Cystine-knot peptide inhibitors of HTRA1 bind to a cryptic pocket within the active site region

Cystine-knot peptides (CKPs) are naturally occurring peptides that exhibit exceptional chemical and proteolytic stability. We leveraged the CKP carboxypeptidase A1 inhibitor as a scaffold to construct phage-displayed CKP libraries and subsequently screened these collections against HTRA1, a trimeric serine protease implicated in age-related macular degeneration and osteoarthritis. The initial hits were optimized by using affinity maturation strategies to yield highly selective and potent picomolar inhibitors of HTRA1. Crystal structures, coupled with biochemical studies, reveal that the CKPs do not interact in a substrate-like manner but bind to a cryptic pocket at the S1' site region of HTRA1 and abolish catalysis by stabilizing a non-competent active site conformation. The opening and closing of this cryptic pocket is controlled by the gatekeeper residue V221, and its movement is facilitated by the absence of a constraining disulfide bond that is typically present in trypsin fold serine proteases, thereby explaining the remarkable selectivity of the CKPs. Our findings reveal an intriguing mechanism for modulating the activity of HTRA1, and highlight the utility of CKP-based phage display platforms in uncovering potent and selective inhibitors against challenging therapeutic targets.

Pathophysiology of cerebral small vessel disease: a journey through recent discoveries

Cerebral small vessel disease (cSVD) encompasses a heterogeneous group of age-related small vessel pathologies that affect multiple regions. Disease manifestations range from lesions incidentally detected on neuroimaging (white matter hyperintensities, small deep infarcts, microbleeds, or enlarged perivascular spaces) to severe disability and cognitive impairment. cSVD accounts for approximately 25% of ischemic strokes and the vast majority of spontaneous intracerebral hemorrhage and is also the most important vascular contributor to dementia. Despite its high prevalence and potentially long therapeutic window, there are still no mechanism-based treatments. Here, we provide an overview of the recent advances in this field. We summarize recent data highlighting the remarkable continuum between monogenic and multifactorial cSVDs involving NOTCH3, HTRA1, and COL4A1/A2 genes. Taking a vessel-centric view, we discuss possible cause-and-effect relationships between risk factors, structural and functional vessel changes, and disease manifestations, underscoring some major knowledge gaps. Although endothelial dysfunction is rightly considered a central feature of cSVD, the contributions of smooth muscle cells, pericytes, and other perivascular cells warrant continued investigation.

Inhibition of the serine protease HtrA1 by SerpinE2 suggests an extracellular proteolytic pathway in the control of neural crest migration

We previously showed that SerpinE2 and the serine protease HtrA1 modulate fibroblast growth factor (FGF) signaling in germ layer specification and head-to-tail development of Xenopus embryos. Here, we present an extracellular proteolytic mechanism involving this serpin-protease system in the developing neural crest (NC). Knockdown of SerpinE2 by injected antisense morpholino oligonucleotides did not affect the specification of NC progenitors but instead inhibited the migration of NC cells, causing defects in dorsal fin, melanocyte, and craniofacial cartilage formation. Similarly, overexpression of the HtrA1 protease impaired NC cell migration and the formation of NC-derived structures. The phenotype of SerpinE2 knockdown was overcome by concomitant downregulation of HtrA1, indicating that SerpinE2 stimulates NC migration by inhibiting endogenous HtrA1 activity. SerpinE2 binds to HtrA1, and the HtrA1 protease triggers degradation of the cell surface proteoglycan Syndecan-4 (Sdc4). Microinjection of Sdc4 mRNA partially rescued NC migration defects induced by both HtrA1 upregulation and SerpinE2 downregulation. These epistatic experiments suggest a proteolytic pathway by a double inhibition mechanism.

SerpinE2 ┤HtrA1 protease ┤Syndecan-4 → NC cell migration.

Levels of the HtrA1 Protein in Serum and Vitreous Humor Are Independent of Genetic Risk for Age-Related Macular Degeneration at the 10q26 Locus

Purpose

The purpose of this study was to determine if levels of the HtrA1 protein in serum or vitreous humor are influenced by genetic risk for age-related macular degeneration (AMD) at the 10q26 locus, age, sex, AMD status, and/or AMD disease severity, and, therefore, to determine the contribution of systemic and ocular HtrA1 to the AMD disease process.

Methods

A custom-made sandwich ELISA assay (SCTM ELISA) for detection of the HtrA1 protein was designed and compared with three commercial assays (R&D Systems, MyBiosource 1 and MyBiosource 2) using 65 serum samples. Concentrations of HtrA1 were thereafter determined in serum and vitreous samples collected from 248 individuals and 145 human donor eyes, respectively.

Results

The SCTM ELISA demonstrated high specificity, good recovery, and parallelism within its linear detection range and performed comparably to the R&D Systems assay. In contrast, we were unable to demonstrate the specificity of the two assays from MyBioSource using either recombinant or native HtrA1. Analyses of concentrations obtained using the validated SCTM assay revealed that genetic risk at the 10q26 locus, age, sex, or AMD status are not significantly associated with altered levels of the HtrA1 protein in serum or in vitreous humor (P > 0.05).

Conclusions

HtrA1 levels in serum and vitreous do not reflect the risk for AMD associated with the 10q26 locus or disease status. Localized alteration in HTRA1 expression in the retinal pigment epithelium, rather than systemic changes in HtrA1, is the most likely driver of elevated risk for developing AMD among individuals with risk variants at the 10q26 locus.

Possible involvement of HtrA1 serine protease in the onset of osteoporotic bone extracellular matrix changes

High-temperature requirement A1 (HtrA1), a multidomain serine protease acting on Extracellular matrix (ECM) rearrangement, is also secreted by osteoblasts and osteoclasts. Recent and conflicting literature highlights HtrA1's role as a controller of bone remodeling, proposing it as a possible target for pathologies with unbalanced bone resorption, like Osteoporosis (OP). To add knowledge on this molecule function in bone physiopathology, here we compared HtrA1 distribution in the ECM of healthy (H) and OP bone tissue, also examining its localization in the sites of new bone formation. HtrA1 was homogeneously expressed in the mature bone ECM of H tissue showing a 55.6 ± 16.4% of the stained area, with a significant (p=0.0001) decrease in OP percentage stained area (21.1 ± 13.1). Moreover, HtrA1 was present in the endosteum and cells involved in osteogenesis, mainly in those "entrapped" in woven bone, whereas osteocytes in mature lamellar bone were negative. Based on our previous observation in OP tissue of a significantly increased expression of Decorin and Osteocalcin, both involved in bone mineralization and remodeling and equally substrates for HtrA1, we speculate that HtrA1 by controlling the proper amount of Decorin and Osteocalcin favors normal bone maturation and mineralization. Besides, we suggest that late-osteoblasts and pre-osteocytes secrete HtrA1 in the adjacent matrix whilst proceeding with their maturation and that HtrA1 expression is further modified during the remodeling from woven to the lamellar bone. Overall, our data suggest HtrA1 as a positive regulator of bone matrix formation and maturation: its reduced expression in mature OP bone, affecting protein content and distribution, could hamper correct bone remodeling and mineralization.

HTRA1 disaggregates α-synuclein amyloid fibrils and converts them into non-toxic and seeding incompetent species

Parkinson's disease (PD) is closely linked to α-synuclein (α-syn) misfolding and accumulation in Lewy bodies. The PDZ serine protease HTRA1 degrades fibrillar tau, which is associated with Alzheimer's disease, and inactivating mutations to mitochondrial HTRA2 are implicated in PD. Here, we report that HTRA1 inhibits aggregation of α-syn as well as FUS and TDP-43, which are implicated in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia. The protease domain of HTRA1 is necessary and sufficient for inhibiting aggregation, yet this activity is proteolytically-independent. Further, HTRA1 disaggregates preformed α-syn fibrils, rendering them incapable of seeding aggregation of endogenous α-syn, while reducing HTRA1 expression promotes α-syn seeding. HTRA1 remodels α-syn fibrils by targeting the NAC domain, the key domain catalyzing α-syn amyloidogenesis. Finally, HTRA1 detoxifies α-syn fibrils and prevents formation of hyperphosphorylated α-syn accumulations in primary neurons. Our findings suggest that HTRA1 may be a therapeutic target for a range of neurodegenerative disorders.

Gene expression profiling of subcutaneous adipose tissue reveals new biomarkers in acromegaly

CONTEXT

Active acromegaly is characterized by lipolysis-induced insulin resistance, which suggests adipose tissue (AT) as a primary driver of metabolic aberrations.

OBJECTIVE

To study the gene expression landscape in AT in patients with acromegaly before and after disease control in order to understand the changes and to identify disease-specific biomarkers.

METHODS

RNA sequencing was performed on paired subcutaneous adipose tissue (SAT) biopsies from six patients with acromegaly at time of diagnosis and after curative surgery. Clustering and pathway analyses were performed in order to identify disease activity-dependent genes. In a larger patient cohort (n = 23), the corresponding proteins were measured in serum by immunoassay. Correlations between growth hormone (GH), insulin-like growth factor I (IGF-I), visceral AT (VAT), SAT, total AT, and serum proteins were analyzed.

RESULTS

743 genes were significantly differentially expressed (P-adjusted < .05) in SAT before and after disease control. The patients clustered according to disease activity. Pathways related to inflammation, cell adhesion and extracellular matrix, GH and insulin signaling, and fatty acid oxidation were differentially expressed.Serum levels of HTRA1, METRNL, S100A8/A9, and PDGFD significantly increased after disease control (P < .05). VAT correlated with HTRA1 (R = 0.73) and S100A8/A9 (R = 0.55) (P < .05 for both).

