Structural Basis for Regulated Proteolysis by the α-Secretase ADAM10.

Cleavage of membrane-anchored proteins by ADAM (a disintegrin and metalloproteinase) endopeptidases plays a key role in a wide variety of biological signal transduction and protein turnover processes. Among ADAM family members, ADAM10 stands out as particularly important because it is both responsible for regulated proteolysis of Notch receptors and catalyzes the non-amyloidogenic α-secretase cleavage of the Alzheimer's precursor protein (APP). We present here the X-ray crystal structure of the ADAM10 ectodomain, which, together with biochemical and cellular studies, reveals how access to the enzyme active site is regulated. The enzyme adopts an unanticipated architecture in which the C-terminal cysteine-rich domain partially occludes the enzyme active site, preventing unfettered substrate access. Binding of a modulatory antibody to the cysteine-rich domain liberates the catalytic domain from autoinhibition, enhancing enzymatic activity toward a peptide substrate. Together, these studies reveal a mechanism for regulation of ADAM activity and offer a roadmap for its modulation.

Disruption of the endopeptidase ADAM10-Notch signaling axis leads to skin dysbiosis and innate lymphoid cell-mediated hair follicle destruction.

Hair follicles (HFs) function as hubs for stem cells, immune cells, and commensal microbes, which must be tightly regulated during homeostasis and transient inflammation. Here we found that transmembrane endopeptidase ADAM10 expression in upper HFs was crucial for regulating the skin microbiota and protecting HFs and their stem cell niche from inflammatory destruction. Ablation of the ADAM10-Notch signaling axis impaired the innate epithelial barrier and enabled Corynebacterium species to predominate the microbiome. Dysbiosis triggered group 2 innate lymphoid cell-mediated inflammation in an interleukin-7 (IL-7) receptor-, S1P receptor 1-, and CCR6-dependent manner, leading to pyroptotic cell death of HFs and irreversible alopecia. Double-stranded RNA-induced ablation models indicated that the ADAM10-Notch signaling axis bolsters epithelial innate immunity by promoting ß-defensin-6 expression downstream of type I interferon responses. Thus, ADAM10-Notch signaling axis-mediated regulation of host-microbial symbiosis crucially protects HFs from inflammatory destruction, which has implications for strategies to sustain tissue integrity during chronic inflammation.

Ectodomain shedding of PLA2R1 is mediated by the metalloproteases ADAM10 and ADAM17.

Phospholipase A2 receptor 1 (PLA2R1) is a 180-kDa transmembrane protein that plays a role in inflammation and cancer, and is the major autoantigen in membranous nephropathy (MN), a rare but severe autoimmune kidney disease. A soluble form of PLA2R1 has been detected in mouse and human serum. It is likely produced by proteolytic shedding of membrane-bound PLA2R1 but the mechanism is unknown. Here, we show that human PLA2R1 is cleaved by A Disintegrin And Metalloprotease 10 (ADAM10) and ADAM17 in HEK293 cells, mouse embryonic fibroblasts and human podocytes. By combining site-directed mutagenesis and sequencing, we determined the exact cleavage site within the extracellular juxtamembrane stalk of human PLA2R1. Orthologs and paralogs of PLA2R1 are also shed. By using pharmacological inhibitors and genetic approaches with RNA interference and knock-out cellular models, we identified a major role of ADAM10 in the constitutive shedding of PLA2R1, and a dual role of ADAM10 and ADAM17 in the stimulated shedding. We did not observe evidence for cleavage by ß- or γ-secretase, suggesting that PLA2R1 may not be a substrate for Regulated Intramembrane Proteolysis. PLA2R1 shedding occurs constitutively and can be triggered by the calcium ionophore ionomycin, the protein kinase C inducer PMA, cytokines and lipopolysaccharides, in vitro and in vivo. Altogether, our results show that PLA2R1 is a novel substrate for ADAM10 and ADAM17, producing a soluble form that is increased in inflammatory conditions and likely exerts various functions in physiological and pathophysiological conditions including inflammation, cancer and MN.

