Cathepsin D-Managing the Delicate Balance

Targeting RPSA to modulate endosomal trafficking and amyloidogenesis in genetic Alzheimer's disease

The "amyloid cascade hypothesis" for Alzheimer's disease (AD) pathogenesis, highlights the accumulation of amyloid-β (Aβ) as a crucial trigger for the pathology. However, AD is an extremely complex disease influenced by multiple pathophysiological processes, making it impossible to attribute its onset to a single hypothesis. The endocytic pathway, where the amyloidogenic processing of APP occurs, has emerged as a pathogenic "hub" for AD. In this study, we found altered homeostasis and dynamics of endolysosomal compartments in fibroblasts from patients affected by a genetic form of AD (APP V717I mutation). These alterations corresponded to an abnormal trafficking of APP along the endolysosomal pathway, favouring its amyloidogenic processing. The identification of APP interactors involved in its trafficking and processing, and finding molecules able to interfere with these interactions, represents a promising therapeutic approach. However, the role of endosomal pathway and the possibility of modulating APP processing through it remains elusive. Among the proteins participating to APP metabolism, the RPSA receptor and its inhibitor molecule NSC47924 have been identified. In this study, we found that the inhibitor, likely by displacing APP from interaction with its receptor, reduced APP accumulation in EEs in AD cells, finally restoring both endosomal dynamics and APP distribution to those of unaffected cells. We also demonstrated that RPSA inhibition affected the aberrant APP cleavage, as it reduced the production of both APP-βCTF (C-Terminal Fragment) and Aβ in AD fibroblasts. These results highlight significant differences in endolysosomal compartments and APP processing in AD-affected cells, refining our understanding of APP/RPSA intersection.

Cathepsins: Novel opportunities for antibody therapeutics in cancer

Cathepsins, the most abundant lysosomal proteases, have key functions in cell maintenance and homeostasis. They are overexpressed and hypersecreted in cancer and associated with poor prognosis. Secreted cathepsins display pro-tumour activities in the tumour microenvironment and thus represent interesting molecular targets in oncology. Recently, several antibody-based cancer therapies have targeted the pro-tumour activity of the extracellular cathepsin pool, altering several cancer hallmarks, but not the intracellular cathepsin levels that are often crucial for cell homeostasis. In this mini-review, we describe advances in antibodies against extracellular cathepsins in cancer, and their effect on the proteolytic cascade, matrix remodelling, proliferation, and modulation of the anti-cancer immune response. We also discuss the add-on value of combination strategies (anti-cathepsin antibodies with chemotherapy and/or biologics) that make anti-cathepsin antibodies a new opportunity for disease management.

Lysosomal Dysfunction in Amyotrophic Lateral Sclerosis: A Familial Case Linked to the p.G376D TARDBP Mutation

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease affecting motor neurons. Consequent to the loss of these cells, neuromuscular functions decline, causing progressive weakness, muscle wasting, and paralysis, leading to death in 2 to 5 years. More than 90% of ALS cases are sporadic, while the remaining 10% of cases are familial, due to mutations in 40 different genes. One of the most common genes to be mutated in ALS is TARDBP (transactive response DNA binding protein 43), which encodes TDP-43 (TAR DNA-binding protein 43). A mutation in exon 6 of TARDBP causes the aminoacidic substitution G376D in the C-terminal region of TDP-43, leading to its cytoplasmic mislocalization and aggregation. In fibroblasts derived from patients carrying this mutation, we found a strong increase in lysosome number, with overexpression and higher nuclear translocation of the transcription factor TFEB. In contrast, lysosomal functionality was deeply compromised. Interestingly, lysosomal activity was unaffected at an early stage of the disease, worsening in more advanced stages. Moreover, we observed the same pathological phenotype in iPSC (induced pluripotent stem cells)-derived patient motor neurons carrying the G376D mutation. Therefore, this mutation compromises the functionality of lysosomes, possibly contributing to neurodegeneration.

Molecular Insights into the Interaction of Cathepsin D and Iron in Chronic Wound Healing: Exploring Therapeutic Potential and Mechanisms

Background: Chronic wounds, such as diabetic ulcers, often fail to progress through healing due to persistent inflammation, infections, and extracellular matrix (ECM) imbalances. Cathepsin D, an aspartate protease active in acidic environments, plays a pivotal role in wound healing by mediating inflammatory responses, ECM remodeling, and macrophage phenotype transitions. Its dysregulation, however, can impair healing, highlighting the need for targeted modulation of its activity. The aim of this study was to investigate the molecular interaction between Fe2+ and cathepsin D's catalytic core and ionic zipper under physiological and acidic conditions to identify strategies to enhance tissue repair and accelerate the healing of chronic wounds. Methods: The molecular structure of active cathepsin D was obtained from the Protein Data Bank (PDB) and analyzed using UCSF Chimera. Molecular interactions between cathepsin D and ferrous ions (Fe2+) were studied, focusing on key residues (D33 and D231) and ionic zipper residues (E5, E180, and D187). Results: Our results showed that the active form of cathepsin D, a 96 kDa dimer, consisted of heterodimers with distinct amino acid chains, where residues D33 and D231 formed the active site, and E5, E180, and D187 constituted the ionic zipper. A functional pocket containing the conserved residues D33 and D231, essential for proteolytic activity, was identified. At physiological pH (~7.5), D33 exhibited the most potent interactions with Fe2+, with interaction energies of -7 × 1017 J at oxygen atoms of the carboxylate group (OD1) and α-carbon (CA) atoms, whereas D231 showed slightly lower energies of -6 × 1017 J at γ-carbon atom (CG) and CA atoms. At acidic pH (~4), E5 was the primary interacting residue, with the shortest distance to Fe2+ (2.69 Å), and showed stable interactions across several atoms, emphasizing its role in metal binding. Conclusions: pH conditions strongly influence the interaction of cathepsin D with Fe2. At physiological pH, residues D33 and D231 demonstrate robust and energetically efficient binding with Fe2+. At the same time, under acidic conditions, E5 emerges as the primary residue involved, potentially affecting the ionic zipper of cathepsin D. These insights provide a molecular foundation for targeting specific residues to modulate cathepsin D activity, presenting promising opportunities for therapeutic strategies aimed at improving chronic wound healing.

