Glycoprotein Nonmetastatic Melanoma Protein Research Articles

DLG2, but not TMEM229B, GPNMB, and ITGA8 polymorphism, is associated with Parkinson's disease in a Taiwanese population

Transmembrane or membrane-associated protein dysfunction is increasingly recognized as an important mechanism of pathogenesis in Parkinson's disease (PD). Previous genome-wide association studies and their meta-analysis in PD genes have identified several risk foci in transmembrane protein-encoding genes. Herein, we investigated the effect of 4 such PD-associated genetic variants reported in Caucasians, including discs-large membrane-associated guanylate kinase scaffolding protein 2 (DLG2 rs3793947), transmembrane protein 229B (TMEM229B rs1555399), glycoprotein nonmetastatic melanoma protein B (GPNMB rs199347), and integrin subunit alpha 8 (ITGA8 rs7077361). A total of 1185 Taiwanese subjects comprising 592 PD patients and 593 unrelated age-matched controls were genotyped. DLG2 rs3793947 AA genotype showed a significantly lower prevalence in female PD patients compared to the female controls (p = 0.019). The recessive model analysis also demonstrated a reduced PD risk for females in AA genotype (odds ratio = 0.573, 95% confidence interval: 0.379–0.868, p = 0.008). The frequencies of TMEM229B rs1555399 and GPNMB rs199347 genotypes and alleles were similar in PD patients and controls. ITG8 rs7077361 was not polymorphic in all subjects of this study. These data suggested that DLG2, but not TMEM229B, GPNMB, and ITGA8, influenced the risk of PD in Taiwan.

Glycoprotein Non-Metastatic Melanoma Protein B (GPNMB) and Cancer: A Novel Potential Therapeutic Target

Glycoprotein non-metastatic melanoma protein B (GPNMB) is a transmembrane protein enriched on the cell surface of cancer cells, including melanoma, glioblastoma, and triple-negative breast cancer. There is growing evidence identifying GPNMB as a tumor-promoter; however, despite its biological and clinical significance, the molecular mechanisms engaged by GPNMB to promote tumorigenesis are not well understood. GPNMB promotes aggressive behaviors such as tumor cell proliferation, migration, and invasion. The extracellular domain of GPNMB shed from the cell surface interacts with integrins to facilitate in the recruitment of immune-suppressive and pro-angiogenic cells to the tumor microenvironment, thereby enhancing tumor migration and invasion. GPNMB also modulates receptor tyrosine kinases and integrin signaling in a cell autonomous fashion, leading to downstream kinase signaling that in turn triggers the expression and secretion of tumorigenic factors such as matrix metalloproteinases (MMPs) and cytokines. Therefore, GPNMB exerts its pro-tumorigenic role both intracellularly and in a paracrine fashion through shedding its extracellular domain. This review highlights the importance of GPNMB in cancer progression and discusses molecular mediators of GPNMB-induced tumor growth and invasion.

GPNMB Induces BiP Expression by Enhancing Splicing of BiP Pre-mRNA during the Endoplasmic Reticulum Stress Response

Glycoprotein nonmetastatic melanoma protein B (GPNMB) has a neuroprotective effect against neuronal cell death caused by the accumulation of abnormal mutated proteins. It is known that the accumulation of pathological proteins induces endoplasmic-reticulum (ER) stress leading to cell damage. The aim of this study was to determine the role of GPNMB in the ER stress response. GPNMB was greatly up-regulated by thapsigargin-induced ER stress. Under the ER stress conditions, GPNMB relocated to the nucleus and specifically up-regulated expression of BiP at the mRNA level by promoting the BiP pre-mRNA splicing, not through the pathways initiated by the three major transducers of the unfolded protein response: IRE1, PERK, and ATF6. Furthermore, we found that the protein level of BiP and the infarction were increased and attenuated, respectively, in Gpnmb-transgenic mice after occlusion of the middle cerebral artery, in comparison with wild-type mice. Thus, our findings indicate that GPNMB enhances the BiP expression by promoting the splicing (thereby preventing cell death caused by ER stress) and could be a therapeutic target in ER stress-related disorders.

Glycoprotein NMB: an Emerging Role in Neurodegenerative Disease.

Neurodegeneration is characterized by severe neuronal loss leading to the cognitive and physical impairments that define various neurodegenerative diseases. Neuroinflammation is one hallmark of neurodegenerative diseases and can ultimately contribute to disease progression. Increased inflammatory cytokines, such as interleukin-6 (IL-6), interleukin-1β (IL-1 β), and tumor necrosis factor-α (TNF-α) are associated with Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and multiple sclerosis (MS). Unfortunately, current therapeutic options lack ability to stop or effectively slow progression of these diseases and are primarily aimed at alleviating symptoms. Thus, it is crucial to discover novel treatment candidates for neurodegenerative diseases. Glycoprotein nonmetastatic melanoma protein B (GPNMB) is a type-I transmembrane glycoprotein first identified in a melanoma cell line. GPNMB augments bone mineral deposition by stimulating osteoblast differentiation. Aside from its anabolic function in the bone, emerging evidence suggests that GPNMB has anti-inflammatory and reparative functions. GPNMB has also been demonstrated to be neuroprotective in an animal model of ALS, cerebral ischemia, and other disease models. Given these discoveries, GPNMB should be investigated as a potential therapeutic option for multiple neurodegenerative diseases.

