Interaction between the ADAM12 and SH3MD1 genes may confer susceptibility to late-onset Alzheimer's disease

The Biochemistry and Physiology of A Disintegrin and Metalloproteinases (ADAMs and ADAM-TSs) in Human Pathologies

Metalloproteinases are a group of proteinases that plays a substantial role in extracellular matrix remodeling and its molecular signaling. Among these metalloproteinases, ADAMs (a disintegrin and metalloproteinases) and ADAM-TSs (ADAMs with thrombospondin domains) have emerged as highly efficient contributors mediating proteolytic processing of various signaling molecules. ADAMs are transmembrane metalloenzymes that facilitate the extracellular domain shedding of membrane-anchored proteins, cytokines, growth factors, ligands, and their receptors and therefore modulate their biological functions. ADAM-TSs are secretory, and soluble extracellular proteinases that mediate the cleavage of non-fibrillar extracellular matrix proteins. ADAMs and ADAM-TSs possess pro-domain, metalloproteinase, disintegrin, and cysteine-rich domains in common, but ADAM-TSs have characteristic thrombospondin motifs instead of the transmembrane domain. Most ADAMs and ADAM-TSs are activated by cleavage of pro-domain via pro-protein convertases at their N-terminus, hence directing them to various signaling pathways. In this article, we are discussing not only the structure and regulation of ADAMs and ADAM-TSs, but also the importance of these metalloproteinases in various human pathophysiological conditions like cardiovascular diseases, colorectal cancer, autoinflammatory diseases (sepsis/rheumatoid arthritis), Alzheimer's disease, proliferative retinopathies, and infectious diseases. Therefore, based on the emerging role of ADAMs and ADAM-TSs in various human pathologies, as summarized in this review, these metalloproteases can be considered as critical therapeutic targets and diagnostic biomarkers.

Effects of Subtoxic Concentrations of Atrazine, Cypermethrin, and Vinclozolin on microRNA-Mediated PI3K/Akt/mTOR Signaling in SH-SY5Y Cells

Endocrine-disrupting chemicals (EDCs) are different natural and synthetic chemicals that may interfere with several mechanisms of the endocrine system producing adverse developmental, metabolic, reproductive, and neurological effects in both human beings and wildlife. Among pesticides, numerous chemicals have been identified as EDCs. MicroRNAs (miRNAs) can regulate gene expression, making fine adjustments in mRNA abundance and regulating proteostasis. We hypothesized that exposure to low doses of atrazine, cypermethrin, and vinclozolin may lead to effects on miRNA expression in SH-SY5Y cells. In particular, the exposure of SH-SY5Y cells to subtoxic concentrations of vinclozolin is able to downregulate miR-29b-3p expression leading to the increase in the related gene expression of ADAM12 and CDK6, which may promote a pro-oncogenic response through the activation of the PI3K/Akt/mTOR pathway and counteracting p53 activity. A better understanding of the molecular mechanisms of EDCs could provide important insight into their role in human disease.

Elevation of ADAM12 facilitates tumor progression by enhancing metastasis and immune infiltration in gastric cancer

A disintegrin and metalloprotease 12 (ADAM12), an essential transmembrane protein with metalloprotease, cell binding and intracellular signal-regulating capabilities, has been reported to play a crucial role in various types of cancers. However, the biological function of ADAM12 in gastric cancer (GC) remains unclear. Bioinformatic and experimental analyses were used to determine the expression level and prognostic value of ADAM12 in GC. The level of DNA methylation and the competing endogenous RNA (ceRNA) network was identified using MethSurv, Starbase3.0, miRNet2.0 and experimental analyses. Then, the co-expression profiles of ADAM12 were determined and subjected to enrichment analysis using the LinkedOmics database. The protein-protein interaction network and the docking model of ADAM12 were constructed using the GeneMANIA, STRING, and HDOCK webservers. The role of ADAM12 in tumor metastasis and immune infiltration was investigated using in vitro assays and TIMER database exploration. It was found that ADAM12 was overexpressed and was correlated with a poor prognosis of GC patients. In addition, the aberrant DNA methylation status and ceRNA regulation may contribute to the upregulation of ADAM12 in GC. Moreover, the enrichment analysis revealed that ADAM12 is involved in multiple vital biological functions and pathways, such as 'macrophage activation', 'extracellular matrix binding' and 'ECM-receptor interaction'. Subsequently, the protein-protein interaction network and molecular docking model demonstrated that follistatin like 3 (FSTL3) is a potential binding partner of ADAM12. Finally, it was demonstrated that ADAM12 promotes tumor metastasis, immune infiltration and M2 macrophage polarization in GC. In summary, these results highlight the potential of ADAM12 to be used as a therapeutic target for GC.

