Evolution of C, D and S-type cystatins in mammals: an extensive gene duplication in primates

Identification and functional characterization of a novel cystatin in amphioxus, ancient origin of vertebrate type-2 cystatin homologues

Cystatins are well known as a vast superfamily of functional proteins participated in the reversible competitive inhibition of cysteine proteases. Currently, increasing evidences point to the extensive phylogenetic diversity and crucial immune roles of type-2 cystatins in the vertebrate species. However, no information is available regarding the homologue in cephalochordate amphioxus, the representative of most basal living chordates, whose immune regulation are still ambiguous. Here, we clearly identified the presence of type-2 cystatin gene in amphioxus Branchiostoma japonicum, termed Bjcystatin-2, which was structurally characterized by typical wedge-shaped cystatin feature. Evolutionary analyses revealed that Bjcystatin-2 is the putative ancestral type-2 cystatin for chordates, with gene diversity emerging through duplication events. The expression of Bjcystatin-2 showed tissue-specific profile and was inducible upon invasive pathogens. Significantly, the recombinant Bjcystatin-2 exhibited not merely cathepsin L inhibitory activity, but also the ability to bind with bacteria and their characteristic molecules. Furthermore, Bjcystatin-2 also showed the capacity to enhance the macrophage-driven bacterial phagocytosis and to attenuate the generation of pro-inflammatory cytokines within macrophages. In summary, these findings demonstrate that Bjcystatin-2 exhibits dual role acting as both a protease inhibitor and an immunoactive molecule, greatly enriching our understanding of immune defense mechanisms of type-2 cystatin within the amphioxus.

Combination of serum CST1 and HE4 for early diagnosis of endometrial cancer

Purpose

Optimal serological biomarkers have been absent for the early diagnosis of endometrial cancer, to date. In this study, we aimed to define the diagnostic performances of individual and combined detection of serum cysteine protease inhibitor 1 (CST1) with traditional tumor markers, including glycated antigen 125 (CA125) and human epididymis protein 4 (HE4), in patients with early-stage endometrial cancer (EC).

Methods

The performances of individual and combined detection of serum CST1, HE4, and CA125 were evaluated by enzyme-linked immunosorbent assay (ELISA) and chemiluminescent immunoassay, respectively. A training data set of 67 patients with early EC, 67 patients with endometrial benign lesion (EBL), and 67 healthy controls (HC) was used to develop a predictive model for early EC diagnosis, which was validated by an independent validation data set.

Results

In the training data set, serum CST1 and HE4 levels in the early EC group were significantly higher than in EBL/HC groups (P < 0.05), while there was no significant difference of serum CA125 level between the early EC and EBL/HC groups (P > 0.05). Serum CST1 and HE4 exhibited areas under the curve (AUC) of 0.715 with 31.3% sensitivity at 90.3% specificity, and 0.706 with 23.9% sensitivity at 95.5% specificity, respectively. Combined detection of serum CST1 and HE4 exhibited an AUC of 0.788 with 49.3% sensitivity at 92.5% specificity. The combination of serum CST1 and HE4 showed promise in diagnosis.

Conclusion

CST1 is a prospective serological biomarker for early EC diagnosis, and the combination of CST1 and HE4 contributes to the further improvement in the diagnosis of patients with early-stage EC.

Type 2 Cystatins and Their Roles in the Regulation of Human Immune Response and Cancer Progression

Cystatins are a family of intracellular and extracellular protease inhibitors that inhibit cysteine cathepsins-a group of lysosomal cysteine proteases that participate in multiple biological processes, including protein degradation and post-translational cleavage. Cysteine cathepsins are associated with the development of autoimmune diseases, tumor progression, and metastasis. Cystatins are categorized into three subfamilies: type 1, type 2, and type 3. The type 2 cystatin subfamily is the largest, containing 10 members, and consists entirely of small secreted proteins. Although type 2 cystatins have many shared biological roles, each member differs in structure, post-translational modifications (e.g., glycosylation), and expression in different cell types. These distinctions allow the type 2 cystatins to have unique biological functions and properties. This review provides an overview of type 2 cystatins, including their biological similarities and differences, their regulatory effect on human immune responses, and their roles in tumor progression, immune evasion, and metastasis.