A specific gene expression program underlies antigen archiving by lymphatic endothelial cells in mammalian lymph nodes

Lymph node (LN) lymphatic endothelial cells (LEC) actively acquire and archive foreign antigens. Here, we address questions of how LECs achieve durable antigen archiving and whether LECs with high levels of antigen express unique transcriptional programs. We used single cell sequencing in dissociated LN tissue and spatial transcriptomics to quantify antigen levels in LEC subsets and dendritic cell populations at multiple time points after immunization and determined that ceiling and floor LECs archive antigen for the longest duration. We identify, using spatial transcriptomics, antigen positive LEC-dendritic cell interactions. Using a prime-boost strategy we find increased antigen levels within LECs after a second immunization demonstrating that LEC antigen acquisition and archiving capacity can be improved over multiple exposures. Using machine learning we defined a unique transcriptional program within archiving LECs that predicted LEC archiving capacity in mouse and human independent data sets. We validated this modeling, showing we could predict lower levels of LEC antigen archiving in chikungunya virus-infected mice and demonstrated in vivo the accuracy of our prediction. Collectively, our findings establish unique properties of LECs and a defining transcriptional program for antigen archiving that can predict antigen archiving capacity in different disease states and organisms.

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.

Cathepsins and neurological diseases: a Mendelian randomization study

Background

The causal relationship between cathepsins and neurological diseases remains uncertain. To address this, we utilized a two-sample Mendelian randomization (MR) approach to assess the potential causal effect of cathepsins on the development of neurological diseases.

Methods

This study conducted a two-sample two-way MR study using pooled data from published genome-wide association studies to evaluate the relationship between 10 cathepsins (B, D, E, F, G, H, L2, O, S, and Z) and 7 neurological diseases, which included ischemic stroke, cerebral hemorrhage, Alzheimer's disease, Parkinson's disease, multiple sclerosis, amyotrophic lateral sclerosis, and epilepsy. The analysis employed various methods such as inverse variance weighting (IVW), weighted median, MR Egger regression, MR pleiotropy residual sum and outlier, Cochran Q statistic, and leave-one-out analysis.

Results

We found a causal relationship between cathepsins and neurological diseases, including Cathepsin B and Parkinson's disease (IVW odds ratio (OR): 0.89, 95% confidence interval (CI): 0.83, 0.95, p = 0.001); Cathepsin D and Parkinson's disease (OR: 0.80, 95%CI: 0.68, 0.95, p = 0.012); Cathepsin E and ischemic stroke (OR: 1.05, 95%CI: 1.01, 1.09, p = 0.015); Cathepsin O and ischemic stroke (OR: 1.05, 95%CI: 1.01, 1.10, p = 0.021). Reverse MR analyses revealed that multiple sclerosis and Cathepsin E (OR: 1.05, 95%CI: 1.01, 1.10, p = 0.030). There is currently no significant relationship has been found between other cathepsins and neurological diseases.

Conclusion

Our study reveals a causal relationship between Cathepsins B, D, E, and O and neurological diseases, offering valuable insights for research aimed at improving the diagnosis and treatment of such conditions.

Pro-cathepsin D prevents aberrant protein aggregation dependent on endoplasmic reticulum protein CLN6

We previously expressed a chimeric protein in which the small heat-shock protein αB-crystallin (αBC) is fused at its N-terminus to the C-terminus of the first transmembrane segment of the endoplasmic reticulum (ER) protein mitsugumin 23 and confirmed its localization to the ER. Moreover, overexpression of this N-terminally modified αBC was shown to prevent the aggregation of the coexpressed R120G αBC variant, which is highly aggregation-prone and associated with the hereditary myopathy αB-crystallinopathy. To uncover a molecular mechanism by which the ER-anchored αBC negatively regulates the protein aggregation, we isolated proteins that bind to the ER-anchored αBC and identified the lysosomal protease cathepsin D (CTSD) as one such interacting protein. Proteolytically active CTSD is produced by multi-step processing of pro-cathepsin D (proCTSD), which is initially synthesized in the ER and delivered to lysosomes. When overexpressed, CTSD itself prevented the coexpressed R120G αBC variant from aggregating. This anti-aggregate activity was also elicited upon overexpression of the W383C CTSD variant, which is predominantly sequestered in the ER and consequently remains unprocessed, suggesting that proCTSD, rather than mature CTSD, serves to suppress the aggregation of the R120G αBC variant. Meanwhile, overexpression of the A58V CTSD variant, which is identical to wild-type CTSD except for the Ala58Val substitution within the pro-peptide, did not suppress the protein aggregation, indicating that the integrity of the pro-peptide is required for proCTSD to exert its anti-aggregate activity. Based on our previous finding that overexpression of the ER transmembrane protein CLN6 (ceroid-lipofuscinosis, neuronal 6), identified as an interacting protein of the ER-anchored αBC, prevents the R120G αBC variant from aggregating, the CLN6-proCTSD coupling was hypothesized to underpin the functionality of proCTSD within the ER. Indeed, CTSD, when overexpressed in CLN6-depleted cells, was unable to exert its anti-aggregate activity, supporting our view. Collectively, we show here that proCTSD prevents the protein aggregation through the functional association with CLN6 in the microenvironment surrounding the ER membrane, shedding light on a novel aspect of proCTSD and its potential involvement in CTSD-related disorders characterized by the accumulation of aberrant protein aggregates.

Broadening Horizons: Exploring the Cathepsin Family as Therapeutic Targets for Alzheimer's Disease

Alzheimer's disease (AD) is an intricate neurodegenerative disorder characterized by the accumulation of misfolded proteins, including beta-amyloid (Aβ) and tau, leading to cognitive decline. Despite decades of research, the precise mechanisms underlying its onset and progression remain elusive. Cathepsins are a family of lysosomal enzymes that play vital roles in cellular processes, including protein degradation and regulation of immune responses. Emerging evidence suggests that cathepsins may be involved in AD pathogenesis. Cathepsins can influence the activation of microglia and astrocytes, the resident immune cells in the brain. However, cathepsin dysfunction may lead to the accumulation of misfolded proteins, notably Aβ and tau. In addition, dysregulated cathepsin activity may induce an exaggerated immune response, promoting chronic inflammation and neuronal dysfunction in patients with AD. By unraveling the classification, functions, and roles of cathepsins in AD's pathogenesis, this review sheds light on their intricate involvement in this devastating disease. Targeting cathepsin activity could be a promising and novel approach for mitigating the pathological processes that contribute to AD, providing new avenues for its treatment and prevention.

