SERPINB12 Is a Slow-Binding Inhibitor of Granzyme A and Hepsin

Diagnostic and therapeutic value of human serpin family proteins

SERPIN (serine proteinase inhibitors) is an acronym for the superfamily of structurally similar proteins found in animals, plants, bacteria, viruses, and archaea. Over 1500 SERPINs are known in nature, while only 37 SERPINs are found in humans, which participate in inflammation, coagulation, angiogenesis, cell viability, and other pathophysiological processes. Both qualitative or quantitative deficiencies or overexpression and/or abnormal accumulation of SERPIN can lead to diseases commonly referred to as "serpinopathies". Hence, strategies involving SERPIN supplementation, elimination, or correction are utilized and/or under consideration. In this review, we discuss relationships between certain SERPINs and diseases as well as putative strategies for the clinical explorations of SERPINs.

Decoding the mechanisms of chimeric antigen receptor (CAR) T cell-mediated killing of tumors: insights from granzyme and Fas inhibition

Chimeric antigen receptor (CAR) T cell show promise in cancer treatments, but their mechanism of action is not well understood. Decoding the mechanisms used by individual T cells can help improve the efficacy of T cells while also identifying mechanisms of T cell failure leading to tumor escape. Here, we used a suite of assays including dynamic single-cell imaging of cell-cell interactions, dynamic imaging of fluorescent reporters to directly track cytotoxin activity in tumor cells, and scRNA-seq on patient infusion products to investigate the cytotoxic mechanisms used by individual CAR T cells in killing tumor cells. We show that surprisingly, overexpression of the Granzyme B (GZMB) inhibitor, protease inhibitor-9 (PI9), does not alter the cytotoxicity mediated by CD19-specific CAR T cells against either the leukemic cell line, NALM6; or the ovarian cancer cell line, SkOV3-CD19. We designed and validated reporters to directly assay T cell delivered GZMB activity in tumor cells and confirmed that while PI9 overexpression inhibits GZMB activity at the molecular level, this is not sufficient to impact the kinetics or magnitude of killing mediated by the CAR T cells. Altering cytotoxicity mediated by CAR T cells required combined inhibition of multiple pathways that are tumor cell specific: (a) B-cell lines like NALM6, Raji and Daudi were sensitive to combined GZMB and granzyme A (GZMA) inhibition; whereas (b) solid tumor targets like SkOV3-CD19 and A375-CD19 (melanoma) were sensitive to combined GZMB and Fas ligand inhibition. We realized the translational relevance of these findings by examining the scRNA-seq profiles of Tisa-cel and Axi-cel infusion products and show a significant correlation between GZMB and GZMA expression at the single-cell level in a T cell subset-dependent manner. Our findings highlight the importance of the redundancy in killing mechanisms of CAR T cells and how this redundancy is important for efficacious T cells.

Optimization of differentiation and transcriptomic profile of THP-1 cells into macrophage by PMA

THP-1 monocyte, which can be differentiated into macrophages by PMA, is widely used in researches on pathogen infection and host innate immunity, but reports on the induction methods of PMA are different and lack a unified standard, and the transcriptome characteristics of macrophage compared with THP-1 cells remains unclear. In this research, we examined the differentiation effect of three factors including induction time, cell seeding density and PMA concentration by detecting the positive rate of CD14 expression. The concentration of 80ng/ml of PMA, the induction time of 24h, and the cell seeding density of 5×105 cells/ml, could respectively facilitates a relatively higher CD14 positive rate in THP-1 cells. Under this optimized conditions, the CD14 positive rate of THP-1 cells can reach 66.52%. Transcriptome sequencing showed that after the above induction, the mRNA expression of 3113 genes which were closely related to cell communication, signal transduction, cell response to stimulus, signaling receptor binding and cytokine activity were up-regulated, and the top 10 genes were RGS1, SPP1, GDF15, IL-1B, HAVCR2, SGK1, EGR2, TRAC, IL-8 and EBI3. While the mRNA expression of 2772 genes which were associated with cell cycle process, DNA binding and replication and cell division, were down-regulated, and the top genes were SERPINB10, TRGC2, SERPINB2, TRGC1, MS4A3, MS4A4E, TRGJP1, MS4A6A, TRGJP2, MS4A4A. This research optimized the induction method on THP-1 cell differentiation from three aspects and delineated the transcriptomic profile of PMA-induced THP-1 cells, laying a foundation for the construction method of cell model and for the functional study of macrophage.