Blood DNA methylation patterns in older adults with evolving dementia

Dementia and cognitive disorders are major aging-associated pathologies. The prevalence and severity of these conditions are influenced by both genetic and environmental factors. Reflecting this, epigenetic alterations have been associated with each of these processes, especially at the level of DNA methylation, and such changes may help explain the observed interindividual variability in the development of the 2 pathologies. However, the importance of epigenetic alterations in explaining their etiology is unclear because little is known about the timing of when they appear. Here, using Illumina MethylationEPIC arrays, we have longitudinally analyzed the peripheral blood methylomes of cognitively healthy older adults (>70 year), some of whom went on to develop dementia while others stayed healthy. We have characterized 34 individuals at the prediagnosis stage and at a 4-year follow-up in the postdiagnosis stage (total n = 68). Our results show multiple DNA methylation alterations linked to dementia status, particularly at the level of differentially methylated regions. These loci are associated with several dementia-related genes, including PON1, AP2A2, MAGI2, POT1, ITGAX, PACSIN1, SLC2A8, and EIF4E. We also provide validation of the previously reported epigenetic alteration of HOXB6 and PM20D1. Importantly, we show that most of these regions are already altered in the prediagnosis stage of individuals who go on to develop dementia. In conclusion, our observations suggest that dementia-associated epigenetic patterns that have specific biological features are already present before diagnosis, and thus may be important in the design of epigenetic biomarkers for disease detection based on peripheral tissues.

Genetics of common cerebral small vessel disease

Cerebral small vessel disease (cSVD) is a leading cause of ischaemic and haemorrhagic stroke and a major contributor to dementia. Covert cSVD, which is detectable with brain MRI but does not manifest as clinical stroke, is highly prevalent in the general population, particularly with increasing age. Advances in technologies and collaborative work have led to substantial progress in the identification of common genetic variants that are associated with cSVD-related stroke (ischaemic and haemorrhagic) and MRI-defined covert cSVD. In this Review, we provide an overview of collaborative studies - mostly genome-wide association studies (GWAS) - that have identified >50 independent genetic loci associated with the risk of cSVD. We describe how these associations have provided novel insights into the biological mechanisms involved in cSVD, revealed patterns of shared genetic variation across cSVD traits, and shed new light on the continuum between rare, monogenic and common, multifactorial cSVD. We consider how GWAS summary statistics have been leveraged for Mendelian randomization studies to explore causal pathways in cSVD and provide genetic evidence for drug effects, and how the combination of findings from GWAS with gene expression resources and drug target databases has enabled identification of putative causal genes and provided proof-of-concept for drug repositioning potential. We also discuss opportunities for polygenic risk prediction, multi-ancestry approaches and integration with other omics data.

Quantitative endophenotypes as an alternative approach to understanding genetic risk in neurodegenerative diseases

Endophenotypes, as measurable intermediate features of human diseases, reflect underlying molecular mechanisms. The use of quantitative endophenotypes in genetic studies has improved our understanding of pathophysiological changes associated with diseases. The main advantage of the quantitative endophenotypes approach to study human diseases over a classic case-control study design is the inferred biological context that can enable the development of effective disease-modifying treatments. Here, we summarize recent progress on biomarkers for neurodegenerative diseases, including cerebrospinal fluid and blood-based, neuroimaging, neuropathological, and clinical studies. This review focuses on how endophenotypic studies have successfully linked genetic modifiers to disease risk, disease onset, or progression rate and provided biological context to genes identified in genome-wide association studies. Finally, we review critical methodological considerations for implementing this approach and future directions.