Urinary concentration of Cathepsin D as a relievable marker of preeclampsia

BACKGROUND

The early and accurate diagnosis of preeclampsia is crucial to avoid serious complications for both the mother and baby. However, the current diagnostic methods are limited, and there is a need for new diagnostic biomarkers. Previous studies have shown that cathepsin D (CTD) participates in the pathophysiology of preeclampsia and is present in urine samples, making it a potential biomarker for the disease. This study aimed to compare urinary and serum levels of CTD in preeclamptic and normotensive women and analyze its potential role as a diagnostic biomarker in preeclampsia.

METHODS

The study included thirty-nine patients with preeclampsia and twelve normotensive pregnant women as controls. Biomarkers were determined using Multiplex Assay kit, and serum prolactin (Prl) and urinary TNF-α levels were also evaluated. Statistical analysis was conducted using the Mann-Whitney U test.

RESULTS

We found that urinary and serum CTD levels were significantly higher in the preeclampsia group than in the normotensive group, suggesting that CTD could be a diagnostic biomarker for preeclampsia. No significant differences were found in the levels of serum prolactin or urinary TNF-α between the two groups.

CONCLUSIONS

The study provides evidence that non-invasive biological samples such as urine can be used to improve new therapeutic strategies for the early management of preeclampsia.

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.

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.

Enhancement of Acetate-Induced Apoptosis of Colorectal Cancer Cells by Cathepsin D Inhibition Depends on Oligomycin A-Sensitive Respiration

Colorectal cancer (CRC) is a leading cause of death worldwide. Conventional therapies are available with varying effectiveness. Acetate, a short-chain fatty acid produced by human intestinal bacteria, triggers mitochondria-mediated apoptosis preferentially in CRC but not in normal colonocytes, which has spurred an interest in its use for CRC prevention/therapy. We previously uncovered that acetate-induced mitochondrial-mediated apoptosis in CRC cells is significantly enhanced by the inhibition of the lysosomal protease cathepsin D (CatD), which indicates both mitochondria and the lysosome are involved in the regulation of acetate-induced apoptosis. Herein, we sought to determine whether mitochondrial function affects CatD apoptotic function. We found that enhancement of acetate-induced apoptosis by CatD inhibition depends on oligomycin A-sensitive respiration. Mechanistically, the potentiating effect is associated with an increase in cellular and mitochondrial superoxide anion accumulation and mitochondrial mass. Our results provide novel clues into the regulation of CatD function and the effect of tumor heterogeneity in the outcome of combined treatment using acetate and CatD inhibitors.

Prominent tauopathy and intracellular β-amyloid accumulation triggered by genetic deletion of cathepsin D: implications for Alzheimer disease pathogenesis

BACKGROUND

Cathepsin D (CatD) is a lysosomal protease that degrades both the amyloid-β protein (Aβ) and the microtubule-associated protein, tau, which accumulate pathognomonically in Alzheimer disease (AD), but few studies have examined the role of CatD in the development of Aβ pathology and tauopathy in vivo.

METHODS

CatD knockout (KO) mice were crossed to human amyloid precursor protein (hAPP) transgenic mice, and amyloid burden was quantified by ELISA and immunohistochemistry (IHC). Tauopathy in CatD-KO mice, as initially suggested by Gallyas silver staining, was further characterized by extensive IHC and biochemical analyses. Controls included human tau transgenic mice (JNPL3) and another mouse model of a disease (Krabbe A) characterized by pronounced lysosomal dysfunction. Additional experiments examined the effects of CatD inhibition on tau catabolism in vitro and in cultured neuroblastoma cells with inducible expression of human tau.

RESULTS

Deletion of CatD in hAPP transgenic mice triggers large increases in cerebral Aβ, manifesting as intense, exclusively intracellular aggregates; extracellular Aβ deposition, by contrast, is neither triggered by CatD deletion, nor affected in older, haploinsufficient mice. Unexpectedly, CatD-KO mice were found to develop prominent tauopathy by just ∼ 3 weeks of age, accumulating sarkosyl-insoluble, hyperphosphorylated tau exceeding the pathology present in aged JNPL3 mice. CatD-KO mice exhibit pronounced perinuclear Gallyas silver staining reminiscent of mature neurofibrillary tangles in human AD, together with widespread phospho-tau immunoreactivity. Striking increases in sarkosyl-insoluble phospho-tau (∼ 1250%) are present in CatD-KO mice but notably absent from Krabbe A mice collected at an identical antemortem interval. In vitro and in cultured cells, we show that tau catabolism is slowed by blockade of CatD proteolytic activity, including via competitive inhibition by Aβ42.

CONCLUSIONS

Our findings support a major role for CatD in the proteostasis of both Aβ and tau in vivo. To our knowledge, the CatD-KO mouse line is the only model to develop detectable Aβ accumulation and profound tauopathy in the absence of overexpression of hAPP or human tau with disease-associated mutations. Given that tauopathy emerges from disruption of CatD, which can itself be potently inhibited by Aβ42, our findings suggest that impaired CatD activity may represent a key mechanism linking amyloid accumulation and tauopathy in AD.

A specific and portable gene expression program underlies antigen archiving by lymphatic endothelial cells

Antigens from protein subunit vaccination traffic from the tissue to the draining lymph node, either passively via the lymph or carried by dendritic cells at the local injection site. Lymph node (LN) lymphatic endothelial cells (LEC) actively acquire and archive foreign antigens, and archived antigen can be released during subsequent inflammatory stimulus to improve immune responses. Here, we answer questions about how LECs achieve durable antigen archiving and whether there are transcriptional signatures associated with LECs containing high levels of antigen. We used single cell sequencing in dissociated LN tissue to quantify antigen levels in LEC and dendritic cell populations at multiple timepoints after immunization, and used machine learning to define a unique transcriptional program within archiving LECs that can predict LEC archiving capacity in independent data sets. Finally, we validated this modeling, showing we could predict antigen archiving from a transcriptional dataset of CHIKV infected mice and demonstrated in vivo the accuracy of our prediction. Collectively, our findings establish a unique transcriptional program in LECs that promotes antigen archiving that can be translated to other systems.