CONCLUSION

AT in active acromegaly is associated with a gene expression profile of fibrosis and inflammation, which may corroborate the hyper-metabolic state and provide a means for identifying novel biomarkers.

Nupr1 deficiency downregulates HtrA1, enhances SMAD1 signaling, and suppresses age-related bone loss in male mice

Nuclear protein 1 (NUPR1) is a stress-induced protein activated by various stresses, such as inflammation and oxidative stress. We previously reported that Nupr1 deficiency increased bone volume by enhancing bone formation in 11-week-old mice. Analysis of differentially expressed genes between wild-type (WT) and Nupr1-knockout (Nupr1-KO) osteocytes revealed that high temperature requirement A 1 (HTRA1), a serine protease implicated in osteogenesis and transforming growth factor-β signaling was markedly downregulated in Nupr1-KO osteocytes. Nupr1 deficiency also markedly reduced HtrA1 expression, but enhanced SMAD1 signaling in in vitro-cultured primary osteoblasts. In contrast, Nupr1 overexpression enhanced HtrA1 expression in osteoblasts, suggesting that Nupr1 regulates HtrA1 expression, thereby suppressing osteoblastogenesis. Since HtrA1 is also involved in cellular senescence and age-related diseases, we analyzed aging-related bone loss in Nupr1-KO mice. Significant spine trabecular bone loss was noted in WT male and female mice during 6-19 months of age, whereas aging-related trabecular bone loss was attenuated, especially in Nupr1-KO male mice. Moreover, cellular senescence-related markers were upregulated in the osteocytes of 6-19-month-old WT male mice but markedly downregulated in the osteocytes of 19-month-old Nupr1-KO male mice. Oxidative stress-induced cellular senescence stimulated Nupr1 and HtrA1 expression in in vitro-cultured primary osteoblasts, and Nupr1 overexpression enhanced p16^ink4a expression in osteoblasts. Finally, NUPR1 expression in osteocytes isolated from the bones of patients with osteoarthritis was correlated with age. Collectively, these results indicate that Nupr1 regulates HtrA1-mediated osteoblast differentiation and senescence. Our findings unveil a novel Nupr1/HtrA1 axis, which may play pivotal roles in bone formation and age-related bone loss.

HTRA1 methylation in peripheral blood as a potential marker for the preclinical detection of stroke: a case-control study and a prospective nested case-control study

BACKGROUND

Stroke is the leading cause of mortality in China. DNA methylation has essential roles in multiple diseases, but its association with stroke was barely studied. We hereby explored the association between blood-based HTRA serine protease 1 (HTRA1) methylation and the risk of stroke.

RESULTS

The association was discovered in a hospital-based case-control study (cases/controls = 190:190) and further validated in a prospective nested case-control study including 139 cases who developed stroke within 2 years after recruitment and 144 matched stroke-free controls. We observed stroke-related altered HTRA1 methylation and expression in both case-control study and prospective study. This blood-based HTRA1 methylation was associated with stroke independently from the known risk factors and mostly affected the older population. The prospective results further showed that the altered HTRA1 methylation was detectable 2 years before the clinical determination of stroke and became more robust with increased discriminatory power for stroke along with time when combined with other known stroke-related variables [onset time ≤ 1 year: area under the curve (AUC) = 0.76].

CONCLUSIONS

In our study, altered HTRA1 methylation was associated with stroke at clinical and preclinical stages and thus may provide a potential biomarker in the blood for the risk evaluation and preclinical detection of stroke.

Stress and the brain transcriptome: Identifying commonalities and clusters in standardized data from published experiments

Interpretation of transcriptomic experiments is hindered by many problems including false positives/negatives inherent to big-data methods and changes in gene nomenclature. To find the most consistent effect of stress on brain transcriptome, we retrieved data from 79 studies applying animal models and 3 human studies investigating post-traumatic stress disorder (PTSD). The analyzed data were obtained either with microarrays or RNA sequencing applied to samples collected from more than 1887 laboratory animals and from 121 human subjects. Based on the initial database containing a quarter million differential expression effect sizes representing transcripts in three species, we identified the most frequently reported genes in 223 stress-control comparisons. Additionally, the analysis considers sex, individual vulnerability and contribution of glucocorticoids. We also found an overlap between gene expression in PTSD patients and animals which indicates relevance of laboratory models for human stress response. Our analysis points to genes that, as far as we know, were not specifically tested for their role in stress response (Pllp, Arrdc2, Midn, Mfsd2a, Ccn1, Htra1, Csrnp1, Tenm4, Tnfrsf25, Sema3b, Fmo2, Adamts4, Gjb1, Errfi1, Fgf18, Galnt6, Slc25a42, Ifi30, Slc4a1, Cemip, Klf10, Tom1, Dcdc2c, Fancd2, Luzp2, Trpm1, Abcc12, Osbpl1a, Ptp4a2). Provided transcriptomic resource will be useful for guiding the new research.

TGF-β/Smad Signalling Activation by HTRA1 Regulates the Function of Human Lens Epithelial Cells and Its Mechanism in Posterior Subcapsular Congenital Cataract

Congenital cataract is the leading cause of blindness among children worldwide. Patients with posterior subcapsular congenital cataract (PSC) in the central visual axis can result in worsening vision and stimulus deprivation amblyopia. However, the pathogenesis of PSC remains unclear. This study aims to explore the functional regulation and mechanism of HTRA1 in human lens epithelial cells (HLECs). HTRA1 was significantly downregulated in the lens capsules of children with PSC compared to normal controls. HTRA1 is a suppression factor of transforming growth factor-β (TGF-β) signalling pathway, which plays a key role in cataract formation. The results showed that the TGF-β/Smad signalling pathway was activated in the lens tissue of PSC. The effect of HTRA1 on cell proliferation, migration and apoptosis was measured in HLECs. In primary HLECs, the downregulation of HTRA1 can promote the proliferation and migration of HLECs by activating the TGF-β/Smad signalling pathway and can significantly upregulate the TGF-β/Smad downstream target genes FN1 and α-SMA. HTRA1 was also knocked out in the eyes of C57BL/6J mice via adeno-associated virus-mediated RNA interference. The results showed that HTRA1 knockout can significantly upregulate p-Smad2/3 and activate the TGF-β/Smad signalling pathway, resulting in abnormal proliferation and irregular arrangement of lens epithelial cells and leading to the occurrence of subcapsular cataract. To conclude, HTRA1 was significantly downregulated in children with PSC, and the downregulation of HTRA1 enhanced the proliferation and migration of HLECs by activating the TGF-β/Smad signalling pathway, which led to the occurrence of PSC.

Caveolar and non-Caveolar Caveolin-1 in ocular homeostasis and disease

Caveolae, specialized plasma membrane invaginations present in most cell types, play important roles in multiple cellular processes including cell signaling, lipid uptake and metabolism, endocytosis and mechanotransduction. They are found in almost all cell types but most abundant in endothelial cells, adipocytes and fibroblasts. Caveolin-1 (Cav1), the signature structural protein of caveolae was the first protein associated with caveolae, and in association with Cavin1/PTRF is required for caveolae formation. Genetic ablation of either Cav1 or Cavin1/PTRF downregulates expression of the other resulting in loss of caveolae. Studies using Cav1-deficient mouse models have implicated caveolae with human diseases such as cardiomyopathies, lipodystrophies, diabetes and muscular dystrophies. While caveolins and caveolae are extensively studied in extra-ocular settings, their contributions to ocular function and disease pathogenesis are just beginning to be appreciated. Several putative caveolin/caveolae functions are relevant to the eye and Cav1 is highly expressed in retinal vascular and choroidal endothelium, Müller glia, the retinal pigment epithelium (RPE), and the Schlemm's canal endothelium and trabecular meshwork cells. Variants at the CAV1/2 gene locus are associated with risk of primary open angle glaucoma and the high risk HTRA1 variant for age-related macular degeneration is thought to exert its effect through regulation of Cav1 expression. Caveolins also play important roles in modulating retinal neuroinflammation and blood retinal barrier permeability. In this article, we describe the current state of caveolin/caveolae research in the context of ocular function and pathophysiology. Finally, we discuss new evidence showing that retinal Cav1 exists and functions outside caveolae.

Allosteric inhibition of HTRA1 activity by a conformational lock mechanism to treat age-related macular degeneration

The trimeric serine protease HTRA1 is a genetic risk factor associated with geographic atrophy (GA), a currently untreatable form of age-related macular degeneration. Here, we describe the allosteric inhibition mechanism of HTRA1 by a clinical Fab fragment, currently being evaluated for GA treatment. Using cryo-EM, X-ray crystallography and biochemical assays we identify the exposed LoopA of HTRA1 as the sole Fab epitope, which is approximately 30 Å away from the active site. The cryo-EM structure of the HTRA1:Fab complex in combination with molecular dynamics simulations revealed that Fab binding to LoopA locks HTRA1 in a non-competent conformational state, incapable of supporting catalysis. Moreover, grafting the HTRA1-LoopA epitope onto HTRA2 and HTRA3 transferred the allosteric inhibition mechanism. This suggests a conserved conformational lock mechanism across the HTRA family and a critical role of LoopA for catalysis, which was supported by the reduced activity of HTRA1-3 upon LoopA deletion or perturbation. This study reveals the long-range inhibition mechanism of the clinical Fab and identifies an essential function of the exposed LoopA for activity of HTRA family proteases.