Neuron-specific gene NSG1 binds to and positively regulates sortilin ectodomain shedding via a metalloproteinase-dependent mechanism.

Increasing evidence suggests that aberrant regulation of sortilin ectodomain shedding can contribute to amyloid-ß pathology and frontotemporal dementia, although the mechanism by which this occurs has not been elucidated. Here, we probed for novel binding partners of sortilin using multiple and complementary approaches and identified two proteins of the neuron-specific gene (NSG) family, NSG1 and NSG2, that physically interact and colocalize with sortilin. We show both NSG1 and NSG2 induce subcellular redistribution of sortilin to NSG1- and NSG2-enriched compartments. However, using cell surface biotinylation, we found only NSG1 reduced sortilin cell surface expression, which caused significant reductions in uptake of progranulin, a molecular determinant for frontotemporal dementia. In contrast, we demonstrate NSG2 has no effect on sortilin cell surface abundance or progranulin uptake, suggesting specificity for NSG1 in the regulation of sortilin cell surface expression. Using metalloproteinase inhibitors and A disintegrin and metalloproteinase 10 KO cells, we further show that NSG1-dependent reduction of cell surface sortilin occurred via proteolytic processing by A disintegrin and metalloproteinase 10 with a concomitant increase in shedding of sortilin ectodomain to the extracellular space. This represents a novel regulatory mechanism for sortilin ectodomain shedding that is regulated in a neuron-specific manner. Furthermore, this finding has implications for the development of strategies for brain-specific regulation of sortilin and possibly sortilin-driven pathologies.

ADAM10- and γ-secretase-dependent cleavage of the transmembrane protein PTPRT attenuates neurodegeneration in the mouse model of Alzheimer's disease.

PTPRT (receptor-type tyrosine-protein phosphatase T), a brain-specific type 1 transmembrane protein, plays an important role in neurodevelopment and synapse formation. However, whether abnormal PTPRT signaling is associated with Alzheimer's disease (AD) remains elusive. Here, we report that Ptprt mRNA expression is found to be downregulated in the brains of both human and mouse models of AD. We further identified that the PTPRT intracellular domain (PICD), which is released by ADAM10- and γ-secretase-dependent cleavage of PTPRT, efficiently translocates to the nucleus via a conserved nuclear localization signal (NLS). We show that inhibition of nuclear translocation of PICD leads to an accumulation of phosphorylated signal transducer and activator of transcription 3 (pSTAT3), a substrate of PTPRT-eventually resulting in neuronal cell death. Consistently, RNA sequencing reveals that overexpression of PICD leads to changes in the expression of genes that are functionally associated with synapse formation, cell adhesion, and protein dephosphorylation. Moreover, overexpression of PICD not only decreases the level of phospho-STAT3Y705 and amyloid ß production in the hippocampus of APP/PS1 mice but also partially improves synaptic function and behavioral deficits in this mouse model of AD. These findings suggest that a novel role of the ADAM 10- and γ-secretase-dependent cleavage of PTPRT may alleviate the AD-like neurodegenerative processes.

Molecular Determinants Involved in the Docking and Uptake of Tumor-Derived Extracellular Vesicles: Implications in Cancer.

Extracellular vesicles produced by tumor cells (TEVs) influence all stages of cancer development and spread, including tumorigenesis, cancer progression, and metastasis. TEVs can trigger profound phenotypic and functional changes in target cells through three main general mechanisms: (i) docking of TEVs on target cells and triggering of intra-cellular signaling; (ii) fusion of TEVs and target cell membranes with release of TEVs molecular cargo in the cytoplasm of recipient cell; and (iii) uptake of TEVs by recipient cells. Though the overall tumor-promoting effects of TEVs as well as the general mechanisms involved in TEVs interactions with, and uptake by, recipient cells are relatively well established, current knowledge about the molecular determinants that mediate the docking and uptake of tumor-derived EVs by specific target cells is still rather deficient. These molecular determinants dictate the cell and organ tropism of TEVs and ultimately control the specificity of TEVs-promoted metastases. Here, we will review current knowledge on selected specific molecules that mediate the tropism of TEVs towards specific target cells and organs, including the integrins, ICAM-1 Inter-Cellular Adhesion Molecule), ALCAM (Activated Leukocyte Cell Adhesion Molecule), CD44, the metalloproteinases ADAM17 (A Disintegrin And Metalloproteinase member 17) and ADAM10 (A Disintegrin And Metalloproteinase member 10), and the tetraspanin CD9.

