SARS-CoV-2 Spike Protein Induces Time-Dependent CTSL Upregulation in HeLa Cells and Alveolarspheres.

Autophagy and lysosomal pathways are involved in the cell entry of SARS-CoV-2 virus. To infect the host cell, the spike protein of SARS-CoV-2 binds to the cell surface receptor angiotensin-converting enzyme 2 (ACE2). To allow the fusion of the viral envelope with the host cell membrane, the spike protein has to be cleaved. One possible mechanism is the endocytosis of the SARS-CoV-2-ACE2 complex and subsequent cleavage of the spike protein, mainly by the lysosomal protease cathepsin L. However, detailed molecular and dynamic insights into the role of cathepsin L in viral cell entry remain elusive. To address this, HeLa cells and iPSC-derived alveolarspheres were treated with recombinant SARS-CoV-2 spike protein, and the changes in mRNA and protein levels of cathepsins L, B, and D were monitored. Additionally, we studied the effect of cathepsin L deficiency on spike protein internalization and investigated the influence of the spike protein on cathepsin L promoters in vitro. Furthermore, we analyzed variants in the genes coding for cathepsin L, B, D, and ACE2 possibly associated with disease progression using data from Regeneron's COVID Results Browser and our own cohort of 173 patients with COVID-19, exhibiting a variant of ACE2 showing significant association with COVID-19 disease progression. Our in vitro studies revealed a significant increase in cathepsin L mRNA and protein levels following exposure to the SARS-CoV-2 spike protein in HeLa cells, accompanied by elevated mRNA levels of cathepsin B and D in alveolarspheres. Moreover, an increase in cathepsin L promoter activity was detected in vitro upon spike protein treatment. Notably, the knockout of cathepsin L resulted in reduced internalization of the spike protein. The study highlights the importance of cathepsin L and lysosomal proteases in the SARS-CoV-2 spike protein internalization and suggests the potential of lysosomal proteases as possible therapeutic targets against COVID-19 and other viral infections.

Cathepsin S (CTSS) in IgA nephropathy: an exploratory study on its role as a potential diagnostic biomarker and therapeutic target.

Introduction: IgA nephropathy (IgAN), a prevalent form of glomerulonephritis globally, exhibits complex pathogenesis. Cathepsins, cysteine proteases within lysosomes, are implicated in various physiological and pathological processes, including renal conditions. Prior observational studies have suggested a potential link between cathepsins and IgAN, yet the precise causal relationship remains unclear. Methods: We conducted a comprehensive bidirectional and multivariable Mendelian randomization (MR) study using publicly available genetic data to explore the causal association between cathepsins and IgAN systematically. Additionally, immunohistochemical (IHC) staining and enzyme-linked immunosorbent assay (ELISA) were employed to evaluate cathepsin expression levels in renal tissues and serum of IgAN patients. We investigated the underlying mechanisms via gene set variation analysis (GSVA), gene set enrichment analysis (GSEA), and immune cell infiltration analysis. Molecular docking and virtual screening were also performed to identify potential drug candidates through drug repositioning. Results: Univariate MR analyses demonstrated a significant link between increased cathepsin S (CTSS) levels and a heightened risk of IgAN. This was evidenced by an odds ratio (OR) of 1.041 (95% CI=1.009-1.073, P=0.012) as estimated using the inverse variance weighting (IVW) method. In multivariable MR analysis, even after adjusting for other cathepsins, elevated CTSS levels continued to show a strong correlation with an increased risk of IgAN (IVW P=0.020, OR=1.037, 95% CI=1.006-1.069). However, reverse MR analyses did not establish a causal relationship between IgAN and various cathepsins. IHC and ELISA findings revealed significant overexpression of CTSS in both renal tissues and serum of IgAN patients compared to controls, and this high expression was unique to IgAN compared with several other primary kidney diseases such as membranous nephropathy, minimal change disease and focal segmental glomerulosclerosis. Investigations into immune cell infiltration, GSEA, and GSVA highlighted the role of CTSS expression in the immune dysregulation observed in IgAN. Molecular docking and virtual screening pinpointed Camostat mesylate, c-Kit-IN-1, and Mocetinostat as the top drug candidates for targeting CTSS. Conclusion: Elevated CTSS levels are associated with an increased risk of IgAN, and this enzyme is notably overexpressed in IgAN patients' serum and renal tissues. CTSS could potentially act as a diagnostic biomarker, providing new avenues for diagnosing and treating IgAN.