Cystatin SN in type 2 inflammatory airway diseases

Cystatin SN, encoded by CST1, belongs to the type 2 (T2) cystatin protein superfamily. In the past decade, several publications have highlighted the association between cystatin SN and inflammatory airway diseases including chronic rhinosinusitis, rhinitis, asthma, chronic obstructive pulmonary disease, and chronic hypersensitivity pneumonitis. It is, therefore, crucial to understand the role of cystatin SN in the wider context of T2 inflammatory diseases. Here, we review the expression of cystatin SN in airway-related diseases with different endotypes. We also emphasize the physiological and pathological roles of cystatin SN. Physiologically, cystatin SN protects host tissues from destructive proteolysis by cysteine proteases present in the external environment or produced via internal dysregulated expression. Pathologically, the secretion of cystatin SN from airway epithelial cells initiates and amplifies T2 immunity and subsequently leads to disease. We further discuss the development of cystatin SN as a T2 immunity marker that can be monitored noninvasively and assist in airway disease management. The discovery, biology, and inhibition capability are also introduced to better understand the role of cystatin SN in airway diseases.

Human endoderm stem cells reverse inflammation-related acute liver failure through cystatin SN-mediated inhibition of interferon signaling

Acute liver failure (ALF) is a life-threatening disease that occurs secondary to drug toxicity, infection or a devastating immune response. Orthotopic liver transplantation is an effective treatment but limited by the shortage of donor organs, the requirement for life-long immune suppression and surgical challenges. Stem cell transplantation is a promising alternative therapy for fulminant liver failure owing to the immunomodulatory abilities of stem cells. Here, we report that when transplanted into the liver, human endoderm stem cells (hEnSCs) that are germ layer-specific and nontumorigenic cells derived from pluripotent stem cells are able to effectively ameliorate hepatic injury in multiple rodent and swine drug-induced ALF models. We demonstrate that hEnSCs tune the local immune microenvironment by skewing macrophages/Kupffer cells towards an anti-inflammatory state and by reducing the infiltrating monocytes/macrophages and inflammatory T helper cells. Single-cell transcriptomic analyses of infiltrating and resident monocytes/macrophages isolated from animal livers revealed dramatic changes, including changes in gene expression that correlated with the change of activation states, and dynamic population heterogeneity among these cells after hEnSC transplantation. We further demonstrate that hEnSCs modulate the activation state of macrophages/Kupffer cells via cystatin SN (CST1)-mediated inhibition of interferon signaling and therefore highlight CST1 as a candidate therapeutic agent for diseases that involve over-activation of interferons. We propose that hEnSC transplantation represents a novel and powerful cell therapeutic treatment for ALF.

Review: Unraveling the origin of the structural and functional diversity of plant cystatins

The regulation of protease activity is a critical factor for the physiological balance during plant growth and development. Among the proteins involved in controlling protease activity are the cystatins, well-described inhibitors of cysteine proteases present in viruses, bacteria and most Eukaryotes. Plant cystatins, commonly called phytocystatins, display unique structural and functional diversity and are classified according to their molecular weight as type-I, -II, and -III. Their gene structure is highly conserved across Viridiplantae and provides insights into their evolutionary relationships. Many type-I phytocystatins with introns share sequence similarities with type-II phytocystatins. New data shows that they could have originated from recent losses of the carboxy-terminal extension present in type-II phytocystatins. Intronless type-I phytocystatins originated from a single event shared by flowering plants. Pieces of evidence show multiple events of gene duplications, intron losses, and gains throughout the expansion and diversity of the phytocystatin family. Gene duplication events in Gymnosperms and Eudicots resulted in inhibitors with amino acid substitutions that may modify their interaction with target proteases and other proteins. This review brings a phylogenomic analysis of plant cystatin evolution and contributes to a broader understanding of their origins. A complete functional genomic analysis among phytocystatins and their roles in plant development and responses to abiotic and biotic stresses remains a question to be fully solved.

