A Disintegrin And Metalloproteinase 10 Activity Research Articles

Acute interleukin-6 modulates key enzymes involved in prefrontal cortex and hippocampal amyloid precursor protein processing.

Exercise is beneficial for individuals with Alzheimer's disease (AD). In rodent models of AD, exercise decreases the amyloidogenic processing of the amyloid precursor protein (APP). Although, it remains unclear how exercise is promoting this shift away from pathological APP processing, there is emerging evidence that exercise-induced factors released from peripheral tissues may facilitate these alterations in brain APP processing. Interleukin-6 (IL-6) is released from multiple organs into peripheral circulation during exercise and is among the most characterized exerkines. The purpose of this study is to examine if acute IL-6 can modulate key enzymes responsible for APP processing, namely a disintegrin and metalloproteinase 10 (ADAM10) and beta-site amyloid precursor protein cleaving enzyme 1 (BACE1), which initiate the non-amyloidogenic and amyloidogenic cascades respectively. Male 10-week-old C57BL/6J mice underwent and acute treadmill exercise bout or were either injected with IL-6 or a PBS control 15 min prior to tissue collection. ADAM10 and BACE1 enzyme activity, mRNA, and protein expression, as well as downstream markers of both cascades, including sAPPa and sAPPβ, were examined. Exercise increased circulating IL-6 and brain IL-6 signaling (pSTAT3 and Socs3 mRNA). This occurred alongside a reduction in BACE1 activity and an increase in ADAM10 activity. IL-6 injection reduced BACE1 activity and increased sAPPa protein content in the prefrontal cortex. In the hippocampus, IL-6 injection decreased BACE1 activity and sAPPβ protein content. Our results show that acute IL-6 injection increases markers of the non-amyloidogenic cascade and decreases markers of the amyloidogenic cascade in the cortex and hippocampus of the brain.

Abstract 133: Coagulation FXI Regulates Endothelial Cell Barrier Function By Inducing VE-cadherin Proteolysis In An ADAM10-dependent Manner

Introduction: Proteolysis of vascular endothelial (VE)-cadherin is a biomarker for disruption of endothelial cell (EC) barrier function, with elevated levels of soluble VE-cadherin associated with atherosclerosis and sepsis. Factor XI (FXI), known for its role in the coagulation cascade, also plays a regulatory role in inflammation. While a relationship between FXI activity, VE-cadherin expression levels, and endothelial barrier function has been observed, the mechanisms by which this process is mediated are unknown. Hypothesis: Activated FXI (FXIa) regulates EC barrier function by inducing VE-cadherin proteolysis. Methods: Human umbilical vein endothelial cells were stimulated with FXIa (30 and 5 nM) for six hours. VE-cadherin proteolysis and expression levels were analyzed by Western blot and immunofluorescence. ECs permeability was quantified by measuring the flux of Evans blue-albumin across the ECs. Immunoprecipitation and Western blot analysis were used to study FXIa-PAI-1 or -very low density lipoprotein receptor (VLDLR) interactions. Results: FXIa (5 nM) generated a VE-cadherin C-terminal fragment and decreased VE-cadherin expression on ECs; this process was reversed by the serine protease inhibitor, PPACK. Thrombin, kallikrein, or FXIIa did not induce VE-cadherin proteolysis. FXIa increased ECs permeability, yet did not induce the expression of VCAM-1. In contrast, while VCAM-1 expression was upregulated by tumor necrosis factor alpha or vascular endothelial growth factor, neither of these induced VE-cadherin proteolysis. A pharmacological inhibitor of a disintegrin and metalloproteinase 10 (ADAM10) abrogated the effects of FXIa on ECs, including proteolysis of VE-cadherin. Similarly, the low density lipoprotein antagonist, receptor-associated protein (RAP), inhibited FXIa-induced VE-cadherin proteolysis by preventing FXIa complex formation with PAI-1 and VLDLR on ECs. Conclusion: These results suggest that FXIa disrupts VE-cadherin-mediated EC permeability by increasing ADAM10 activity through complex formation and internalization by PAI-1 and VLDLR. It remains to be seen whether this pathway represents a druggable target to protect EC barrier function in inflammatory diseases by inhibiting FXIa.