Novel proteolytic activation of Ebolavirus glycoprotein GP by TMPRSS2 and cathepsin L at an uncharted position can compensate for furin cleavage.

A multistep priming process involving furin and endosomal cathepsin B and L (CatB/L) has been described for the Orthoebolavirus zairense (EBOV) glycoprotein GP. Inhibition or knockdown of either furin or endosomal cathepsins, however, did not prevent virus multiplication in cell cultures. Moreover, an EBOV mutant lacking the furin cleavage motif (RRTRR→AGTAA) was able to replicate and cause fatal disease in nonhuman primates, indicating that furin cleavage may be dispensable for virus infectivity. Here, by using protease inhibitors and EBOV GP-carrying recombinant vesicular stomatitis virus (VSV) and transcription and replication-competent virus-like particles (trVLPs) we found that processing of EBOV GP is mediated by different proteases in different cell lines depending on the protease repertoire available. Endosomal cathepsins were essential for EBOV GP entry in Huh-7 but not in Vero cells, in which trypsin-like proteases and stably expressed trypsin-like transmembrane serine protease 2 (TMPRSS2) supported wild-type EBOV GP and EBOV GP_AGTAA mutant entry. Furthermore, we show that the EBOV GP_AGTAA mutant is cleaved into fusion-competent GP2 by TMPRSS2 and by CatL at a so far unknown site. Fluorescence microscopy co-localization studies indicate that EBOV GP cleavage by TMPRSS2 may occur in the TGN prior to virus release or in the late endosome at the stage of virus entry into a new cell. Our data show that EBOV GP must be proteolytically activated to support virus entry but has even greater flexibility in terms of proteases and the precise cleavage site than previously assumed.

Relationship between cathepsins and cardiovascular diseases: a Mendelian randomized study.

Background: Cardiovascular diseases (CVDs) are the leading age-related disorders worldwide, with their prevalence increasing annually. Cathepsins are protein-degrading enzymes essential for processes such as intracellular protein breakdown, apoptosis, and immune responses. Recent studies suggest a potential link between cathepsins and CVDs, yet the exact causal relationship remains to be elucidated. To address this, we propose using Mendelian randomization (MR) to explore the causal relationships between cathepsins and CVDs. Methods: We obtained single nucleotide polymorphism (SNP) data for cathepsins from the INTERVAL study, a publicly accessible genome-wide association study (GWAS) dataset. Outcome SNP data were sourced from seven distinct GWAS datasets, ensuring a comprehensive analysis across multiple cardiovascular outcomes. For MR analysis, we primarily employed the inverse variance weighted (IVW) method, known for its efficiency when all SNPs are valid instruments. This was supplemented by the weighted median and MR-Egger methods to provide robustness against potential violations of MR assumptions, such as pleiotropy. The IVW method offers precision and efficiency, the weighted median method adds robustness against invalid instruments, and the MR-Egger method helps identify and correct for pleiotropic biases. Cochran's Q test was utilized to assess heterogeneity, and sensitivity analyses were conducted using MR-PRESSO and the leave-one-out approach. Results: The strength of the associations between exposure and outcome was measured using odds ratios (ORs), and results were presented with 95% confidence intervals (CIs). The cathepsin E increases the risk of myocardial infarction (MI) (OR = 1.053%, 95% CI: 1.007-1.101, p = 0.024) and ischemic stroke (IS) (OR = 1.06%, 95% CI: 1.019-1.103, p = 0.004). Conversely, cathepsin L2 decreases the risk of chronic heart failure (CHF) (OR = 0.922%, 95% CI: 0.859-0.99, p = 0.025) and atrial fibrillation (AF) (OR = 0.956%, 95% CI: 0.918-0.996, p = 0.033). Cathepsin O was associated with an increased risk of IS (OR = 1.054%, 95% CI: 1.008-1.102, p = 0.021) and AF (OR = 1.058%, 95% CI: 1.02-1.098, p = 0.002). Conclusion: Our MR analysis reveals that cathepsin E is a risk factor for MI and IS, cathepsin L2 offers protective effects against CHF and AF, and cathepsin O increases the risk for IS and AF.