Evolution of Fc Receptor-Like Scavenger in Mammals

Fc receptor-like (FCRL) molecules comprise a large family of receptors, homologous to the receptors for the Fc portion of immunoglobulins (FCR). Within this family, an unusual gene known to exist in mice, rats and dogs, termed FCRLS, encodes a chimeric protein with both Ig-like FCRL and type B scavenger-receptor cysteine-rich (SRCR)-like domains. In mice, FCRLS is located next to the CD5L and KIRREL1 genes. Here, we show that the curious FCRLS gene is actually present across major mammalian groups, but its annotation is generally incorrect or absent. Anchored on mouse FCRLS and FCRL2 genomic sequence alignments, phylogenetic analyses demonstrated that many mammalian sequences currently annotated as FCRL2 cluster with FCRLS, supported by a conserved genetic synteny among organisms. This analysis shows that FCRLS is present in Rodentia, some Carnivora (Canidae and Ursidae), Chiroptera, Arctiodactyla, Proboscidae, and some Primata. Thus, the FCRLS most likely originated in a eutherian mammal ancestor since it is not present in Monotremata or Marsupialia. FCRLS has a peculiar distribution pattern across mammalian lineages, being present in some species, but absent in others from the same family, as in carnivores for example. The most parsimonious hypothesis to explain this FCRLS evolution is that it was convergently lost in several independent mammalian lineages. Analyses of branch-specific nucleotide evolutionary rates, show that FCRL2 and FCRLS have similar ranges of rates across mammals, suggesting that both genes have crucial, but separate functions in the immune system. Bayesian estimates of evolutionary rates for FCRLS in mammalian lineages revealed that carnivores display the highest mutation rate after rodents. Additionally, positive diversifying selection was detected for both FCRL2 and FCRLS. Our results show that the presence of the FCRLS gene is older and more widespread across mammals than previously thought and appears to be functional, being under positive selection. Its precise physiologic role should thus be investigated.

Natural cystatin C fragments inhibit GPR15-mediated HIV and SIV infection without interfering with GPR15L signaling

GPR15 is a G protein-coupled receptor (GPCR) proposed to play a role in mucosal immunity that also serves as a major entry cofactor for HIV-2 and simian immunodeficiency virus (SIV). To discover novel endogenous GPR15 ligands, we screened a hemofiltrate (HF)-derived peptide library for inhibitors of GPR15-mediated SIV infection. Our approach identified a C-terminal fragment of cystatin C (CysC95-146) that specifically inhibits GPR15-dependent HIV-1, HIV-2, and SIV infection. In contrast, GPR15L, the chemokine ligand of GPR15, failed to inhibit virus infection. We found that cystatin C fragments preventing GPR15-mediated viral entry do not interfere with GPR15L signaling and are generated by proteases activated at sites of inflammation. The antiretroviral activity of CysC95-146 was confirmed in primary CD4+ T cells and is conserved in simian hosts of SIV infection. Thus, we identified a potent endogenous inhibitor of GPR15-mediated HIV and SIV infection that does not interfere with the physiological function of this GPCR.

Salivary cystatin SN is a factor predicting iron bioavailability after phytic acid rich meals in female participants

Phytic acid is an inhibitor of iron bioavailability, but it has been suggested that individuals may adapt to phytic acid over time, and that the salivary protein, cystatin SN, may be involved. This study evaluated the relationship between human cystatin SN levels and iron bioavailability after a phytic acid rich meal. Three groups of ten women consumed meals with: (1) 500 mg phytate sprinkles, (2) 500 mg phytate capsules, or (3) no phytic acid. Iron bioavailability was measured by the mealtime percentage of maximum iron recovery; cystatin SN was measured pre-and post-meal by enzyme-linked immunosorbent assay. Pre-to-post meal cystatin SN was positively correlated with improved iron bioavailability in group 1. Pre-to-post meal cystatin SN was correlated with improved iron absorption in groups 1 and 2. Cystatin SN recovery after phytic acid rich meals may be a physiological factor predicting iron bioavailability.

Salivary proteomic profile of dogs with and without dental calculus

BACKGROUND

Dogs' saliva is a complex mixture of inorganic and organic constituents, rich in proteins. Therefore, knowing the saliva composition of these animals is extremely important to identify the presence of proteins that may be involved in physiological and pathological mechanisms of their oral cavity. The present study aimed to characterize the proteomic profile of saliva from dogs with and without dental calculus.

