory role of cathepsin L in induction of nuclear laminopathy in Alzheimer's disease

Experimental and clinical therapies in the field of Alzheimer's disease (AD) have focused on elimination of extracellular amyloid beta aggregates or prevention of cytoplasmic neuronal fibrillary tangles formation, yet these approaches have been generally ineffective. Interruption of nuclear lamina integrity, or laminopathy, is a newly identified concept in AD pathophysiology. Unraveling the molecular players in the induction of nuclear lamina damage may lead to identification of new therapies. Here, using 3xTg and APP/PS1 mouse models of AD, and in vitro model of amyloid beta42 (Aβ42) toxicity in primary neuronal cultures and SH‐SY5Y neuroblastoma cells, we have uncovered a key role for cathepsin L in the induction of nuclear lamina damage. The applicability of our findings to AD pathophysiology was validated in brain autopsy samples from patients. We report that upregulation of cathepsin L is an important process in the induction of nuclear lamina damage, shown by lamin B1 cleavage, and is associated with epigenetic modifications in AD pathophysiology. More importantly, pharmacological targeting and genetic knock out of cathepsin L mitigated Aβ42 induced lamin B1 degradation and downstream structural and molecular changes. Affirming these findings, overexpression of cathepsin L alone was sufficient to induce lamin B1 cleavage. The proteolytic activity of cathepsin L on lamin B1 was confirmed using mass spectrometry. Our research identifies cathepsin L as a newly identified lamin B1 protease and mediator of laminopathy observed in AD. These results uncover a new aspect in the pathophysiology of AD that can be pharmacologically prevented, raising hope for potential therapeutic interventions.

Novel Cysteine Protease Inhibitor Derived from the Haementeria vizottoi Leech: Recombinant Expression, Purification, and Characterization

Cathepsin L (CatL) is a lysosomal cysteine protease primarily involved in the terminal degradation of intracellular and endocytosed proteins. More specifically, in humans, CatL has been implicated in cancer progression and metastasis, as well as coronary artery diseases and others. Given this, the search for potent CatL inhibitors is of great importance. In the search for new molecules to perform proteolytic activity regulation, salivary secretions from hematophagous animals have been an important source, as they present protease inhibitors that evolved to disable host proteases. Based on the transcriptome of the Haementeria vizzotoi leech, the cDNA of Cystatin-Hv was selected for this study. Cystatin-Hv was expressed in Pichia pastoris and purified by two chromatographic steps. The kinetic results using human CatL indicated that Cystatin-Hv, in its recombinant form, is a potent inhibitor of this protease, with a K_i value of 7.9 nM. Consequently, the present study describes, for the first time, the attainment and the biochemical characterization of a recombinant cystatin from leeches as a potent CatL inhibitor. While searching out for new molecules of therapeutic interest, this leech cystatin opens up possibilities for the future use of this molecule in studies involving cellular and in vivo models.

Molecular probes for selective detection of cysteine cathepsins

Cysteine cathepsins are proteases critical in physiopathological processes and show potential as targets or biomarkers for diseases and medical conditions. The 11 members of the cathepsin family are redundant in some cases but remarkably independent of others, demanding the development of both pan-cathepsin targeting tools as well as probes that are selective for specific cathepsins with little off-target activity. This review addresses the diverse design strategies that have been employed to accomplish this tailored selectivity among cysteine cathepsin targets and the imaging modalities incorporated. The power of these diverse tools is contextualized by briefly highlighting the nature of a few prominent cysteine cathepsins, their involvement in select diseases, and the application of cathepsin imaging probes in research spanning basic biochemical studies to clinical applications.

The Uncovered Function of the Drosophila GBA1a-Encoded Protein

Human GBA1 encodes lysosomal acid β-glucocerebrosidase (GCase), which hydrolyzes cleavage of the beta-glucosidic linkage of glucosylceramide (GlcCer). Mutations in this gene lead to reduced GCase activity, accumulation of glucosylceramide and glucosylsphingosine, and development of Gaucher disease (GD). Drosophila melanogaster has two GBA1 orthologs. Thus far, GBA1b was documented as a bone fide GCase-encoding gene, while the role of GBA1a encoded protein remained unclear. In the present study, we characterized a mutant variant of the fly GBA1a, which underwent ERAD and mildly activated the UPR machinery. RNA-seq analyses of homozygous mutant flies revealed upregulation of inflammation-associated as well as of cell-cycle related genes and reduction in programmed cell death (PCD)-associated genes, which was confirmed by qRT-PCR. We also observed compromised cell death in the midgut of homozygous larvae and a reduction in pupation. Our results strongly indicated that GBA1a-encoded protein plays a role in midgut maturation during larvae development.