Differential Competitive Growth of Transgenic Subclones of Neuroblastoma Cells Expressing Different Levels of Cathepsin D Co-Cultured in 2D and 3D in Response to EGF: Implications in Tumor Heterogeneity and Metastasis

Neuroblastoma (NB) is an embryonal tumor arising from the sympathetic central nervous system. The epidermal growth factor (EGF) plays a role in NB growth and metastatic behavior. Recently, we have demonstrated that cathepsin D (CD) contrasts EGF-induced NB cell growth in 2D by downregulating EGFR/MAPK signaling. Aggressive NB is highly metastatic to the bone and the brain. In the metastatic process, adherent cells detach to form clusters of suspended cells that adhere once they reach the metastatic site and form secondary colonies. Whether CD is involved in the survival of metastatic NB clones is not known. Therefore, in this study, we addressed how CD differentially affects cell growth in suspension versus the adherent condition. To mimic tumor heterogeneity, we co-cultured transgenic clones silenced for or overexpressing CD. We compared the growth kinetics of such mixed clones in 2D and 3D models in response to EGF, and we found that the Over CD clone had an advantage for growth in suspension, while the CD knocked-down clone was favored for the adherent growth in 2D. Interestingly, on switching from 3D to 2D culture conditions, the expression of E-cadherin and of N-cadherin increased in the KD-CD and Over CD clones, respectively. The fact that CD plays a dual role in cancer cell growth in 2D and 3D conditions indicates that during clonal evolution, subclones expressing different level of CD may arise, which confers survival and growth advantages depending on the metastatic step. By searching the TCGA database, we found up to 38 miRNAs capable of downregulating CD. Interestingly, these miRNAs are associated with biological processes controlling cell adhesion and cell migration. The present findings support the view that during NB growth on a substrate or when spreading as floating neurospheres, CD expression is epigenetically modulated to confer survival advantage. Thus, epigenetic targeting of CD could represent an additional strategy to prevent NB metastases.

Synthesis and biological evaluation of selective Pepstatin based trifluoromethylated inhibitors of Cathepsin D

Cathepsin D (CD) is overexpressed in several types of cancer and constitutes an important biological target. Pepstatin A, a pentapeptide incorporating two non-proteinogenic statin residues, is among the most potent inhibitor of CD but lacks selectivity and suffers from poor bioavailability. Eight analogues of Pepstatin A, were synthesized, replacing residues in P3 or P1 position by non-canonical (S)- and (R)-α-Trifluoromethyl Alanine (TfmAla), (S)- and (R)-Trifluoromethionine (TFM) or non-natural d-Valine. The biological activities of those analogues were quantified on isolated CD and Pepsin by fluorescence-based assay (FRET) and cytotoxicity of the best fluorinated inhibitors was evaluated on SKOV3 ovarian cancer cell line. (R)-TFM based analog of Pepstatin A (compound 6) returned a sub-nanomolar IC50 against CD and an increased selectivity. Molecular Docking experiments could partially rationalize these results. Stabilized inhibitor 6 in the catalytic pocket of CD showed strong hydrophobic interactions of the long and flexible TFM side chain with lipophilic residues of S1 and S3 sub-pockets of the catalytic pocket. The newly synthesized inhibitors returned no cytotoxicity at IC50 concentrations on SKOV3 cancer cells, however the compounds derived from (S)-TfmAla and (R)-TFM led to modifications of cells morphologies, associated with altered organization of F-actin and extracellular Fibronectin.

Berberine Alleviates Ischemic Brain Injury by Enhancing Autophagic Flux via Facilitation of TFEB Nuclear Translocation

Berberine has been demonstrated to alleviate cerebral ischemia/reperfusion injury, but its neuroprotective mechanism has yet to be understood. Studies have indicated that ischemic neuronal damage was frequently driven by autophagic/lysosomal dysfunction, which could be restored by boosting transcription factor EB (TFEB) nuclear translocation. Therefore, this study investigated the pharmacological effects of berberine on TFEB-regulated autophagic/lysosomal signaling in neurons after cerebral stroke. A rat model of ischemic stroke and a neuronal ischemia model in HT22 cells were prepared using middle cerebral artery occlusion (MCAO) and oxygen-glucose deprivation (OGD), respectively. Berberine was pre-administered at a dose of 100[Formula: see text]mg/kg/d for three days in rats and 90[Formula: see text][Formula: see text]M in HT22 neurons for 12[Formula: see text]h. 24[Formula: see text]h after MCAO and 2[Formula: see text]h after OGD, the penumbral tissues and OGD neurons were obtained to detect nuclear and cytoplasmic TFEB, and the key proteins in the autophagic/lysosomal pathway were examined using western blot and immunofluorescence, respectively. Meanwhile, neuron survival, infarct volume, and neurological deficits were assessed to evaluate the therapeutic efficacy. The results showed that berberine prominently facilitated TFEB nuclear translocation, as indicated by increased nuclear expression in penumbral neurons as well as in OGD HT22 cells. Consequently, both autophagic activity and lysosomal capacity were simultaneously augmented to alleviate the ischemic injury. However, berberine-conferred neuroprotection could be greatly counteracted by lysosomal inhibitor Bafilomycin A1 (Baf-A1). Meanwhile, autophagy inhibitor 3-Methyladenine (3-MA) also slightly neutralized the pharmacological effect of berberine on ameliorating autophagic/lysosomal dysfunction. Our study suggests that berberine-induced neuroprotection against ischemic stroke is elicited by enhancing autophagic flux via facilitation of TFEB nuclear translocation in neurons.

