Mesenchymal Transglutaminase 2 Activates Epithelial ADAM17: Link to G-Protein-Coupled Receptor 56 (ADGRG1) Signalling

A wound healing model was developed to elucidate the role of mesenchymal-matrix-associated transglutaminase 2 (TG2) in keratinocyte re-epithelialisation. TG2 drives keratinocyte migratory responses by activation of disintegrin and metalloproteinase 17 (ADAM17). We demonstrate that epidermal growth factor (EGF) receptor ligand shedding leads to EGFR-transactivation and subsequent rapid keratinocyte migration on TG2-positive ECM. In contrast, keratinocyte migration was impaired in TG2 null conditions. We show that keratinocytes express the adhesion G-protein-coupled receptor, ADGRG1 (GPR56), which has been proposed as a TG2 receptor. Using ADAM17 activation as a readout and luciferase reporter assays, we demonstrate that TG2 activates GPR56. GPR56 activation by TG2 reached the same level as observed with an agonistic N-GPR56 antibody. The N-terminal GPR56 domain is required for TG2-regulated signalling response, as the constitutively active C-GPR56 receptor was not activated by TG2. Signalling required the C-terminal TG2 β-barrel domains and involved RhoA-associated protein kinase (ROCK) and ADAM17 activation, which was blocked by specific inhibitors. Cell surface binding of TG2 to the N-terminal GPR56 domain is rapid and is associated with TG2 and GPR56 endocytosis. TG2 and GPR56 represent a ligand receptor pair causing RhoA and EGFR transactivation. Furthermore, we determined a binding constant for the interaction of human TG2 with N-GPR56 and show for the first time that only the calcium-enabled "open" TG2 conformation associates with N-GPR56.

Contribution of ADAM17 and related ADAMs in cardiovascular diseases

A disintegrin and metalloproteases (ADAMs) are key mediators of cell signaling by ectodomain shedding of various growth factors, cytokines, receptors and adhesion molecules at the cellular membrane. ADAMs regulate cell proliferation, cell growth, inflammation, and other regular cellular processes. ADAM17, the most extensively studied ADAM family member, is also known as tumor necrosis factor (TNF)-α converting enzyme (TACE). ADAMs-mediated shedding of cytokines such as TNF-α orchestrates immune system or inflammatory cascades and ADAMs-mediated shedding of growth factors causes cell growth or proliferation by transactivation of the growth factor receptors including epidermal growth factor receptor. Therefore, increased ADAMs-mediated shedding can induce inflammation, tissue remodeling and dysfunction associated with various cardiovascular diseases such as hypertension and atherosclerosis, and ADAMs can be a potential therapeutic target in these diseases. In this review, we focus on the role of ADAMs in cardiovascular pathophysiology and cardiovascular diseases. The main aim of this review is to stimulate new interest in this area by highlighting remarkable evidence.

TMEFF2 promoter hypermethylation is an unfavorable prognostic marker in gliomas

BACKGROUND

Transmembrane protein with EGF-like and two follistatin-like domains 2 (TMEFF2) is a transmembrane protein in the tomoregulin family. Little research has been performed to determine whether TMEFF2 methylation is a prognostic marker in adult diffuse gliomas.

METHODS

In this study, we investigated TMEFF2 expression in surgical glioma tissue samples. In addition, we conducted bisulfite amplicon sequencing (BSAS) and methylation-specific PCR (MSP) to evaluate TMEFF2 methylation in glioblastoma (GBM) cells. Subsequently, we investigated the biological function of TMEFF2 in GBM cells. Moreover, we explored the prognostic significance of TMEFF2 in gliomas by analysing a cohort dataset from TCGA.

RESULTS

Immunohistochemistry analysis of 75 paired glioma tumour and peritumoural tissues demonstrated that glioma tumour tissues expressed lower TMEFF2 levels than peritumoural tissues (P < 0.001). TMEFF2 promoter methylation levels were increased in glioblastoma cells compared with SVG p12 cells (P < 0.001). Inhibition of methylation reduced TMEFF2 methylation and increased its expression in LN229 and T98G cells (P < 0.05). Knockdown of TMEFF2 expression significantly promoted the proliferation of U87MG cells and primary GBM cells (P < 0.05). TMEFF2 methylation is negatively associated with IDH1, ATRX and TP53 mutations, and the subtype of glioma harbouring combined IDH1/ATRX/TP53 mutations was associated with low TMEFF2 methylation levels. Survival analysis confirmed that low TMEFF2 methylation levels are associated with good prognosis in glioma patients.

CONCLUSIONS

Our results suggest that TMEFF2 DNA methylation might be associated with glioma tumour progression and could serve as a valuable prognostic marker for adult diffuse gliomas.

TMEFF2: A Transmembrane Proteoglycan with Multifaceted Actions in Cancer and Disease

Simple Summary

We recently came across an intriguing protein while screening for tumour-specific apoptosis inducers. It is known as the transmembrane protein with an EGF-like and two Follistatin-like domains 2 (TMEFF2). The gene was identified and characterized by five different groups almost simultaneously around 2000. Physiological function of TMEFF2 is elusive; however, the protein is reported to be involved in wide-ranging physiological and pathological functions including neuroprotection in Alzheimer’s diseases, interferon induction and one-carbon metabolism. Moreover, the TMEFF2 promoter and 5′-upstream regions harbour a CpG island which is progressively methylated upon progression in a wide variety of cancers. Numerous primary publications suggest the methylation of TMEFF2 as a prognostic and even diagnostic marker in different cancers. The primary literature regarding TMEFF2 is distributed far and wide, and despite having more than 150 primary publications mentioning TMEFF2 (or its aliases) in the title or abstract on PubMed, a comprehensive literature review is not available. We believe the reason behind this is firstly the sheer diversity of subjects of these publications and secondly the numerous primary publications reporting contradictory information about TMEFF2, especially when it comes to its oncogenic versus the onco-suppressive roles. The interest in TMEFF2 is growing again; PubMed returning at least 60 publications mentioning TMEFF2 (or its aliases) within the last year. We have made a laborious effort and written a comprehensive review article on TMEFF2 where we have not only compiled and contextualized the information regarding it but also critically analysed the information in the major primary publications. In addition, we have proposed some answers to the apparent TMEFF2 disagreements on its function. This information could serve as a valuable tool for readers not only about TMEFF2 but also on the dual role of type-I transmembrane proteoglycans (harbouring Follistatin-like domains) in oncogenesis and onco-suppression.