Procathepsin V Is Secreted in a TSH Regulated Manner from Human Thyroid Epithelial Cells and Is Accessible to an Activity-Based Probe

The significance of cysteine cathepsins for the liberation of thyroid hormones from the precursor thyroglobulin was previously shown by in vivo and in vitro studies. Cathepsin L is most important for thyroglobulin processing in mice. The present study aims at specifying the possible contribution of its closest relative, cysteine cathepsin L2/V, to thyroid function. Immunofluorescence analysis on normal human thyroid tissue revealed its predominant localization at the apical plasma membrane of thyrocytes and within the follicle lumen, indicating the secretion of cathepsin V and extracellular tasks rather than its acting within endo-lysosomes. To explore the trafficking pathways of cathepsin V in more detail, a chimeric protein consisting of human cathepsin V tagged with green fluorescent protein (GFP) was stably expressed in the Nthy-ori 3-1 thyroid epithelial cell line. Colocalization studies with compartment-specific markers and analyses of post-translational modifications revealed that the chimeric protein was sorted into the lumen of the endoplasmic reticulum and subsequently transported to the Golgi apparatus, while being N-glycosylated. Immunoblotting showed that the chimeric protein reached endo-lysosomes and it became secreted from the transduced cells. Astonishingly, thyroid stimulating hormone (TSH)-induced secretion of GFP-tagged cathepsin V occurred as the proform, suggesting that TSH upregulates its transport to the plasma membrane before it reaches endo-lysosomes for maturation. The proform of cathepsin V was found to be reactive with the activity-based probe DCG-04, suggesting that it possesses catalytic activity. We propose that TSH-stimulated secretion of procathepsin V is the default pathway in the thyroid to enable its contribution to thyroglobulin processing by extracellular means.

The Interplay Between Genetic Risk Factors and Proteolytic Dysregulation in the Pathophysiology of Inflammatory Bowel Disease

Crohn's disease [CD] and ulcerative colitis [UC] are the two main forms of inflammatory bowel disease [IBD]. Previous studies reported increased levels of proteolytic activity in stool and tissue samples from IBD patients, whereas the re-establishment of the proteolytic balance abrogates the development of experimental colitis. Furthermore, recent data suggest that IBD occurs in genetically predisposed individuals who develop an abnormal immune response to intestinal microbes once exposed to environmental triggers. In this review, we highlight the role of proteases in IBD pathophysiology, and we showcase how the main cellular pathways associated with IBD influence proteolytic unbalance and how functional proteomics are allowing the unambiguous identification of dysregulated proteases in IBD, paving the way to the development of new protease inhibitors as a new potential treatment.

Significance of nuclear cathepsin V in normal thyroid epithelial and carcinoma cells

Altered expression and/or localization of cysteine cathepsins is believed to involve in thyroid diseases including cancer. Here, we examined the localization of cathepsins B and V in human thyroid tissue sections of different pathological conditions by immunolabeling and morphometry. Cathepsin B was mostly found within endo-lysosomes as expected. In contrast, cathepsin V was detected within nuclei, predominantly in cells of cold nodules, follicular and papillary thyroid carcinoma tissue, while it was less often detected in this unusual localization in hot nodules and goiter tissue. To understand the significance of nuclear cathepsin V in thyroid cells, this study aimed to establish a cellular model of stable nuclear cathepsin V expression. As representative of a specific form lacking the signal peptide and part of the propeptide, N-terminally truncated cathepsin V fused to eGFP recapitulated the nuclear localization of endogenous cathepsin V throughout the cell cycle in Nthy-ori 3-1 cells. Interestingly, the N-terminally truncated cathepsin V-eGFP was more abundant in the nuclei during S phase. These findings suggested a possible contribution of nuclear cathepsin V forms to cell cycle progression. Indeed, we found that N-terminally truncated cathepsin V-eGFP expressing cells were more proliferative than those expressing full-length cathepsin V-eGFP or wild type controls. We conclude that a specific molecular form of cathepsin V localizes to the nucleus of thyroid epithelial and carcinoma cells, where it might involve in deregulated pathways leading to hyperproliferation. These findings highlight the necessity to better understand cathepsin trafficking in health and disease. In particular, cell type specificity of mislocalization of cysteine cathepsins, which otherwise act in a functionally redundant manner, seems to be important to understand their non-canonical roles in cell cycle progression.