Interleukin-13: association with inflammation and cysteine proteolysis in varicose transformation of the vascular wall

The present review considers current data on the structure, functions and role of interleukin-13 in the pathogenesis of vascular wall varicose transformation in terms of proteolysis and inflammatory response. It is known that interleukin-13 is able to interact with transforming growth factor-1 in diseases associated with fibrosis. The latter activates fibroblasts and excessive formation of the extracellular matrix, thereby inducing fibrosis of the vascular wall, which is one of the links in the pathogenesis of varicose veins. Also, to date, there is evidence of the interleukin-13 participation in the induction of certain proteolytic enzymes synthesis, such as matrix metalloproteinases. For the latter, participation in the transformation of the venous wall has been proven to date. The remodeling of the venous wall itself can lead to an increase in the expression of proteinases, providing a proteolytic mechanism for changing the structural organization of the venous wall in varicose veins of the lower extremities. At the same time, the involvement of lysosomal cysteine proteinases remains poorly understood. The expression and production of individual cathepsins are regulated by biologically active molecules: interleukin-1, interleukin-6, tumor necrosis factor , which are directly involved in inflammatory reactions in the wall of varicose veins. In particular, venous pathology develops in a vicious circle of inflammation with the formation of abnormal venous blood flow, chronic venous hypertension and dilation, and the recruitment of leukocytes. This leads to a further, deeper, remodeling of the walls and valves of the veins, an increase in blood pressure and the release of pro-inflammatory mediators chemokines and cytokines. In connection with the above, in order to understand the mechanisms of proteolysis in the vascular wall in varicose veins of the lower extremities, it is important to have an idea about the possible interactions of interleukin-13 with transforming growth factor-1, inflammatory cytokines, and cathepsins.

Anti-cathepsin D immunotherapy triggers both innate and adaptive anti-tumour immunity in breast cancer

BACKGROUND AND PURPOSE

Triple-negative breast cancer (TNBC) has poorer outcomes than other breast cancers (BC), including HER2+ BC. Cathepsin D (CathD) is a poor prognosis marker overproduced by BC cells, hypersecreted in the tumour microenvironment with tumour-promoting activity. Here, we characterized the immunomodulatory activity of the anti-CathD antibody F1 and its improved Fab-aglycosylated version (F1M1) in immunocompetent mouse models of TNBC (C57BL/6 mice harbouring E0771 cell grafts) and HER2-amplified BC (BALB/c mice harbouring TUBO cell grafts).

EXPERIMENTAL APPROACH

CathD expression was evaluated by western blotting and immunofluorescence, and antibody binding to CathD by ELISA. Antibody anti-tumour efficacy was investigated in mouse models. Immune cell recruitment and activation were assessed by immunohistochemistry, immunophenotyping, and RT-qPCR.

KEY RESULTS

F1 and F1M1 antibodies remodelled the tumour immune landscape. Both antibodies promoted innate antitumour immunity by preventing the recruitment of immunosuppressive M2-polarized tumour-associated macrophages (TAMs) and by activating natural killer cells in the tumour microenvironment of both models. This translated into a reduction of T-cell exhaustion markers in the tumour microenvironment that could be locally supported by enhanced activation of anti-tumour antigen-presenting cell (M1-polarized TAMs and cDC1 cells) functions. Both antibodies inhibited tumour growth in the highly-immunogenic E0771 model, but only marginally in the immune-excluded TUBO model, indicating that anti-CathD immunotherapy is more relevant for BC with a high immune cell infiltrate, as often observed in TNBC.

CONCLUSION AND IMPLICATION

Anti-CathD antibody-based therapy triggers the anti-tumour innate and adaptive immunity in preclinical models of BC and is a promising immunotherapy for immunogenic TNBC.

Prominent tauopathy and intracellular β-amyloid accumulation triggered by genetic deletion of cathepsin D: Implications for Alzheimer disease pathogenesis

Background

Cathepsin D (CatD) is a lysosomal protease that degrades both the amyloid-β protein (Aβ) and the microtubule-associated protein, tau, which accumulate pathognomonically in Alzheimer disease (AD), but few studies have examined the role of CatD in the development of Aβ pathology and tauopathy in vivo.

Methods

CatD knockout (KO) mice were crossed to human amyloid precursor protein (hAPP) transgenic mice, and amyloid burden was quantified by ELISA and immunohistochemistry (IHC). Tauopathy in CatD-KO mice, as initially suggested by Gallyas silver staining, was further characterized by extensive IHC and biochemical analyses. Controls included human tau transgenic mice (JNPL3) and another mouse model characterized by pronounced lysosomal dysfunction (Krabbe A). Additional experiments examined the effects of CatD inhibition on tau catabolism in vitro and in cultured neuroblastoma cells with inducible expression of human tau.

Results

Deletion of CatD in hAPP transgenic mice triggers large increases in cerebral Aβ, manifesting as intense, exclusively intracellular aggregates; extracellular Aβ deposition, by contrast, is neither triggered by CatD deletion, nor affected in older, haploinsufficient mice. Unexpectedly, CatDKO mice were found to develop prominent tauopathy by just ~ 3 weeks of age, accumulating sarkosyl-insoluble, hyperphosphorylated tau exceeding the pathology in aged JNPL3 mice. CatDKO mice exhibit pronounced perinuclear Gallyas silver staining reminiscent of mature neurofibrillary tangles in human AD, together with widespread phospho-tau immunoreactivity. Striking increases in sarkosyl-insoluble phospho-tau (~ 1250%) are present in CatD-KO mice, but notably absent from Krabbe A mice collected at an identical antemortem interval. In vitro and in cultured cells, we show that tau catabolism is slowed by blockade of CatD proteolytic activity, including via competitive inhibition by Aβ42.

Conclusions

Our findings support a major role for CatD in the proteostasis of both Aβ and tau in vivo. To our knowledge, CatD-KO mice are the only model to develop detectable Aβ acumulation and profound tauopathy in the absence of overexpression of hAPP or human tau with disease-associated mutations. Given that tauopathy emerges from disruption of CatD, which can itself be potently inhibited by Aβ42, our findings suggest that impaired CatD activity may represent a key mechanism linking amyloid accumulation and tauopathy in AD.

Mitochondrial and Proteasome Dysfunction Occurs in the Hearts of Mice Treated with Triazine Herbicide Prometryn

Prometryn is a methylthio-s-triazine herbicide used to control the growth of annual broadleaf and grass weeds in many cultivated plants. Significant traces of prometryn are documented in the environment, mainly in waters, soil, and plants used for human and domestic consumption. Previous studies have shown that triazine herbicides have carcinogenic potential in humans. However, there is limited information about the effects of prometryn on the cardiac system in the literature, or the mechanisms and signaling pathways underlying any potential cytotoxic effects are not known. It is important to understand the possible effects of exogenous compounds such as prometryn on the heart. To determine the mechanisms and signaling pathways affected by prometryn (185 mg/kg every 48 h for seven days), we performed proteomic profiling of male mice heart with quantitative liquid chromatography-tandem mass spectrometry (LC-MS/MS) using ten-plex tandem mass tag (TMT) labeling. The data suggest that several major pathways, including energy metabolism, protein degradation, fatty acid metabolism, calcium signaling, and antioxidant defense system were altered in the hearts of prometryn-treated mice. Proteasome and immunoproteasome activity assays and expression levels showed proteasome dysfunction in the hearts of prometryn-treated mice. The results suggest that prometryn induced changes in mitochondrial function and various signaling pathways within the heart, particularly affecting stress-related responses.