Lysosome-Disrupting Agents in Combination with Venetoclax Increase Apoptotic Response in Primary Chronic Lymphocytic Leukemia (CLL) Cells Mediated by Lysosomal Cathepsin D Release and Inhibition of Autophagy.

Venetoclax and obinutuzumab are becoming frontline therapies for chronic lymphocytic leukemia (CLL) patients. Unfortunately, drug resistance still occurs, and the combination could be immunosuppressive. Lysosomes have previously been identified as a target for obinutuzumab cytotoxicity in CLL cells, but the mechanism remains unclear. In addition, studies have shown that lysosomotropic agents can cause synergistic cell death in vitro when combined with the BTK inhibitor, ibrutinib, in primary CLL cells. This indicates that targeting lysosomes could be a treatment strategy for CLL. In this study, we have shown that obinutuzumab induces lysosome membrane permeabilization (LMP) and cathepsin D release in CLL cells. Inhibition of cathepsins reduced obinutuzumab-induced cell death in CLL cells. We further determined that the lysosomotropic agent siramesine in combination with venetoclax increased cell death in primary CLL cells through an increase in reactive oxygen species (ROS) and cathepsin release. Siramesine treatment also induced synergistic cytotoxicity when combined with venetoclax. Microenvironmental factors IL4 and CD40L or incubation with HS-5 stromal cells failed to significantly protect CLL cells from siramesine- and venetoclax-induced apoptosis. We also found that siramesine treatment inhibited autophagy through reduced autolysosomes. Finally, the autophagy inhibitor chloroquine failed to further increase siramesine-induced cell death. Taken together, lysosome-targeting drugs could be an effective strategy in combination with venetoclax to overcome drug resistance in CLL.

Functional characterization of a cystatin A from the bat Myotis davidii.

Myotis davidii cystatin A (MdCSTA), a stefin A-like from the Chinese native bat species M. davidii, was expressed as a recombinant protein and functionally characterized as a strong inhibitor of the cysteine proteases papain, human cathepsins L and B and the tick cathepsin L-like BmCL1. Despite the highly conserved amino acid sequences among stefins A from different vertebrates, MdCSTA presents a Methionine-2 residue at the N-terminal region and the second binding loop (pos 73-79) that differs from human stefin A (HsCSTA) and might be related to the lower inhibition constant (Ki) value presented by this inhibitor in comparison to human stefin A inhibition to cathepsin B. Therefore, to investigate the importance of these variable regions in cathepsin B inhibition, recombinant stefins A MdCSTA and HsCSTA containing mutations at the second amino acid residue and second binding loop were expressed and evaluated in kinetic assays. Enzymatic inhibition assays with cathepsin B revealed that switching the amino acid residues at position 2 and second binding loop region between bat and human CSTAs improved the HsCSTA's and reduced MdCSTA's inhibitory activity. Additionally, molecular docking analysis estimated lower energy values for the complex between MdCSTA-cathepsin B, in comparison to human CSTA-cathepsin B, while the mutants presented intermediate values, suggesting that other regions might contribute to the higher inhibitory activity against cathepsin B by MdCSTA. In conclusion, MdCSTA, the first bat's stefin A-like inhibitor to be functionally characterized, presented a higher inhibitory activity against cathepsin B in comparison to the human inhibitor, which is partially related to the glutamine-rich second binding loop and Met-2. Further structural analysis should be performed to elucidate potential inhibitor effects on cysteine proteinases.

Cathepsins and cancer risk: a Mendelian randomization study.