Postexercise serum from humans influences the biological tug of war of APP processing in human neuronal cells.

Neurodegenerative diseases such as Alzheimer's disease (AD) are becoming more prevalent in our aging society. One specific neuropathological hallmark of this disease is the accumulation of amyloid-β (Aβ) peptides, which aggregate to form extraneuronal plaques. Increased Aβ peptides are often observed well before symptoms of AD develop, highlighting the importance of targeting Aβ-producing pathways early on in disease progression. Evidence indicates that exercise has the capacity to reduce Aβ peptide production in the brain; however, the mechanisms remain unknown. Exercise-induced signaling mediators could be the driving force behind some of the beneficial effects observed in the brain with exercise. The purpose of this study was to examine if postexercise serum and the factors it contains can alter neuronal amyloid precursor protein (APP) processing. Human SH-SY5Y neuronal cells were differentiated with retinoic acid for 5 days and treated with 10% pre- or postexercise serum from humans for 30 min. Cells were collected for analysis of acute (30 min; n = 6) or adaptive (24 h posttreatment; n = 6) responses. There were no statistical differences in a disintegrin and metalloproteinase 10 (ADAM10) and β-site amyloid precursor protein cleaving enzyme 1 (BACE1) mRNA or protein expression with postexercise serum treatment at either time point. However, there was an increase in the ratio of soluble amyloid precursor protein α (sAPPα) to soluble amyloid precursor protein β (sAPPβ) protein content (P = 0.05) after 30 min of postexercise serum treatment. In addition, 30 min of postexercise serum treatment increased ADAM10 (P = 0.01) and BACE1 (P = 0.02) activity. These findings suggest that postexercise serum modulates important enzymes involved in APP processing, potentially pushing the cascade toward the nonamyloidogenic arm.

Fibrin exposure triggers αIIbβ3‐independent platelet aggregate formation, ADAM10 activity and glycoprotein VI shedding in a charge‐dependent manner

BackgroundCollagen and fibrin engagement and activation of glycoprotein (GP) VI induces proteolytic cleavage of the GPVI ectodomain generating shed soluble GPVI (sGPVI). Collagen‐mediated GPVI shedding requires intracellular signalling to release the sGPVI, mediated by A Disintegrin And Metalloproteinase 10 (ADAM10); however, the precise mechanism by which fibrin induces GPVI shedding remains elusive. Plasma sGPVI levels are elevated in patients with coagulopathies, sepsis, or inflammation and can predict onset of sepsis and sepsis‐related mortality; therefore, it is clinically important to understand the mechanisms of GPVI shedding under conditions of minimal collagen exposure. ObjectivesOur aim was to characterize mechanisms by which fibrin‐GPVI interactions trigger GPVI shedding. MethodsPlatelet aggregometry, sGPVI ELISA, and an ADAM10 fluorescence resonance energy transfer assay were used to measure fibrin‐mediated platelet responses. ResultsFibrin induced αIIbβ3‐independent washed platelet aggregate formation, GPVI shedding, and increased ADAM10 activity, all of which were insensitive to pre‐treatment with inhibitors of Src family kinases but were divalent cation‐ and metalloproteinase‐dependent. In contrast, treatment of washed platelets with other GPVI ligands, collagen, and collagen‐related peptide caused αIIbβ3‐dependent platelet aggregation and GPVI release but did not increase constitutive ADAM10 activity. ConclusionsFibrin engages GPVI in a manner that differs from other GPVI ligands. Inclusion of polyanionic molecules disrupted fibrin‐induced platelet aggregate formation and sGPVI release, suggesting that electrostatic charge may play a role in fibrin/GPVI engagement. It may be feasible to exploit this property and specifically disrupt GPVI/fibrin interactions whilst sparing GPVI/collagen engagement.Fibrin engages GPVI in a manner that differs from other GPVI ligands. Inclusion of polyanionic molecules disrupted fibrin‐induced platelet aggregate formation and sGPVI release, suggesting that electrostatic charge may play a role in fibrin/GPVI engagement. It may be feasible to exploit this property and specifically disrupt GPVI/fibrin interactions whilst sparing GPVI/collagen engagement.