ADAM10 as a biomarker for Alzheimer's disease: A systematic review.

BACKGROUND: Studies have shown that A Disintegrin and Metalloproteinase 10 (ADAM10) is the main α-secretase in the non-amyloidogenic cleavage of the amyloid precursor protein (APP), avoiding the production of amyloid-ß peptide (Aß), one of the pathological hallmarks of Alzheimer's disease (AD). OBJECTIVE: To investigate ADAM10 from cerebrospinal fluid (CSF) and plasma/serum as a potential biomarker for AD. METHODS: A systematic review was carried out in the MEDLINE/PubMed, Web of Science, Embase, and Scopus databases using the terms and Boolean operators: "Alzheimer" AND "ADAM10" AND "biomarker". Citation searching was also adopted. The inclusion criteria were original studies of ADAM10 in blood or CSF in patients with AD. The risk of bias was assessed using the Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. The analysis methods were registered in the PROSPERO database (#CRD42021274239). RESULTS: Of the 97 records screened, 17 were included. There is strong evidence for lower levels of ADAM10 in platelets of persons with AD compared to cognitively healthy participants. On the other hand, higher levels of ADAM10 were found in plasma. Regarding CSF, controversial results were found with lower and higher levels of ADAM10 in persons with AD compared to healthy older adults. The differences may be due to diverse reasons, including different sample collection and processing and different antibodies, highlighting the importance of standardizing the experiments and choosing the appropriate antibodies for ADAM10 detection. CONCLUSION: Evidence shows that ADAM10 levels are altered in platelets, plasma, serum, and CSF of individuals with AD. The alteration was evident in all stages of the disease, and therefore, the protein may represent a complementary biomarker for the disease. However, more studies must be performed to establish cut-off values for ADAM10 levels to discriminate AD participants from cognitively unimpaired older adults.

Inhibition of clathrin-mediated endocytosis by knockdown of AP-2 leads to alterations in the plasma membrane proteome.

In eukaryotic cells, clathrin-mediated endocytosis (CME) is a central pathway for the internalization of proteins from the cell surface, thereby contributing to the maintenance of the plasma membrane protein composition. A key component for the formation of endocytic clathrin-coated vesicles (CCVs) is AP-2, as it sequesters cargo membrane proteins, recruits a multitude of other endocytic factors and initiates clathrin polymerization. Here, we inhibited CME by depletion of AP-2 and explored the consequences for the plasma membrane proteome. Quantitative analysis revealed accumulation of major constituents of the endosomal-lysosomal system reflecting a block in retrieval by compensatory CME. The noticeable enrichment of integrins and blockage of their turnover resulted in severely impaired cell migration. Rare proteins such as the anti-cancer drug target CA9 and tumor markers (CD73, CD164, CD302) were significantly enriched. The AP-2 knockdown attenuated the global endocytic capacity, but clathrin-independent entry pathways were still operating, as indicated by persistent internalization of specific membrane-spanning and GPI-anchored receptors (PVR, IGF1R, CD55, TNAP). We hypothesize that blocking AP-2 function and thus inhibiting CME may be a novel approach to identify new druggable targets, or to increase their residence time at the plasma membrane, thereby increasing the probability for efficient therapeutic intervention.

Potential impact of ADAM-10 genetic variants with the clinical features of oral squamous cell carcinoma.