HtrA1L364P leads to cognitive dysfunction and vascular destruction through TGF-β/Smad signaling pathway in CARASIL model mice

AIMS

Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is a life-threatening, inherited, nonhypertensive arteriole disease of the brain. Therapeutic strategy for CARASIL is limited because its pathogenesis is not clear. We previously reported the first family with CARASIL in China, which involves a high-temperature requirement serine protease gene mutation (HtrA1^L364P ). Based on this previous study, we constructed a CARASIL mouse model (Mut-hHtrA1^L364P mouse, hereinafter referred to as Mut). This paper aimed to systematically study the behavior, pathology, and molecular biology of Mut mice and explore the pathogenesis and possible therapeutic strategies of CARASIL.

METHODS

Food maze and water maze experiments were used in the behavioral studies. Pathological studies were carried out by arteriole labeling staining and electron microscopy. The mRNA and protein expression levels of the key factors of TGF-β/Smad signaling pathway (TGF-β, Smad2, Smad3, and Smad4) in the brain of the model mice were detected by immunohistochemistry, real-time quantitative polymerase chain reaction (RT-PCR), and Western blot assay.

RESULTS

The food maze and water maze experiment data showed significant differences between the Mut and wild-type (WT) mice in the first time to find food, the time to contact the escape table for the first time, and the number of times to travel in the escape table quadrant (p < 0.001). The results of vascular labeling staining showed that some small arteries in the brain of Mut mice lost normal structure. The results of electron microscopy showed that the cell morphologies in the cortex and hippocampus of Mut mice were abnormal; the number of synapses was reduced; the walls of capillaries, venules, and arterioles thickened; lumen stenosis and other abnormal phenomenon occurred; and lipofuscin deposition and autophagosomes were found in the hippocampus. Immunohistochemistry, RT-PCR, and Western Blot results showed that the mRNA and protein expression levels of TGF-β, Smad2, and Smad3 in the brain of Mut mice increased to different degrees.

CONCLUSIONS

The most significant innovation of this study is the first study on the pathogenesis of CARASIL disease using model animals. The Mut mice can well simulate the pathogenesis of CARASIL in behavioral and pathological aspects. The TGF-β/Smad signaling pathway, which is involved in the pathogenesis of CARASIL, is abnormally upregulated in the brain of Mut mice.

Hereditary cerebral small vessel disease: Assessment of a HTRA1 variant using protein stability predictors and 3D modelling

Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is an autosomal recessive vascular disorder caused by biallellic variants in HTRA1. Recently, it has been reported that several heterozygous mutations in HTRA1 are responsible for a milder late-onset cerebral small vessel disease (CSVD) with an autosomal dominant pattern of inheritance. The majority of them are missense that affects the Htr1A protease activity due to a dominant-negative effect caused by defective trimerization or monomer activation. The molecular mechanism related to the structural destabilization of the protein supports the practical utility of integrating computational stability predictors to prioritize candidate variants in this gene. In this work, we report a family with several members diagnosed with subcortical ischemic events and progressive cognitive impairment caused by the novel c.820C > G, p.(Arg274Gly) heterozygous variant in HTRA1 segregating in an autosomal dominant manner and propose its molecular mechanism by a three-dimensional model of the protein's structure.

Forward and reverse degradomics defines the proteolytic landscape of human knee osteoarthritic cartilage and the role of the serine protease HtrA1

OBJECTIVES

Proteolytic destruction of articular cartilage, a major pathogenic mechanism in osteoarthritis (OA), was not previously investigated by terminomics strategies. We defined the degradome of human knee OA cartilage and the contribution therein of the protease HtrA1 using Terminal Amine Isotopic Labeling of Substrates (TAILS).

DESIGN

Proteins from OA cartilage taken at knee arthroplasty (n = 6) or separately, from healthy cartilage incubated in triplicate with/without active HtrA1, were labeled at natural and proteolytically cleaved N-termini by reductive dimethylation, followed by trypsin digestion, enrichment of N-terminally labeled/blocked peptides, tandem mass spectrometry and positional peptide annotation to identify cleavage sites. Biglycan proteolysis by HtrA1 was validated biochemically and Amino-Terminal Oriented Mass Spectrometry of Substrates (ATOMS) was used to define the HtrA1 cleavage sites.

RESULTS

We identified 10,155 unique internal peptides from 2,162 proteins, suggesting at least 10,797 cleavage sites in OA cartilage. 7,635 internal peptides originated in 371 extracellular matrix/secreted components, many undergoing extensive proteolysis. Rampant ragging of protein termini suggested pervasive exopeptidase activity. HtrA1, the most abundant protease in OA cartilage, experimentally generated 323 cleavages in 109 cartilage proteins, accounting for 171 observed cleavages in the OA degradome. ATOMS identified HtrA1 cleavage sites in a selected substrate, biglycan, whose direct cleavage by HtrA1 was thus orthogonally validated.

CONCLUSIONS

OA cartilage demonstrates widespread proteolysis by endo- and exopeptidases. HtrA1 contributes broadly to cartilage proteolysis. Forward degradomics of OA cartilage together with reverse degradomics of proteases active in OA, e.g., HtrA1, can potentially fully annotate OA proteolytic pathways and provide new biomarkers.

The amyloid plaque proteome in early onset Alzheimer's disease and Down syndrome

Amyloid plaques contain many proteins in addition to beta amyloid (Aβ). Previous studies examining plaque-associated proteins have shown these additional proteins are important; they provide insight into the factors that drive amyloid plaque development and are potential biomarkers or therapeutic targets for Alzheimer's disease (AD). The aim of this study was to comprehensively identify proteins that are enriched in amyloid plaques using unbiased proteomics in two subtypes of early onset AD: sporadic early onset AD (EOAD) and Down Syndrome (DS) with AD. We focused our study on early onset AD as the drivers of the more aggressive pathology development in these cases is unknown and it is unclear whether amyloid-plaque enriched proteins differ between subtypes of early onset AD. Amyloid plaques and neighbouring non-plaque tissue were microdissected from human brain sections using laser capture microdissection and label-free LC-MS was used to quantify the proteins present. 48 proteins were consistently enriched in amyloid plaques in EOAD and DS. Many of these proteins were more significantly enriched in amyloid plaques than Aβ. The most enriched proteins in amyloid plaques in both EOAD and DS were: COL25A1, SMOC1, MDK, NTN1, OLFML3 and HTRA1. Endosomal/lysosomal proteins were particularly highly enriched in amyloid plaques. Fluorescent immunohistochemistry was used to validate the enrichment of four proteins in amyloid plaques (moesin, ezrin, ARL8B and SMOC1) and to compare the amount of total Aβ, Aβ40, Aβ42, phosphorylated Aβ, pyroglutamate Aβ species and oligomeric species in EOAD and DS. These studies showed that phosphorylated Aβ, pyroglutamate Aβ species and SMOC1 were significantly higher in DS plaques, while oligomers were significantly higher in EOAD. Overall, we observed that amyloid plaques in EOAD and DS largely contained the same proteins, however the amount of enrichment of some proteins was different in EOAD and DS. Our study highlights the significant enrichment of many proteins in amyloid plaques, many of which may be potential therapeutic targets and/or biomarkers for AD.

Melatonin regulates trophoblast pyroptosis, invasion and migration in preeclampsia by inhibiting HtrA1 transcription through the microRNA-520c-3p/SETD7 axis

OBJECTIVE

Melatonin has an inhibitory effect on preeclampsia (PE). This study was launched to explore the way that melatonin regulated trophoblast migration, invasion, and pyroptosis in PE and to provide new ideas for the diagnosis and treatment of PE.

METHODS

Expression levels of melatonin receptors (MT1 and MT2), microRNA (miR)-520c-3p, SETD7, and HtrA1 in placental tissues and HTR8/SVneo cells were measured by RT-qPCR and Western blot. Scratch, Transwell, and Western blot assays were performed to detect migration, invasion, and pyroptosis of hypoxia/reoxygenation (H/R)-treated HTR8/SVneo cells. Dual-luciferase reporter assay was utilized to verify the targeting relationship between miR-520c-3p and SETD7. ChIP experiment was conducted to detect the enrichment of H3K4me3 and SETD7 in HtrA1 promoter.

RESULTS

Low expression of MT1, MT2, and miR-520c-3p and high expression of SETD7 and HtrA1 were observed in the placental tissues of PE patients and H/R-treated HTR8/Svneo cells. A high concentration of melatonin promoted migration and invasion and inhibited pyroptosis of PE cell models. Knockdown of miR-520c-3p, overexpression of SETD7, or overexpression of HtrA1 impaired migration and invasion and accelerated pyroptosis of H/R-treated HTR8/SVneo cells, but these outcomes could be reversed by treatment with 1000 μM melatonin. miR-520c-3p targeted SETD7 which promoted histone methylation in the promoter region of HtrA1.

CONCLUSION

Melatonin may inhibit HtrA1 transcription through the miR-520c-3p/SETD7 axis to promote trophoblast invasion and migration and reduce trophoblast pyroptosis in PE.