PP2A enables IL-2 signaling by preserving IL-2Rβ chain expression during Treg development.

Tregs require IL-2 signaling for signal transducer and activator of transcription 5 (STAT5)-mediated induction of Foxp3. While phosphatase 2A (PP2A) is a negative regulator of IL-2 production in effector T cells and Tregs do not produce IL-2, it is not known whether PP2A controls IL-2 signaling in Tregs. To address the role of PP2A in IL-2 signaling in Tregs we studied mice engineered to lack PP2A in all Foxp3-expressing cells. We report that PP2A is required to enable Foxp3 expression and to maintain sufficient numbers of Tregs in the thymus. We show for the first time that PP2A prevents the selective loss of surface IL-2Rβ and preserves IL-2R signaling potency in Tregs. The loss of IL-2Rβ in thymus- and spleen-derived Tregs that lack PP2A is due to increased sheddase activity. Pan-sheddase or selective A disintegrin and metalloproteinase 10 (ADAM10) inhibition, like forced expression of IL-2Rβ in PP2A-deficient Tregs restored IL-2Rβ expression and signaling. Thus, PP2A restrains the sheddase activity of ADAM10 in Treg cells to prevent the cleavage of IL-2Rβ from the cell surface to enable competent IL-2R signaling which is essential for Tregs development and homeostasis.

Amyloid-\u03b2 Oligomers Regulate ADAM10 Synaptic Localization Through Aberrant Plasticity Phenomena

A disintegrin and metalloproteinase 10 (ADAM10) is a synaptic enzyme that has been previously shown to limit amyloid-β1–42 (Aβ1–42) peptide formation in Alzheimer’s disease (AD). Furthermore, ADAM10 participates to spine shaping through the cleavage of adhesion molecules and its activity is under the control of synaptic plasticity events. In particular, long-term depression (LTD) promotes ADAM10 synaptic localization triggering its forward trafficking to the synapse, while long-term potentiation elicits ADAM10 internalization. Here, we show that a short-term in vitro exposure to Aβ1–42 oligomers, at a concentration capable of inducing synaptic depression and spine loss, triggers an increase in ADAM10 synaptic localization in hippocampal neuronal cultures. However, the Aβ1–42 oligomers-induced synaptic depression does not foster ADAM10 delivery to the synapse, as the physiological LTD, but impairs ADAM10 endocytosis. Moreover, Aβ1–42 oligomers-induced inhibition of ADAM10 internalization requires neuronal activity and the activation of the NMDA receptors. These data suggest that, at the synaptic level, Aβ1–42 oligomers trigger an aberrant plasticity mechanism according to which Aβ1–42 oligomers can downregulate Aβ generation through the modulation of ADAM10 synaptic availability. Moreover, the increased activity of ADAM10 towards its synaptic substrates could also affect the structural plasticity phenomena. Overall, these data shed new lights on the strict and complex relationship existing between synaptic activity and the primary mechanisms of AD pathogenesis.

Elevated serum HER‐2 predicts poor prognosis in breast cancer and is correlated to ADAM10 expression

Human epidermal growth factor receptor‐2 (HER‐2) overexpression in breast tumor tissues is associated with a poor prognosis but may benefit from treatment with trastuzumab. The extracellular domain (ECD) of HER‐2 can be measured in serum and which has been a new inspection item in clinical laboratory of several hospitals. However, whether serum HER‐2 ECD can be a marker of HER‐2 status in tumor tissues still confused clinicians. This study is a retrospective observation to explore the correlation between serum HER‐2 ECD shedding and tissue HER‐2 status in breast cancer patients. Meanwhile, we will further uncover the potential clinical significance of serum HER‐2 ECD detection. A total of 545 unselected breast cancer patients from Fudan University Shanghai Cancer Center were enrolled in this study. At primary diagnosis without any treatment, serum HER‐2 ECD was measured on ADVIA Centaur assay; meanwhile, tissue HER‐2 from core needle biopsy was tested through immunohistochemistry (IHC) and fluorescent in situ hybridization (FISH). We showed that serum HER‐2 ECD concentration was related to tissue HER‐2 status. Nevertheless, 36.9% of patients with tissue HER‐2 overexpression had low levels of HER‐2 ECD shedding (<15 ng/mL) in serum. Here, we demonstrated that HER‐2 ECD shedding was also associated with protein expression and alpha‐secretase activity of a disintegrin and metalloproteinase 10 (ADAM10) using tumor tissues and cell lines. Progression‐free survival (PFS) data from breast cancer patients in TNM phase II and III with tissue HER‐2 IHC 3+ were analyzed using Kaplan‐Meier plotter. The patients with serum HER‐2 ECD above 15 ng/mL had lower progression‐free survival than those with serum HER‐2 ECD <15 ng/mL. Thus, serum HER‐2 ECD could be a biomarker to identify the subgroup of poorer outcome among HER‐2 overexpression breast cancer patients. Inhibition of ADAM10 activity may have potential therapeutic benefit for this most aggressive tumor subgroup.