From putative brain tumor marker to high cognitive abilities: Emerging roles of a disintegrin and metalloprotease (ADAM) 12 in the brain

ADAM (a disintergin and metalloprotease) 12 is a member of the large family of multidomain metalloprotease-disintegrins, which possess cell-binding and metalloprotease properties. The enzyme is responsible for the shedding of a number of membrane-bound proteins (heparin-binding-EGF, insulin-like growth factor 2-binding proteins 3 and 5, oxytocinase, glycoprotein non-metastatic melanoma protein B and basigin). In rat and human CNS, ADAM12 is predominantly localized in white and gray matter oligodendrocytes. In addition it can be detected in astrocytes, neurons and endothelial cells. Its function in healthy brain is not well established yet, but prominent roles in CNS development, myelination and high cognitive abilities are discussed. There is increasing evidence that ADAM12 is involved in numerous major diseases of the CNS, which are summarized in the present review (brain tumors, multiple sclerosis, amyotrophic lateral sclerosis, Alzheimer´s disease, stroke, schizophrenia, autism and bipolar disorder).

IgM response against amyloid-beta in aging: a potential peripheral protective mechanism

BACKGROUND

The immune system plays a major role in the pathogenesis of age-related dementia, including Alzheimer's disease (AD). An insight into age-associated changes in the immune response to amyloid-beta (Aβ) in individuals without AD may be beneficial in identifying mechanisms preventing accumulation of Aβ.

METHODS

We examined the response of human monocyte-derived dendritic cells (DCs), T cells, and peripheral blood mononuclear cells (PBMCs) from healthy aged and young subjects to Aβ peptide 1-42, Aβ fibrils, and recombinant, nonaggregated tau-4 protein with a view to understand the role of peripheral immunity in AD.

RESULTS

Our studies revealed that DCs from healthy aged subjects display weak reactivity towards the Aβ peptide and no reactivity towards Aβ fibrils and tau compared with their young counterparts. An analysis of old and young PBMCs revealed that there is no significant T-cell memory against Aβ peptide, fibrils, or tau. Remarkably, the plasma levels of IgM antibodies specific to Aβ peptide 1-42 were significantly increased in aged subjects compared with young subjects, while IgG levels were comparable. Aβ peptide-specific IgM and IgG levels were also determined in the plasma of AD subjects compared with age-matched controls to demonstrate that the immune response against Aβ is stronger in AD patients. A decline in Aβ peptide-specific IgM antibodies was observed in AD patients compared with age-matched controls. In contrast, the levels of IgG as well as interleukin-21, the major cytokine involved in class switching, were increased in AD and patients with mild cognitive impairment, indicating a strong immune response against Aβ.

CONCLUSIONS

Collectively, low immunogenicity of Aβ in healthy controls may prevent inflammation while the generation of specific IgM antibodies may help in the clearance of Aβ in healthy subjects.

Human Polymorphisms in Placentally Expressed Genes and Their Association With Susceptibility to Congenital Trypanosoma cruzi Infection

BACKGROUND

It is currently unclear why only a proportion of children born to Trypanosoma cruzi-infected mothers acquire the infection. We have examined the association of 11 single-nucleotide polymorphisms (SNPs) located in genes coding for placental expression enzymes as genetic markers of susceptibility to congenital T. cruzi infection (hereafter, "congenital infection"): rs2014683 and rs1048988 in ALPP; rs11244787 and rs1871054 in ADAM12; rs243866, rs243865, rs17859821, rs243864, and rs2285053 in MMP2; and rs3918242 and rs2234681 in MMP9.