The multifaced role of HtrA1 in the development of joint and skeletal disorders

HtrA1 (High temperature requirement A1) family proteins include four members, widely conserved from prokaryotes to eukaryotes, named HtrA1, HtrA2, HtrA3 and HtrA4. HtrA1 is a serine protease involved in a variety of biological functions regulating many signaling pathways degrading specific components and playing key roles in many human diseases such as neurodegenerative disorders, pregnancy complications and cancer. Due to its role in the breakdown of many ExtraCellular Matrix (ECM) components of articular cartilage such as fibronectin, decorin and aggrecan, HtrA1 encouraged many researches on studying its role in several skeletal diseases (SDs). These studies were further inspired by the fact that HtrA1 is able to regulate the signaling of one of the most important cytokines involved in SDs, the TGFβ-1. This review aims to summarize the data currently available on the role of HtrA1 in skeletal diseases such as Osteoporosis, Rheumatoid Arthritis, Osteoarthritis and Intervertebral Disc Degeneration (IDD). The use of HtrA1 as a marker of frailty in geriatric medicine would represent a powerful tool for identifying older individuals at risk of developing skeletal disorders, evaluating an appropriate intervention to improve quality care in these people avoiding or improving age-related SDs in the elderly population.

A Pilot Application of an iTRAQ-Based Proteomics Screen Estimates the Effects of Cigarette Smokers' Serum on RPE Cells With AMD High-Risk Alleles

PURPOSE

The aim of this study was to explore whether there are interactions between genetic (ARMS2/HTRA1) and environmental factors (cigarette smoking) in the pathogenesis of age-related macular degeneration (AMD).

METHODS

Primary human retinal pigment epithelial (hRPE) cells were obtained from four donors' eyes with AMD high-risk ARMS2/HTRA1 alleles, and two donors' eyes with wild-type alleles were used as controls. The pooled serum from 32 smokers and 35 nonsmokers were collected and used separately to treat hRPE cells. The isobaric tag for relative and absolute quantitation (iTRAQ)-based proteomics was used to identify associated proteins and comparing the differences between AMD high-risk and low-risk HTRA1/ARMS2 alleles after exposure to smokers' serum.

RESULTS

After stimulation with the smokers' serum, 400 differentially expressed proteins (DEPs) were detected in the high-risk allele cells. Several DEPs are involved in neuronal protein degeneration and oxidative stress pathways. The smokers' serum stimulation or HTRA1 overexpression can both upregulate caveolin-1, which was one of the DEPs. Besides, the smokers' serum enhanced the phagocytosis of cultured human RPE cells.

CONCLUSIONS

The study confirmed the AMD high-risk alleles, HTRA1, and cigarette smoking can promote AMD development by regulating caveolin-1 expression.

TRANSLATIONAL RELEVANCE

AMD high-risk alleles and environmental risk factors can promote the occurrence and development of AMD by regulating caveolin-1 expression, upregulation of which will induce apoptotic cell death in response to cellular stress in early AMD conditions.

Proteomic profiling in cerebral amyloid angiopathy reveals an overlap with CADASIL highlighting accumulation of HTRA1 and its substrates

Cerebral amyloid angiopathy (CAA) is an age-related condition and a major cause of intracerebral hemorrhage and cognitive decline that shows close links with Alzheimer's disease (AD). CAA is characterized by the aggregation of amyloid-β (Aβ) peptides and formation of Aβ deposits in the brain vasculature resulting in a disruption of the angioarchitecture. Capillaries are a critical site of Aβ pathology in CAA type 1 and become dysfunctional during disease progression. Here, applying an advanced protocol for the isolation of parenchymal microvessels from post-mortem brain tissue combined with liquid chromatography tandem mass spectrometry (LC-MS/MS), we determined the proteomes of CAA type 1 cases (n = 12) including a patient with hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D), and of AD cases without microvascular amyloid pathology (n = 13) in comparison to neurologically healthy controls (n = 12). ELISA measurements revealed microvascular Aβ1-40 levels to be exclusively enriched in CAA samples (mean: > 3000-fold compared to controls). The proteomic profile of CAA type 1 was characterized by massive enrichment of multiple predominantly secreted proteins and showed significant overlap with the recently reported brain microvascular proteome of patients with cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), a hereditary cerebral small vessel disease (SVD) characterized by the aggregation of the Notch3 extracellular domain. We found this overlap to be largely attributable to the accumulation of high-temperature requirement protein A1 (HTRA1), a serine protease with an established role in the brain vasculature, and several of its substrates. Notably, this signature was not present in AD cases. We further show that HTRA1 co-localizes with Aβ deposits in brain capillaries from CAA type 1 patients indicating a pathologic recruitment process. Together, these findings suggest a central role of HTRA1-dependent protein homeostasis in the CAA microvasculature and a molecular connection between multiple types of brain microvascular disease.

Transcriptomics Analysis of Lens from Patients with Posterior Subcapsular Congenital Cataract

To gain insight into the aetiology of posterior subcapsular congenital cataract from the perspective of transcriptional changes, we conducted an mRNA sequencing analysis of the lenses in posterior subcapsular congenital cataract patients and in normal children. There were 1533 differentially expressed genes from 19,072 genes in the lens epithelial cells of the posterior subcapsular congenital cataract patients compared to in the normal controls at a cut-off criteria of |log2 fold change| of >1 and a p-value of <0.05, including 847 downregulated genes and 686 upregulated genes. To further narrow down the DEGs, we utilised the stricter criteria of |log2 fold change| of >1 and an FDR value of <0.05, and we identified 551 DEGs, including 97 upregulated genes and 454 downregulated genes. This study also identified 1263 differentially expressed genes of the 18,755 genes in lens cortex and nuclear fibres, including 646 downregulated genes and 617 upregulated genes. The downregulated genes in epithelial cells were significantly enriched in the structural constituent of lenses, lens development and lens fibre cell differentiation. After filtering the DEGs using the databases iSyTE and Cat-Map, several high-priority candidate genes related to posterior subcapsular congenital cataract such as GRIFIN, HTRA1 and DAPL1 were identified. The findings of our study may provide a deeper understanding of the mechanisms of posterior subcapsular congenital cataract and help in the prevention and treatment of this disease.

Mutations That Affect the Surface Expression of TRPV6 Are Associated with the Upregulation of Serine Proteases in the Placenta of an Infant

Recently, we reported a case of an infant with neonatal severe under-mineralizing skeletal dysplasia caused by mutations within both alleles of the TRPV6 gene. One mutation results in an in frame stop codon (R510stop) that leads to a truncated, nonfunctional TRPV6 channel, and the second in a point mutation (G660R) that, surprisingly, does not affect the Ca2+ permeability of TRPV6. We mimicked the subunit composition of the unaffected heterozygous parent and child by coexpressing the TRPV6 G660R and R510stop mutants and combinations with wild type TRPV6. We show that both the G660R and R510stop mutant subunits are expressed and result in decreased calcium uptake, which is the result of the reduced abundancy of functional TRPV6 channels within the plasma membrane. We compared the proteomic profiles of a healthy placenta with that of the diseased infant and detected, exclusively in the latter two proteases, HTRA1 and cathepsin G. Our results implicate that the combination of the two mutant TRPV6 subunits, which are expressed in the placenta of the diseased child, is responsible for the decreased calcium uptake, which could explain the skeletal dysplasia. In addition, placental calcium deficiency also appears to be associated with an increase in the expression of proteases.

Circ_0011460 upregulates HTRA1 expression by sponging miR-762 to suppress HTR8/SVneo cell growth, migration, and invasion

BACKGROUND

Aberrant expression of circular RNAs (circRNAs) during placental development could affect fetal growth and contribute to preeclampsia (PE). Circ_0011460 was found to be differentially expressed in placental samples of PE. However, the exact function and mechanism of circ_0011460 in PE process remain largely undefined.

METHODS

Levels of circ_0011460, microRNA (miR)-762, and high-temperature requirement-A serine peptidase 1 (HTRA1) were detected using quantitative real-time polymerase chain reaction and Western blot. In vitro experiments in HTR8/SVneo cells were conducted using cell counting kit-8, wound healing, transwell, flow cytometry and Western blot assays. The direct interactions between miR-762 and circ_0011460 or HTRA1 were verified using dual-luciferase reporter, RNA immunoprecipitation (RIP) and RNA pull-down assays.

RESULTS

Circ_0011460 possessed a loop structure and was highly expressed in placental tissues of PE patients. Overexpression of circ_0011460 greatly suppressed HTR8/SVneo cell proliferation, migration, and invasion, and accelerated cell apoptosis. While circ_0011460 knockdown yielded the opposite trends on above biological behaviors. Mechanistically, we confirmed that circ_0011460 could up-regulate HTRA1 expression via serving as a sponge of miR-762. Further rescue studies demonstrated that circ_0011460 exerted its roles via targeting miR-762, and miR-762 promoted HTR8/SVneo cell growth, migration and invasion via regulating HTRA1.

CONCLUSION

In all, circ_0011460 suppressed HTR8/SVneo cell growth, migration, and invasion via miR-762/HTRA1 axis, suggesting a new insight into the pathogenesis of PE.