Regulation of Alpha-Secretase ADAM10 In vitro and In vivo: Genetic, Epigenetic, and Protein-Based Mechanisms.

ADAM10 (A Disintegrin and Metalloproteinase 10) has been identified as the major physiological alpha-secretase in neurons, responsible for cleaving APP in a non-amyloidogenic manner. This cleavage results in the production of a neuroprotective APP-derived fragment, APPs-alpha, and an attenuated production of neurotoxic A-beta peptides. An increase in ADAM10 activity shifts the balance of APP processing toward APPs-alpha and protects the brain from amyloid deposition and disease. Thus, increasing ADAM10 activity has been proposed an attractive target for the treatment of neurodegenerative diseases and it appears to be timely to investigate the physiological mechanisms regulating ADAM10 expression. Therefore, in this article, we will (1) review reports on the physiological regulation of ADAM10 at the transcriptional level, by epigenetic factors, miRNAs and/or protein interactions, (2) describe conditions, which change ADAM10 expression in vitro and in vivo, (3) report how neuronal ADAM10 expression may be regulated in humans, and (4) discuss how this knowledge on the physiological and pathophysiological regulation of ADAM10 may help to preserve or restore brain function.

Dissecting the role of ADAM10 as a mediator of Staphylococcus aureus α-toxin action.

Staphylococcus aureus is a leading cause of bacterial infections in humans, including life-threatening diseases such as pneumonia and sepsis. Its small membrane-pore-forming α-toxin is considered an important virulence factor. By destroying cell-cell contacts through cleavage of cadherins, the metalloproteinase ADAM10 (a disintegrin and metalloproteinase 10) critically contributes to α-toxin-dependent pathology of experimental S. aureus infections in mice. Moreover, ADAM10 was proposed to be a receptor for α-toxin. However, it is unclear whether the catalytic activity or specific domains of ADAM10 are involved in mediating binding and/or subsequent cytotoxicity of α-toxin. Also, it is not known how α-toxin triggers ADAM10's enzymatic activity, and whether ADAM10 is invariably required for all α-toxin action on cells. In the present study, we show that efficient cleavage of the ADAM10 substrate epithelial cadherin (E-cadherin) requires supra-cytotoxic concentrations of α-toxin, leading to significant increases in intracellular [Ca(2+)]; the fall in cellular ATP levels, typically following membrane perforation, became observable at far lower concentrations. Surprisingly, ADAM10 was dispensable for α-toxin-dependent xenophagic targeting of S. aureus, whereas a role for α-toxin attack on the plasma membrane was confirmed. The catalytic site of ADAM10, furin cleavage site, cysteine switch and intracellular domain of ADAM10 were not required for α-toxin binding and subsequent cytotoxicity. In contrast, an essential role for the disintegrin domain and the prodomain emerged. Thus, co-expression of the prodomain with prodomain-deficient ADAM10 reconstituted binding of α-toxin and susceptibility of ADAM10-deficient cells. The results of the present study may help to inform structural analyses of α-toxin-ADAM10 interactions and to design novel strategies to counteract S. aureus α-toxin action.

Serum Level of Soluble Receptor for Advanced Glycation End Products Is Associated with A Disintegrin And Metalloproteinase 10 in Type 1 Diabetes.