Background: Previous observational epidemiological studies reported an association between cathepsins and cancer, however, a causal relationship is uncertain. This study evaluated the causal relationship between cathepsins and cancer using Mendelian randomization (MR) analysis. Methods: We used publicly available genome-wide association study (GWAS) data for bidirectional MR analysis. Inverse variance weighting (IVW) was used as the primary MR method of MR analysis. Results: After correction for the False Discovery Rate (FDR), two cathepsins were found to be significantly associated with cancer risk: cathepsin H (CTSH) levels increased the risk of lung cancer (OR = 1.070, 95% CI = 1.027-1.114, P = 0.001, PFDR = 0.009), and CTSH levels decreased the risk of basal cell carcinoma (OR = 0.947, 95% CI = 0.919-0.975, P = 0.0002, P FDR = 0.002). In addition, there was no statistically significant effect of the 20 cancers on the nine cathepsins. Some unadjusted low P-value phenotypes are worth mentioning, including a positive correlation between cathepsin O (CTSO) and breast cancer (OR = 1.012, 95% CI = 1.001-1.025, P = 0.041), cathepsin S (CTSS) and pharyngeal cancer (OR = 1.017, 95% CI = 1.001-1.034, P = 0.043), and CTSS and endometrial cancer (OR = 1.055, 95% CI = 1.012-1.101, P = 0.012); and there was a negative correlation between cathepsin Z and ovarian cancer (CTSZ) (OR = 0.970, 95% CI = 0.949-0.991, P = 0.006), CTSS and prostate cancer (OR = 0.947, 95% CI = 0.902-0.944, P = 0.028), and cathepsin E (CTSE) and pancreatic cancer (OR = 0.963, 95% CI = 0.938-0.990, P = 0.006). Conclusion: Our MR analyses showed a causal relationship between cathepsins and cancers and may help provide new insights for further mechanistic and clinical studies of cathepsin-mediated cancer.

Biomechanical dysregulation of SGK-1 dependent aortic pathologic markers in hypertension.

Introduction: In hypertension (HTN), biomechanical stress may drive matrix remodeling through dysfunctional VSMC activity. Prior evidence has indicated VSMC tension-induced signaling through the serum and glucocorticoid inducible kinase-1 (SGK-1) can impact cytokine abundance. Here, we hypothesize that SGK-1 impacts production of additional aortic pathologic markers (APMs) representing VSMC dysfunction in HTN. Methods: Aortic VSMC expression of APMs was quantified by QPCR in cyclic biaxial stretch (Stretch) +/- AngiotensinII (AngII). APMs were selected to represent VSMC dedifferentiated transcriptional activity, specifically Interleukin-6 (IL-6), Cathepsin S (CtsS), Cystatin C (CysC), Osteoprotegerin (OPG), and Tenascin C (TNC). To further assess the effect of tension alone, abdominal aortic rings from C57Bl/6 WT mice were held in a myograph at experimentally derived optimal tension (OT) or OT + 30% +/-AngII. Dependence on SGK-1 was assessed by treating with EMD638683 (SGK-1 inhibitor) and APMs were measured by QPCR. Then, WT and smooth muscle cell specific SGK-1 heterozygous knockout (SMC-SGK-1KO+/-) mice had AngII-induced HTN. Systolic blood pressure and mechanical stress parameters were assessed on Day 0 and Day 21. Plasma was analyzed by ELISA to quantify APMs. Statistical analysis was performed by ANOVA. Results: In cultured aortic VSMCs, expression of all APMs was increased in response to biomechanical stimuli (Stretch +/-AngII,). Integrating the matrix contribution to signal transduction in the aortic rings led to IL-6 and CysC demonstrating SGK-1 dependence in response to elevated tension and interactive effect with concurrent AngII stimulation. CtsS and TNC, on the other hand, primarily responded to AngII, and OPG expression was unaffected in aortic ring experimentation. Both mouse strains had >30% increase in blood pressure with AngII infusion, reduced aortic distensibility and increased PPV, indicating increased aortic stiffness. In WT + AngII mice, IL-6, CtsS, CysC, and TNC plasma levels were significantly elevated, but these APMs were unaffected by HTN in the SMC-SGK-1KO+/- +AngII mice, suggesting SGK-1 plays a major role in VSMC biomechanical signaling to promote dysfunctional production of selected APMs. Conclusion: In HTN, changes in the plasma levels of markers associated with aortic matrix homeostasis can reflect remodeling driven by mechanobiologic signaling in dysfunctional VSMCs, potentially through the activity of SGK-1. Further defining these pathways may identify therapeutic targets to reduce cardiovascular morbidity and mortality.