The Ins and Outs of Cathepsins: Physiological Function and Role in Disease Management

Cathepsins are the most abundant lysosomal proteases that are mainly found in acidic endo/lysosomal compartments where they play a vital role in intracellular protein degradation, energy metabolism, and immune responses among a host of other functions. The discovery that cathepsins are secreted and remain functionally active outside of the lysosome has caused a paradigm shift. Contemporary research has unraveled many versatile functions of cathepsins in extralysosomal locations including cytosol and extracellular space. Nevertheless, extracellular cathepsins are majorly upregulated in pathological states and are implicated in a wide range of diseases including cancer and cardiovascular diseases. Taking advantage of the differential expression of the cathepsins during pathological conditions, much research is focused on using cathepsins as diagnostic markers and therapeutic targets. A tailored therapeutic approach using selective cathepsin inhibitors is constantly emerging to be safe and efficient. Moreover, recent development of proteomic-based approaches for the identification of novel physiological substrates offers a major opportunity to understand the mechanism of cathepsin action. In this review, we summarize the available evidence regarding the role of cathepsins in health and disease, discuss their potential as biomarkers of disease progression, and shed light on the potential of extracellular cathepsin inhibitors as safe therapeutic tools.

The expression of Cathepsin L in oral lichen planus

Background

Malignant transformation of oral lichen planus (OLP) was reported particularly in erosive type, however, it remains inconclusive. Cathepsin L was shown to promote tumor growth and invasion in many cancers. Therefore, cathepsin L expression in erosive and non-erosive OLP compared with oral epithelial dysplasia and oral squamous cell carcinoma (OSCC) were investigated.

Methods

Thirty specimens of OLP (15 cases each of erosive and non-erosive OLP), 10 cases of oral epithelial dysplasia and 10 cases of OSCC were included. Ten healthy gingiva specimens were served as controls. All specimens were stained with cathepsin L antibody using immunohistochemistry technique.

Results

Cathepsin L was expressed in all OLP and OSCC cases. In oral epithelial dysplasia and healthy gingiva, the expression was found at 90% and 50% respectively. The percentage of positive cells was the highest in erosive OLP (27.26 ± 12.09%), followed by non-erosive OLP (20.85 ± 7.43%), OSCC (20.15 ± 15.70%), oral epithelial dysplasia (9.24 ± 7.00%) and healthy gingiva (2.27 ± 5.65%). Most of non-erosive OLP cases showed mild staining intensity while erosive OLP and OSCC showed moderate staining intensity. Cathepsin L was mainly expressed at basement membrane zone and inflammatory cells of OLP. In OSCC, the expression was found in tumor islands and keratin pearls. In oral epithelial dysplasia and normal gingiva, cathepsin L expressions were low and presented in scattered pattern in both epithelium and connective tissue.

Conclusion

According to the patterns of expression in this study, cathepsin L could be implicated in pathogenesis and severity of OLP.

Spatiotemporal proteomics uncovers cathepsin-dependent macrophage cell death during Salmonella infection

The interplay between host and pathogen relies heavily on rapid protein synthesis and accurate protein targeting to ensure pathogen destruction. To gain insight into this dynamic interface, we combined click-chemistry with pulsed stable isotope labeling of amino acids in cell culture (pSILAC-AHA) to quantify the host proteome response during macrophage infection with the intracellular bacterial pathogen, Salmonella enterica Typhimurium (STm). We monitored newly synthesised proteins across different host cell compartments and infection stages. Within this rich resource, we detected aberrant trafficking of lysosomal proteases to the extracellular space and the nucleus. We verified active cathepsins re-traffic to the nucleus and are linked to cell death. Pharmacological cathepsin inhibition and nuclear-targeting of a cellular cathepsin inhibitor (Stefin B) suppressed STm-induced cell death. We demonstrate that cathepsin activity is required for pyroptotic cell death via the non-canonical inflammasome, and that LPS transfection into the host cytoplasm is sufficient to trigger active cathepsin accumulation in the host nucleus and cathepsin-dependent cell death. Finally, cathepsin inhibition reduced Gasdermin D expression, thus revealing an unexpected role for cathepsin activity in non-canonical inflammasome regulation. Overall, our study illustrates how resolving host proteome dynamics during infection can drive the discovery of biological mechanisms at the host-microbe interface.