Identification of intracellular glycosaminoglycan-interacting proteins by affinity purification mass spectrometry

Glycosaminoglycans (GAGs) are essential functional components of the extracellular matrix (ECM). Artificial GAGs like sulfated hyaluronan (sHA) exhibit pro-osteogenic properties and boost healing processes. Hence, they are of high interest for supporting bone regeneration and wound healing. Although sulfated GAGs (sGAGs) appear intracellularly, the knowledge about intracellular effects and putative interaction partners is scarce. Here we used an affinity-purification mass spectrometry-based (AP-MS) approach to identify novel and particularly intracellular sGAG-interacting proteins in human bone marrow stromal cells (hBMSC). Overall, 477 proteins were found interacting with at least one of four distinct sGAGs. Enrichment analysis for protein localization showed that mainly intracellular and cell-associated interacting proteins were identified. The interaction of sGAG with α2-macroglobulin receptor-associated protein (LRPAP1), exportin-1 (XPO1), and serine protease HTRA1 (HTRA1) was confirmed in reverse assays. Consecutive pathway and cluster analysis led to the identification of biological processes, namely processes involving binding and processing of nucleic acids, LRP1-dependent endocytosis, and exosome formation. Respecting the preferentially intracellular localization of sGAG in vesicle-like structures, also the interaction data indicate sGAG-specific modulation of vesicle-based transport processes. By identifying many sGAG-specific interacting proteins, our data provide a resource for upcoming studies aimed at molecular mechanisms and understanding of sGAG cellular effects.

Placental HTRA1 cleaves α1-antitrypsin to generate a NET-inhibitory peptide

Neutrophil extracellular traps (NETs) are important components of innate immunity. Neonatal neutrophils (polymorphonuclear leukocytes [PMNs]) fail to form NETs due to circulating NET-inhibitory peptides (NIPs), cleavage fragments of α1-antitrypsin (A1AT). How fetal and neonatal blood NIPs are generated remains unknown, however. The placenta expresses high-temperature requirement serine protease A1 (HTRA1) during fetal development, which can cleave A1AT. We hypothesized that placentally expressed HTRA1 regulates the formation of NIPs and that NET competency changed in PMNs isolated from neonatal HTRA1 knockout mice (HTRA1-/-). We found that umbilical cord blood plasma has elevated HTRA1 levels compared with adult plasma and that recombinant and placenta-eluted HTRA1 cleaves A1AT to generate an A1AT cleavage fragment (A1ATM383S-CF) of molecular weight similar to previously identified NIPs that block NET formation by adult neutrophils. We showed that neonatal mouse pup plasma contains A1AT fragments that inhibit NET formation by PMNs isolated from adult mice, indicating that NIP generation during gestation is conserved across species. Lipopolysaccharide-stimulated PMNs isolated from HTRA1+/+ littermate control pups exhibit delayed NET formation after birth. However, plasma from HTRA1-/- pups had no detectable NIPs, and PMNs from HTRA1-/- pups became NET competent earlier after birth compared with HTRA1+/+ littermate controls. Finally, in the cecal slurry model of neonatal sepsis, A1ATM383S-CF improved survival in C57BL/6 pups by preventing pathogenic NET formation. Our data indicate that placentally expressed HTRA1 is a serine protease that cleaves A1AT in utero to generate NIPs that regulate NET formation by human and mouse PMNs.

Chromosome 10q26-driven age-related macular degeneration is associated with reduced levels of HTRA1 in human retinal pigment epithelium

Genome-wide association studies have identified the chromosome 10q26 (Chr10) locus, which contains the age-related maculopathy susceptibility 2 (ARMS2) and high temperature requirement A serine peptidase 1 (HTRA1) genes, as the strongest genetic risk factor for age-related macular degeneration (AMD) [L.G. Fritsche et al., Annu. Rev. Genomics Hum. Genet. 15, 151-171, (2014)]. To date, it has been difficult to assign causality to any specific single nucleotide polymorphism (SNP), haplotype, or gene within this region because of high linkage disequilibrium among the disease-associated variants [J. Jakobsdottir et al. Am. J. Hum. Genet. 77, 389-407 (2005); A. Rivera et al. Hum. Mol. Genet. 14, 3227-3236 (2005)]. Here, we show that HTRA1 messenger RNA (mRNA) is reduced in retinal pigment epithelium (RPE) but not in neural retina or choroid tissues derived from human donors with homozygous risk at the 10q26 locus. This tissue-specific decrease is mediated by the presence of a noncoding, cis-regulatory element overlapping the ARMS2 intron, which contains a potential Lhx2 transcription factor binding site that is disrupted by risk variant rs36212733. HtrA1 protein increases with age in the RPE-Bruch's membrane (BM) interface in Chr10 nonrisk donors but fails to increase in donors with homozygous risk at the 10q26 locus. We propose that HtrA1, an extracellular chaperone and serine protease, functions to maintain the optimal integrity of the RPE-BM interface during the aging process and that reduced expression of HTRA1 mRNA and protein in Chr10 risk donors impairs this protective function, leading to increased risk of AMD pathogenesis. HtrA1 augmentation, not inhibition, in high-risk patients should be considered as a potential therapy for AMD.

Alpha-1 Antitrypsin-Induced Endoplasmic Reticulum Stress Promotes Invasion by Extravillous Trophoblasts

Alpha-1 antitrypsin (A1AT) is a glycoprotein that has been shown to protect tissues from proteolytic damage under various inflammatory conditions. Several studies show that A1AT may be associated with pre-eclampsia. However, the role of A1AT expression in placental physiology is not fully understood. In the present study, we aim to characterize the expression and function of placental A1AT. A1AT knockdown is found to reduce the expression of the serine protease HTRA1 in a trophoblast cell line. In addition, A1AT overexpression (A1AT-OE) increases the expression of HTRA1, IL6, CXCL8, and several markers of endoplasmic reticulum (ER) stress. Treatment with tunicamycin or thapsigargin, which induces ER stress, increases HTRA1 expression. Furthermore, immunohistochemistry reveals that HTRA1 is expressed in trophoblasts and the endometrial decidual cells of human placentas. An invasion assay shows that A1AT and HTRA1 stimulate cell invasion, but treatment with the ER stress inhibitors reduces the expression of HTRA1 and ER stress markers and prevents cell invasion in A1AT-OE trophoblasts. These results suggest that endogenous A1AT regulates inflammatory cytokine expression and HTRA1-induced trophoblast invasion via the induction of ER stress. It is concluded that an imbalance in the functional link between A1AT and ER stress at the maternal-fetal interface might cause abnormal placental development.

Cross-sectional associations among P3NP, HtrA, Hsp70, Apelin and sarcopenia in Taiwanese population

BACKGROUND

Sarcopenia is a multifactorial pathophysiologic condition of skeletal muscle mass and muscle strength associated with aging. However, biomarkers for predicting the occurrence of sarcopenia are rarely discussed in recent studies. The aim of the study was to elucidate the relationship between sarcopenia and several pertinent biomarkers.

METHODS

Using the Gene Expression Omnibus (GEO) profiles of the National Center for Biotechnology Information, the associations between mRNA expression of biomarkers and sarcopenia were explored, including high temperature requirement serine protease A1 (HtrA1), procollagen type III N-terminal peptide (P3NP), apelin, and heat shock proteins 70 (Hsp72). We enrolled 408 community-dwelling adults aged 65 years and older with sarcopenia and nonsarcopenia based on the algorithm proposed by the Asian Working Group for Sarcopenia (AWGS). Muscle strength is identified by hand grip strength using an analogue isometric dynamometer. Muscle mass is estimated by skeletal mass index (SMI) using a bioelectrical impedance analysis. Physical performance is measured by gait speed using 6 m walking distance. The associations between these biomarkers and sarcopenia were determined using receiver operating characteristic (ROC) curve analysis and multivariate regression models.

RESULTS

From the GEO profiles, the sarcopenia gene set variation analysis score was correlated significantly with the mRNA expression of APLNR (p < 0.001) and HSPA2 (p < 0.001). In our study, apelin was significantly associated with decreased hand grip strength with β values of - 0.137 (95%CI: - 0.229, - 0.046) in men. P3NP and HtrA1 were significantly associated with increased SMI with β values of 0.081 (95%CI: 0.010, 0.153) and 0.005 (95%CI: 0.001, 0.009) in men, respectively. Apelin and HtrA1 were inversely associated with the presence of sarcopenia with an OR of 0.543 (95%CI: 0.397-0.743) and 0.003 (95%CI: 0.001-0.890) after full adjustment. The cutoff point of HtrA1 was associated with the presence of sarcopenia with an OR of 0.254 (95%CI: 0.083-0.778) in men. The cutoff point of apelin was negatively associated with the presence of sarcopenia with an OR of 0.254 (95%CI: 0.083-0.778).

CONCLUSION

Our study highlights that P3NP, HtrA, and apelin are useful for diagnosis of sarcopenia in the clinical setting.

Analysis of RPL37A, MTSS1, and HTRA1 expression as potential markers for pathologic complete response and survival

BACKGROUND

Non-metastatic locally advanced breast carcinoma (LABC) treatment involves neoadjuvant chemotherapy (NCT). We evaluated the association of clinical-pathological data and immunoexpression of hormone receptors, HER2 and Ki67, and new biomarkers, RPL37A, MTSS1 and HTRA1, with pathological complete response (PCR) or tumour resistance (stable disease or disease progression), disease-free survival (DFS) and cancer-specific survival (CSS).

METHODS

This is a retrospective study of 333 patients with LABC who underwent NCT. Expression of MTSS1, RPL37A and HTRA1/PRSS11 was evaluated by immunohistochemistry in TMA slides. Cutoff values were established for low and high tumour expression. ROC plotter evaluated response to NCT. Chi-square test for factors related to PCR, and Kaplan-Meier test and Cox model for factors related to DFS and CSS were prformed.