BackgroundThe receptor for advanced glycation end products (RAGE) is involved in the pathogenesis of diabetic complications, and soluble forms of the receptor (sRAGE) can counteract the detrimental action of the full-length receptor by acting as decoy. Soluble RAGE is produced by alternative splicing [endogenous secretory RAGE (esRAGE)] and/or by proteolytic cleavage of the membrane-bound receptor. We have investigated the role of A Disintegrin And Metalloproteinase 10 (ADAM10) in the ectodomain shedding of RAGE.MethodsConstitutive and insulin-induced shedding of RAGE in THP-1 macrophages by ADAM10 was evaluated using an ADAM10-specific metalloproteinase inhibitor. Serum ADAM10 level was measured in type 1 diabetes and control subjects, and the association with serum soluble RAGE was determined. Serum total sRAGE and esRAGE were assayed by ELISA and the difference between total sRAGE and esRAGE gave an estimated measure of soluble RAGE formed by cleavage (cRAGE).ResultsRAGE shedding (constitutive and insulin-induced) was significantly reduced after inhibition of ADAM10 in macrophages, and insulin stimulated ADAM10 expression and activity. Diabetic subjects have higher serum total sRAGE and esRAGE (p<0.01) than controls, and serum ADAM10 was also increased (p<0.01). Serum ADAM10 correlated with serum cRAGE in type 1 diabetes (r = 0.40, p<0.01) and in controls (r = 0.31. p<0.01) but no correlations were seen with esRAGE. The association remained significant after adjusting for age, gender, BMI, smoking status and HbA1c.ConclusionOur data suggested that ADAM10 contributed to the shedding of RAGE. Serum ADAM10 level was increased in type 1 diabetes and was a significant determinant of circulating cRAGE.

Metallothionein-III increases ADAM10 activity in association with furin, PC7, and PKCα during non-amyloidogenic processing.

A-disintegrin and metalloproteinase 10 (ADAM10) is involved in the generation of amyloid-β (Aβ) during amyloid precursor protein (APP) processing, and has a protective effect against Aβ neurotoxicity. We explored how metallothionein-III (MT-III) is regulated in the non-amyloidogenic pathway to generate soluble APPα (sAPPα). MT-ІІІ increased sAPPα levels and reduced Aβ peptide levels, but did not affect ADAM10 expression. However, MT-III increased the activity of ADAM10. MT-ІІІ-induced sAPPα secretion, and Aβ peptide formation was blocked by specific inhibitors of furin, proprotein convertase7 (PC7), and PKCα. These results demonstrate that MT-ІІІ increases the amount of active ADAM10 in association with furin, PC7 and PKCα.

LC–MS Based Cleavage Site Profiling of the Proteases ADAM10 and ADAM17 Using Proteome-Derived Peptide Libraries

A Disintegrin and Metalloproteinase 10 (ADAM10) and ADAM17 catalyze ectodomain shedding of a number of cell surface proteins important for embryonic development and tissue homeostasis. Changes in the expression levels or dysregulated proteolytic activity of ADAM10 and ADAM17 have been shown to play important roles in multiple diseases such as inflammation, cancer, and neurodegenerative disorders. Despite the well documented substrate repertoire of ADAM10 and ADAM17, little is known about their cleavage site specificity. We optimized Q-PICS (Quantitative Proteomics for the Identification of Cleavage Sites) to elucidate the cleavage site specificity of recombinant murine ADAM10 and ADAM17. Two different yeast proteome-derived peptide libraries were used and samples were analyzed by LC-MALDI and LC-ESI MS in parallel. We show that the largest difference in the cleavage site specificities of ADAM10 and ADAM17 is at the P1' site: while both enzymes cleave N-terminal of leucine, only ADAM10 shows additional preference toward aromatic amino acids, whereas ADAM17 exhibits the highest preference for valine. Together with further amino acid preferences more adjacent to the scissile bond, our data is in good agreement with ADAM10/17 cleavage sites previously identified in native substrates. Overall, the precise identification of ADAM10 and ADAM17 cleavage site specificity provides the basis for better substrate identification in vivo and the generation of specific inhibitors or activity based probes.