Cysteine Cathepsins Inhibition Affects Their Expression and Human Renal Cancer Cell Phenotype

Renal cancer would greatly benefit from new therapeutic strategies since, in advanced stages, it is refractory to classical chemotherapeutic approaches. In this context, lysosomal protease cysteine cathepsins may represent new pharmacological targets. In renal cancer, they are characterized by a higher expression, and they were shown to play a role in its aggressiveness and spreading. Traditional studies in the field were focused on understanding the therapeutic potentialities of cysteine cathepsin inhibition, while the direct impact of such therapeutics on the expression of these enzymes was often overlooked. In this work, we engineered two fluoromethyl ketone-based peptides with inhibitory activity against cathepsins to evaluate their potential anticancer activity and impact on the lysosomal compartment in human renal cancer. Molecular modeling and biochemical assays confirmed the inhibitory properties of the peptides against cysteine cathepsin B and L. Different cell biology experiments demonstrated that the peptides could affect renal cancer cell migration and organization in colonies and spheroids, while increasing their adhesion to biological substrates. Finally, these peptide inhibitors modulated the expression of LAMP1, enhanced the expression of E-cadherin, and altered cathepsin expression. In conclusion, the inhibition of cysteine cathepsins by the peptides was beneficial in terms of cancer aggressiveness; however, they could affect the overall expression of these proteases.

Cysteine Cathepsins in Tumor-Associated Immune Cells

Cysteine cathepsins are key regulators of the innate and adaptive arms of the immune system. Their expression, activity, and subcellular localization are associated with the distinct development and differentiation stages of immune cells. They promote the activation of innate myeloid immune cells since they contribute to toll-like receptor signaling and to cytokine secretion. Furthermore, they control lysosomal biogenesis and autophagic flux, thus affecting innate immune cell survival and polarization. They also regulate bidirectional communication between the cell exterior and the cytoskeleton, thus influencing cell interactions, morphology, and motility. Importantly, cysteine cathepsins contribute to the priming of adaptive immune cells by controlling antigen presentation and are involved in cytotoxic granule mediated killing in cytotoxic T lymphocytes and natural killer cells. Cathepins'aberrant activity can be prevented by their endogenous inhibitors, cystatins. However, dysregulated proteolysis contributes significantly to tumor progression also by modulation of the antitumor immune response. Especially tumor-associated myeloid cells, such as tumor-associated macrophages and myeloid-derived suppressor cells, which are known for their tumor promoting and immunosuppressive functions, constitute the major source of excessive cysteine cathepsin activity in cancer. Since they are enriched in the tumor microenvironment, cysteine cathepsins represent exciting targets for development of new diagnostic and therapeutic moieties.

Lost or Forgotten: The nuclear cathepsin protein isoforms in cancer

While research into the role of cathepsins has been progressing at an exponential pace over the years, research into their respective isoform proteins has been less frenetic. In view of the functional and biological potential of such protein isoforms in model systems for cancer during their initial discovery, much later they have offered a new direction in the field of cathepsin basic and applied research. Consequently, the analysis of such isoforms has laid strong foundations in revealing other important regulatory aspects of the cathepsin proteins in general. In this review article, we address these key aspects of cathepsin isoform proteins, with particular emphasis on how they have shaped what is now known in the context of nuclear cathepsin localization and what potential these hold as nuclear-based therapeutic targets in cancer.

The Role of Cysteine Cathepsins in Cancer Progression and Drug Resistance

Cysteine cathepsins are lysosomal enzymes belonging to the papain family. Their expression is misregulated in a wide variety of tumors, and ample data prove their involvement in cancer progression, angiogenesis, metastasis, and in the occurrence of drug resistance. However, while their overexpression is usually associated with highly aggressive tumor phenotypes, their mechanistic role in cancer progression is still to be determined to develop new therapeutic strategies. In this review, we highlight the literature related to the role of the cysteine cathepsins in cancer biology, with particular emphasis on their input into tumor biology.

Treatment of rat thyrocytes in vitro with cathepsin B and L inhibitors results in disruption of primary cilia leading to redistribution of the trace amine associated receptor 1 to the endoplasmic reticulum

Taar1 is a G protein-coupled receptor (GPCR) confined to primary cilia of rodent thyroid epithelial cells. Taar1-deficient mouse thyroid follicles feature luminal accumulation of thyroglobulin suggesting that Taar1 acts as a regulator of extra- and pericellular thyroglobulin processing, which is mediated by cysteine cathepsin proteases present at the apical plasma membrane of rodent thyrocytes. Here, by immunostaining and confocal laser scanning microscopy, we demonstrated co-localization of cathepsin L, but only little cathepsin B, with Taar1 at primary cilia of rat thyrocytes, the FRT cells. Because proteases were shown to affect half-lives of certain receptors, we determined the effect of cathepsin activity inhibition on sub-cellular localization of Taar1 in FRT cells, whereupon Taar1 localization altered such that it was retained in compartments of the secretory pathway. Since the same effect on Taar1 localization was observed in both cathepsin B and L inhibitor-treated cells, the interaction of cathepsin activities and sub-cellular localization of Taar1 was thought to be indirect. Indeed, we observed that cathepsin inhibition resulted in a lack of primary cilia from FRT cells. Next, we proved that primary cilia are a necessity for Taar1 trafficking to reach the plasma membrane of FRT cells, since the disruption of primary cilia by treatment with β-cyclodextrin resulted in Taar1 retention in compartments of the secretory pathway. Furthermore, in less well-polarized rat thyrocytes, namely in FRTL-5 cells lacking primary cilia, Taar1 was mainly confined to the compartments of the secretory pathway. We conclude that Taar1 localization in polarized thyroid epithelial cells requires the presence of primary cilia, which is dependent on the proteolytic activity of cysteine cathepsins B and L.