Abstract

Transmembrane protein with an EGF-like and two Follistatin-like domains 2 (TMEFF2) is a 374-residue long type-I transmembrane proteoglycan which is proteolytically shed from the cell surface. The protein is involved in a range of functions including metabolism, neuroprotection, apoptosis, embryonic development, onco-suppression and endocrine function. TMEFF2 is methylated in numerous cancers, and an inverse correlation with the stage, response to therapy and survival outcome has been observed. Moreover, TMEFF2 methylation increases with breast, colon and gastric cancer progression. TMEFF2 is methylated early during oncogenesis in breast and colorectal cancer, and the detection of methylated free-circulating TMEFF2 DNA has been suggested as a potential diagnostic tool. The TMEFF2 downregulation signature equals and sometimes outperforms the Gleason and pathological scores in prostate cancer. TMEFF2 is downregulated in glioma and cotricotropinomas, and it impairs the production of adrenocorticotropic hormone in glioma cells. Interestingly, through binding the amyloid β protein, its precursor and derivatives, TMEFF2 provides neuroprotection in Alzheimer’s disease. Despite undergoing extensive investigation over the last two decades, the primary literature regarding TMEFF2 is incoherent and offers conflicting information, in particular, the oncogenic vs. onco-suppressive role of TMEFF2 in prostate cancer. For the first time, we have compiled, contextualised and critically analysed the vast body of TMEFF2-related literature and answered the apparent discrepancies regarding its function, tissue expression, intracellular localization and oncogenic vs. onco-suppressive role.

The substrate repertoire of γ-secretase/presenilin

The intramembrane protease γ-secretase is a hetero-tetrameric protein complex with presenilin as the catalytic subunit and cleaves its membrane protein substrates within their single transmembrane domains. γ-Secretase is well known for its role in Notch signalling and in Alzheimer's disease, where it catalyzes the formation of the pathogenic amyloid β (Aβ) peptide. However, in the 21 years since its discovery many more substrates and substrate candidates of γ-secretase were identified. Although the physiological relevance of the cleavage of many substrates remains to be studied in more detail, the substrates demonstrate a broad role for γ-secretase in embryonic development, adult tissue homeostasis, signal transduction and protein degradation. Consequently, chronic γ-secretase inhibition may cause significant side effects due to inhibition of cleavage of multiple substrates. This review provides a list of 149 γ-secretase substrates identified to date and highlights by which expeirmental approach substrate cleavage was validated. Additionally, the review lists the cleavage sites where they are known and discusses the functional implications of γ-secretase cleavage with a focus on substrates identified in the recent past, such as CHL1, TREM2 and TNFR1. A comparative analysis demonstrates that γ-secretase substrates mostly have a long extracellular domain and require ectodomain shedding before γ-secretase cleavage, but that γ-secretase is also able to cleave naturally short substrates, such as the B cell maturation antigen. Taken together, the list of substrates provides a resource that may help in the future development of drugs inhibiting or modulating γ-secretase activity in a substrate-specific manner.

HPP1 Ectodomain Shedding is Mediated by ADAM17 and is Necessary for Tumor Suppression in Colon Cancer

BACKGROUND

Hyperplastic polyposis protein 1 (HPP1) encodes a tumor-suppressive transmembrane cleavable epidermal growth factor-like ligand. It is unclear as to whether cleavage and shedding of HPP1 are essential steps in achieving its tumor suppressive properties. ADAM proteins are key players in cellular ectodomain shedding processes with ADAM17 being well characterized and representing the most likely sheddase for HPP1. In this study, we explore the mechanisms and importance of ectodomain shedding in contributing to HPP1-mediated tumor suppression.

METHODS

Baseline characterization of HPP1 ectodomain shedding and ADAM family member expression was performed in HCT116 colon cancer cells with forced overexpression of HPP1 and controls. Subsequent impact of attenuation of ADAM expression by short interfering RNA on HPP1 shedding was evaluated. Furthermore, we examined the functional impact of an uncleavable HPP1 mutant construct (HPP1-Δstalk) generated by site-directed mutagenesis. Cellular growth potential functions were analyzed by MTT and soft agar assays.

RESULTS

Select proinflammatory cytokines enhanced HPP1 ectodomain shedding, whereas short interfering RNA-mediated knockdown of ADAM17 resulted in abrogation of HPP1 ectodomain shedding. ADAM17 knockdown concomitantly resulted in increased cell proliferation and anchorage-independent growth. HPP1-Δstalk-transfected cells exhibited significantly higher proliferation and reduced STAT1 activation relative to full-length HPP1, further suggesting a critical role for ectodomain shedding in HPP1-mediated tumor suppression.

CONCLUSION

The tumor-suppressive properties of HPP1 in colorectal cancer require cleavage and shedding of its ectodomain which in turn are mediated by ADAM17. Further investigations into the regulation of HPP1 may lead to a greater understanding of epidermal growth factor-like ligand family biology and potential novel therapeutic strategies.

Frameshift mutation of candidate tumor suppressor genes QK1 and TMEFF2 in gastric and colorectal cancers

BACKGROUND

Both QKI and TMEFF2 genes are considered putative tumor suppressor genes (TSGs). In gastric (GC) and colorectal (CRC) cancers, downregulation of their expressions is known to be frequent. However, QKI and TMEFF2 mutations that could potentially inactivate their functions are not reported in cancers.

METHODS

In a genome database, we observed that both QKI and TMEFF2 harbor mononucleotide repeats, which could be mutated in cancers with high microsatellite instability (MSI-H). For this, we studied 79 GCs and 124 CRCs for the mutations and their intratumoral heterogeneity (ITH).