METHODS

Two groups of children born to mothers seropositive for T. cruzi were compared: 101 had congenital infection, and 116 were uninfected. Novel high-resolution melting and capillary electrophoresis genotyping techniques were designed and used.

RESULTS

Logistic regression analysis showed that mutations in rs11244787 and rs1871054 (in ADAM12) and rs243866, rs17859821, and rs2285053 (in MMP2) were associated with susceptibility to congenital infection. Multifactor dimensionality reduction revealed that genotyping results for rs11244787, rs1871054, rs243866, rs17859821 and rs243864 sites would be a good predictor of congenital infection.

CONCLUSIONS

Our results suggest an important role of human polymorphisms in proteins involved in extracellular matrix remodeling and the immune response during congenital infection. To our knowledge, this is the first study demonstrating the association between mutations in placentally expressed genes and susceptibility to congenital infection.

β-Amyloid: the key peptide in the pathogenesis of Alzheimer's disease

The amyloid β peptide (Aβ) is a critical initiator that triggers the progression of Alzheimer's Disease (AD) via accumulation and aggregation, of which the process may be caused by Aβ overproduction or perturbation clearance. Aβ is generated from amyloid precursor protein through sequential cleavage of β- and γ-secretases while Aβ removal is dependent on the proteolysis and lysosome degradation system. Here, we overviewed the biogenesis and toxicity of Aβ as well as the regulation of Aβ production and clearance. Moreover, we also summarized the animal models correlated with Aβ that are essential in AD research. In addition, we discussed current immunotherapeutic approaches targeting Aβ to give some clues for exploring the more potentially efficient drugs for treatment of AD.

Multiethnic genome-wide association study of cerebral white matter hyperintensities on MRI

BACKGROUND

The burden of cerebral white matter hyperintensities (WMH) is associated with an increased risk of stroke, dementia, and death. WMH are highly heritable, but their genetic underpinnings are incompletely characterized. To identify novel genetic variants influencing WMH burden, we conducted a meta-analysis of multiethnic genome-wide association studies.

METHODS AND RESULTS

We included 21 079 middle-aged to elderly individuals from 29 population-based cohorts, who were free of dementia and stroke and were of European (n=17 936), African (n=1943), Hispanic (n=795), and Asian (n=405) descent. WMH burden was quantified on MRI either by a validated automated segmentation method or a validated visual grading scale. Genotype data in each study were imputed to the 1000 Genomes reference. Within each ethnic group, we investigated the relationship between each single-nucleotide polymorphism and WMH burden using a linear regression model adjusted for age, sex, intracranial volume, and principal components of ancestry. A meta-analysis was conducted for each ethnicity separately and for the combined sample. In the European descent samples, we confirmed a previously known locus on chr17q25 (P=2.7×10(-19)) and identified novel loci on chr10q24 (P=1.6×10(-9)) and chr2p21 (P=4.4×10(-8)). In the multiethnic meta-analysis, we identified 2 additional loci, on chr1q22 (P=2.0×10(-8)) and chr2p16 (P=1.5×10(-8)). The novel loci contained genes that have been implicated in Alzheimer disease (chr2p21 and chr10q24), intracerebral hemorrhage (chr1q22), neuroinflammatory diseases (chr2p21), and glioma (chr10q24 and chr2p16).

CONCLUSIONS

We identified 4 novel genetic loci that implicate inflammatory and glial proliferative pathways in the development of WMH in addition to previously proposed ischemic mechanisms.

Transcriptional analysis of apoptotic cerebellar granule neurons following rescue by gastric inhibitory polypeptide

Apoptosis triggered by exogenous or endogenous stimuli is a crucial phenomenon to determine the fate of neurons, both in physiological and in pathological conditions. Our previous study established that gastric inhibitory polypeptide (Gip) is a neurotrophic factor capable of preventing apoptosis of cerebellar granule neurons (CGNs), during its pre-commitment phase. In the present study, we conducted whole-genome expression profiling to obtain a comprehensive view of the transcriptional program underlying the rescue effect of Gip in CGNs. By using DNA microarray technology, we identified 65 genes, we named survival related genes, whose expression is significantly de-regulated following Gip treatment. The expression levels of six transcripts were confirmed by real-time quantitative polymerase chain reaction. The proteins encoded by the survival related genes are functionally grouped in the following categories: signal transduction, transcription, cell cycle, chromatin remodeling, cell death, antioxidant activity, ubiquitination, metabolism and cytoskeletal organization. Our data outline that Gip supports CGNs rescue via a molecular framework, orchestrated by a wide spectrum of gene actors, which propagate survival signals and support neuronal viability.