Cysteine Cathepsin Protease Inhibition: An update on its Diagnostic, Prognostic and Therapeutic Potential in Cancer

In keeping with recent developments in basic research; the importance of the Cathepsins as targets in cancer therapy have taken on increasing importance and given rise to a number of key areas of interest in the clinical setting. In keeping with driving basic research in this area in a translational direction; recent findings have given rise to a number of exciting developments in the areas of cancer diagnosis; prognosis and therapeutic development. As a fast-moving area of research; the focus of this review brings together the latest findings and highlights the translational significance of these developments.

Application of nanotechnology to target and exploit tumour associated proteases

Proteases are hydrolytic enzymes fundamental for a variety of physiological processes, but the loss of their regulation leads to aberrant functions that promote onset and progression of many diseases including cancer. Proteases have been implicated in almost every hallmark of cancer and whilst widely investigated for tumour therapy, clinical adoption of protease inhibitors as drugs remains a challenge due to issues such as off-target toxicity and inability to achieve therapeutic doses at the disease site. Now, nanotechnology-based solutions and strategies are emerging to circumvent these issues. In this review, preclinical advances in approaches to enhance the delivery of protease drugs and the exploitation of tumour-derived protease activities to promote targeting of nanomedicine formulations is examined. Whilst this field is still in its infancy, innovations to date suggest that nanomedicine approaches to protease targeting or inhibition may hold much therapeutic and diagnostic potential.

Cathepsin L activated by mutant p53 and Egr-1 promotes ionizing radiation-induced EMT in human NSCLC

BACKGROUND

Ionizing radiation (IR) is one of the major clinical therapies of cancer, although it increases the epithelial-mesenchymal transition (EMT) of non-small cell lung cancer (NSCLC), unexpectedly. The cellular and molecular mechanisms underlying this role are not completely understood.

METHODS

We used NSCLC cell lines as well as tumor specimens from 78 patients with NSCLC to evaluate p53, Cathepsin L (CTSL) and EMT phenotypic changes. Xenograft models was also utilized to examine the roles of mutant p53 (mut-p53) and CTSL in regulating IR-induced EMT of NSCLC.

RESULTS

Expression of CTSL was markedly increased in human NSCLC tissues with mutant p53 (mut-p53), and p53 mutation positively correlated with metastasis of NSCLC patients. In human non-small cell lung cancer cell line, H1299 cells transfected with various p53 lentivirus vectors, mut-p53 could promote the invasion and motility of cells under IR, mainly through the EMT. This EMT process was induced by elevating intranuclear CTSL which was regulated by mut-p53 depending on Early growth response protein-1 (Egr-1) activation. In the subcutaneous tumor xenograft model, IR promoted the EMT of the cancer cells in the presence of mut-p53, owing to increase expression and nuclear transition of its downstream protein CTSL.

CONCLUSION

Taken together, these data reveal the role of the mut-p53/Egr-1/CTSL axis in regulating the signaling pathway responsible for IR-induced EMT.

Apoferritin encapsulation of cysteine protease inhibitors for cathepsin L inhibition in cancer cells

Cysteine proteases play a key role in tumorigenesis causing protein degradation and promoting invasive tumour growth. Cathepsin L is overexpressed in cancer cells and could provide a specific target for delivery of anticancer agents. We encapsulated novel dipeptidyl nitrile based cysteine protease inhibitors (Neq0551, Neq0554 and Neq0568) into biocompatible apoferritin (AFt) protein nanocages to achieve specific delivery to tumours and pH-induced drug release. AFt-encapsulated Neq0554 demonstrated ∼3-fold enhanced in vitro activity (GI₅₀ = 79 μM) compared to naked agent against MiaPaCa-2 pancreatic carcinoma cells. Selectivity for cancer cells was confirmed by comparing their activity to non-tumourigenic human fibroblasts (GI₅₀ > 200 μM). Transferrin receptor (TfR-1) expression, detected only in lysates prepared from carcinoma cells, may contribute to the cancer-selectivity. The G₁ cell cycle arrest caused by AFt-Neq0554 resulting in cytostasis was corroborated by clonogenic assays. Superior and more persistent inhibition of cathepsin L up to 80% was achieved with AFt-encapsulated agent in HCT-116 cells following 6 h exposure to 50 μM agent. The selective anticancer activity of AFt-encapsulated cysteine protease inhibitor Neq0554 reported here warrants further preclinical in vivo evaluation.