RESULTS

The mean follow-up was 70.0 months and PCR rate was 15.6%. At 120 months, DFS rate was 32.5% and CSS rate was 67.1%. In multivariate analysis, there was an association between: (1) necrosis presence, intense inflammatory infiltrate, ER absence, HER2 molecular subtype and high RPL3A expression with increased odds of PCR; (2) lymph node involvement (LNI), high Ki67, low RPL37A and high HTRA1 expression with increased risk for NCT non-response; (3) LNI, high proliferation, necrosis absence, low RPL37A and high HTRA1 expression with increased recurrence risk; (4) advanced LNI, ER negative tumours, high HTRA1, low RPL37A expression and desmoplasia presence with higher risk of cancer death.

CONCLUSION

RPL37A is a potential biomarker for response to NCT and for prognosis. Additional studies evaluating HTRA1 and MTSS1 prognostic value are needed.

Binding of Gtf2i-β/δ transcription factors to the ARMS2 gene leads to increased circulating HTRA1 in AMD patients and in vitro

The disease-initiating molecular events for age-related macular degeneration (AMD), a multifactorial retinal disease affecting many millions of elderly individuals worldwide, are still unknown. Of the over 30 risk and protective loci so far associated with AMD through whole genome-wide association studies (GWAS), the Age-Related Maculopathy Susceptibility 2 (ARMS2) gene locus represents one of the most highly associated risk regions for AMD. A unique insertion/deletion (in/del) sequence located immediately upstream of the High Temperature Requirement A1 (HTRA1) gene in this region confers high risk for AMD. Using electrophoretic mobility shift assay (EMSA), we identified that two Gtf2i-β/δ transcription factor isoforms bind to the cis-element 5'- ATTAATAACC-3' contained in this in/del sequence. The binding of these transcription factors leads to enhanced upregulation of transcription of the secretory serine protease HTRA1 in transfected cells and AMD patient-derived induced pluripotent stem cells (iPSCs). Overexpression of Htra1 in mice using a CAG-promoter demonstrated increased blood concentration of Htra1 protein, caused upregulation of vascular endothelial growth factor (VEGF), and produced a choroidal neovascularization (CNV)-like phenotype. Finally, a comparison of 478 AMD patients to 481 healthy, age-matched controls from Japan, India, Australia, and the USA showed a statistically increased level of secreted HTRA1 blood concentration in AMD patients compared with age-matched controls. Taken together, these results suggest a common mechanism across ethnicities whereby increased systemic blood circulation of secreted serine protease HTRA1 leads to subsequent degradation of Bruch's membrane and eventual CNV in AMD.

Genetic Variants Affecting Anti-VEGF Drug Response in Polypoidal Choroidal Vasculopathy Patients: A Systematic Review and Meta-Analysis

Polypoidal choroidal vasculopathy (PCV) is usually regarded as a subtype of choroidal neovascularization (CNV) that is secondary to age-related macular degeneration (AMD) characterized by choroidal vessel branching, ending in polypoidal lesions. Despite their close association, PCV and neovascular AMD have shown differences, especially regarding patients' treatment response. Currently, antivascular endothelial growth factor (anti-VEGF) drugs, such as ranibizumab, bevacizumab and aflibercept, have demonstrated their efficacy in CNV patients. However, in PCV, anti-VEGF treatments have shown inconclusive results. Many genetic polymorphisms have been associated with a variable response in exudative/wet AMD patients. Thus, the aim of this study is to explore the genetic variants affecting anti-VEGF drug response in PCV patients. In this regard, we performed a systematic review and meta-analysis. We found four variants (CFH I62V, CFH Y402H, ARMS2 A69S, and HTRA1-62A/G) that have been significantly related to response. Among them, the ARMS2 A69S variant is assessed in our meta-analysis. In conclusion, in order to implement anti-VEGF pharmacogenetics in clinical routines, further studies should be performed, distinguishing physio-pathogenic circumstances between PCV and exudative AMD and the combined effect on treatment response of different genetic variants.

RUNX2 co-operates with EGR1 to regulate osteogenic differentiation through Htra1 enhancers

Runt-related transcription factor 2 (Runx2) has been shown to regulate osteoblast differentiation by directly or indirectly regulating numerous osteoblast-related genes. However, our understanding of the transcriptional mechanisms of RUNX2 is mainly restricted to its transactivation, while the mechanism underlying its inhibitory effect during osteoblast differentiation remains largely unknown. Here, we incorporated the anti-RUNX2 chromatin immunoprecipitation (ChIP) sequencing in MC3T3-E1 cells and RNA-sequencing of parietal bone from Runx2 heterozygous mutant mice, to identify the putative genes negatively regulated by RUNX2. We identified HtrA serine peptidase 1 (Htra1) as a target gene and found ten candidate Htra1 enhancers potentially regulated by RUNX2, among which seven were verified by dual-luciferase assays. Furthermore, we investigated the motifs in the vicinity of RUNX2-binding sites and identified early growth response 1 (EGR1) as a potential partner transcription factor (TF) potentially regulating Htra1 expression, which was subsequently confirmed by Re-ChIP assays. RUNX2 and EGR1 co-repressed Htra1 and increased the expression levels of other osteoblast marker genes, such as osterix, osteocalcin, and osteoprotegerin at the messenger RNA and protein level. Moreover, Alizarin red staining combined with alkaline phosphatase (ALP) staining showed decreased calcified nodules and ALP activity in the siRUNX2+siEGR1 group compared with siRUNX2 group. Our findings revealed the detailed mechanism of the inhibitory function of RUNX2 towards its downstream genes, along with its partner TFs, to promote osteoblast differentiation.

HTRA1 expression profile and activity on TGF-β signaling in HTRA1 mutation carriers

High temperature requirement A1 (HTRA1) is a serine protease playing a modulatory role in various cell processes, particularly in the regulation of transforming growth factor-β (TGF-β) signaling. A deleterious role in late-onset cerebral small vessel diseases (CSVDs) of heterozygous HTRA1 mutations, otherwise causative in homozygosity of cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy, was recently suggested. However, the pathomechanism of these heterozygous mutations is still undefined. Our aim is to evaluate the expression profile and activity of HTRA1 on TGF-β signaling in fibroblasts from four subjects carrying the HTRA1 heterozygous mutations-p.E42Dfs*173, p.A321T, p.G295R, and p.Q151K. We found a 50% reduction of HTRA1 expression in HTRA1 mutation carriers compared to the control. Moreover, we showed no changes in TGF-β signaling pathway downstream intermediate, Phospho Smad2/3. However, we found overexpression of genes involved in the extracellular matrix formation in two heterozygous HTRA1 carriers. Our results suggest that each heterozygous HTRA1 missense mutation displays a different and peculiar HTRA1 expression pattern and that CSVD phenotype may also result from 50% of HTRA1 expression.

Activity-Based Probes for the High Temperature Requirement A Serine Proteases

The high temperature requirement A (HTRA) family of serine proteases mediates protein quality control. These proteins process misfolded proteins in several diseases including Alzheimer's disease (AD) and Parkinson's disease (PD). While their structures and activation mechanisms have been studied, the precise details of the regulation of their activity under physiological conditions have not been completely elucidated, partly due to the lack of suitable chemical probes. In the present study, we developed novel activity-based probes (ABPs) targeting the HTRAs and demonstrated their utility in the monitoring and quantification of changes in enzyme activity in live cells. Using our probes, we found the activity of HTRA1 to be highly elevated in an AD-like cell-based model. We also observed the active HTRA2 in live cells by using a mitochondrion-targeted probe. We believe that our probes can serve as a useful tool to study the role of human HTRAs in neurodegenerative diseases.

Cell density-dependent proteolysis by HtrA1 induces translocation of zyxin to the nucleus and increased cell survival

Proteases modulate critical processes in cutaneous tissue repair to orchestrate inflammation, cell proliferation and tissue remodeling. However, the functional consequences and implications in healing impairments of most cleavage events are not understood. Using iTRAQ-based Terminal Amine Isotopic Labeling of Substrates (TAILS) we had characterized proteolytic signatures in a porcine wound healing model and identified two neo-N termini derived from proteolytic cleavage of the focal adhesion protein and mechanotransducer zyxin. Here, we assign these proteolytic events to the activity of either caspase-1 or serine protease HtrA1 and analyze the biological relevance of the resultant zyxin truncations. By cellular expression of full-length and truncated zyxin proteins, we demonstrate nuclear translocation of a C-terminal zyxin fragment that could also be generated in vitro by HtrA1 cleavage and provide evidence for its anti-apoptotic activities, potentially by regulating the expression of modulators of cell proliferation, protein synthesis and genome stability. Targeted degradomics correlated endogenous generation of the same zyxin fragment with increased cell density in human primary dermal fibroblasts. Hence, this newly identified HtrA1-zyxin protease signaling axis might present a novel mechanism to transiently enhance cell survival in environments of increased cell density like in wound granulation tissue.

The 10q26 Risk Haplotype of Age-Related Macular Degeneration Aggravates Subretinal Inflammation by Impairing Monocyte Elimination

A minor haplotype of the 10q26 locus conveys the strongest genetic risk for age-related macular degeneration (AMD). Here, we examined the mechanisms underlying this susceptibility. We found that monocytes from homozygous carriers of the 10q26 AMD-risk haplotype expressed high amounts of the serine peptidase HTRA1, and HTRA1 located to mononuclear phagocytes (MPs) in eyes of non-carriers with AMD. HTRA1 induced the persistence of monocytes in the subretinal space and exacerbated pathogenic inflammation by hydrolyzing thrombospondin 1 (TSP1), which separated the two CD47-binding sites within TSP1 that are necessary for efficient CD47 activation. This HTRA1-induced inhibition of CD47 signaling induced the expression of pro-inflammatory osteopontin (OPN). OPN expression increased in early monocyte-derived macrophages in 10q26 risk carriers. In models of subretinal inflammation and AMD, OPN deletion or pharmacological inhibition reversed HTRA1-induced pathogenic MP persistence. Our findings argue for the therapeutic potential of CD47 agonists and OPN inhibitors for the treatment of AMD.