Insights into the PX (phox-homology) domain and SNX (sorting nexin) protein families: structures, functions and roles in disease

The mammalian genome encodes 49 proteins that possess a PX (phox-homology) domain, responsible for membrane attachment to organelles of the secretory and endocytic system via binding of phosphoinositide lipids. The PX domain proteins, most of which are classified as SNXs (sorting nexins), constitute an extremely diverse family of molecules that play varied roles in membrane trafficking, cell signalling, membrane remodelling and organelle motility. In the present review, we present an overview of the family, incorporating recent functional and structural insights, and propose an updated classification of the proteins into distinct subfamilies on the basis of these insights. Almost all PX domain proteins bind PtdIns3P and are recruited to early endosomal membranes. Although other specificities and localizations have been reported for a select few family members, the molecular basis for binding to other lipids is still not clear. The PX domain is also emerging as an important protein–protein interaction domain, binding endocytic and exocytic machinery, transmembrane proteins and many other molecules. A comprehensive survey of the molecular interactions governed by PX proteins highlights the functional diversity of the family as trafficking cargo adaptors and membrane-associated scaffolds regulating cell signalling. Finally, we examine the mounting evidence linking PX proteins to different disorders, in particular focusing on their emerging importance in both pathogen invasion and amyloid production in Alzheimer's disease.

ADAM12 is expressed by astrocytes during experimental demyelination

A disintegrin and metalloproteinase (ADAM) 12 represents a member of a large family of similarly structured multi-domain proteins. In the central nervous system (CNS), ADAM12 has been suggested to play a role in brain development, glioblastoma cell proliferation, and in experimental autoimmune encephalomyelitis. Furthermore, ADAM12 was reported to be almost exclusively expressed by oligodendrocytes and could, therefore, be considered as suitable marker for this cell type. In the present study, we investigated ADAM12 expression in the healthy and pathologically altered murine CNS. As pathological paradigm, we used the cuprizone demyelination model in which myelin loss during multiple sclerosis is imitated. Besides APC(+) oligodendrocytes, SMI311(+) neurons and GFAP(+) astrocytes express ADAM12 in the adult mouse brain. ADAM12 expression was further analyzed in vitro. After the induction of demyelination, we observed that activated astrocytes are the main source of ADAM12 in brain regions affected by oligodendrocyte loss. Exposure of astrocytes in vitro to either lipopolysaccharides (LPS), tumor necrosis factor alpha (TNFalpha), glutamate, or hydrogen peroxide revealed a highly stimulus-specific regulation of ADAM12 expression which was not seen in microglial BV2 cells. It appears that LPS- and TNFalpha-induced ADAM12 expression is mediated via the classic NFkappaB pathway. In summary, we demonstrated that ADAM12 is not a suitable marker for oligodendrocytes. Our results further suggest that ADAM12 might be implicated in the course of distinct CNS diseases such as demyelinating disorders.

Reduced density of ADAM 12-immunoreactive oligodendrocytes in the anterior cingulate white matter of patients with schizophrenia

OBJECTIVES

Abnormalities of brain white matter and oligodendroglia are replicated findings in schizophrenia research. The largely oligodendroglia-associated enzyme ADAM (A disintegrin and metalloprotease) 12 might be involved in the patho-physiology of schizophrenia, because the gene coding for human ADAM12 is located on chromosome 10q26.3, a gene locus which has been linked to schizophrenia, and some of its putative substrates are altered in schizophrenia.