Novel apoferritin encapsulated cysteine protease inhibitors are developed with enhanced and selective uptake by cancer cells, and sustained pH-induced release of the agent. The persistent inhibition of cathepsin L is demonstrated in vitro.

Protease-Activated Receptors in the Intestine: Focus on Inflammation and Cancer

Protease-activated receptors (PARs) belong to the G protein-coupled receptor (GPCR) family. Compared to other GPCRs, the specificity of the four PARs is the lack of physiologically soluble ligands able to induce their activation. Indeed, PARs are physiologically activated after proteolytic cleavage of their N-terminal domain by proteases. The resulting N-terminal end becomes a tethered activation ligand that interact with the extracellular loop 2 domain and thus induce PAR signal. PARs expression is ubiquitous and these receptors have been largely described in chronic inflammatory diseases and cancer. In this review, after describing their discovery, structure, mechanisms of activation, we then focus on the roles of PARs in the intestine and the two main diseases affecting the organ, namely inflammatory bowel diseases and cancer.

Association of Epithelial Mesenchymal Transition with prostate and breast health disparities

African Americans (AA) have higher death rates due to prostate and breast cancer as compared to Caucasian Americans (CA), and few biomarkers have been associated with this disparity. In our study we investigated whether epithelial-mesenchymal transition (EMT) with a focus on Snail and Cathepsin L (Cat L), could potentially be two markers associated with prostate and breast health disparities. We have previously shown that Snail can increase Cat L protein and activity in prostate and breast cancer. Western blot and real-time PCR analyses showed that mesenchymal protein expression (Snail, vimentin, Cat L) and Cat L activity (shown by zymography) was higher in AA prostate cancer cells as compared to CA normal transformed RWPE-1 prostate epithelial cells, and androgen-dependent cells, and comparable to metastatic CA cell lines. With respect to breast cancer, mesenchymal markers were higher in TNBC compared to non-TNBC cells. The higher mesenchymal marker expression was functionally associated with higher proliferative and migratory rates. Immunohistochemistry showed that both nuclear Snail and Cat L expression was significantly higher in cancer compared to normal for CA and Bahamas prostate patient tissue. Interestingly, AA normal tissue stained higher for nuclear Snail and Cat L that was not significantly different to cancer tissue for both prostate and breast tissue, but was significantly higher than CA normal tissue. AA TNBC tissue also displayed significantly higher nuclear Snail expression compared to CA TNBC, while no significant differences were observed with Luminal A cancer tissue. Therefore, increased EMT in AA compared to CA that may contribute to the more aggressive disease.

Cysteine cathepsins as a prospective target for anticancer therapies-current progress and prospects

Cysteine cathepsins (CTS), being involved in both physiological and pathological processes, play an important role in the human body. During the last 30 years, it has been shown that CTS are highly upregulated in a wide variety of cancer types although they have received a little attention as a potential therapeutic target as compared to serine or metalloproteinases. Studies on the increasing problem of neoplastic progression have revealed that secretion of cell-surface- and intracellular cysteine proteases is aberrant in tumor cells and has an impact on their growth, invasion, and metastasis by taking part in tumor angiogenesis, in apoptosis, and in events of inflammatory and immune responses. Considering the role of CTS in carcinogenesis, inhibition of these enzymes becomes an attractive strategy for cancer therapy. The downregulation of natural CTS inhibitors (CTSsis), such as cystatins, observed in various types of cancer, supports this claim. The intention of this review is to highlight the relationship of CTS with cancer and to present illustrations that explain how some of their inhibitors affect processes related to neoplastic progression.

Host Cell Proteases: Cathepsins

Cathepsins are proteolytic enzymes with a broad spectrum of substrates. They are known to reside within endo-lysosomes where they acquire optimal conditions for proteolytic activity and substrate cleavage. However, cathepsins have been detected in locations other than the canonical compartments of the endocytotic pathway. They are often secreted from cells in either proteolytically inactive proform or as mature and active enzyme; this may happen in both physiological and pathological conditions. Moreover, cytosolic and nuclear forms of cathepsins have been described and are currently an emerging field of research aiming at understanding their functions in such unexpected cellular locations. This chapter summarizes the canonical pathways of biosynthesis and transport of cathepsins in healthy cells. We further describe how cathepsins can reach unexpected locations such as the extracellular space or the cytosol and the nuclear matrix. No matter where viruses and cathepsins encounter, several outcomes can be perceived. Thus, scenarios are discussed on how cathepsins may support virus entry into host cells, involve in viral fusion factor and polyprotein processing in different host cell compartments, or help in packaging of viral particles during maturation. It is of note to mention that this review is not meant to comprehensively cover the present literature on viruses encountering cathepsins but rather illustrates, on some representative examples, the possible roles of cathepsins in replication of viruses and in the course of disease.