A disintegrin and metalloproteinase domain-containing protein 10 (ADAM-10) involves in the tumour progression, but the impacts of single-nucleotide polymorphism (SNP) of ADAM-10 on oral squamous cell carcinoma (OSCC) remain unclear. The aim of this study was to investigate the influence of SNP of ADAM-10 on the clinical features of OSCC in male Taiwanese. Five loci of ADAM-10 SNPs including rs653765 (C/T), rs2305421 (A/G), rs514049 (A/C), rs383902 (T/C) and rs2054096 (A/T) were genotyped by TaqMan allelic discrimination in 1138 OSCC patients and 1199 non-OSCC individuals. The ADAM-10 SNP rs2305421 GG (AOR: 1.399, 95% CI: 1.045-1.874, p = 0.024) and G allele (AOR: 1.170, 95% CI: 1.012-1.351, p = 0.034) illustrated a significantly higher genotypic frequencies in the OSCC group compared to the distribution of the ADAM-10 SNP rs2305421 AA wild type. In the subgroup analysis, the ADAM-10 SNP rs383902 TC+CC was significantly correlated to tumour size larger than T2 in betel quid chewer (AOR: 1.375, 95% CI: 1.010-1.872, p = 0.043), while the ADAM-10 SNP rs653765 CT+TT was significantly associated with tumour size larger than T2 in cigarette smoker (AOR: 1.346, 95% CI: 1.023-1.772, p = 0.034). The results from The Cancer Genome Atlas revealed highest ADAM-10 mRNA level in T2 stage of current smokers with head and neck squamous cell carcinoma (HNSCC). In conclusions, the ADAM-10 SNP rs2305421 G allele is associated with the presence of OSCC, and the ADAM-10 SNP rs383902 TC+CC and ADAM-10 SNP rs653765 CT+TT correlates to large tumour size in specific conditions.

The metalloprotease ADAM10 generates soluble interleukin-2 receptor alpha (sCD25) in vivo.

The cytokine interleukin-2 (IL-2) plays a critical role in controlling the immune homeostasis by regulating the proliferation and differentiation of immune cells, especially T cells. IL-2 signaling is mediated via the IL-2 receptor (IL-2R) complex, which consists of the IL-2Rα (CD25), the IL-2Rß, and the IL-2Rγ. While the latter are required for signal transduction, IL-2Rα controls the ligand-binding affinity of the receptor complex. A soluble form of the IL-2Rα (sIL-2Rα) is found constitutively in human serum, though its levels are increased under various pathophysiological conditions. The sIL-2Rα originates partly from activated T cells through proteolytic cleavage, but neither the responsible proteases nor stimuli that lead to IL-2Rα cleavage are known. Here, we show that the metalloproteases ADAM10 and ADAM17 can cleave the IL-2Rα and generate a soluble ectodomain, which functions as a decoy receptor that inhibits IL-2 signaling in T cells. We demonstrate that ADAM10 is mainly responsible for constitutive shedding of the IL-2Rα, while ADAM17 is involved in IL-2Rα cleavage upon T cell activation. In vivo, we found that mice with a CD4-specific deletion of ADAM10, but not ADAM17, show reduced steady-state sIL-2Rα serum levels. We propose that the identification of proteases involved in sIL-2Rα generation will allow for manipulation of IL-2Rα cleavage, especially as constitutive and induced cleavage of IL-2Rα are executed by different proteases, and thus offer a novel opportunity to alter IL-2 function.

Dysregulation of ADAM10 shedding activity in naked mole-rat fibroblasts is due to deficient phosphatidylserine externalization.

The naked mole-rat (NMR, Heterocephalus glaber) is of significant interest to biogerontological research, rarely developing age-associated diseases, such as cancer. The transmembrane glycoprotein CD44 is upregulated in certain cancers and CD44 cleavage by a disintegrin and metalloproteinase 10 (ADAM10) regulates cellular migration. Here we provide evidence that mature ADAM10 is expressed in NMR primary skin fibroblasts (NPSF), and that ionomycin increases cell surface ADAM10 localization. However, we observed an absence of ADAM10 mediated CD44 cleavage, as well as shedding of exogenous and overexpressed betacellulin in NPSF, whereas in mouse primary skin fibroblasts ionomycin induced ADAM10-dependent cleavage of both CD44 and betacellulin. Overexpressing a hyperactive form of the Ca2+ -dependent phospholipid scramblase ANO6 in NPSF increased phosphatidylserine (PS) externalization, which rescued the ADAM10 sheddase activity and promoted cell migration in NPSF in an ADAM10-dependent manner. These findings suggest that dysregulation of ADAM10 shedding activity is due to a deficient PS externalization in NMR.