RESULTS

Six of 34 GCs (17.6%) and 10 of 79 CRCs (12.7%) with MSI-H exhibited QKI frameshift mutations while five of 79 CRCs (6.3%) with high MSI (MSI-H) exhibited TMEFF2 frameshift mutations. However, we found no such mutation in microsatellite stable/low MSI (MSS/MSI-L) cancers within the mononucleotide repeats. We also studied ITH for the detected frameshift mutations in 16 cases of CRCs and detected that QKI and TMEFF2 frameshift mutations showed regional ITH in 2 (12.5%) and 1 (6.3%) cases, respectively.

CONCLUSIONS

Our data show that candidate TSG genes QKI and TMEFF2 harbor mutational ITH as well as the frameshift mutations in GC and CRC with MSI-H. From this observation, frameshift mutations of QKI and TMEFF2 may play a role in tumorigenesis through their TSG inactivation in GC and CRC.

[The role of exosomal tetraspanins and proteases in tumor progression]

Major (CD9, CD63, CD81) and others (CD82, CD151, Tspan8) tetraspanins are widely represented in exosomes, where they interact with various proteins and form functional tetraspanin complexes. Tetraspanin complexes include proteases. Tetraspanin-associated exosomal proteases (ADAM proteases, MMPs, EMMPRIN) play an important role in the processes of cell motility, migration, invasion and formation of metastases. Also, a significant contribution to tumor progression is made by proteases that are not associated with tetraspanins. They destabilize intercellular contacts, promote migration and invasion of tumor cells, participate in the regulation of the expression IGF-I, VEGF and transcription factors activation/deactivation. The role of other proteases of exosomes in the processes of tumor progression is being clarified.

Cellular sheddases are induced by Merkel cell polyomavirus small tumour antigen to mediate cell dissociation and invasiveness

Merkel cell carcinoma (MCC) is an aggressive skin cancer with a high propensity for recurrence and metastasis. Merkel cell polyomavirus (MCPyV) is recognised as the causative factor in the majority of MCC cases. The MCPyV small tumour antigen (ST) is considered to be the main viral transforming factor, however potential mechanisms linking ST expression to the highly metastatic nature of MCC are yet to be fully elucidated. Metastasis is a complex process, with several discrete steps required for the formation of secondary tumour sites. One essential trait that underpins the ability of cancer cells to metastasise is how they interact with adjoining tumour cells and the surrounding extracellular matrix. Here we demonstrate that MCPyV ST expression disrupts the integrity of cell-cell junctions, thereby enhancing cell dissociation and implicate the cellular sheddases, A disintegrin and metalloproteinase (ADAM) 10 and 17 proteins in this process. Inhibition of ADAM 10 and 17 activity reduced MCPyV ST-induced cell dissociation and motility, attributing their function as critical to the MCPyV-induced metastatic processes. Consistent with these data, we confirm that ADAM 10 and 17 are upregulated in MCPyV-positive primary MCC tumours. These novel findings implicate cellular sheddases as key host cell factors contributing to virus-mediated cellular transformation and metastasis. Notably, ADAM protein expression may be a novel biomarker of MCC prognosis and given the current interest in cellular sheddase inhibitors for cancer therapeutics, it highlights ADAM 10 and 17 activity as a novel opportunity for targeted interventions for disseminated MCC.

TMEFF2 shedding is regulated by oxidative stress and mediated by ADAMs and transmembrane serine proteases implicated in prostate cancer

TMEFF2 is a type I transmembrane protein with two follistatin (FS) and one EGF-like domain over-expressed in prostate cancer; however its biological role in prostate cancer development and progression remains unclear, which may, at least in part, be explained by its proteolytic processing. The extracellular part of TMEFF2 (TMEFF2-ECD) is cleaved by ADAM17 and the membrane-retained fragment is further processed by the gamma-secretase complex. TMEFF2 shedding is increased with cell crowding, a condition associated with the tumour microenvironment, which was mediated by oxidative stress signalling, requiring jun-kinase (JNK) activation. Moreover, we have identified that TMEFF2 is also a novel substrate for other proteases implicated in prostate cancer, including two ADAMs (ADAM9 and ADAM12) and the type II transmembrane serine proteinases (TTSPs) matriptase-1 and hepsin. Whereas cleavage by ADAM9 and ADAM12 generates previously identified TMEFF2-ECD, proteolytic processing by matriptase-1 and hepsin produced TMEFF2 fragments, composed of TMEFF2-ECD or FS and/or EGF-like domains as well as novel membrane retained fragments. Differential TMEFF2 processing from a single transmembrane protein may be a general mechanism to modulate transmembrane protein levels and domains, dependent on the repertoire of ADAMs or TTSPs expressed by the target cell.

SheddomeDB: the ectodomain shedding database for membrane-bound shed markers

BACKGROUND

A number of membrane-anchored proteins are known to be released from cell surface via ectodomain shedding. The cleavage and release of membrane proteins has been shown to modulate various cellular processes and disease pathologies. Numerous studies revealed that cell membrane molecules of diverse functional groups are subjected to proteolytic cleavage, and the released soluble form of proteins may modulate various signaling processes. Therefore, in addition to the secreted protein markers that undergo secretion through the secretory pathway, the shed membrane proteins may comprise an additional resource of noninvasive and accessible biomarkers. In this context, identifying the membrane-bound proteins that will be shed has become important in the discovery of clinically noninvasive biomarkers. Nevertheless, a data repository for biological and clinical researchers to review the shedding information, which is experimentally validated, for membrane-bound protein shed markers is still lacking.