Neurobiochemical, Peptidomic, and Bioinformatic Approaches to Characterize Tauopathy Peptidome Biomarker Candidates in Experimental Mouse Model of Traumatic Brain Injury

Traumatic brain injury (TBI) is a multidimensional damage, and currently, no FDA-approved medicine is available. Multiple pathways in the cell are triggered through a head injury (e.g., calpain and caspase activation), which truncate tau and generate variable fragment sizes (MW 400-45,000 K). In this study, we used an open-head TBI mouse model generated by controlled cortical impact (CCI) and collected ipsilateral (IC) and contralateral (CC) mice htau brain cortices at one (D1) three (D3), and seven (D7) days post-injury. We implemented immunological (antibody-based detection) and peptidomic approaches (nano-reversed-phase liquid chromatography/tandem mass spectrometry) to investigate proteolytic tau peptidome (low molecular weight (LMW) < 10 K)) and pathological phosphorylation sites (high-molecular-weight (HMW); > 10 K) derived from CCI-TBI animal models. Our immunoblotting analysis verified tau hyperphosphorylation, HMW, and HMW breakdown products (HMW-BDP) formation of tau (e.g., pSer₂₀₂, pThr₁₈₁, pThr₂₃₁, pSer₃₉₆, and pSer₄₀₄), following CCI-TBI. Peptidomic data revealed unique sequences of injury-dependent proteolytic peptides generated from human tau protein. Among the N-terminal tau peptides, EIPEGTTAEEAGIGDTPSLEDEAAGHVTQA (a.a. 96-125) and AQPHTEIPEGTTAEEAGIGDTPSLEDEAAGHVTQARM (a.a. 91-127). Examples of tau C-terminal peptides identified include NVSSTGSIDMVDSPQLATLADEVSASLAKQGL (a.a. 410-441) and QLATLADEVSASLAKQGL (a.a. 424-441). Our peptidomic bioinformatic tools showed the association of proteases, such as CAPN1, CAPN2, and CTSL; CASP1, MMP7, and MMP9; and ELANE, GZMA, and MEP1A, in CCI-TBI tau peptidome. In clinical trials for novel TBI treatments, it might be useful to monitor a subset of tau peptidome as targets for biomarker utility and use them for a "theranostic" approach.

Role of the granzyme family in rheumatoid arthritis: Current Insights and future perspectives

Rheumatoid arthritis (RA) is a complex autoimmune disease characterized by chronic inflammation that affects synovial tissues of multiple joints. Granzymes (Gzms) are serine proteases that are released into the immune synapse between cytotoxic lymphocytes and target cells. They enter target cells with the help of perforin to induce programmed cell death in inflammatory and tumor cells. Gzms may have a connection with RA. First, increased levels of Gzms have been found in the serum (GzmB), plasma (GzmA, GzmB), synovial fluid (GzmB, GzmM), and synovial tissue (GzmK) of patients with RA. Moreover, Gzms may contribute to inflammation by degrading the extracellular matrix and promoting cytokine release. They are thought to be involved in RA pathogenesis and have the potential to be used as biomarkers for RA diagnosis, although their exact role is yet to be fully elucidated. The purpose of this review was to summarize the current knowledge regarding the possible role of the granzyme family in RA, with the aim of providing a reference for future research on the mechanisms of RA and the development of new therapies.

Noncytotoxic Roles of Granzymes in Health and Disease

Granzymes are serine proteases previously believed to play exclusive and somewhat redundant roles in lymphocyte-mediated target cell death. However, recent studies have challenged this paradigm. Distinct substrate profiles and functions have since emerged for each granzyme while their dysregulated proteolytic activities have been linked to diverse pathologies.