RESULTS

Saliva samples were collected from 20 dogs. Before the collection, a visual clinical examination was performed and 8 subjects (40%) did not present any signs of dental calculus, while 12 (60%) presented dental calculus. After saliva collection, the samples were submitted to protein quantification (mBCA), and then they were prepared for analysis by nLC-ESI-MS/MS. A total of 658 unique proteins were identified, of which 225 were specific to dogs without dental calculus, 300 were specific to dogs with dental calculus, and 133 were common to all subjects. These proteins presented functions including transportation, immune response, structural, enzymatic regulation, signal transduction, transcription, metabolism, and some proteins perform functions as yet unknown. Several salivary proteins in dogs with dental calculus differed from those found in the group without dental calculus. Among the abundant proteins detected in periodontal affected cases, can be highlighting calcium-sensing receptor and transforming growth factor beta. Enrichment analysis reveled the presence of Rho GTPases signaling pathway.

CONCLUSIONS

This research identified salivary proteins, that should be further investigated as potencial biomarkers of chronic periodontits with dental calculus formation in dogs.

Cystatin SN Affects Cell Proliferation by Regulating the ERα/PI3K/AKT/ERα Loopback Pathway in Breast Cancer

Background

Cystatin SN (CST1) has been reported to act as an oncogene in cancers, but its underlying mechanism remains unclear.

Methods

We performed Western blotting analyses to observe protein expression and conducted transwell invasion, wound healing, and colony formation assays to assess cell invasion, migration, and proliferation, respectively. We also performed cell cycle analyses by flow cytometry to determine the role of CST1 in the cell cycle. In vivo experiments used subcutaneous tumor models in BALB/c-nu athymic female mice to evaluate the effect of CST1 on tumor growth.

Results

Western blotting analyses showed that CST1 was upregulated in ER+ breast cancer cells such as MCF7, T47D, and BT474. CST1 knockdown led to slower cell growth and inhibited the G1 to S phase transition in ER+ breast cancer cells. In vivo experiments showed that CST1 deletion inhibited tumor growth, and led to decreased expression of estrogen receptor α (ERα) and p-AKT. In vitro experiments showed that the over-expression of CST1 led to the upregulation of ERα, and inhibition of CST1 inhibited the expression of ERα. Western blotting analyses showed that CST1 regulated the activity of the PI3K/AKT signaling pathway in breast cancer cells. We confirmed that CST1 acted as an oncogene in ER+ breast cancer by regulating the ERα/PI3K/AKT/ERα loopback pathway.

Conclusion

CST1 acts as an oncogene in ER+ breast cancer, and CST1 contributes to cancer development by regulating the ERα/PI3K/AKT/ERα loopback pathway in ER+ breast cancer. Our findings indicate that CST1 could be a significant therapeutic target for ER+ breast cancer patients. Our discovery should inspire further studies on the role of CST1 in cancers.

Up-regulated CST5 inhibits bone resorption and activation of osteoclasts in rat models of osteoporosis via suppression of the NF-κB pathway

Here, we aim at exploring the effect of CST5 on bone resorption and activation of osteoclasts in osteoporosis (OP) rats through the NF‐κB pathway. Microarray analysis was used to screen the OP‐related differentially expressed genes. Osteoporosis was induced in rats by intragastric retinoic acid administration. The serum levels of tartrate‐resistant acid phosphatase (TRAP), bone alkaline phosphatase (BALP) and osteocalcin (OC) and the expression of CD61 on the surface of osteoclasts were examined. The number of osteoclasts and the number and area of resorption pits were detected. Besides, the pathological changes and bone mineral density in bone tissues of rats were assessed. Also, the relationship between CST5 and the NF‐κB pathway was identified through determining the expression of CST5, RANKL, RANK, OPG, p65 and IKB. Poorly expressed CST5 was indicated to affect the OP. CST5 elevation and inhibition of the NF‐κB pathway decreased serum levels of TRAP, BALP and OC and expression of CD61 in vivo and in vitro. In OP rats, CST5 overexpression increased trabecular bones and bone mineral density of bone tissues, but decreased trabecular separation, fat within the bone marrow cavities and the number of osteoclasts through inhibiting the NF‐κB pathway. In vivo experiments showed that CST5 elevation inhibited growth in number and area of osteoclastic resorption pits and restrained osteoclastic bone absorption by inhibiting the NF‐κB pathway. In summary, overexpression of CST5 suppresses the activation and bone resorption of osteoclasts by inhibiting the activation of the NF‐κB pathway.