RESULTS

In this study, the database SheddomeDB was developed to integrate publicly available data of the shed membrane proteins. A comprehensive literature survey was performed to collect the membrane proteins that were verified to be cleaved or released in the supernatant by immunological-based validation experiments. From 436 studies on shedding, 401 validated shed membrane proteins were included, among which 199 shed membrane proteins have not been annotated or validated yet by existing cleavage databases. SheddomeDB attempted to provide a comprehensive shedding report, including the regulation of shedding machinery and the related function or diseases involved in the shedding events. In addition, our published tool ShedP was embedded into SheddomeDB to support researchers for predicting the shedding event on unknown or unrecorded membrane proteins.

CONCLUSIONS

To the best of our knowledge, SheddomeDB is the first database for the identification of experimentally validated shed membrane proteins and currently may provide the most number of membrane proteins for reviewing the shedding information. The database included membrane-bound shed markers associated with numerous cellular processes and diseases, and some of these markers are potential novel markers because they are not annotated or validated yet in other databases. SheddomeDB may provide a useful resource for discovering membrane-bound shed markers. The interactive web of SheddomeDB is publicly available at http://bal.ym.edu.tw/SheddomeDB/ .

Tomoregulin (TMEFF2) Binds Alzheimer's Disease Amyloid-β (Aβ) Oligomer and AβPP and Protects Neurons from Aβ-Induced Toxicity

Amyloid-β (Aβ) protein causes neurotoxicity and its abnormal aggregation into amyloid is a pathological hallmark of Alzheimer's disease (AD). Cellular proteins able to interact with Aβ or its precursor, AβPP (amyloid-β protein precursor), may regulate Aβ production and neurotoxicity. We identified a brain-enriched type I transmembrane protein, tomoregulin (TR), that directly binds Aβ and Aβ oligomers (AβO). TR co-immunoprecipitated with Aβ and AβO in cultured cells and co-localized with amyloid plaques and intraneuronal Aβ in the 5xFAD AD mouse model. TR was also enriched in astrocytic processes reactive to amyloid plaques. Surface plasmon resonance spectroscopy studies showed that the extracellular domain of TR binds to AβO with a high affinity (KD = 76.8 nM). Electron paramagnetic resonance spectroscopy also demonstrated a physical interaction between spin-labeled Aβ and the TR extracellular domain in solution. Furthermore, TR also interacted with AβPP and enhanced its cleavage by α-secretase. Both cellular expression of TR and application of recombinant TR extracellular domain protected N2a neurons from AβO-induced neuronal death. These data provide first evidence that neuronal and astrocytic expression of TR is intimately related to Aβ metabolism and toxicity, and could be neuroprotective through its direct interaction with Aβ and AβPP.

Specific and redundant activities of ETV1 and ETV4 in prostate cancer aggressiveness revealed by co-overexpression cellular contexts

Genomic rearrangements involving ETS transcription factors are found in 50–70% of prostate carcinomas. While the large majority of the rearrangements involve ERG, around 10% involve members of the PEA3 subfamily (ETV1, ETV4 and ETV5). Using a panel of prostate cancer cell lines we found co-overexpression of ETV1 and ETV4 in two cell line models of advanced prostate cancer (MDA-PCa-2b and PC3) and questioned whether these PEA3 family members would cooperate in the acquisition of oncogenic properties or show functional redundancy. Using shRNAs we found that ETV1 and ETV4 have partially overlapping functions, with ETV1 being more relevant for cell invasion and ETV4 for anchorage-independent growth. In vitro expression signatures revealed the regulation of both specific and shared candidate targets that may resemble cellular mechanisms in vivo by interaction with the same intermediate partners. By combining the phenotypic impact data and the gene expression profiles of in vitro models with clinico-pathological features and gene expression profiles of ETS-subtyped tumors, we identified a set of eight genes associated with advanced stage and a set of three genes associated with higher Gleason score, supporting an oncogenic role of ETV1 and ETV4 overexpression and revealing gene sets that may be useful as prognostic markers.

Analysis of TMEFF2 allografts and transgenic mouse models reveals roles in prostate regeneration and cancer

BACKGROUND

Previous results from our lab indicate a tumor suppressor role for the transmembrane protein with epidermal growth factor and two follistatin motifs 2 (TMEFF2) in prostate cancer (PCa). Here, we further characterize this role and uncover new functions for TMEFF2 in cancer and adult prostate regeneration.

METHODS

The role of TMEFF2 was examined in PCa cells using Matrigel(TM) cultures and allograft models of PCa cells. In addition, we developed a transgenic mouse model that expresses TMEFF2 from a prostate specific promoter. Anatomical, histological, and metabolic characterizations of the transgenic mouse prostate were conducted. The effect of TMEFF2 in prostate regeneration was studied by analyzing branching morphogenesis in the TMEFF2-expressing mouse lobes and alterations in branching morphogenesis were correlated with the metabolomic profiles of the mouse lobes. The role of TMEFF2 in prostate tumorigenesis in whole animals was investigated by crossing the TMEFF2 transgenic mice with the TRAMP mouse model of PCa and analyzing the histopathological changes in the progeny.

RESULTS

Ectopic expression of TMEFF2 impairs growth of PCa cells in Matrigel or allograft models. Surprisingly, while TMEFF2 expression in the TRAMP mouse did not have a significant effect on the glandular prostate epithelial lesions, the double TRAMP/TMEFF2 transgenic mice displayed an increased incidence of neuroendocrine type tumors. In addition, TMEFF2 promoted increased branching specifically in the dorsal lobe of the prostate suggesting a potential role in developmental processes. These results correlated with data indicating an alteration in the metabolic profile of the dorsal lobe of the transgenic TMEFF2 mice.

CONCLUSIONS

Collectively, our results confirm the tumor suppressor role of TMEFF2 and suggest that ectopic expression of TMEFF2 in mouse prostate leads to additional lobe-specific effects in prostate regeneration and tumorigenesis. This points to a complex and multifunctional role for TMEFF2 during PCa progression.