Association between cathepsins and benign prostate diseases: a bidirectional two-sample Mendelian randomization study.

Objectives: The relationship between cathepsins and prostate cancer (PCa) has been reported. However, there is a lack of research on cathepsins and benign prostate diseases (BPDs). This study investigated the potential genetic link between cathepsins and BPDs through the utilization of Mendelian randomization (MR) analysis to determine if a causal relationship exists. Methods: Publicly accessible summary statistics on BPDs were obtained from FinnGen Biobank. The data comprised 149,363 individuals, with 30,066 cases and 119,297 controls for BPH, and 123,057 individuals, with 3,760 cases and 119,297 controls for prostatitis. The IEU OpenGWAS provided the Genome-wide association data on ten cathepsins. To evaluate the causal relationship between BPDs and cathepsins, five distinct MR analyses were employed, with the primary method being the inverse variance weighted (IVW) approach. Additionally, sensitivity analyses were conducted to examine the horizontal pleiotropy and heterogeneity of the findings. Results: The examination of IVW MR findings showed that cathepsin O had a beneficial effect on BPH (IVW OR=0.94, 95% CI 0.89-0.98, P=0.0055), while cathepsin X posed a threat to prostatitis (IVW OR=1.08, 95% CI 1.00-1.16, P=0.047). Through reverse MR analysis, it was revealed that prostatitis had an adverse impact on cathepsin V (IVW OR=0.89, 95% CI 0.80-0.99, P=0.035), while no favorable association was observed between BPH and cathepsins. The results obtained from MR-Egger, weighted median, simple mode, and weighted mode methods were consistent with the findings of the IVW approach. Based on sensitivity analyses, heterogeneity, and horizontal pleiotropy are unlikely to distort the results. Conclusion: This study offers the initial evidence of a genetic causal link between cathepsins and BPDs. Our findings revealed that cathepsin O was beneficial in preventing BPH, whereas cathepsin X posed a potential threat to prostatitis. Additionally, prostatitis negatively affected cathepsin V level. These three cathepsins could be targets of diagnosis and treatment for BPDs, which need further research.

Unveiling the Roles of Cysteine Proteinases F and W: From Structure to Pathological Implications and Therapeutic Targets.

Cysteine cathepsins F and W are members of the papain-like cysteine protease family, which have distinct structural features and functional roles in various physiological and pathological processes. This review provides a comprehensive overview of the current understanding of the structure, biological functions, and pathological implications of cathepsins F and W. Beginning with an introduction to these proteases, we delve into their structural characteristics and elucidate their unique features that dictate their enzymatic activities and substrate specificity. We also explore the intricate involvement of cathepsins F and W in malignancies, highlighting their role as potential biomarkers and therapeutic targets in cancer progression. Furthermore, we discuss the emerging roles of these enzymes in immune response modulation and neurological disorders, shedding light on their implications in autoimmune and neurodegenerative diseases. Finally, we review the landscape of inhibitors targeting these proteases, highlighting their therapeutic potential and challenges in clinical translation. This review brings together the diverse facets of cysteine cathepsins F and W, providing insights into their roles in health and disease and guiding future investigations for therapeutic advances.

Enzyme-Activatable Near-Infrared Hemicyanines as Modular Scaffolds for in vivo Photodynamic Therapy.

Photodynamic therapy is an anti-cancer treatment that requires illumination of photosensitizers to induce local cell death. Current near-infrared organic photosensitizers are built from large and non-modular structures that cannot be tuned to improve safety and minimize off-target toxicity. This work describes a novel chemical platform to generate enzyme-activatable near-infrared photosensitizers. We optimized the Se-bridged hemicyanine scaffold to include caging groups and biocompatible moieties, and generated cathepsin-triggered photosensitizers for effective ablation of human glioblastoma cells. Furthermore, we demonstrated that enzyme-activatable Se-bridged hemicyanines are effective photosensitizers for the safe ablation of microtumors in vivo, creating new avenues in the chemical design of targeted anti-cancer photodynamic therapy agents.

Genetic insights into the role of cathepsins in cardiovascular diseases: a Mendelian randomization study.