Research progress of cystatin SN in cancer

Cystatin SN, belonging to the type 2 cystatin superfamily, is widely expressed and distributed in mammals. Cystatin SN is involved in inflammation, cell cycle, cellular senescence, tumorigenesis, and metastasis. Cystatin SN is also known to participate in signaling pathways like Wnt signaling pathway, GSK3 signaling pathway, AKT signaling pathway, and IL-6 signaling pathway. Cystatin SN was found to be highly expressed in peritumoral normal tissues in esophageal squamous cell carcinoma (ESCC); however, low cystatin SN expression was found in ESCC cancer tissues. Conversely, in other cancer types such as lung cancer, breast cancer, gastric cancer, pancreatic cancer, and colorectal cancer, high cystatin SN expression in cancer tissues but low cystatin SN expression in peritumoral normal tissues was found. Survival analyses showed that high cystatin SN expression benefited ESCC patients but did harm to other types of cancer patients. Univariate and multivariate analyses indicated that cystatin SN possibly acts as a marker for cancer prognosis. Here, we provide a brief introduction about the role of cystatin SN in cancer and discuss the different prognostic effects of cystatin SN on different tumors. Cystatin SN might be a potential marker for cancer prognosis and a target for cancer therapy.

Human cystatin SN is an endogenous protease inhibitor that prevents allergic rhinitis

BACKGROUND

Protease allergens disrupt epithelial barriers to exert their allergenicity. Cystatin SN (encoded by CST1) is an endogenous cysteine protease inhibitor upregulated in nasal epithelia in patients with allergic rhinitis (AR).

OBJECTIVE

We sought to investigate the protective effect of human cystatin SN on AR symptoms using pollen-induced AR mouse models.

METHODS

We performed an in vitro protease activity assay to evaluate the effect of recombinant human cystatin SN (rhCystatin SN) on Japanese cedar (JC) or ragweed proteases. A human nasal epithelial cell line, RPMI 2650, was used to examine tight junction (TJ) disruption in vitro. Mice were sensitized and nasally challenged with JC or ragweed pollens with or without rhCystatin SN to examine the effect of rhCystatin SN on AR symptoms and the epithelial barrier in vivo. Because mice lack CST1, we generated transgenic (Tg) mice expressing human CST1 under control of its genomic control region (hCST1-Tg mice) to examine the role of cystatin SN in physiologically expressed conditions.

RESULTS

rhCystatin SN inhibited JC but not ragweed protease activities and prevented JC-induced but not ragweed-induced TJ disruption in vitro. Exogenous administration of rhCystatin SN ameliorated JC-induced but not ragweed-induced sneezing and nasal TJ disruption in vivo. Furthermore, hCST1-Tg mice showed decreased JC-induced but not ragweed-induced sneezing symptoms and nasal TJ disruption compared with wild-type mice.

CONCLUSION

Human cystatin SN suppresses AR symptoms through inhibiting allergen protease activities and protecting the nasal TJ barrier in an allergen-specific manner. We propose that upregulation of nasal endogenous protease inhibitors, including cystatin SN, is a novel therapeutic strategy for protease allergen-induced AR.

Putative salivary protein biomarkers for the diagnosis of oral lichen planus: a case-control study

BACKGROUND

Salivary protein biomarkers for screening and diagnosis of oral lichen planus (OLP) are not well-defined. The objective of this study was to identify putative protein biomarkers for OLP using proteomic approaches.

METHODS

Pooled unstimulated whole saliva was collected from five OLP patients and five healthy control participants. Saliva samples were then subjected to two-dimensional gel electrophoresis, followed by mass spectrometry to identify putative protein biomarkers. Subsequently, a subset of these putative biomarkers were validated in 24 OLP patients and 24 age-matched healthy control subjects, using an enzyme-linked immunosorbent assay (ELISA). Immunoblotting analyses were then performed in 3 pairs of age- and sex-matched OLP patients and healthy controls to confirm results from the ELISA study.