Evolutionary Adaptation of Protein Turnover in White Muscle of Stenothermal Antarctic Fish: Elevated Cold Compensation at Reduced Thermal Responsiveness

Protein turnover is highly energy consuming and overall relates to an organism's growth performance varying largely between species, e.g., due to pre-adaptation to environmental characteristics such as temperature. Here, we determined protein synthesis rates and capacity of protein degradation in white muscle of the cold stenothermal Antarctic eelpout (Pachycara brachycephalum) and its closely related temperate counterpart, the eurythermal common eelpout (Zoarces viviparus). Both species were exposed to acute warming (P. brachycephalum, 0 °C + 2 °C day-1; Z. viviparus, 4 °C + 3 °C day-1). The in vivo protein synthesis rate (Ks) was monitored after injection of 13C-phenylalanine, and protein degradation capacity was quantified by measuring the activity of cathepsin D in vitro. Untargeted metabolic profiling by nuclear magnetic resonance (NMR) spectroscopy was used to identify the metabolic processes involved. Independent of temperature, the protein synthesis rate was higher in P. brachycephalum (Ks = 0.38-0.614 % day-1) than in Z. viviparus (Ks= 0.148-0.379% day-1). Whereas protein synthesis remained unaffected by temperature in the Antarctic species, protein synthesis in Z. viviparus increased to near the thermal optimum (16 °C) and tended to fall at higher temperatures. Most strikingly, capacities for protein degradation were about ten times higher in the Antarctic compared to the temperate species. These differences are mirrored in the metabolic profiles, with significantly higher levels of complex and essential amino acids in the free cytosolic pool of the Antarctic congener. Together, the results clearly indicate a highly cold-compensated protein turnover in the Antarctic eelpout compared to its temperate confamilial. Constant versus variable environments are mirrored in rigid versus plastic functional responses of the protein synthesis machinery.

Myricitrin from bayberry as a potential inhibitor of cathepsin-D: Prospects for squamous lung carcinoma prevention

Cathepsin-D (CATD) inhibitors' design and development drawn interest due to their potential therapeutic applications in managing different cancer types, including lung cancer. This study investigated myricitrin, a flavonol-3-O-rhamnoside, for its binding affinity to CATD. Molecular docking experiments revealed a strong binding affinity (-7.8 kcal/mol). Molecular dynamics (MD) simulation confirmed the complex's stability, while enzyme activity studies showed inhibitory concentration (IC50) of 35.14 ± 6.08 μM (in cell-free) and 16.00 ± 3.48 μM (in cell-based) test systems. Expression analysis indicated downregulation of CATD with a fold change of 1.35. Myricitrin demonstrated antiproliferative effects on NCIH-520 cells [IC50: 64.11 μM in Sulphorhodamine B (SRB), 24.44 μM in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)], but did not affect healthy CHANG cells. It also prolonged the G2/M phase (at 10 μM: 1.19-fold; at 100 μM: 1.13-fold) and increased sub-diploid population by 1.35-fold. Based on the analysis done using SwissADME program, it is predicted that myricitrin is not a cytochrome p450s (CYPs) inhibitor, followed the rule of Ghose and found not permeable to the blood-brain barrier (BBB) which suggests it as a safe molecule. In summary, the experimental findings may establish the foundation for myricitrin and its analogues to be used therapeutically in CATD-mediated lung cancer prevention.

Identification of Fangjihuangqi Decoction as a late-stage autophagy inhibitor with an adjuvant anti-tumor effect against non-small cell lung cancer

BACKGROUND

Clinically, although chemotherapy is one of the most commonly used methods of treating tumors, chemotherapeutic drugs can induce autophagic flux and increase tumor cell resistance, leading to drug tolerance. Therefore, theoretically, inhibiting autophagy may improve the efficacy of chemotherapy. The discovery of autophagy regulators and their potential application as adjuvant anti-cancer drugs is of substantial importance. In this study, we clarified that Fangjihuangqi Decoction (FJHQ, traditional Chinese medicine) is an autophagy inhibitor, which can synergistically enhance the effect of cisplatin and paclitaxel on non-small cell lung cancer (NSCLC) cells.

METHODS

We observed the changes of autophagy level in NSCLC cells under the effect of FJHQ, and verified the level of the autophagy marker protein and cathepsin. Apoptosis was detected after the combination of FJHQ with cisplatin or paclitaxel, and NAC (ROS scavenger) was further used to verify the activation of ROS-MAPK pathway by FJHQ.

RESULTS

We observed that FJHQ induced autophagosomes in NSCLC cells and increased the levels of P62 and LC3-II protein expression in a concentration- and time-gradient-dependent manner, indicating that autophagic flux was inhibited. Co-localization experiments further showed that while FJHQ did not inhibit autophagosome and lysosome fusion, it affected the maturation of cathepsin and thus inhibited the autophagic pathway. Finally, we found that the combination of FJHQ with cisplatin or paclitaxel increased the apoptosis rate of NSCLC cells, due to increased ROS accumulation and further activation of the ROS-MAPK pathway. This synergistic effect could be reversed by NAC.

CONCLUSION

Collectively, these results demonstrate that FJHQ is a novel late-stage autophagy inhibitor that can amplify the anti-tumor effect of cisplatin and paclitaxel against NSCLC cells.

Cathepsins in oral diseases: mechanisms and therapeutic implications

Cathepsins are a type of lysosomal globulin hydrolase and are crucial for many physiological processes, including the resorption of bone matrix, innate immunity, apoptosis, proliferation, metastasis, autophagy, and angiogenesis. Findings regarding their functions in human physiological processes and disorders have drawn extensive attention. In this review, we will focus on the relationship between cathepsins and oral diseases. We highlight the structural and functional properties of cathepsins related to oral diseases, as well as the regulatory mechanisms in tissue and cells and their therapeutic uses. Elucidating the associated mechanism between cathepsins and oral diseases is thought to be a promising strategy for the treatment of oral diseases and may be a starting point for further studies at the molecular level.