Synthesis and biological evaluation of novel synthetic chalcone derivatives as anti-tumor agents targeting Cat L and Cat K

A series of chalcone derivatives bearing benzamide or benzenesulfonamide moieties were synthesized and evaluated for their anti-tumor effect on HCT116, MCF7 and 143B cell lines in vitro. SAR analysis showed that compounds bearing a benzenesulfonamide group had greater potency than those bearing a benzamide group. It was also shown that compounds with a mono-methyl or mono-halogen group at the 3-position on the terminal phenyl ring were more effective than those with trifluoromethyl or methoxy groups. Compound 8e exhibited the most potent anti-tumor activities against HCT116, MCF7 and 143B cell lines, with IC₅₀ values of 0.597, 0.886 and 0.791μM, respectively. Molecular docking studies and enzymatic assays demonstrated that the anti-tumor activity of compound 8e might be regulated by Cat L and Cat K.

Snail transcription factor NLS and importin β1 regulate the subcellular localization of Cathepsin L and Cux1

Several recent studies have highlighted an additional unexpected localization and site of action for Cathepsin L (Cat L) protease within the nucleus in breast, colon and prostate cancer, however, its role in the nucleus was unclear. It was proposed to mediate proteolytic processing of the transcription factor CCAAT-displacement protein/cut homeobox transcription factor (Cux1) from the full-length p200 isoform to generate the p110 and p90 isoforms, of which the p110 isoform was shown to act as a cell cycle regulator to accelerate entry into the S phase. The p110 isoform has also been shown to bind to the promoter regions of Snail and E-cadherin to activate Snail and inactivate E-cadherin transcription, thus promoting epithelial mesenchymal transition (EMT). Mechanistic studies on what drives Cat L nuclear localization have not been reported. Our hypothesis is that Snail shuttles into the nucleus with Cat L through binding to importin-β. Snail knockdown with siRNA in MDA-MB-468 breast cancer cells led to nuclear to cytoplasmic shuttling of Cat L and decreased levels of Cux1, while overexpression of Snail in MCF-7 breast cancer cells or HEK-293 human embryonic kidney cells led to increased nuclear expression of both Cat L and Cux1. Additionally, transient transfection of Snail NLS mutants not only abrogated Snail nuclear localization but also nuclear localization of Cat L and Cux1. Interestingly, importin β1 knockdown with siRNA decreased Snail and Cux1 levels, as well as nuclear localization of Cat L. Therefore, we show for the first time that the nuclear localization of Cat L and its substrate Cux1can be positively regulated by Snail NLS and importin β1, suggesting that Snail, Cat L and Cux1 all utilize importin β1 for nuclear import.

Metabolome Comparison of Bioactive and Inactive Rhododendron Extracts and Identification of an Antibacterial Cannabinoid(s) from Rhododendron collettianum

INTRODUCTION

The science of metabolomics offers the possibility to measure full secondary plant metabolomes with limited experimental effort to allow identification of metabolome differences using principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) of liquid chromatography mass spectrometry (LC-MS) data.

OBJECTIVE

To demonstrate a bioinformatics driven hypothesis generator for identification of biologically active compounds in plant crude extracts, which is validated by activity guided fractionation.

METHODOLOGY

Crude extracts of Rhododendron leaves were tested for their antibacterial activity using agar diffusion and minimum inhibitory concentration assays. Extracts were profiled by LC-MS. PCA and PLS-DA were used for differentiation of bioactive and inactive extracts and their metabolites. Preparative-high performance liquid chromatography (HPLC) and nuclear magnetic resonance (NMR) spectroscopy were used for separation and structure elucidation of pure compound(s) respectively.

RESULTS

An antibacterial Rhododendron collettianum was compared to a series of inactive extracts. Three metabolites were found to distinguish R. collettianum from other species indicating the ability of PCA and PLS-DA to suggest potential bioactive substances. An activity-guided fractionation of R. collettianum extracts was carried out and cannabiorcichromenic acid (CCA) was identified as antibacterial compound thereby validating the PCA and PLS-DA generated hypothesis. Four mammalian cell lines were used to estimate possible cytotoxicity of CCA.