RESULTS

Thirty-one protein spots were identified, corresponding to 20 unique proteins. Notably, fibrinogen fragment D and complement component C3c exhibited increased expression in OLP patients, while cystatin SA exhibited decreased expression in OLP patients, compared with healthy control subjects. ELISA analyses indicated increased expression of fibrinogen fragment D and complement component C3c, and decreased expression of cystatin SA, in the saliva of OLP patients. Statistical differences in the expression of salivary complement C3c were observed between OLP patients and healthy control subjects. Immunoblotting analyses confirmed the results of our ELISA study.

CONCLUSION

Complement C3c, fibrinogen fragment D and cystatin SA may serve as salivary biomarkers for screening and/or diagnosis of OLP.

Salivary proteomics of healthy dogs: An in depth catalog

Objective

To provide an in-depth catalog of the salivary proteome and endogenous peptidome of healthy dogs, evaluate proteins and peptides with antimicrobial properties, and compare the most common salivary proteins and peptides between different breed phylogeny groups.

Methods

36 healthy dogs without evidence of periodontal disease representing four breed phylogeny groups, based upon single nucleotide polymorphism haplotypes (ancient, herding/sighthound, and two miscellaneous groups). Saliva collected from dogs was pooled by phylogeny group and analyzed using nanoscale liquid chromatography-tandem mass spectrometry. Resulting tandem mass spectra were compared to databases for identification of endogenous peptides and inferred proteins.

Results

2,491 proteins and endogenous peptides were found in the saliva of healthy dogs with no periodontal disease. All dog phylogeny groups’ saliva was rich in proteins and peptides with antimicrobial functions. The ancient breeds group was distinct in that it contained unique proteins and was missing many proteins and peptides present in the other groups.

Conclusions and clinical relevance

Using a sophisticated nanoscale liquid chromatography-tandem mass spectrometry, we were able to identify 10-fold more salivary proteins than previously reported in dogs. Seven of the top 10 most abundant proteins or peptides serve immune functions and many more with various antimicrobial mechanisms were found. This is the most comprehensive analysis of healthy canine saliva to date, and will provide the groundwork for future studies analyzing salivary proteins and endogenous peptides in disease states.

Salivary protein changes in response to acute stress in medical residents performing advanced clinical simulations: a pilot proteomics study

CONTEXT

Quantitative changes of salivary proteins due to acute stress were detected.

OBJECTIVE

To explore protein markers of stress in saliva of eight medical residents who performed emergency medicine simulations.

MATERIALS AND METHODS

Saliva was collected before the simulations, after the simulations, and following morning upon waking. Proteins were separated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), identified by mass spectrometry (MS), and relatively quantified by densitometry.

RESULTS

Salivary alpha-amylase and S-type cystatins significantly increased, while the ∼26 kDa and low-molecular weight (MW) (<10 kDa) SDS-PAGE bands exhibited changes after stress.

DISCUSSION AND CONCLUSION

Alpha-amylase and cystatins are potential salivary markers of acute stress, but further validation should be performed using larger sample populations.

Cross-species comparison of mammalian saliva using an LC-MALDI based proteomic approach

Despite the importance of saliva in the regulation of oral cavity homeostasis, few studies have been conducted to quantitatively compare the saliva of different mammal species. Aiming to define a proteome signature of mammals' saliva, an in-depth SDS-PAGE-LC coupled to MS/MS (GeLC-MS/MS) approach was used to characterize the saliva from primates (human), carnivores (dog), glires (rat and rabbit), and ungulates (sheep, cattle, horse). Despite the high variability in the number of distinct proteins identified per species, most protein families were shared by the mammals studied with the exception of cattle and horse. Alpha-amylase is an example that seems to reflect the natural selection related to digestion efficacy and food recognition. Casein protein family was identified in all species but human, suggesting an alternative to statherin in the protection of hard tissues. Overall, data suggest that different proteins might assure a similar role in the regulation of oral cavity homeostasis, potentially explaining the specific mammals' salivary proteome signature. Moreover, some protein families were identified for the first time in the saliva of some species, the presence of proline-rich proteins in rabbit's saliva being a good example.