A Dual-Function "TRE-Lox" System for Genetic Deletion or Reversible, Titratable, and Near-Complete Downregulation of Cathepsin D

Commonly employed methods for reversibly disrupting gene expression, such as those based on RNAi or CRISPRi, are rarely capable of achieving >80-90% downregulation, making them unsuitable for targeting genes that require more complete disruption to elicit a phenotype. Genetic deletion, on the other hand, while enabling complete disruption of target genes, often produces undesirable irreversible consequences such as cytotoxicity or cell death. Here we describe the design, development, and detailed characterization of a dual-function "TRE-Lox" system for effecting either (a) doxycycline (Dox)-mediated downregulation or (b) genetic deletion of a target gene-the lysosomal aspartyl protease cathepsin D (CatD)-based on targeted insertion of a tetracycline-response element (TRE) and two LoxP sites into the 5' end of the endogenous CatD gene (CTSD). Using an optimized reverse-tetracycline transrepressor (rtTR) variant fused with the Krüppel-associated box (KRAB) domain, we show that CatD expression can be disrupted by as much as 98% in mouse embryonic fibroblasts (MEFs). This system is highly sensitive to Dox (IC₅₀ = 1.46 ng/mL) and results in rapid (t_1/2 = 0.57 d) and titratable downregulation of CatD. Notably, even near-total disruption of CatD expression was completely reversed by withdrawal of Dox. As expected, transient expression of Cre recombinase results in complete deletion of the CTSD gene. The dual functionality of this novel system will facilitate future studies of the involvement of CatD in various diseases, particularly those attributable to partial loss of CatD function. In addition, the TRE-Lox approach should be applicable to the regulation of other target genes requiring more complete disruption than can be achieved by traditional methods.

Identification of a mitochondrial targeting sequence in cathepsin D and its localization in mitochondria

Cathepsin D (CTSD) is a major lysosomal protease harboring an N-terminal signal peptide (amino acids 1-20) to enable vesicular transport from endoplasmic reticulum to lysosomes. Here, we report the possibility of a mitochondrial targeting sequence and mitochondrial localization of CTSD in cells. Live-cell imaging analysis with C-terminal enhanced green fluorescent protein-tagged CTSD (EGFP-CTSD) indicated that CTSD localizes to mitochondria. CTSD amino acids 21-35 are responsible for its mitochondrial localization, which exhibit typical features of mitochondrial targeting sequences, and are evolutionarily conserved. A proteinase K protection assay and sucrose gradient analysis showed that a small population of endogenous CTSD molecules exists in mitochondria. These results suggest that CTSD is a dual-targeted protein that may localize in both lysosomes and mitochondria.

Gouty arthritis involves impairment of autophagic degradation via cathepsin D inactivation-mediated lysosomal dysfunction that promotes apoptosis in macrophages

This study examined autophagy-lysosome pathway (ALP) perturbations in synovial monocytes/macrophages from patients with gouty arthritis (GA) and the associations of ALP perturbations with cell death. Synovial fluid mononuclear cells (SFMCs) and synovial tissues (STs) from patients with GA, as well as monosodium urate (MSU) crystal-exposed macrophages, underwent immunoblotting, quantitative polymerase chain reaction, and immunofluorescence analyses of markers linked to the ALP (microtubule-associated protein 1 light chain 3B [LC3B], p62, cathepsin D [CTSD], and lysosome-associated membrane protein 2 [LAMP2]) and cell death (caspase-3). GA STs underwent immunohistochemistry and immunofluorescence analyses to determine the distributions of LC3B-positive autophagosomes and macrophages. GA SFMCs and STs exhibited impaired autophagic degradation, indicated by elevated levels of LC3B and p62, along with CTSD upregulation and caspase-3 activation. Macrophages from GA STs exhibited significant accumulation of LC3B-positive autophagosomes. The temporal effects of MSU crystals on the ALP and the associations of these effects with cell death were investigated using a macrophage model of GA. MSU crystal-exposed macrophages exhibited early (2 h) autophagosome formation but later (6-24 h) autophagic flux impairment, demonstrated by p62 accumulation, lysosomal inhibitor failure to increase LC3B accumulation, and LC3B colocalization with p62. These macrophages exhibited autophagic flux impairment because of CTSD inactivation-mediated lysosomal dysfunction, which caused immature CTSD to accumulate within damaged LAMP2-positive lysosomes. This accumulation coincided with caspase-3-dependent cell death (24 h) that was unaffected by CTSD inhibition. These findings indicate that GA involves MSU crystal-induced impairment of autophagic degradation via CTSD inactivation-mediated lysosomal dysfunction, which promotes apoptosis in macrophages.

Multiple approaches to repurposing drugs for neuroblastoma

Neuroblastoma (NB) is the second leading extracranial solid tumor of early childhood with about two-thirds of cases presenting before the age of 5, and accounts for roughly 15 percent of all pediatric cancer fatalities in the United States. Treatments against NB are lacking, resulting in a low survival rate in high-risk patients. A repurposing approach using already approved or clinical stage compounds can be used for diseases for which the patient population is small, and the commercial market limited. We have used Bayesian machine learning, in vitro cell assays, and combination analysis to identify molecules with potential use for NB. We demonstrated that pyronaridine (SH-SY5Y IC50 1.70 µM, SK-N-AS IC50 3.45 µM), BAY 11-7082 (SH-SY5Y IC50 0.85 µM, SK-N-AS IC50 1.23 µM), niclosamide (SH-SY5Y IC50 0.87 µM, SK-N-AS IC50 2.33 µM) and fingolimod (SH-SY5Y IC50 4.71 µM, SK-N-AS IC50 6.11 µM) showed cytotoxicity against NB. As several of the molecules are approved drugs in the US or elsewhere, they may be repurposed more readily for NB treatment. Pyronaridine was also tested in combinations in SH-SY5Y cells and demonstrated an antagonistic effect with either etoposide or crizotinib. Whereas when crizotinib and etoposide were combined with each other they had a synergistic effect in these cells. We have also described several analogs of pyronaridine to explore the structure-activity relationship against cell lines. We describe multiple molecules demonstrating cytotoxicity against NB and the further evaluation of these molecules and combinations using other NB cells lines and in vivo models will be important in the future to assess translational potential.