Differential regulation of TROP2 release by PKC isoforms through vesicles and ADAM17

TROP2, a cancer cell surface protein with both pro-oncogenic and anti-oncogenic properties is cleaved by ADAM17. ADAM17 dependent cleavage requires novel PKC activity which is blocked by the ADAM10/ADAM17 inhibitor GW64 as well as by the PKC inhibitor Bim-1. Full length TROP2 release is induced by classical PKC activation and blocked by Gö6979, without affecting ADAM17 dependent TROP2 cleavage. Full length TROP2 is released in ectosomes, as inhibition of endocytosis did not prevent release. Inhibition of the atypical PKC isoform PKCζ stimulated metalloproteinase dependent N-terminal alternative TROP2 cleavage. The resulting alternative TROP2 cleavage product remains membrane associated via a disulphide bond, but is released in microvesicles with an average size of 107nm. Inhibition of endocytosis following PKCζ inhibition prevented alternative cleavage and release of TROP2, suggesting that these events require endocytic uptake and exosomal release of the corresponding microvesicles. The alternative TROP2 cleavage product was also found in PC3 cell lysates following deglycosylation, and may represent a novel biomarker in prostate cancer.

TMEFF2 is an endogenous inhibitor of the CRH signal transduction pathway

TMEFF2 is a transmembrane protein with unknown function, containing an altered epidermal growth factor (EGF)-like motif, two follistatin-like domains, and a cytosolic tail with a putative G-protein-activating motif. TMEFF2 is predominantly expressed in brain and prostate and has been implicated in cell signaling, neuronal cell survival, and tumor suppression. We found that expression of TMEFF2 in pituitary corticotrope cells inhibits the effects of corticotropin-releasing hormone (CRH) on the production of intracellular cAMP, and CREB, and transcription of Pomc. Regulation of the activity of CRH by TMEFF2 requires neither the cytoplasmic tail nor the EGF domain, while deletion of the follistatin modules abolishes the inhibitory function of TMEFF2. Moreover, a soluble secreted protein containing the complete extracellular domain is sufficient for inhibition of CRH signaling. TMEFF2-induced inhibition depends on serum components. Furthermore, TMEFF2 regulates the non-canonical activin/BMP4 signaling, PI3K, and Ras/ERK1/2 pathways. Thus, TMEFF2 inhibits the CRH signaling pathway and the PI3K/AKT and Ras/ERK1/2 pathways, contributing to a significant inhibition of transcription of Pomc. We found that expression of TMEFF2 in human Cushing's adenoma is reduced when compared with normal human pituitary, which may indicate that TMEFF2 acts as a tumor suppressor in these adenomas. Furthermore, the overexpression of TMEFF2 decreased proliferation of corticotrope cells. Our results indicate a potential therapeutic use of TMEFF2 or factors that stimulate the activity of TMEFF2 for the treatment of corticotrope tumors in order to reduce their secretion of ACTH and proliferation.

Bidirectional regulation between TMEFF2 and STAT3 may contribute to Helicobacter pylori-associated gastric carcinogenesis

The transmembrane protein with epidermal growth factor and two follistatin motifs 2 (TMEFF2) is a single-pass transmembrane protein, and it is downregulated in human gastric cancer and levels correlate with tumor progression and time of survival. However, the mechanism of its dysregulation in gastric cancer is little known. Here we investigate its regulatory mechanism and the bidirectional regulation between TMEFF2 and STAT3 in gastric carcinogenesis. TMEFF2 expression was decreased after Helicobacter pylori (H. pylori) infection in vivo and in vitro. STAT3 directly binds to the promoter of TMEFF2 and regulates H. pylori-induced TMEFF2 downregulation in normal gastric GES-1 cells and gastric cancer AGS cells. Conversely, TMEFF2 may suppress the phosphorylation of STAT3 and TMEFF2-induced downregulation of STAT3 phosphorylation may depend on SHP-1. A highly inverse correlation between the expression of TMEFF2 and pSTAT3 was also revealed in gastric tissues. We now show the deregulation mechanism of TMEFF2 in gastric carcinogenesis and identify TMEFF2 as a new target gene of STAT3. The phosphorylation of STAT3 may be negatively regulated by TMEFF2, and the bidirectional regulation between TMEFF2 and STAT3 may contribute to H. pylori-associated gastric carcinogenesis.

TMEFF2 deregulation contributes to gastric carcinogenesis and indicates poor survival outcome

PURPOSE

The role and clinical implication of the transmembrane protein with EGF and two follistatin motifs 2 (TMEFF2) in gastric cancer is poorly understood.

EXPERIMENTAL DESIGN

Gene expression profile analyses were performed and Gene Set Enrichment Analysis (GSEA) was used to explore its gene signatures. AGS and MKN45 cells were transfected with TMEFF2 or control plasmids and analyzed for gene expression patterns, proliferation, and apoptosis. TMEFF2 expression was knocked down with shRNAs, and the effects on genome stability were assessed. Interactions between TMEFF2 and SHP-1 were determined by mass spectrometry and immunoprecipitation assays.

RESULTS

Integrated analysis revealed that TMEFF2 expression was significantly decreased in gastric cancer cases and its expression was negatively correlated with the poor pathologic stage, large tumor size, and poor prognosis. GSEA in The Cancer Genome Atlas (TCGA) and Jilin datasets revealed that cell proliferation, apoptosis, and DNA damage-related genes were enriched in TMEFF2 lower expression patients. Gain of TMEFF2 function decreased cell proliferation by increasing of apoptosis and blocking of cell cycle in gastric cancer cells. The protein tyrosine phosphatase SHP-1 was identified as a binding partner of TMEEF2 and mediator of TMEFF2 function. TMEFF2 expression positively correlated with SHP-1, and a favorable prognosis was more likely in patients with gastric cancer with higher levels of both TMEFF2 and SHP-1.

CONCLUSION

TMEFF2 acts as a tumor suppressor in gastric cancer through direct interaction with SHP-1 and can be a potential biomarker of carcinogenesis.