Endocytosis of synaptic ADAM10 in neuronal plasticity and Alzheimer’s disease

A disintegrin and metalloproteinase 10 (ADAM10), a disintegrin and metalloproteinase that resides in the postsynaptic densities (PSDs) of excitatory synapses, has previously been shown to limit β-amyloid peptide (Aβ) formation in Alzheimer's disease (AD). ADAM10 also plays a critical role in regulating functional membrane proteins at the synapse. Using human hippocampal homogenates, we found that ADAM10 removal from the plasma membrane was mediated by clathrin-dependent endocytosis. Additionally, we identified the clathrin adaptor AP2 as an interacting partner of a previously uncharacterized atypical binding motif in the ADAM10 C-terminal domain. This domain was required for ADAM10 endocytosis and modulation of its plasma membrane levels. We found that the ADAM10/AP2 association was increased in the hippocampi of AD patients compared with healthy controls. Long-term potentiation (LTP) in hippocampal neuronal cultures induced ADAM10 endocytosis through AP2 association and decreased surface ADAM10 levels and activity. Conversely, long-term depression (LTD) promoted ADAM10 synaptic membrane insertion and stimulated its activity. ADAM10 interaction with the synapse-associated protein-97 (SAP97) was necessary for LTD-induced ADAM10 trafficking and required for LTD maintenance and LTD-induced changes in spine morphogenesis. These data identify and characterize a mechanism controlling ADAM10 localization and activity at excitatory synapses that is relevant to AD pathogenesis.

Tetraspanin15 regulates cellular trafficking and activity of the ectodomain sheddase ADAM10.

A disintegrin and metalloproteinase10 (ADAM10) has been implicated as a major sheddase responsible for the ectodomain shedding of a number of important surface molecules including the amyloid precursor protein and cadherins. Despite a well-documented role of ADAM10 in health and disease, little is known about the regulation of this protease. To address this issue we conducted a split-ubiquitin yeast two-hybrid screen to identify membrane proteins that interact with ADAM10. The yeast experiments and co-immunoprecipitation studies in mammalian cell lines revealed tetraspanin15 (TSPAN15) to specifically associate with ADAM10. Overexpression of TSPAN15 or RNAi-mediated knockdown of TSPAN15 led to significant changes in the maturation process and surface expression of ADAM10. Expression of an endoplasmic reticulum (ER) retention mutant of TSPAN15 demonstrated an interaction with ADAM10 already in the ER. Pulse-chase experiments confirmed that TSPAN15 accelerates the ER-exit of the ADAM10-TSPAN15 complex and stabilizes the active form of ADAM10 at the cell surface. Importantly, TSPAN15 also showed the ability to mediate the regulation of ADAM10 protease activity exemplified by an increased shedding of N-cadherin and the amyloid precursor protein. In conclusion, our data show that TSPAN15 is a central modulator of ADAM10-mediated ectodomain shedding. Therapeutic manipulation of its expression levels may be an additional approach to specifically regulate the activity of the amyloid precursor protein alpha-secretase ADAM10.

The Role of the Anti-Amyloidogenic Secretase ADAM10 in Shedding the APP-like Proteins

ADAM10 (A disintegrin and metalloproteinase 10) has been demonstrated as an enzyme with protective properties in Alzheimer's disease: in mouse models it not only lowered generation of toxic A-beta peptides and formation of senile plaques but also alleviated learning deficits and enhanced synaptic density. This is due to cleavage of the amyloid precursor protein (APP) within its A-beta stretch and to the release of the extracellular domain of APP with neuroprotective function. Aside from cleaving APP, ADAM10 has been linked to over 40 putative substrates at least in cell culture. These substrates are connected with important cellular functions such as cell migration, stress response and transport. For this contribution we focussed on ADAM10 acting on the APP-like proteins since for some of their representatives - in particular APLP2 and APP-L - a shedding by ADAM10 has been demonstrated in vivo. In addition, the importance of these proteins, especially of APLP2, has been repeatedly shown by intense analysis of double and triple transgenic mice which lack APP in combination with one or both APLPs: several phenotypes such as defects in migration of neuroblasts, in formation of synapses and synaptic transmission have been reported. However, the specific contribution of either the uncleaved full-length proteins or their extracellular domains secreted upon ADAM10 activity has not been elucidated. In this review, we report on recent findings concerning shedding of APP-like proteins and resulting functional consequences.