AIMS: This study aimed to explore the causal relationships between cathepsins and cardiovascular diseases (CVDs) by Mendelian randomization (MR) analysis. METHODS AND RESULTS: Single nucleotide polymorphisms (SNPs) associated with nine cathepsin types (cathepsins B, E, F, G, H, O, S, L2, and Z) were obtained from the INTERVAL study (3301 individuals). CVDs data were acquired from the UK Biobank (coronary atherosclerosis: 14 334 cases, 346 860 controls) and a genome-wide association study (GWAS) (myocardial infarction: 20 917 cases, 440 906 controls; myocarditis: 633 cases, 427 278 controls; chronic heart failure: 14 262 cases, 471 898 controls; angina pectoris: 30 025 cases, 440 906 controls; stable angina pectoris: 17 894 cases, 325 132 controls; unstable angina pectoris: 9481 cases, 446 987 controls; pericarditis: 1795 cases, 453 370 controls). Inverse variance weighted (IVW), MR-Egger, weighted median methods were adopted to conduct univariable MR (UVMR), reverse MR, multivariable MR (MVMR) analyses to estimate causality. The UVMR analyses demonstrated significant causal relationships between higher cathepsin E levels and increased risk of coronary atherosclerosis [IVW: P = 0.0051, odds ratio (OR) = 1.0033, 95% confidence interval (CI) = 1.0010-1.0056] and myocardial infarction (IVW: P = 0.0097, OR = 1.0553, 95% CI = 1.0131-1.0993), while elevated cathepsin L2 levels were causally related to reduced risk of myocarditis (IVW: P = 0.0120, OR = 0.6895, 95% CI = 0.5158-0.9216) and chronic heart failure (IVW: P = 0.0134, OR = 0.9316, 95% CI = 0.8807-0.9854). Reverse MR analyses revealed that myocardial infarction increased cathepsin O levels (IVW: P = 0.0400, OR = 1.0708, 95% CI = 1.0031-1.1431). MVMR analyses treating nine cathepsins together revealed that the positive causality between cathepsin E levels and coronary atherosclerosis risk (IVW: P = 0.0390, OR = 1.0030, 95% CI = 1.0000-1.0060), and the protective effect of cathepsin L2 levels on myocarditis (IVW: P = 0.0030, OR = 0.6610, 95% CI = 0.5031-0.8676) and chronic heart failure (IVW: P = 0.0090, OR = 0.9259, 95% CI = 0.8737-0.9812) remained, as higher cathepsin O levels were found to be causally related to increased risks of myocarditis (IVW: P = 0.0030, OR = 1.6145, 95% CI = 1.1829-2.2034) and chronic heart failure (IVW: P = 0.0300, OR = 1.0779, 95% CI = 1.0070-1.1537). CONCLUSIONS: The study highlights the causalities of cathepsin E, L2, and O on CVDs, offering insights into their roles in cardiovascular biomarkers and therapeutic targets development. Further research is required to apply these genetic findings clinically.

Cellular depletion of major cathepsin proteases reveals their concerted activities for lysosomal proteolysis.

Proteins delivered by endocytosis or autophagy to lysosomes are degraded by exo- and endoproteases. In humans 15 lysosomal cathepsins (CTS) act as important physiological regulators. The cysteine proteases CTSB and CTSL and the aspartic protease CTSD are the most abundant and functional important lysosomal proteinases. Whereas their general functions in proteolysis in the lysosome, their individual substrate, cleavage specificity, and their possible sequential action on substrate proteins have been previously studied, their functional redundancy is still poorly understood. To address a possible common role of highly expressed and functional important CTS proteases, we generated CTSB-, CTSD-, CTSL-, and CTSBDL-triple deficient (KO) human neuroblastoma-derived SH-SY5Y cells and CTSB-, CTSD-, CTSL-, CTSZ and CTSBDLZ-quadruple deficient (KO) HeLa cells. These cells with a combined cathepsin deficiency exhibited enlarged lysosomes and accumulated lipofuscin-like storage material. The lack of the three (SH-SY5Y) or four (HeLa) major CTSs caused an impaired autophagic flux and reduced degradation of endocytosed albumin. Proteome analyses of parental and CTS-depleted cells revealed an enrichment of cleaved peptides, lysosome/autophagy-associated proteins, and potentially endocytosed membrane proteins like the amyloid precursor protein (APP), which can be subject to endocytic degradation. Amino- and carboxyterminal APP fragments accumulated in the multiple CTS-deficient cells, suggesting that multiple CTS-mediated cleavage events regularly process APP. In summary, our analyses support the idea that different lysosomal cathepsins act in concert, have at least partially and functionally redundant substrates, regulate protein degradation in autophagy, and control cellular proteostasis, as exemplified by their involvement in the degradation of APP fragments.