The TMEFF2 tumor suppressor modulates integrin expression, RhoA activation and migration of prostate cancer cells

Cell adhesion and migration play important roles in physiological and pathological states, including embryonic development and cancer invasion and metastasis. The type I transmembrane protein with epidermal growth factor and two follistatin motifs 2 (TMEFF2) is expressed mainly in brain and prostate and its expression is deregulated in prostate cancer. We have previously shown that TMEFF2 can function as a tumor suppressor by inhibiting cell migration and invasion of prostate cells. However, the molecular mechanisms involved in this inhibition are not clear. In this study we demonstrate that TMEFF2 affects cell adhesion and migration of prostate cancer cells and that this effect correlates with changes in integrin expression and RhoA activation. Deletion of a 13 basic-rich amino acid region in the cytoplasmic domain of TMEFF2 prevented these effects. Overexpression of TMEFF2 reduced cell attachment and migration on vitronectin and caused a concomitant decrease in RhoA activation, stress fiber formation and expression of αv, β1 and β3 integrin subunits. Conversely, TMEFF2 interference in 22Rv1 prostate cancer cells resulted in an increased integrin expression. Results obtained with a double TRAMP/TMEFF2 transgenic mouse also indicated that TMEFF2 expression reduced integrin expression in the mouse prostate. In summary, the data presented here indicate an important role of TMEFF2 in regulating cell adhesion and migration that involves integrin signaling and is mediated by its cytoplasmic domain.

A disintegrin and metalloprotease (ADAM) 10 and ADAM17 are major sheddases of T cell immunoglobulin and mucin domain 3 (Tim-3)

T cell immunoglobulin and mucin domain 3 (Tim-3) dampens the response of CD4(+) and CD8(+) effector T cells via induction of cell death and/or T cell exhaustion and enhances the ability of macrophages to clear pathogens via binding to galectin 9. Here we provide evidence that human Tim-3 is a target of A disintegrin and metalloprotease (ADAM)-mediated ectodomain shedding resulting in a soluble form of Tim-3. We identified ADAM10 and ADAM17 as major sheddases of Tim-3 as shown by ADAM-specific inhibitors and the ADAM10 pro-domain in HEK293 cells and ADAM10/ADAM17-deficient murine embryonic fibroblasts. PMA-induced shedding of Tim-3 was abrogated by deletion of amino acids Glu(181)-Asp(190) of the stalk region and Tim-3 lacking the intracellular domain was not efficiently cleaved after PMA stimulation. Surprisingly, a single lysine residue within the intracellular domain rescues shedding of Tim-3. Shedding of endogenous Tim-3 was found in primary human CD14(+) monocytes after PMA and ionomycin stimulation. Importantly, the recently described down-regulation of Tim-3 from Toll-like receptor-activated CD14(+) monocytes was caused by ADAM10- and ADAM17-mediated shedding. Inhibition of Tim-3 shedding from lipopolysaccharide-induced monocytes did not influence lipopolysaccharide-induced TNFα and IL-6 but increases IL-12 expression. In summary, we describe Tim-3 as novel target for ADAM-mediated ectodomain shedding and suggest a role of Tim-3 shedding in TLR-mediated immune responses of CD14(+) monocytes.

Identification and characterization of five intramembrane metalloproteases in Anabaena variabilis

Regulated intramembrane proteolysis (RIP) involves cleavage of a transmembrane segment of a protein, releasing the active form of a membrane-anchored transcription factor (MTF) or a membrane-tethered signaling protein in response to an extracellular or intracellular signal. RIP is conserved from bacteria to humans and governs many important signaling pathways in both prokaryotes and eukaryotes. Proteases that carry out these cleavages are named intramembrane cleaving proteases (I-CLips). To date, little is known about I-CLips in cyanobacteria. In this study, five putative site-2 type I-Clips (Ava_1070, Ava_1730, Ava_1797, Ava_3438, and Ava_4785) were identified through a genome-wide survey in Anabaena variabilis. Biochemical analysis demonstrated that these five putative A. variabilis site-2 proteases (S2Ps(Av)) have authentic protease activities toward an artificial substrate pro-σ(K), a Bacillus subtilis MTF, in our reconstituted Escherichia coli system. The enzymatic activities of processing pro-σ(K) differ among these five S2Ps(Av). Substitution of glutamic acid (E) by glutamine (Q) in the conserved HEXXH zinc-coordinated motif caused the loss of protease activities in these five S2Ps(Av), suggesting that they belonged to the metalloprotease family. Further mapping of the cleaved peptides of pro-σ(K) by Ava_4785 and Ava_1797 revealed that Ava_4785 and Ava_1797 recognized the same cleavage site in pro-σ(K) as SpoIVFB, a cognate S2P of pro-σ(K) from B. subtilis. Taking these results together, we report here for the first time the identification of five metallo-intramembrane cleaving proteases in Anabaena variabilis. The experimental system described herein should be applicable to studies of other RIP events and amenable to developing in vitro assays for I-CLips.

Methylation of TMEFF2 gene in tissue and serum DNA from patients with non-small cell lung cancer

Lung cancer remains a global health problem with a high mortality rate. CpG island methylation is a common aberration frequently associated with gene silencing in multiple tumor types, emerging as a highly promising biomarker. The transmembrane protein with a single EGF-like and two follistatin domains (TMEFF2) is epigenetically silenced in numerous tumor types, suggesting a potential role as a potential tumor suppressor. However, the role of TMEFF2 in lung cancer remains to be fully elucidated. We explored the methylation status of TMEFF2 gene in 139 patients with non-small cell lung cancer (NSCLC) and the feasibility of detecting circulating methylated DNA as a screening tool for NSCLC using methylation-specific PCR in 316 patients and 50 age-matched health controls. TMEFF2 methylation in tumor tissues was found in 73 of the 139 NSCLCs (52.5%) and was related to gene expression. The frequency of TMEFF2 methylation was higher in females and never-smokers than in males and smokers with borderline significance (65.8% vs 47.8%, p = 0.06; 65.7% vs 48.1%, p = 0.07). Notably, in adenocarcinomas, TMEFF2 methylation was significantly more frequent in tumors without EGFR mutation than those with EGFR mutation (adjusted odds ratio = 7.13, 95% confidence interval = 2.05-24.83, P = 0.002). Furthermore, TMEFF2 methylation was exclusively detected in the serum of NSCLC patients at a frequency of 9.2% (29/316). These findings suggest that methylation-associated down-regulation of TMEFF2 gene may be involved in lung tumorigenesis and TMEFF2 methylation can serve as a specific blood-based biomarker for NSCLC.