Serine protease inhibitor derived from Trichinella spiralis (TsSERP) inhibits neutrophil elastase and impairs human neutrophil functions

During early infection with Trichinella spiralis, host neutrophils destroy newborn larvae migrating in the bloodstream, preventing infection. However, parasites secrete various immunomodulatory molecules to escape the host’s defense mechanisms, allowing them to infect the host and live for long periods. T. spiralis secretes serine protease inhibitors (TsSERPs), which are key inhibitory molecules that regulate serine proteases involved in digestion and inflammation. However, the modulatory roles of TsSERP in the inhibition of neutrophil serine proteases (NSPs) and neutrophil functions are unknown. Therefore, the immunomodulatory properties of recombinant TsSERP1 (rTsSERP1) on NSPs and neutrophil functions were investigated in this study. rTsSERP1 preferentially inhibited human neutrophil elastase (hNE). In addition, incubation of rTsSERP1 with fMLP-induced neutrophils impaired their phagocytic ability. The formation of neutrophil extracellular traps (NETs) was activated with phorbol myristate acetate (PMA), and NETs were dramatically reduced when treated with rTsSERP1. Furthermore, rTsSERP1 suppressed the production of proinflammatory cytokines and chemokines during neutrophil activation, which are essential for neutrophil-mediated local or systemic inflammation regulation. In conclusion, T. spiralis immune evasion mechanisms are promoted by the inhibitory properties of TsSERP1 against neutrophil elastase and neutrophil defense functions, and these might be promising alternative treatment targets for inflammatory disorders.

Hepsin: a multifunctional transmembrane serine protease in pathobiology

Cell membrane-bound serine proteases are important in the maintenance of physiological homeostasis. Hepsin is a type II transmembrane serine protease highly expressed in the liver. Recent studies indicate that hepsin activates prohepatocyte growth factor in the liver to enhance Met signaling, thereby regulating glucose, lipid, and protein metabolism. In addition, hepsin functions in nonhepatic tissues, including the adipose tissue, kidney, and inner ear, to regulate adipocyte differentiation, urinary protein processing, and auditory function, respectively. In mouse models, hepsin deficiency lowers blood glucose, lipid, and protein levels, impairs uromodulin assembly in renal epithelial cells, and causes hearing loss. Elevated hepsin expression has also been found in many cancers. As a type II transmembrane protease, cell surface expression and zymogen activation are essential for hepsin activity. In this review, we discuss the current knowledge regarding hepsin biosynthesis, activation, and functions in pathobiology.

Priming of SARS-CoV-2 S protein by several membrane-bound serine proteinases could explain enhanced viral infectivity and systemic COVID-19 infection

The ongoing COVID-19 pandemic has already caused over a million deaths worldwide, and this death toll will be much higher before effective treatments and vaccines are available. The causative agent of the disease, the coronavirus SARS-CoV-2, shows important similarities with the previously emerged SARS-CoV-1, but also striking differences. First, SARS-CoV-2 possesses a significantly higher transmission rate and infectivity than SARS-CoV-1 and has infected in a few months over 60 million people. Moreover, COVID-19 has a systemic character, as in addition to the lungs, it also affects the heart, liver, and kidneys among other organs of the patients and causes frequent thrombotic and neurological complications. In fact, the term "viral sepsis" has been recently coined to describe the clinical observations. Here I review current structure-function information on the viral spike proteins and the membrane fusion process to provide plausible explanations for these observations. I hypothesize that several membrane-associated serine proteinases (MASPs), in synergy with or in place of TMPRSS2, contribute to activate the SARS-CoV-2 spike protein. Relative concentrations of the attachment receptor, ACE2, MASPs, their endogenous inhibitors (the Kunitz-type transmembrane inhibitors, HAI-1/SPINT1 and HAI-2/SPINT2, as well as major circulating serpins) would determine the infection rate of host cells. The exclusive or predominant expression of major MASPs in specific human organs suggests a direct role of these proteinases in e.g., heart infection and myocardial injury, liver dysfunction, kidney damage, as well as neurological complications. Thorough consideration of these factors could have a positive impact on the control of the current COVID-19 pandemic.