Combined proteomics and CRISPR‒Cas9 screens in PDX identify ADAM10 as essential for leukemia in vivo.

BACKGROUND: Acute leukemias represent deadly malignancies that require better treatment. As a challenge, treatment is counteracted by a microenvironment protecting dormant leukemia stem cells. METHODS: To identify responsible surface proteins, we performed deep proteome profiling on minute numbers of dormant patient-derived xenograft (PDX) leukemia stem cells isolated from mice. Candidates were functionally screened by establishing a comprehensive CRISPR‒Cas9 pipeline in PDX models in vivo. RESULTS: A disintegrin and metalloproteinase domain-containing protein 10 (ADAM10) was identified as an essential vulnerability required for the survival and growth of different types of acute leukemias in vivo, and reconstitution assays in PDX models confirmed the relevance of its sheddase activity. Of translational importance, molecular or pharmacological targeting of ADAM10 reduced PDX leukemia burden, cell homing to the murine bone marrow and stem cell frequency, and increased leukemia response to conventional chemotherapy in vivo. CONCLUSIONS: These findings identify ADAM10 as an attractive therapeutic target for the future treatment of acute leukemias.

The collectrin-like part of the SARS-CoV-1 and -2 receptor ACE2 is shed by the metalloproteinases ADAM10 and ADAM17.

The transmembrane protease angiotensin converting enzyme 2 (ACE2) is a protective regulator within the renin angiotensin system and additionally represents the cellular receptor for SARS-CoV. The release of soluble ACE2 (sACE2) from the cell surface is hence believed to be a crucial part of its (patho)physiological functions, as both, ACE2 protease activity and SARS-CoV binding ability, are transferred from the cell membrane to body fluids. Yet, the molecular sources of sACE2 are still not completely investigated. In this study, we show different sources and prerequisites for the release of sACE2 from the cell membrane. By using inhibitors as well as CRISPR/Cas9-derived cells, we demonstrated that, in addition to the metalloprotease ADAM17, also ADAM10 is an important novel shedding protease of ACE2. Moreover, we observed that ACE2 can also be released in extracellular vesicles. The degree of either ADAM10- or ADAM17-mediated ACE2 shedding is dependent on stimulatory conditions and on the expression level of the pro-inflammatory ADAM17 regulator iRhom2. Finally, by using structural analysis and in vitro verification, we determined for the first time that the susceptibility to ADAM10- and ADAM17-mediated shedding is mediated by the collectrin-like part of ACE2. Overall, our findings give novel insights into sACE2 release by several independent molecular mechanisms.

Treadmill workout activates PPARα in the hippocampus to upregulate ADAM10, decrease plaques and improve cognitive functions in 5XFAD mouse model of Alzheimer's disease.

Although liver is rich in peroxisome proliferator-activated receptor α (PPARα), recently we have described the presence of PPARα in hippocampus where it is involved in non-amyloidogenic metabolism of amyloid precursor protein (APP) via ADAM10, decreasing amyloid plaques and improving memory and learning. However, mechanisms to upregulate PPARα in vivo in the hippocampus are poorly understood. Regular exercise has multiple beneficial effects on human health and here, we describe the importance of regular mild treadmill exercise in upregulating PPARα in vivo in the hippocampus of 5XFAD mouse model of Alzheimer's disease. We also demonstrate that treadmill exercise remained unable to stimulate ADAM10, reduce plaque pathology and improve cognitive functions in 5XFADΔPPARα mice (5XFAD mice lacking PPARα). On the other hand, treadmill workout increased ADAM10, decreased plaque pathology and protected memory and learning in 5XFADΔPPARß mice (5XFAD mice lacking PPARß). Moreover, the other PPAR (PPARγ) also did not play any role in the transcription of ADAM10 in vivo in the hippocampus of treadmill exercised 5XFAD mice. These results underline an important role of PPARα in which treadmill exercise remains unable to exhibit neuroprotection in the hippocampus in the absence of PPARα.