Circular RNA circ_0111277 attenuates human trophoblast cell invasion and migration by regulating miR-494/HTRA1/Notch-1 signal pathway in pre-eclampsia

Mounting evidence has revealed that impaired spiral artery remodeling, placental dysfunction, and inadequate trophoblast invasion are closely correlated with the etiology and pathogenesis of pre-eclampsia (PE). Moreover, defective trophoblast invasion may trigger poor maternal-fetal circulation and placental hypoxia, leading to PE. However, the detailed molecular pathology of PE remains unclear. Although circRNAs, as a new type of stable and abundant endogenous noncoding RNA, have been proven to be essential to the pathogenesis of various diseases, their role in PE requires further verification. In this context, it is necessary to unveil the roles of circRNAs in regulating the migration and invasion of extravillous trophoblasts. In this study, using quantitative real-time PCR, we confirmed that hsa_circ_0111277 was upregulated in PE placentas relative to the level in normal pregnancy placentas. In addition, positive correlations between hsa_circ_0111277 expression and PE-related factors (proteinuria level at 24 h and placental weight) were identified by Pearson's analysis based on the clinical data of 25 PE patients. Moreover, fluorescence in situ hybridization analysis illustrated that circ_0111277 was preferentially localized within the cytoplasm. Mechanistically, circ_0111277 sponged hsa-miR-494-3p in trophoblast cells to attenuate the latter's repression by regulating HTRA1/Notch-1 expression. In conclusion, trophoblast cell migration and invasion were shown to be promoted and modulated by the hsa_circ_0111277/miR-494-3p/HTRA1/Notch-1 axis, which provides useful insight for exploring a new therapeutic approach for PE.

A novel heterozygous HTRA1 mutation is associated with autosomal dominant hereditary cerebral small vessel disease

BACKGROUND

We investigated whether a heterozygous mutation that we newly identified in HTRA1 (high-temperature requirement serine protease A1 gene) in a pedigree with autosomal dominant hereditary cerebral small vessel disease (SVD) reduces the function of HTRA1 and affects the transforming growth factor-β1 (TGF-β1)/Smad signaling.

METHODS

Whole-exome sequence from the proband and her two sisters was examined using whole-exome enrichment and sequencing. Expression of HTRA1 and TGF-β1/Smad and HTRA1 activity were assayed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and western blotting analyses after transfecting wild-type and mutant HTRA1 genes into HEK293 cells.

RESULTS

A new heterozygous mutation (c.614C>G:p.Ser205Cys) in HTRA1 was identified in the sequence encoding the trypsin-like serine protease domain. The mutation was predicted to be deleterious by in silico tools. Moreover, in vitro activity and protein analyses revealed a loss-of-function effect of the mutation: the proteolytic activity of mutant HTRA1 was decreased, and, notably, this was accompanied by an increase in TGF-β1/Smad protein levels.

CONCLUSIONS

The heterozygous mutation HTRA1 S205C causing diminished protease activity is associated with-and could represent a cause of-autosomal dominant hereditary cerebral SVD. Our results also indicate a relationship between HTRA1 and TGF-β1/Smad signaling.

Activation by substoichiometric inhibition

Startling reports described the paradoxical triggering of the human mitogen-activated protein kinase pathway when a small-molecule inhibitor specifically inactivates the BRAF V600E protein kinase but not wt-BRAF. We performed a conceptual analysis of the general phenomenon "activation by inhibition" using bacterial and human HtrA proteases as models. Our data suggest a clear explanation that is based on the classic biochemical principles of allostery and cooperativity. Although substoichiometric occupancy of inhibitor binding sites results in partial inhibition, this effect is overrun by a concomitant activation of unliganded binding sites. Therefore, when an inhibitor of a cooperative enzyme does not reach saturating levels, a common scenario during drug administration, it may cause the contrary of the desired effect. The implications for drug development are discussed.

Late-onset retinal degeneration pathology due to mutations in CTRP5 is mediated through HTRA1

Late-onset retinal degeneration (L-ORD) is an autosomal dominant macular degeneration characterized by the formation of sub-retinal pigment epithelium (RPE) deposits and neuroretinal atrophy. L-ORD results from mutations in the C1q-tumor necrosis factor-5 protein (CTRP5), encoded by the CTRP5/C1QTNF5 gene. To understand the mechanism underlying L-ORD pathology, we used a human cDNA library yeast two-hybrid screen to identify interacting partners of CTRP5. Additionally, we analyzed the Bruch's membrane/choroid (BM-Ch) from wild-type (Wt), heterozygous S163R Ctrp5 mutation knock-in (Ctrp5S163R/wt ), and homozygous knock-in (Ctrp5S163R/S163R ) mice using mass spectrometry. Both approaches showed an association between CTRP5 and HTRA1 via its C-terminal PDZ-binding motif, stimulation of the HTRA1 protease activity by CTRP5, and CTRP5 serving as an HTRA1 substrate. The S163R-CTRP5 protein also binds to HTRA1 but is resistant to HTRA1-mediated cleavage. Immunohistochemistry and proteomic analysis showed significant accumulation of CTRP5 and HTRA1 in BM-Ch of Ctrp5S163R/S163R and Ctrp5S163R/wt mice compared with Wt. Additional extracellular matrix (ECM) components that are HTRA1 substrates also accumulated in these mice. These results implicate HTRA1 and its interaction with CTRP5 in L-ORD pathology.

Thermosensitive PBP2a requires extracellular folding factors PrsA and HtrA1 for Staphylococcus aureus MRSA β-lactam resistance

Staphylococcus aureus is a major human pathogen and represents a clinical challenge because of widespread antibiotic resistance. Methicillin resistant Staphylococcus aureus (MRSA) is particularly problematic and originates by the horizontal acquisition of mecA encoding PBP2a, an extracellular membrane anchored transpeptidase, which confers resistance to β-lactam antibiotics by allosteric gating of its active site channel. Herein, we show that dual disruption of PrsA, a lipoprotein chaperone displaying anti-aggregation activity, together with HtrA1, a membrane anchored chaperone/serine protease, resulted in severe and synergistic attenuation of PBP2a folding that restores sensitivity to β-lactams such as oxacillin. Purified PBP2a has a pronounced unfolding transition initiating at physiological temperatures that leads to irreversible precipitation and complete loss of activity. The concordance of genetic and biochemical data highlights the necessity for extracellular protein folding factors governing MRSA β-lactam resistance. Targeting the PBP2a folding pathway represents a particularly attractive adjuvant strategy to combat antibiotic resistance.

Establishment and identification of a novel HTRA1 mutation mice model

Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathyis a rare form of inherited cerebral small vessel disease associated with mutations in the high-temperature requirement serine peptidase A1 gene. As of now, only about 50 cases have been reported. In 2012, our group reported a family with a novel mutant of the high-temperature requirement serine peptidase A1 gene in China for the first time. To further explore the molecular pathogenesis of cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy, a recombination mouse model expressed human high-temperature requirement serine peptidase A1 gene mutant identified by our group was generated using the Donor & Clustered Regularly Interspaced Short Palindromic Repeats/Cas9 system and termed the Mut-high-temperature requirement serine peptidase A1 geneL364P mouse model. Results show that Mut-high-temperature requirement serine peptidase A1 geneL364P mice present similar pathological characteristics to patients with cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy, suggesting that the Mut-high-temperature requirement serine peptidase A1 geneL364P mouse model was generated successfully. Moreover, apoptosis was induced in mouse brain vascular smooth muscle cells derived from Mut-high-temperature requirement serine peptidase A1 geneL364P mice. In summary, the cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy mouse model described in this study will be beneficial to demonstrate the pathological mechanism of cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy and provide new therapeutic targets for clinical treatment.

The serine protease HtrA1 cleaves misfolded transforming growth factor β-induced protein (TGFBIp) and induces amyloid formation

The serine protease high-temperature requirement protein A1 (HtrA1) is associated with protein-misfolding disorders such as Alzheimer's disease and transforming growth factor β-induced protein (TGFBIp)-linked corneal dystrophy. In this study, using several biochemical and biophysical approaches, including recombinant protein expression, LC-MS/MS and 2DE analyses, and thioflavin T (ThT) fluorescence assays for amyloid fibril detection, and FTIR assays, we investigated the role of HtrA1 both in normal TGFBIp turnover and in corneal amyloid formation. We show that HtrA1 can cleave WT TGFBIp but prefers amyloidogenic variants. Corneal TGFBIp is extensively processed in healthy people, resulting in C-terminal degradation products spanning the FAS1-4 domain of TGFBIp. We show here that HtrA1 cleaves the WT FAS1-4 domain only inefficiently, whereas the amyloidogenic FAS1-4 mutations transform this domain into a considerably better HTRA1 substrate. Moreover, HtrA1 cleavage of the mutant FAS1-4 domains generated peptides capable of forming in vitro amyloid aggregates. Significantly, these peptides have been previously identified in amyloid deposits in vivo, supporting the idea that HtrA1 is a causative agent for TGFBIp-associated amyloidosis in corneal dystrophy. In summary, our results indicate that TGFBIp is an HtrA1 substrate and that some mutations in the gene encoding TGFBIp cause aberrant HtrA1-mediated processing that results in amyloidogenesis in corneal dystrophies.