Granzymes in cardiovascular injury and disease

Chronic inflammation and impaired wound healing play important roles in the pathophysiology of cardiovascular diseases. Moreover, the aberrant secretion of proteases plays a critical role in pathological tissue remodeling in chronic inflammatory conditions. Human Granzymes (Granule secreted enzymes - Gzms) comprise a family of five (GzmA, B, H, K, M) cell-secreted serine proteases. Although each unique in function and substrate specificities, Gzms were originally thought to share redundant, intracellular roles in cytotoxic lymphocyte-induced cell death. However, an abundance of evidence has challenged this dogma. It is now recognized, that individual Gzms exhibit unique substrate repertoires and functions both intracellularly and extracellularly. In the extracellular milieu, Gzms contribute to inflammation, vascular dysfunction and permeability, reduced cell adhesion, release of matrix-sequestered growth factors, receptor activation, and extracellular matrix cleavage. Despite these recent findings, the non-cytotoxic functions of Gzms in the context of cardiovascular disease pathogenesis remain poorly understood. Minimally detected in tissues and bodily fluids of normal individuals, GzmB is elevated in patients with acute coronary syndromes, coronary artery disease, and myocardial infarction. Pre-clinical animal models have exemplified the importance of GzmB in atherosclerosis, aortic aneurysm, and cardiac fibrosis as animals deficient in GzmB exhibit reduced tissue remodeling, improved disease phenotypes and increased survival. Although a role for GzmB in cardiovascular disease is described, further work to elucidate the mechanisms that underpin the remaining human Gzms activity in cardiovascular disease is necessary. The present review provides a summary of the pre-clinical and clinical evidence, as well as emerging areas of research pertaining to Gzms in tissue remodeling and cardiovascular disease.

Skin tape proteomics identifies pathways associated with transepidermal water loss and allergen polysensitization in atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) and food allergy (FA) are associated with skin barrier dysfunction.

OBJECTIVE

Skin biomarkers are needed for skin barrier interventions studies.

METHODS

In this study, skin tape strip (STS) samples were collected from nonlesional skin of 62 children in AD FA+, AD FA-, and nonatopic groups for mass spectrometry proteomic analysis. transepidermal water loss and allergic sensitization were assessed. STS proteomic analysis results were validated in an independent cohort of 41 adults with AD with and without FA versus nonatopic controls.

RESULTS

A group of 45 proteins was identified as a principal component 1 (PC1) with the highest expression in AD FA+ STSs. This novel set of STS proteins was highly correlative to skin transepidermal water loss and allergic sensitization. PC1 proteins included keratin intermediate filaments; proteins associated with inflammatory responses (S100 proteins, alarmins, protease inhibitors); and glycolysis and antioxidant defense enzymes. Analysis of PC1 proteins expression in an independent adult AD cohort validated differential expression of STS PC1 proteins in the skin of adult patients with AD with the history of clinical reactions to peanut.

CONCLUSIONS

STS analysis of nonlesional skin of AD children identified a cluster of proteins with the highest expression in AD FA+ children. The differential expression of STS PC1 proteins was confirmed in a replicate cohort of adult AD patients with FA to peanut, suggesting a unique STS proteomic endotype for AD FA+ that persists into adulthood. Collectively, PC1 proteins are associated with abnormalities in skin barrier integrity and may increase the risk of epicutaneous sensitization to food allergens.

Molecular characterization of serine protease inhibitor isoform 3, SmSPI, from Schistosoma mansoni

Serine protease inhibitors, known as serpins, are pleiotropic regulators of endogenous and exogenous proteases, and molecule transporters. They have been documented in animals, plants, fungi, bacteria, and viruses; here, we characterize a serpin from the trematode platyhelminth Schistosoma mansoni. At least eight serpins have been found in the genome of S. mansoni, but only two have characterized molecular properties and functions. Here, the function of S. mansoni serpin isoform 3 (SmSPI) was analyzed, using both computational and molecular biological approaches. Phylogenetic analysis showed that SmSPI was closely related to Schistosoma haematobium serpin and Schistosoma japonicum serpin B10. Structure determined in silico confirmed that SmSPI belonged to the serpin superfamily, containing nine α-helices, three β-sheets, and a reactive central loop. SmSPI was highly expressed in schistosomules, predominantly in the head gland, and in adult male and female with intensive accumulation on the spines, which suggests that it may have a role in facilitating intradermal and intravenous survival. Recombinant SmSPI was overexpressed in Escherichia coli; the recombinant protein was of the same size (46 kDa) as the native protein. Immunological analysis suggested that mice infected with S. mansoni responded to rSmSPI at 8 weeks postinfection (wpi) but not earlier. The inhibitory activity of rSmSPI was specific to chymotrypsin but not trypsin, neutrophil elastase, and porcine pancreatic elastase. Elucidating the biological and physiological functions of SmSPI as well as other serpins will lead to further understanding of host-parasite interaction machinery that may provide novel strategies to prevent and control schistosomiasis in the future.