Repositioning Drugs for Rare Diseases Based on Biological Features and Computational Approaches

Rare diseases are a group of uncommon diseases in the world population. To date, about 7000 rare diseases have been documented. However, most of them do not have a known treatment. As a result of the relatively low demand for their treatments caused by their scarce prevalence, the pharmaceutical industry has not sufficiently encouraged the research to develop drugs to treat them. This work aims to analyse potential drug-repositioning strategies for this kind of disease. Drug repositioning seeks to find new uses for existing drugs. In this context, it seeks to discover if rare diseases could be treated with medicines previously indicated to heal other diseases. Our approaches tackle the problem by employing computational methods that calculate similarities between rare and non-rare diseases, considering biological features such as genes, proteins, and symptoms. Drug candidates for repositioning will be checked against clinical trials found in the scientific literature. In this study, 13 different rare diseases have been selected for which potential drugs could be repositioned. By verifying these drugs in the scientific literature, successful cases were found for 75% of the rare diseases studied. The genetic associations and phenotypical features of the rare diseases were examined. In addition, the verified drugs were classified according to the anatomical therapeutic chemical (ATC) code to highlight the types with a higher predisposition to be repositioned. These promising results open the door for further research in this field of study.

FRET-based cathepsin probes for simultaneous detection of cathepsin B and D activities

Fluorescent cathepsin probes were prepared by modification of peptidic substrates for cathepsin B (CTSB) and cathepsin D (CTSD) with FRET pairs. Fluorophores with distinguishable emission characteristics were applied to CTSB and CTSD probes with their appropriate quenchers to simultaneously monitor the activity of CTSB and/or CTSD. Conjugation of both the CTSB and CTSD probes with short single-stranded DNA drastically increased their reactivity to cathepsins over the parent probes possibly by improving their solubility. The activity of CTSB and CTSD were simultaneously detected by using these orthogonal FRET-based cathepsin probes.

New Advances in the Understanding of Proteases as Diagnostic and Pharmaceutical Targets in Homeostatic and Pathologic Conditions

Protease biology represents a hot topic in biomedical research because of their pivotal role in regulating cell and tissue homeostasis, regeneration and pathogenesis [...]

Lysosomal peptidases – Intriguing roles in cancer progression and neurodegeneration

Lysosomal peptidases are hydrolytic enzymes capable of digesting waste proteins that are targeted to lysosomes via endocytosis and autophagy. Besides intracellular protein catabolism, they play more specific roles in several other cellular processes and pathologies, either within lysosomes, upon secretion into the cell cytoplasm or extracellular space, or bound to the plasma membrane. In cancer, lysosomal peptidases are generally associated with disease progression, as they participate in crucial processes leading to changes in cell morphology, signaling, migration, and invasion, and finally metastasis. However, they can also enhance the mechanisms resulting in cancer regression, such as apoptosis of tumor cells or antitumor immune responses. Lysosomal peptidases have also been identified as hallmarks of aging and neurodegeneration, playing roles in oxidative stress, mitochondrial dysfunction, abnormal intercellular communication, dysregulated trafficking, and the deposition of protein aggregates in neuronal cells. Furthermore, deficiencies in lysosomal peptidases may result in other pathological states, such as lysosomal storage disease. The aim of this review was to highlight the role of lysosomal peptidases in particular pathological processes of cancer and neurodegeneration and to address the potential of lysosomal peptidases in diagnosing and treating patients.

Intravitreal gene therapy restores the autophagy-lysosomal pathway and attenuates retinal degeneration in cathepsin D-deficient mice

Loss of vision due to progressive retinal degeneration is a hallmark of neuronal ceroid lipofuscinoses (NCL), a group of fatal neurodegenerative lysosomal storage diseases. Enzyme substitution therapies represent promising treatment options for NCLs caused by dysfunctions of soluble lysosomal enzymes. Here, we compared the efficacy of a cell-based enzyme substitution strategy and a gene therapy approach to attenuate the retinal pathology in cathepsin D- (CTSD) deficient mice, an animal model of CLN10 disease. Levels of enzymatically active CTSD in mutant retinas were significantly higher after an adeno-associated virus vector-mediated CTSD transfer to retinal glial cells and retinal pigment epithelial cells than after intravitreal transplantations of a CTSD overexpressing clonal neural stem cell line. In line with this finding, the gene therapy treatment restored the disrupted autophagy-lysosomal pathway more effectively than the cell-based approach, as indicated by a complete clearance of storage, significant attenuation of lysosomal hypertrophy, and normalized levels of the autophagy marker sequestosome 1/p62 and microtubule-associated protein 1 light chain 3-II. While the cell-based treatment did not prevent the rapidly progressing loss of various retinal cell types, the gene therapy approach markedly attenuated retinal degeneration as demonstrated by a pronounced rescue of photoreceptor cells and rod bipolar cells.

Ergothioneine exhibits longevity-extension effect in Drosophila melanogaster via regulation of cholinergic neurotransmission, tyrosine metabolism, and fatty acid oxidation

Many studies have demonstrated the protective effect of ergothioneine (EGT), the unique sulfur-containing antioxidant found in mushrooms, on several aging-related diseases. Nevertheless, to date, no single study has explored the potential role of EGT in the lifespan of animal models. We show here that EGT consistently extends fly lifespan in diverse genetic backgrounds and both sexes, as well as in a dose and gender-dependent manner. Additionally, EGT is shown to increases the climbing activity of flies, enhance acetylcholinesterase (AchE) activity, and maintain the ratio of reduced glutathione (GSH) to oxidized glutathione (GSSG)of aged flies. The increase in lifespan by EGT is gut microorganism dependent. We proposed potential mechanisms of lifespan extension in Drosophila by EGT through RNA-seq analysis: preservation of the normal status of the central nervous system via the coordination of cholinergic neurotransmission, tyrosine metabolism, and peroxisomal proteins, regulation of autophagic activity by altering the lysosomal protein CTSD, and the preservation of normal mitochondrial function through controlled substrate feeding into the tricarboxylic acid (TCA) cycle, the major energy-yielding metabolic process in cells.