CONCLUSION

It was shown that bioinformatics tools facilitate early stage identification of a biologically active compound(s) using LC-MS data, which reduce complexity and number of separation steps in bioactive screening. Copyright © 2017 John Wiley & Sons, Ltd.

Cysteine proteases in atherosclerosis

Atherosclerosis predisposes patients to cardiovascular diseases, such as myocardial infarction and stroke. Instigation of vascular injury is triggered by retention of lipids and inflammatory cells in the vascular endothelium. Whereas these vascular lesions develop in young adults and are mostly considered harmless, over time persistent inflammatory and remodeling processes will ultimately damage the arterial wall and cause a thrombotic event due to exposure of tissue factors into the lumen. Evidence from human tissues and preclinical animal models has clearly established the role of cathepsin cysteine proteases in the development and progression of vascular lesions. Hence, understanding the function of cathepsins in atherosclerosis is important for developing novel therapeutic strategies and advanced point of care diagnostics. In this review we will describe the roles of cysteine cathepsins in different cellular process that become dysfunctional in atherosclerosis, such as lipid metabolism, inflammation and apoptosis, and how they contribute to arterial remodeling and atherogenesis. Finally, we will explore new horizons in protease molecular imaging, which may potentially become a surrogate marker to identify future cardiovascular events.

Cathepsin K modulates invasion, migration and adhesion of oral squamous cell carcinomas in vitro

OBJECTIVE

Cathepsin K was initially discovered as an osteoclast-specific cysteine proteinase, but the enzyme is also expressed in various cancers including oral squamous cell carcinomas. This study aimed to clarify the function of cathepsin K in oral squamous cell carcinomas.

MATERIALS AND METHODS

Expression levels of cathepsin K were examined in six types of cell carcinomas. Carcinomas overexpressing cathepsin K were constructed. Effects of cathepsin K overexpression and treatment with odanacatib, a specific cathepsin K inhibitor, on cell invasion, migration and adhesion were analysed.

RESULTS

Different levels of cathepsin K were expressed in carcinomas. Cathepsin K was predominantly localised in lysosomes. Cathepsin K overexpression impaired the proliferation of carcinomas. Invasion analysis showed that cathepsin K overexpression enhanced invasion and migration of carcinomas, whereas inhibition of cathepsin K by odanacatib caused the opposite effects in carcinomas. Cathepsin K overexpression also increased cell adhesion and slightly increased surface expression of the adhesion receptor CD29/integrin β₁ .

CONCLUSIONS

The enhanced invasion of carcinomas resulting from cathepsin K overexpression is probably due to the increased cell migration and adhesion. Thus, cathepsin K is implicated not only in protein degradation but also in invasion, migration and adhesion of oral squamous cell carcinomas.

Targeting the Nuclear Cathepsin L CCAAT Displacement Protein/Cut Homeobox Transcription Factor-Epithelial Mesenchymal Transition Pathway in Prostate and Breast Cancer Cells with the Z-FY-CHO Inhibitor

The epithelial mesenchymal transition (EMT) promotes tumor migration and invasion by downregulating epithelial markers such as E-cadherin and upregulating mesenchymal markers such as vimentin. Cathepsin L (Cat L) is a cysteine protease that can proteolytically activate CCAAT displacement protein/cut homeobox transcription factor (CUX1). We hypothesized that nuclear Cat L may promote EMT via CUX1 and that this could be antagonized with the Cat L-specific inhibitor Z-FY-CHO. Mesenchymal prostate (ARCaP-M and ARCaP-E overexpressing Snail) and breast (MDA-MB-468, MDA-MB-231, and MCF-7 overexpressing Snail) cancer cells expressed lower E-cadherin activity, higher Snail, vimentin, and Cat L activity, and a p110/p90 active CUX1 form, compared to epithelial prostate (ARCaP-E and ARCaP-Neo) and breast (MCF-7 and MCF-7 Neo) cancer cells. There was increased binding of CUX1 to Snail and the E-cadherin promoter in mesenchymal cells compared to epithelial prostate and breast cells. Treatment of mesenchymal cells with the Cat L inhibitor Z-FY-CHO led to nuclear-to-cytoplasmic relocalization of Cat L, decreased binding of CUX1 to Snail and the E-cadherin promoter, reversed EMT, and decreased cell migration/invasion. Overall, our novel data suggest that a positive feedback loop between Snail-nuclear Cat L-CUX1 drives EMT, which can be antagonized by Z-FY-CHO. Therefore, Z-FY-CHO may be an important therapeutic tool to antagonize EMT and cancer progression.