Acitretin, an Enhancer of Alpha-Secretase Expression, Crosses the Blood-Brain Barrier and Is Not Eliminated by P-Glycoprotein

Background: ADAM10 (a disintegrin and metalloproteinase 10) has been demonstrated to act as the main physiological α-secretase. Enzymatic activity of the α-secretase on the one hand prevents the formation of toxic Aβ peptides and on the other hand promotes the secretion of a neurotrophic and neuroprotective amyloid precursor protein fragment (APPs-α) by cleaving the amyloid precursor protein within its Aβ sequence. Enhancement of ADAM10’s gene expression may therefore present a valuable therapeutic approach for the treatment of Alzheimer’s disease (AD), where Aβ peptides are severely involved in the pathogenesis. Objective: In cell culture and in a transgenic mouse model of AD, retinoids led to increased ADAM10 expression and activity. We therefore endeavor to develop a clinical application of synthetic retinoids such as acitretin in AD. Methods: The effect of synthetic retinoids on ADAM10 gene expression was analyzed by reporter gene assays in human neuroblastoma cell line SH-SY5Y. Penetrance of acitretin into the murine brain was analyzed by high-performance liquid chromatography. P-glycoprotein (P-gp) double-knockout mice with a deficiency in both isoforms, mdr1a and 1b, were used to analyze a possible role of P-gp-dependent efflux on acitretin distribution. Results: Acitretin and tamibarotene are both potent activators of ADAM10 promoter activity. Acitretin crosses the murine blood-brain barrier and its level in the mouse brain is not reduced by P-gp. Conclusion: Synthetic retinoids and especially acitretin seem to be ideal candidates to establish an ADAM10-based AD treatment, and therefore have already entered first clinical trials.

ADAM10 overexpression dysregulates S2/S3 cleavage of Notch, shifting hematopoietic lineage commitment in favor of myelopoiesis (153.3)

Abstract Although the mechanism by which A Disintegrin and Metalloproteinase 10 (ADAM10) regulates hematopoiesis remains unclear, recent reports indicate its essential role in performing S2 cleavage of Notch receptors. Thus to determine the role of ADAM10 activity in hematopoiesis, we generated ADAM10 overexpressing mice (A10Tg). Transgene expression alters hematopoiesis post-hematopoietic Lineage-Sca-1+c-kit+ (LSK) subset differentiation but prior to lineage commitment of progenitor populations, which are dramatically affected in A10Tg mice. This results in delayed T cell development, abrogated B cell development, and expansion of myeloid derived suppressor cells (MDSCs). Albeit being in a tumor-free host, A10Tg MDSCs are functionally and phenotypically analogous to tumor-derived MDSCs. Given ADAM10’s role in Notch signaling, we hypothesized that the observed hematopoietic alterations may be a consequence of perturbed Notch signaling. In fact, blockade of ADAM10 (S2) rescues B cell development and reduces myeloid cells in A10Tg LSKs. Additionally, inhibition of γ-secretase (S3) in wild type LSKs results in enhanced myelopoiesis, mimicking the phenotype of A10Tg mice. Collectively, these findings indicate that the differential cleavage of Notch into S2 and S3 products regulated by ADAM10 is critical to hematopoietic cell-fate determination. Additionally, A10Tg mice provide a novel model for the examination of MDSC-mediated immune suppression in a tumor free environment.

An Arginine Stretch Limits ADAM10 Exit from the Endoplasmic Reticulum

A disintegrin and metalloproteinase 10 (ADAM10) is a type I transmembrane glycoprotein responsible for the ectodomain shedding of a number of proteins implicated in the pathogenesis of diseases ranging from cancer to Alzheimer Disease. ADAM10 is synthesized in an inactive form, which is proteolytically activated during its forward transport along the secretory pathway and at the plasma membrane. Therefore, modulation of its trafficking could provide a mechanism to finely tune its shedding activity. Here we report the identification of an endoplasmic reticulum (ER) retention motif within the ADAM10 intracellular C-terminal tail. Sequential deletion/mutagenesis analyses showed that an arginine-rich ((723)RRR) sequence was responsible for the retention of ADAM10 in the ER and its inefficient surface trafficking. Mutating the second arginine to alanine was sufficient to allow ER exit and surface expression in both heterologous cells and hippocampal neurons. As synapse-associated protein 97 (SAP97) binds ADAM10 at its cytoplasmic tail and facilitates forward ADAM10 trafficking in neurons, we tested whether SAP97 could modulate ER export. However, neither expression nor Ser-39 phosphorylation of SAP97 in heterologous cells or hippocampal neurons were sufficient to allow the ER exit of ADAM10, suggesting that other signaling pathways or alternative binding partners are responsible for ADAM10 ER exit. Together, these results identify a novel mechanism regulating the intracellular trafficking and membrane delivery of ADAM10.