HTRA1 promotes transdifferentiation of normal fibroblasts to cancer-associated fibroblasts through activation of the NF-κB/bFGF signaling pathway in gastric cancer

Cancer-associated fibroblasts comprise the major stromal cell populations in gastric cancer, which is a significant contributor to cancer-related death worldwide. As a member of the serine protease family, HTRA1 is reportedly involved in malignant transformation of various tumor types. In the present study, we observed that HTRA1 is positively correlated with α-SMA expression in gastric cancer tissues, which was also confirmed by correlation analysis and Gene Set Enrichment Analysis (GSEA) using the GEO database. Upregulation of HTRA1 in gastric cancer cell lines induces expression of α-SMA in normal fibroblasts. To explore how HTRA1 activates normal fibroblasts, an ELISA assay was performed. Secretion of bFGF/FGF2 from gastric cancer cells was significantly increased in response to HTRA1 overexpression. However, upreguation of α-SMA in normal fibroblasts induced by HTRA1 was restored by inhibiting the expression of bFGF. Furthermore, HTRA1 promotes bFGF/FGF2 expression through activation of NF-κB signaling in gastric cancer cells. Inhibition of the NF-κB signaling pathway partially restored baseline expression levels of α-SMA induced by HTRA1. In conclusion, HTRA1 promotes transdifferentiation of normal fibroblasts to cancer-associated fibroblasts by increasing bFGF/FGF2 expression, which is dependent upon activation of NF-κB signaling in gastric cancer.

Association of variants in HTRA1 and NOTCH3 with MRI-defined extremes of cerebral small vessel disease in older subjects

We report a composite extreme phenotype design using distribution of white matter hyperintensities and brain infarcts in a population-based cohort of older persons for gene-mapping of cerebral small vessel disease. We demonstrate its application in the 3C-Dijon whole exome sequencing (WES) study (n = 1924, nWESextremes = 512), with both single variant and gene-based association tests. We used other population-based cohort studies participating in the CHARGE consortium for replication, using whole exome sequencing (nWES = 2,868, nWESextremes = 956) and genome-wide genotypes (nGW = 9924, nGWextremes = 3308). We restricted our study to candidate genes known to harbour mutations for Mendelian small vessel disease: NOTCH3, HTRA1, COL4A1, COL4A2 and TREX1. We identified significant associations of a common intronic variant in HTRA1, rs2293871 using single variant association testing (Pdiscovery = 8.21 × 10-5, Preplication = 5.25 × 10-3, Pcombined = 4.72 × 10-5) and of NOTCH3 using gene-based tests (Pdiscovery = 1.61 × 10-2, Preplication = 3.99 × 10-2, Pcombined = 5.31 × 10-3). Follow-up analysis identified significant association of rs2293871 with small vessel ischaemic stroke, and two blood expression quantitative trait loci of HTRA1 in linkage disequilibrium. Additionally, we identified two participants in the 3C-Dijon cohort (0.4%) carrying heterozygote genotypes at known pathogenic variants for familial small vessel disease within NOTCH3 and HTRA1. In conclusion, our proof-of-concept study provides strong evidence that using a novel composite MRI-derived phenotype for extremes of small vessel disease can facilitate the identification of genetic variants underlying small vessel disease, both common variants and those with rare and low frequency. The findings demonstrate shared mechanisms and a continuum between genes underlying Mendelian small vessel disease and those contributing to the common, multifactorial form of the disease.

Murine osteoclasts secrete serine protease HtrA1 capable of degrading osteoprotegerin in the bone microenvironment

Osteoclasts are multinucleated cells responsible for bone resorption. The differentiation of osteoclasts from bone marrow macrophages (BMMs) is induced by receptor activator of NF-κB ligand (RANKL). Osteoprotegerin (OPG), a decoy receptor of RANKL, inhibits osteoclastogenesis by blocking RANKL signaling. Here we investigated the degradation of OPG in vitro. Osteoclasts, but not BMMs, secreted OPG-degrading enzymes. Using mass spectrometry and RNA-sequencing analysis, we identified high-temperature requirement A serine peptidase 1 (HtrA1) as an OPG-degrading enzyme. HtrA1 did not degrade OPG pre-reduced by dithiothreitol, suggesting that HtrA1 recognizes the three-dimensional structure of OPG. HtrA1 initially cleaved the amide bond between leucine 90 and glutamine 91 of OPG, then degraded OPG into small fragments. Inhibitory activity of OPG on RANKL-induced osteoclastogenesis was suppressed by adding HtrA1 in RAW 264.7 cell cultures. These results suggest that osteoclasts potentially prepare a microenvironment suitable for osteoclastogenesis. HtrA1 may be a novel drug target for osteoporosis.

High-Temperature Requirement A 1 Causes Photoreceptor Cell Death in Zebrafish Disease Models

Age-related macular degeneration (AMD) is an important cause of blindness. It is characterized by a retinal pigment epithelium (RPE) disorder that leads to death of photoreceptor cells (PRCs). AMD has a strong genetic association with high-temperature requirement A 1 (HTRA1). The relationship between HTRA1 and the AMD phenotype is unknown. In this study, we show that the expression of HTRA1 in PRCs, as well as in RPE, is increased by the disease-associated HTRA1 mutation and aging. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay and quantitative PCR of apoptosis-associated caspases confirmed that PRC-specific overexpression of HTRA1 induced PRC death. Transgenic zebrafish overexpressing human HTRA1 in rod PRCs showed morphologic changes of the RPE, including PRC death and lipofuscin accumulation, features similar to those of early AMD. htra1 expression was also increased in a retinitis pigmentosa zebrafish model compared with wild type. In both fish lines, PRC death was rescued by the suppression of htra1 by the inhibitor 6-boroV. AKT-forkhead box O3 signaling downstream of HTRA1 was activated via a tumor growth factor β signal, resulting in PRC death. These findings suggest that HTRA1 derived from PRCs is associated with early AMD via PRC death. HTRA1 is a potentially effective target for neuroprotective therapy of early AMD and other degenerative diseases of PRCs.

HtrA1 suppresses the growth of pancreatic cancer cells by modulating Notch-1 expression

Pancreatic cancer is well known to be the most deadly malignancy with the worst survival rate of all cancers. High temperature requirement factor A1 (HtrA1) plays an important role in cancer cell proliferation, migration, apoptosis, and differentiation. This study aimed to explore the function of HtrA1 in pancreatic cancer cell growth and its underlying mechanism. We found that the expression of HtrA1 was lower in pancreatic cancer tissue compared to the adjacent normal tissue. Consistently, HtrA1 levels were also decreased in two human pancreatic cancer cell lines, PANC-1 and BXPC-3. Moreover, enforced expression of HtrA1 inhibited cell viability and colony formation of PANC-1 and BXPC-3 cells. Overexpression of HtrA1 promoted apoptosis and suppressed migratory ability of tumor cells. On the contrary, siRNA-mediated knockdown of HtrA1 promoted the growth potential of pancreatic cancer cells. In addition, we found that up-regulation of HtrA1 reduced the expression of Notch-1 in pancreatic cancer cells. On the contrary, knockdown of HtrA1 increased the expression levels of Notch-1. Furthermore, overexpression of Notch-1 abolished the anti-proliferative effect of HtrA1 on pancreatic cancer cells. Taken together, our findings demonstrated that HtrA1 could inhibit pancreatic cancer cell growth via regulating Notch-1 expression, which implied that HtrA1 might be developed as a novel molecular target for pancreatic cancer therapy.

Elevated HTRA1 and HTRA4 in severe preeclampsia and their roles in trophoblast functions

Aberrant gene expression during placental development may affect fetal growth and contribute to preeclampsia. The high‑temperature requirement A (HTRA) family of proteins are serine proteases that may serve in the quality control of misfolded or mislocalized proteins. Recently, the potential involvement of HTRA1 and HTRA4 in the normal development of the placenta and in the pathogenesis of preeclampsia has been reported. The present study collected placental tissues from patients with severe preeclampsia and gestational age‑matched control samples. The expression of HTRA1 and HTRA4 was analyzed using reverse transcription‑quantitative polymerase chain reaction, western blotting and immunohistochemistry. The human trophoblast line HTR‑8 was transfected with HTRA1 or HTRA4, and cell function was assessed. The present study also detected the expression of HTRA1 and HTRA4 in HTR‑8/SVneo transfected cells under hypoxia (1% O2) and further studied the effects of hypoxia on HTR‑8 cell migration. HTRA1 and HTRA4 were mainly localized to the cytoplasm of syncytiotrophoblasts. The expression levels of the two genes were elevated in the placental tissues of patients with severe preeclampsia. Finally, it was determined in vitro that ectopic expression of HTRA1 and HTRA4 significantly attenuated HTR‑8 cell migration, and elevated HTRA1 limited HTR‑8 cell growth. Under hypoxic conditions, the expression levels of HTRA1 and HTRA4 improved significantly. It was hypothesized that the aberrant expression of HTRA1 or HTRA4 may be involved in the onset of preeclampsia, and increased HTRA1 or HTRA4 expression may affect trophoblast functions.