Generation and characterization of Tmeff2 mutant mice

TMEFF2 is a single-transmembrane protein containing one EGF-like and two follistatin-like domains. Some studies implicated TMEFF2 as a tumor suppressor for prostate and other cancers, whereas others reported TMEFF2 functioning as a growth factor for neurons and other cells. To gain insights into the apparently conflicting roles of TMEFF2, we generated a null allele of Tmeff2 gene by replacing its first coding exon with human placental alkaline phosphatase cDNA (Tmeff2(PLAP)). Tmeff2(PLAP/PLAP) homozygous mutant mice are born normal, but show growth retardation and die around weaning age. Tmeff2 is widely expressed in the nervous system, and the Tmeff2(PLAP) knock-in allele enables the visualization of neuronal innervations of skin and internal organs with a simple alkaline phosphatase staining. Tmeff2 is also highly expressed in prostate gland and white adipose tissues (WAT). However, with the exception of reduced WAT mass, extensive anatomical and molecular analyses failed to detect any structural or molecular abnormalities in the brain, the spinal cord, the enteric nervous system, or the prostate in the Tmeff2 mutants. No tumors were found in Tmeff2-mutant mice. The Tmeff2(PLAP/PLAP) knock-in mouse is an useful tool for studying the in vivo biological functions of TMEFF2.

A genome wide association study of pulmonary tuberculosis susceptibility in Indonesians

Background

There is reason to expect strong genetic influences on the risk of developing active pulmonary tuberculosis (TB) among latently infected individuals. Many of the genome wide linkage and association studies (GWAS) to date have been conducted on African populations. In order to identify additional targets in genetically dissimilar populations, and to enhance our understanding of this disease, we performed a multi-stage GWAS in a Southeast Asian cohort from Indonesia.

Methods

In stage 1, we used the Affymetrix 100 K SNP GeneChip marker set to genotype 259 Indonesian samples. After quality control filtering, 108 cases and 115 controls were analyzed for association of 95,207 SNPs. In stage 2, we attempted validation of 2,453 SNPs with promising associations from the first stage, in 1,189 individuals from the same Indonesian cohort, and finally in stage 3 we selected 251 SNPs from this stage to test TB association in an independent Caucasian cohort (n = 3,760) from Russia.

Results

Our study suggests evidence of association (P = 0.0004-0.0067) for 8 independent loci (nominal significance P < 0.05), which are located within or near the following genes involved in immune signaling: JAG1, DYNLRB2, EBF1, TMEFF2, CCL17, HAUS6, PENK and TXNDC4.

Conclusions

Mechanisms of immune defense suggested by some of the identified genes exhibit biological plausibility and may suggest novel pathways involved in the host containment of infection with TB.

Refined mapping of blood pressure quantitative trait loci using congenic strains developed from two genetically hypertensive rat models

Previously linkage and substitution mapping were conducted between the Dahl Salt-sensitive (S) rat and the Spontaneously Hypertensive Rat (SHR) to address the hypothesis that genetic contributions to blood pressure (BP) in two genetically hypertensive rat strains are different. Among the BP quantitative trait loci (QTLs) detected, two are located on chromosome 9 within large genomic segments. The goal of the current study was to develop new iterations of congenic substrains, to further resolve both of these BP QTLs on chromosome 9 as independent congenic segments. A total of 10 new congenic substrains were developed and characterized. The newly developed congenic substrains S.SHR(9)x8Ax11A and S.SHR(9)x10Ax1, with introgressed segments of 2.05 and 6.14 Mb, represented the shortest genomic segments. Both of these congenic substrains, S.SHR(9)x8Ax11A and S.SHR(9)x10Ax1 lowered BP of the S rat by 56 mm Hg (P<0.001) and 15 mm Hg (P<0.039), respectively. The BP measurements were corroborated by radiotelemetry. Urinary protein excretion was significantly lowered by SHR alleles within S.SHR(9)x10Ax1 but not by S.SHR(9)x8Ax11A. The shorter of the two congenic segments, 2.05 Mb was further characterized and found to contain a single differentially expressed protein-coding gene, Tomoregulin-2 (Tmeff2). The protein expression of Tmeff2 was higher in the S rat compared with S.SHR(9)x8Ax11A, which also had lower cardiac hypertrophy as measured by echocardiography. Tmeff2 is known to be upregulated in patients from multiple cohorts with cardiac hypertrophy. Taken together, Tmeff2 can be prioritized as a candidate gene for hypertension and associated cardiac hypertrophy in both rats and in humans.

ADAM17: a molecular switch to control inflammation and tissue regeneration

A disintegrin and metalloproteinase 17 (ADAM17), also known as tumor necrosis factor-α converting enzyme (TACE), is a membrane-bound enzyme that cleaves cell surface proteins, such as cytokines (e.g. TNFα), cytokine receptors (e.g. IL-6R and TNF-R), ligands of ErbB (e.g. TGFα and amphiregulin) and adhesion proteins (e.g. L-selectin and ICAM-1). Here we examine how ectodomain shedding of these molecules can alter their biology and impact on immune and inflammatory responses and cancer development. Gene targeting of Adam17 is embryonic lethal, highlighting the importance of ectodomain shedding during development. Tissue-specific deletion, or hypomorphic knock-in, of Adam17 demonstrates an in vivo role for ADAM17 in controlling inflammation and tissue regeneration. The potential of ADAM17 as therapeutic target is also discussed.