Therapeutic potential of ADAM10 modulation in Alzheimer's disease: a review of the current evidence.

Alzheimer's disease (AD), the most common neurodegenerative disease worldwide, is caused by loss of neurons and synapses in central nervous system. Several causes for neuronal death in AD have been introduced, the most important of which are extracellular amyloid ß (Aß) accumulation and aggregated tau proteins. Increasing evidence suggest that targeting the process of Aß production to reduce its deposition can serve as a therapeutic option for AD management. In this regard, therapeutic interventions shown that a disintegrin and metalloproteinase domain-containing protein (ADAM) 10, involved in non-amyloidogenic pathway of amyloid precursor protein processing, is known to be a suitable candidate. Therefore, this review aims to examine the molecular properties of ADAM10, its role in AD, and introduce it as a therapeutic target to reduce the progression of the disease. Video abstract.

Tspan15-ADAM10 signalling enhances cancer stem cell-like properties and induces chemoresistance via Notch1 activation in ICC.

BACKGROUND & AIMS: Notch1 activation promotes ICC progression and is associated with chemoresistance; however, therapies directly targeting Notch1 showed severe adverse effects. Notch1 activation is mediated by ADAM10, a molecular scissor that separates the target protein from its substrates in the cell membrane. Tspan15 regulates ADAM10 function, but the role of Tspan15 in ICC progression is unclear. METHODS: Tspan15, ADAM10, and Notch1 expression and activation in fresh surgical specimens from 80 ICC patients and ICC cells were evaluated by immunohistochemistry, RT-PCR, western blotting, and flow cytometry. RESULTS: Tspan15 expression was increased in ICC compared with adjacent liver tissue, and high Tspan15 expression was an independent factor for poor prognosis. In ICC with high Tspan15 expression, vascular invasion, lymph node metastasis, and haematogenous recurrence were increased. Tspan15 was co-expressed with ADAM10 in ICC, and associated with the expression of stemness and EMT markers. In ICC cells, Tspan15 induced ADAM10 activation by mediating the translocation of activated m-ADAM10 from the cytoplasm to the surface of the cell membrane, which further activated Notch1 by separating the intracellular domain of Notch1 from its extracellular domain, leading to enhancement of CSC-like properties and EMT. This signalling was associated with enhanced chemoresistance against gemcitabine and cisplatin. Inhibition of Tspan15 or ADAM10 is a promising therapeutic strategy in ICC, as Tspan15 or ADAM10 knockdown or treatment with ADAM10 inhibitor reduced chemoresistance and invasiveness by suppressing Notch1-mediated CSC-like properties and EMT. CONCLUSIONS: Tspan15-ADAM10-Notch1 signalling is associated with aggressive tumour progression and poor prognosis in ICC.

ADAM10-a "multitasker" in sepsis: focus on its posttranslational target.

BACKGROUND: Sepsis has a complex pathogenesis in which the uncontrolled systemic inflammatory response triggered by infection leads to vascular barrier disruption, microcirculation dysfunction and multiple organ dysfunction syndrome. Numerous recent studies reveal that a disintegrin and metalloproteinase 10 (ADAM10) acts as a "molecular scissor" playing a pivotal role in the inflammatory response during sepsis by regulating proteolysis by cleaving various membrane protein substrates, including proinflammatory cytokines, cadherins and Notch, which are involved in intercellular communication. ADAM10 can also act as the cellular receptor for Staphylococcus aureus α-toxin, leading to lethal sepsis. However, its substrate-specific modulation and precise targets in sepsis have not yet to be elucidated. METHODS: We performed a computer-based online search using PubMed and Google Scholar for published articles concerning ADAM10 and sepsis. CONCLUSIONS: In this review, we focus on the functions of ADAM10 in sepsis-related complex endothelium-immune cell interactions and microcirculation dysfunction through the diversity of its substrates and its enzymatic activity. In addition, we highlight the posttranslational mechanisms of ADAM10 at specific subcellular sites, or in multimolecular complexes, which will provide the insight to intervene in the pathophysiological process of sepsis caused by ADAM10 dysregulation.