Triptolide: An inhibitor of a disintegrin and metalloproteinase 10 (ADAM10) in cancer cells

Triptolide, a diterpene triepoxide derived from Trypterygium wilfordii, is documented to have antitumor activity in a broad range of solid tumors and leukemia. The mechanisms that are involved in triptolide-mediated apoptosis or growth inhibition in cancer cells are not fully understood. We identified a disintegrin and metalloproteinase 10 (ADAM10) as a novel molecular target of triptolide using affinity chromatography and mass spectrometry. The identification was confirmed by Western blot analysis using an anti-ADAM10 antibody. The expression of ADAM10 is enhanced in several tumors including leukemia and is involved in malignant cell growth and cancer progression. ADAM10 is a type 1 transmembrane glycoprotein that cleaves several plasma membrane proteins. We show that triptolide, at concentrations in the nM range, resulted in a significant decrease in ADAM10 expression followed by the appearance of ADAM10 cleaved product. Furthermore, triptolide reduced the viability of monocytic leukemic U937 cells. Triptolide treatment of MCF-7 breast cancer cells expressing ectopic ADAM10 or dominant negative ADAM10 (DN ADAM10) resulted in a decreased expression of ADAM10 with a concomitant increase in ADAM10 cleaved products. Moreover, siRNA-mediated knockdown of ADAM10 mRNA significantly affected the growth of MCF-7 cells. Interestingly, the combination of siRNA-mediated knockdown of ADAM10 mRNA expression and triptolide treatment lead to a further reduction in cell growth. Taken together, we provide evidence that ADAM10 is a novel target of triptolide, presenting a novel strategy to inhibit ADAM10 activity in tumorigenesis.

Anticancer Chemotherapy Inhibits MHC Class I–Related Chain A Ectodomain Shedding by Downregulating ADAM10 Expression in Hepatocellular Carcinoma

MHC class I-related chain A (MICA) is a ligand for the NKG2D-activating immunoreceptor that mediates activation of natural killer (NK) cells. The ectodomain of MICA is shed from tumor cells, which may be an important means of evading antitumor immunity. We previously reported that patients with hepatocellular carcinoma (HCC) display high levels of soluble MICA in circulation, which could be downregulated by chemotherapy. The present study shows that anti-HCC drugs suppress MICA ectodomain shedding by inhibiting expression of a disintegrin and metalloproteinase 10 (ADAM10). Both ADAM10 and CD44, a typical substrate of the ADAM10 protease, were expressed in human HCC tissues and HCC cells but not in normal liver tissues or cultured hepatocytes. Small interfering RNA-mediated knockdown experiments revealed that ADAM10 is a critical sheddase for both MICA and CD44 in HCC cells. Of interest is the finding that epirubicin clearly downregulated ADAM10 expression and MICA shedding in HCC cells; its suppressive effect on MICA shedding was abolished in ADAM10-depleted cells. Epirubicin treatment also enhanced the NKG2D-mediated NK sensitivity of HCC cells. Patients with HCC had significantly higher levels of serum-soluble CD44, which correlated well with serum-soluble MICA levels, thus suggesting a close link between ADAM10 activity and MICA shedding in these patients. Soluble MICA and CD44 levels were downregulated with a significant correlation in patients treated by transarterial chemoembolization using epirubicin. In conclusion, anticancer drugs can modulate expression of ADAM10, which is critically involved in MICA ectodomain shedding. Epirubicin therapy may have a previously unrecognized effect on antitumor immunity in HCC patients.