METHODS

We studied the numerical density of ADAM12 expressing oligodendrocytes in post-mortem prefrontal brains of patients with haloperidol treated, chronic schizophrenia and matched controls.

RESULTS

A significantly reduced numerical density of ADAM12 immunoreactive oligodendrocytes was found in the white matter of the anterior cingulate cortex of schizophrenic patients.

CONCLUSIONS

Although the pathophysiological implications of this finding are currently unknown, it is well conveyable that reduced ADAM12 protein contributes to a deviant metabolism of some of its substrates. These substrates are either parts of important signalling cascades (EGF, betacellulin, TGF-beta) or chemical components of myelin (neurofascin-ankyrin) known to be compromised in schizophrenia.

A study of the association between the ADAM12 and SH3PXD2A (SH3MD1) genes and Alzheimer's disease

Several observations suggest that neurotoxicity in Alzheimer's disease (AD) can be partly attributed to beta-amyloid (Abeta) and senile plaques. Recent work has suggested that the FISH (five SH3 domains) adapter protein and ADAM12 (a disintegrin and metalloprotease) may mediate the neurotoxic effect of Abeta. Both genes are located on chromosome 10, within a region linked to AD (for SH3PXD2A) or nearby (for ADAM12). A recent study reported a statistically significant interaction between 2 variants of these genes (rs3740473 for SH3PXD2A and rs11244787 for ADAM12) with respect to the risk of developing AD. With a view to replicating this observation, we genotyped the two SNPs in four European case-control cohorts of Caucasian origin (1913 cases and 1468 controls) but were unable to confirm the initial results.

The role of ADAMs in disease pathophysiology

The ADAMs are a family of multidomain transmembrane and secreted proteins involved in both proteolysis and cell adhesion. Altered expression of specific ADAMs is implicated in the pathophysiology of several diseases including rheumatoid arthritis, Alzheimer's disease, cardiac hypertrophy, asthma and cancer. Of these different diseases, it is in cancer where most research has been carried out. Multiple ADAMs, including ADAM-9, ADAM-10, ADAM-12, ADAM-15 and ADAM-17, have been shown to play a role in either cancer formation or progression. Consistent with these findings, increased expression of specific ADAMs in several cancer types was found to correlate with features of aggressive disease and poor prognosis. Currently, selective ADAM inhibitors against ADAM-10 and ADAM-17 are undergoing clinical trials for the treatment of cancer. Further work is required in order to establish a causative role for ADAMs in rheumatoid arthritis, Alzheimer's disease, cardiac hypertrophy and asthma.

Cellular roles of ADAM12 in health and disease

ADAM12 belongs to the large family of ADAMs (a disintegrin and metalloproteases) and possesses extracellular metalloprotease and cell-binding functions, as well as intracellular signaling capacities. Interest in ADAM12 has increased recently because its expression is related to tumor progression and it is a potential biomarker for breast cancer. It is therefore important to understand ADAM12's functions. Many cellular roles for ADAM12 have been suggested. It is an active metalloprotease, and has been implicated in insulin-like growth factor (IGF) receptor signaling, through cleavage of IGF-binding proteins, and in epidermal growth factor receptor (EGFR) pathways, via ectodomain shedding of membrane-tethered EGFR ligands. These proteolytic events may regulate diverse cellular responses, such as altered cell differentiation, proliferation, migration, and invasion. ADAM12 may also regulate cell-cell and cell-extracellular matrix contacts through interactions with cell surface receptors - integrins and syndecans - potentially influencing the actin cytoskeleton. Moreover, ADAM12 interacts with several cytoplasmic signaling and adaptor molecules through its intracellular domain, thereby directly transmitting signals to or from the cell interior. These ADAM12-mediated cellular effects appear to be critical events in both biological and pathological processes. This review presents current knowledge on ADAM12 functions gained from in vitro and in vivo observations, describes ADAM12's role in both normal physiology and pathology, particularly in cancer, and discusses important areas for future investigation.