Initial study of the detection of ADAM 10 in the urine of type-2 diabetic patients.

Diabetes mellitus (DM) is a disease of civilization. If left untreated, it can cause serious complications and significantly shortens the life time. DM is one of the leading causes of end-stage renal disease (uremia) worldwide. Early diagnosis is a prerequisite for successful treatment, preferably before the first symptoms appear. In this paper, we describe the optimization and synthesis of the internally quenched fluorescent substrate disintegrin and metalloproteinase 10 (ADAM10). Using combinatorial chemistry methods with iterative deconvolution, the substrate specificity of the enzyme in non-primed and primed positions was determined. We used the ABZ-Lys-Ile-Ile-Asn-Leu-Lys-Arg-Tyr(3-NO2)-NH2 peptide to study ADAM10 activity in urine samples collected from patients diagnosed with type 2 diabetes, compared to urine samples from healthy volunteers. The proteolytically active enzyme was present in diabetes samples, while in the case of healthy people we did not observe any activity. In conclusion, our study provides a possible basis for further research into the potential role of ADAM10 in the diagnosis of type 2 diabetes.

The development of ADAM10 endocytosis inhibitors for the treatment of Alzheimer's disease.

The development of new therapeutic avenues that target the early stages of Alzheimer's disease (AD) is urgently necessary. A disintegrin and metalloproteinase domain 10 (ADAM10) is a sheddase that is involved in dendritic spine shaping and limits the generation of amyloid-ß. ADAM10 endocytosis increases in the hippocampus of AD patients, resulting in the decreased postsynaptic localization of the enzyme. To restore this altered pathway, we developed a cell-permeable peptide (PEP3) with a strong safety profile that is able to interfere with ADAM10 endocytosis, upregulating the postsynaptic localization and activity of ADAM10. After extensive validation, experiments in a relevant animal model clarified the optimal timing of the treatment window. PEP3 administration was effective for the rescue of cognitive defects in APP/PS1 mice only if administered at an early disease stage. Increased ADAM10 activity promoted synaptic plasticity, as revealed by changes in the molecular compositions of synapses and the spine morphology. Even though further studies are required to evaluate efficacy and safety issues of long-term administration of PEP3, these results provide preclinical evidence to support the therapeutic potential of PEP3 in AD.

Influence of leptin and compression in GAS-6 mediated homeostasis of periodontal ligament cell.

Growth arrest-specific protein 6 (GAS-6) regulates immunomodulatory and inflammatory mechanisms in periodontium and may participate in obesity predisposition. This study aimed to determine whether GAS-6 is associated with the homeostasis of periodontal ligament (SV-PDL) cells in the presence of adipokines or compressive forces. The SV-PDL cell line was used. Western blots were employed for TAM receptors detection. Cells were stimulated using different concentrations of GAS-6. The migration, viability, and proliferation were measured by a standard scratch test, MTS assay, and immunofluorescent staining. The mRNA expression was analyzed by RT-PCR. Release of TGF-ß1, GAS-6, and Axl were verified by ELISA. Western blot shows that TAM receptors are expressed in SV-PDL cells. GAS-6 has a promoting effect on cell migration and proliferation. RT-PCR analysis showed that GAS-6 induces Collagen-1, Collagen-3, Periostin, and TGF-ß1 mRNA expression whereas it reduces Caspase-3, Caspase-8, Caspase-9, and IL-6 mRNA expression. Further, secreted GAS-6 in SV-PDL is reduced in response to both compressive forces and leptin and upregulated by IL-6. Additionally, ADAM-10 inhibition reduces GAS-6 and Axl release on SV-PDL cells. TAM receptors especially Axl are identified as the receptors of GAS-6. GAS-6/TAM interactions contribute to periodontal ligament cells homeostasis. Leptin inhibits the GAS-6 release independently of ADAM-10 metalloprotease.