The Intricate Balance between Life and Death: ROS, Cathepsins, and Their Interplay in Cell Death and Autophagy.

Cellular survival hinges on a delicate balance between accumulating damages and repair mechanisms. In this intricate equilibrium, oxidants, currently considered physiological molecules, can compromise vital cellular components, ultimately triggering cell death. On the other hand, cells possess countermeasures, such as autophagy, which degrades and recycles damaged molecules and organelles, restoring homeostasis. Lysosomes and their enzymatic arsenal, including cathepsins, play critical roles in this balance, influencing the cell's fate toward either apoptosis and other mechanisms of regulated cell death or autophagy. However, the interplay between reactive oxygen species (ROS) and cathepsins in these life-or-death pathways transcends a simple cause-and-effect relationship. These elements directly and indirectly influence each other's activities, creating a complex web of interactions. This review delves into the inner workings of regulated cell death and autophagy, highlighting the pivotal role of ROS and cathepsins in these pathways and their intricate interplay.

ATF6 supports lysosomal function in tumor cells to enable ER stress-activated macroautophagy and CMA: impact on mutant TP53 expression.

The inhibition of the unfolded protein response (UPR), which usually protects cancer cells from stress, may be exploited to potentiate the cytotoxic effect of drugs inducing ER stress. However, in this study, we found that ER stress and UPR activation by thapsigargin or tunicamycin promoted the lysosomal degradation of mutant (MUT) TP53 and that the inhibition of the UPR sensor ATF6, but not of ERN1/IRE1 or EIF2AK3/PERK, counteracted such an effect. ATF6 activation was indeed required to sustain the function of lysosomes, enabling the execution of chaperone-mediated autophagy (CMA) as well as of macroautophagy, processes involved in the degradation of MUT TP53 in stressed cancer cells. At the molecular level, by pharmacological and genetic approaches, we demonstrated that the inhibition of ATF6 correlated with the activation of MTOR and with TFEB and LAMP1 downregulation in thapsigargin-treated MUT TP53 carrying cells. We hypothesize that the rescue of MUT TP53 expression by ATF6 inhibition, could further activate MTOR and maintain lysosomal dysfunction, further inhibiting MUT TP53 degradation, in a vicious circle. The findings of this study suggest that the presence of MUT TP53, which often exerts oncogenic properties, should be considered before approaching treatments combining ER stressors with ATF6 inhibitors against cancer cells, while it could represent a promising strategy against cancer cells that harbor WT TP53.

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.

The causal relationship between cathepsins and digestive system tumors: a Mendelian randomization study.

Background: Multiple studies have confirmed the significant role of cathepsins in the development and progression of digestive system tumors. However, further investigation is needed to determine the causal relationships. Methods: We conducted a two-sample bidirectional Mendelian randomization (MR) study using pooled data from a genome-wide association study (GWAS) to assess the causal associations between nine cathepsins (cathepsin B, E, F, G, H, L2, O, S, and Z) and six types of digestive system tumors, including hepatocellular carcinoma (HCC), pancreatic cancer (PCa), biliary tract cancer (BTC), colorectal cancer (CRC), gastric carcinoma (GC), and esophageal cancer (EC). We employed the following methods including inverse variance weighting (IVW), MR-Egger, weighted median (WM), Cochran's Q, MR-PRESSO, MR-Egger intercept test and leave-one-out sensitivity analysis. The STROBE-MR checklist for the reporting of MR studies was used in this study. Results: The risk of HCC increased with high levels of cathepsin G (IVW: p = 0.029, odds ratio (OR) = 1.369, 95% confidence interval (CI) = 1.033-1.814). Similarly, BTC was associated with elevated cathepsin B levels (IVW: p = 0.025, OR = 1.693, 95% CI = 1.070-2.681). Conversely, a reduction in PCa risk was associated with increased cathepsin H levels (IVW: p = 0.027, OR = 0.896, 95% CI = 0.812-0.988). Lastly, high levels of cathepsin L2 were found to lower the risk of CRC (IVW: p = 0.034, OR = 0.814, 95% CI = 0.674-0.985). Conclusion: Our findings confirm the causal relationship between cathepsins and digestive system tumors, which can offer valuable insights for the diagnosis and treatment of digestive system tumors.