The tumor suppressor activity of the transmembrane protein with epidermal growth factor and two follistatin motifs 2 (TMEFF2) correlates with its ability to modulate sarcosine levels

The type I transmembrane protein with epidermal growth factor and two follistatin motifs 2 (TMEFF2) is expressed in brain and prostate and overexpressed in prostate cancer, but its role in this disease is unclear. Several studies have suggested that TMEFF2 plays a role in suppressing the growth and invasive potential of human cancer cells, whereas others suggest that the shed portion of TMEFF2, which lacks the cytoplasmic region, has a growth-promoting activity. Here we show that TMEFF2 has a dual mode of action. Ectopic expression of wild-type full-length TMEFF2 inhibits soft agar colony formation, cellular invasion, and migration and increases cellular sensitivity to apoptosis. However, expression of the ectodomain portion of TMEFF2 increases cell proliferation. Using affinity chromatography and mass spectrometry, we identify sarcosine dehydrogenase (SARDH), the enzyme that converts sarcosine to glycine, as a TMEFF2-interacting protein. Co-immunoprecipitation and immunofluorescence analysis confirms the interaction of SARDH with full-length TMEFF2. The ectodomain does not bind to SARDH. Moreover, expression of the full-length TMEFF2 but not the ectodomain results in a decreased level of sarcosine in the cells. These results suggest that the tumor suppressor activity of TMEFF2 requires the cytoplasmic/transmembrane portion of the protein and correlates with its ability to bind to SARDH and to modulate the level of sarcosine.

Basic fibroblast growth factor activates MEK/ERK cell signaling pathway and stimulates the proliferation of chicken primordial germ cells

BACKGROUND

Long-term maintenance of avian primordial germ cells (PGCs) in vitro has tremendous potential because it can be used to deepen our understanding of the biology of PGCs. A transgenic bioreactor based on the unique migration of PGCs toward the recipients' sex cord via the bloodstream and thereby creating a germline chimeric bird has many potential applications. However, the growth factors and the signaling pathway essential for inducing proliferation of chicken PGCs are unknown.

METHODOLOGY/PRINCIPAL FINDINGS

Therefore, we conducted this study to investigate the effects of various combinations of growth factors on the survival and proliferation of PGCs under feeder-free conditions. We observed proliferation of PGCs in media containing bFGF. Subsequent characterization confirmed that the cultured PGCs maintained expression of PGC-specific markers, telomerase activity, normal migrational activity, and germline transmission. We also found that bFGF activates the mitogen-activated protein kinase kinase/extracellular-signal regulated kinase (MEK/ERK) signaling. Also, the expression of 133 transcripts was reversibly altered by bFGF withdrawal.

CONCLUSIONS/SIGNIFICANCE

Our results demonstrate that chicken PGCs can be maintained in vitro without any differentiation or dedifferentiation in feeder free culture conditions, and subsequent analysis revealed that bFGF is one of the key factors that enable proliferation of chicken PGCs via MEK/ERK signaling regulating downstream genes that may be important for PGC proliferation and survival.

Basic fibroblast growth factor activates MEK/ERK cell signaling pathway and stimulates the proliferation of chicken primordial germ cells

BACKGROUND

Long-term maintenance of avian primordial germ cells (PGCs) in vitro has tremendous potential because it can be used to deepen our understanding of the biology of PGCs. A transgenic bioreactor based on the unique migration of PGCs toward the recipients' sex cord via the bloodstream and thereby creating a germline chimeric bird has many potential applications. However, the growth factors and the signaling pathway essential for inducing proliferation of chicken PGCs are unknown.

METHODOLOGY/PRINCIPAL FINDINGS

Therefore, we conducted this study to investigate the effects of various combinations of growth factors on the survival and proliferation of PGCs under feeder-free conditions. We observed proliferation of PGCs in media containing bFGF. Subsequent characterization confirmed that the cultured PGCs maintained expression of PGC-specific markers, telomerase activity, normal migrational activity, and germline transmission. We also found that bFGF activates the mitogen-activated protein kinase kinase/extracellular-signal regulated kinase (MEK/ERK) signaling. Also, the expression of 133 transcripts was reversibly altered by bFGF withdrawal.

CONCLUSIONS/SIGNIFICANCE

Our results demonstrate that chicken PGCs can be maintained in vitro without any differentiation or dedifferentiation in feeder free culture conditions, and subsequent analysis revealed that bFGF is one of the key factors that enable proliferation of chicken PGCs via MEK/ERK signaling regulating downstream genes that may be important for PGC proliferation and survival.

Role of ADAMs in cancer formation and progression

The ADAMs (a disintegrin and metalloproteinase) comprise a family of multidomain transmembrane and secreted proteins. One of their best-established roles is the release of biologically important ligands, such as tumor necrosis factor-alpha, epidermal growth factor, transforming growth factor-alpha, and amphiregulin. Because these ligands have been implicated in the formation and progression of tumors, it might be expected that the specific ADAMs involved in their release would also be involved in malignancy. Consistent with this hypothesis, emerging data from model systems suggest that ADAMs, such as ADAM-9, ADAM-12, ADAM-15, and ADAM-17, are causally involved in tumor formation/progression. In human cancer, specific ADAMs are up-regulated, with levels generally correlating with parameters of tumor progression and poor outcome. In preclinical models, selective ADAM inhibitors against ADAM-10 and ADAM-17 have been shown to synergize with existing therapies in decreasing tumor growth. The ADAMs are thus a new family of potential targets for the treatment of cancer, especially malignancies that are dependent on human epidermal growth factor receptor ligands or tumor necrosis factor-alpha.

Trafficking of receptor tyrosine kinases to the nucleus

It has been known for at least 20 years that growth factors induce the internalization of cognate receptor tyrosine kinases (RTKs). The internalized receptors are then sorted to lysosomes or recycled to the cell surface. More recently, data have been published to indicate other intracellular destinations for the internalized RTKs. These include the nucleus, mitochondria, and cytoplasm. Also, it is recognized that trafficking to these novel destinations involves new biochemical mechanisms, such as proteolytic processing or interaction with translocons, and that these trafficking events have a function in signal transduction, implicating the receptor itself as a signaling element between the cell surface and the nucleus.