The role of multiple vitellogenins in early development of fishes.

Functions of vitellogenins have been in the limelight of fish reproductive physiology research for decades. The Vtg system of acanthomorph teleosts consists of two complete forms of Vtgs (VtgAa and VtgAb) and an incomplete form, VtgC. Insufficient uptake and processing of Vtgs and their yolk proteins lead to inadequate oocyte hydration ensuing failure in acquisition of egg buoyancy and early developmental deficiencies. This review presents a summary of our studies on utilization of multiple Vtgs in species with different egg buoyancy characteristics, as examples. Studies of moronids revealed limited degradation of all three forms of lipovitellin heavy chain derived from their three respective forms of Vtg, by which they contribute to the free amino acid pool driving oocyte hydration during oocyte maturation. In later studies, CRISPR/Cas9 was employed to invalidate zebrafish type I, type II and type III Vtgs, which are orthologs of acanthamorph VtgAa, VtgAb and VtgC, respectively. Results revealed type I Vtg to have essential developmental and nutritional functions in both late embryos and larvae. Genomic disturbance of type II Vtg led to high mortalities during the first 24 h of embryonic development. Despite being a minor form of Vtg in zebrafish and most other species, type III Vtg was also found to contribute essentially to the developmental potential of zebrafish zygotes and early embryos. Apart from severe effects on progeny survival, these studies also disclosed previously unreported regulatory effects of Vtgs on fecundity and fertility, and on embryo hatching. We recently utilized parallel reactions monitoring based liquid chromatography tandem mass spectrometry to assess the processing and utilization of lipovitellins derived from different forms of Vtg in Atlantic halibut and European plaice. Results showed the Lv heavy chain of VtgAa (LvHAa) to be consumed during oocyte maturation and the Lv light chain of VtgAb (LvLAb) to be utilized specifically during late larval stages, while all remaining YPs (LvLAa, LvHAb, LvHC, and LvLC) were utilized during or after hatching up until first feeding in halibut. In plaice, all YPs except LvHAa, which similarly to halibut supports oocyte maturation, are utilized from late embryo to late larval development up until first feeding. The collective findings from these studies affirm substantial disparity in modes of utilization of different types of Vtgs among fish species with various egg buoyancy characteristics, and they reveal previously unknown regulatory functions of Vtgs in maintenance of reproductive assets such as maternal fecundity and fertility, and in embryonic hatching. Despite the progress that has been made over the past two decades by examining multiple Vtgs and their functions, a higher complexity of these systems with much greater diversity between species in modes of Vtg utilization is now evident. Further research is needed to reveal novel ways each species has evolved to utilize these complex multiple Vtg systems and to discover unifying principles for this evolution in fishes of diverse lineages, habitats and life history characteristics.

Therapeutic cysteine protease inhibitors: a patent review (2018-present).

INTRODUCTION: Cysteine proteases are involved in a broad range of biological functions, ranging from extracellular matrix turnover to immunity. Playing an important role in the onset and progression of several diseases, including cancer, immune-related and neurodegenerative disease, viral and parasitic infections, cysteine proteases represent an attractive drug target for the development of therapeutic tools. AREAS COVERED: Recent scientific and patent literature focusing on the design and study of cysteine protease inhibitors with potential therapeutic application has been reviewed. EXPERT OPINION: The discovery of a number of effective structurally diverse cysteine protease inhibitors opened up new challenges and opportunities for the development of therapeutic tools. Mechanistic studies and the availability of X-ray crystal structures of some proteases, alone and in complex with inhibitors, provide crucial information for the rational design and development of efficient and selective cysteine protease inhibitors as preclinical candidates for the treatment of different diseases.