Identification of Novel Agents for the Treatment of Brain Metastases of Breast Cancer.

Brain cancer from metastasized breast cancer has a high mortality rate in women. The treatment of lesions is hampered in large part by the blood-brain barrier (BBB), which prevents adequate distribution of anti-cancer compounds to brain metastases. In this study we used a novel screening method to identify candidate molecules that are well-suited to utilizing the BBB choline transporter for distribution into the brain parenchyma. From our screen we identified two compounds, Ch-1 and Ch-2 that were able to reduce the brain tumor burden in a murine mouse model of brain metastasis of breast cancer. These compounds also significantly increased the survival of mice by more than 10 days. Mechanistic studies indicated that Ch-1 is able to prevent the activation of the pro-survival mitogen-activated kinases (MAPKs) by osteoactivin (OA; Glycoprotein nonmetastatic melanoma protein B GPNMB). The results from this study show that nutrient transporter virtual screening is a viable novel alternative to traditional drug screening programs to identify anti-cancer compounds for the treatment of brain cancers.

Increased brain expression of GPNMB is associated with genome wide significant risk for Parkinson\u2019s disease on chromosome 7p15.3

Genome wide association studies (GWAS) for Parkinson’s disease (PD) have previously revealed a significant association with a locus on chromosome 7p15.3, initially designated as the glycoprotein non-metastatic melanoma protein B (GPNMB) locus. In this study, the functional consequences of this association on expression were explored in depth by integrating different expression quantitative trait locus (eQTL) datasets (Braineac, CAGEseq, GTEx, and Phenotype-Genotype Integrator (PheGenI)). Top risk SNP rs199347 eQTLs demonstrated increased expressions of GPNMB, KLHL7, and NUPL2 with the major allele (AA) in brain, with most significant eQTLs in cortical regions, followed by putamen. In addition, decreased expression of the antisense RNA KLHL7-AS1 was observed in GTEx. Furthermore, rs199347 is an eQTL with long non-coding RNA (AC005082.12) in human tissues other than brain. Interestingly, transcript-specific eQTLs in immune-related tissues (spleen and lymphoblastoid cells) for NUPL2 and KLHL7-AS1 were observed, which suggests a complex functional role of this eQTL in specific tissues, cell types at specific time points. Significantly increased expression of GPNMB linked to rs199347 was consistent across all datasets, and taken in combination with the risk SNP being located within the GPNMB gene, these results suggest that increased expression of GPNMB is the causative link explaining the association of this locus with PD. However, other transcript eQTLs and subsequent functional roles cannot be excluded. This highlights the importance of further investigations to understand the functional interactions between the coding genes, antisense, and non-coding RNA species considering the tissue and cell-type specificity to understand the underlying biological mechanisms in PD.

Knocking down glycoprotein nonmetastatic melanoma protein B suppresses the proliferation, migration, and invasion in bladder cancer cells.

Glycoprotein nonmetastatic melanoma protein B is a type 1 transmembrane protein that has been recently found to play a role in cancer cell proliferation, angiogenesis, and invasion. Due to its potential responsibility in cancer aggressiveness, the main objective of this work was to investigate its expression in bladder cancer and the biological functions in bladder cancer cells. Using immunohistochemistry, western blot, and reverse transcription polymerase chain reaction, we analyzed the expression of glycoprotein nonmetastatic melanoma protein B in bladder cancer tissues and bladder cancer cell lines. The effects of glycoprotein nonmetastatic melanoma protein B on proliferation, migration, and invasion were tested after knocking down the glycoprotein nonmetastatic melanoma protein B in bladder cancer cells with small interfering RNAs by CCK-8, Transwell, and Matrigel assays. Our results showed that glycoprotein nonmetastatic melanoma protein B protein was highly expressed in the bladder cancer tissues and cell lines. Downregulating glycoprotein nonmetastatic melanoma protein B could suppress the proliferation, migration, and invasion in bladder cancer cells. Glycoprotein nonmetastatic melanoma protein B expression was related to the poor differentiation and recurrence by immunohistochemistry analysis. The survival analysis also showed that glycoprotein nonmetastatic melanoma protein B was related to the patient prognosis. In conclusion, Glycoprotein nonmetastatic melanoma protein B protein was highly expressed in the bladder cancer, which was related to the poor prognosis in bladder cancer patients. Glycoprotein nonmetastatic melanoma protein B promoted the proliferation, migration, and invasion in bladder cancer cells.

Glycoprotein non-metastatic melanoma protein b (Gpnmb) is highly expressed in macrophages of acute injured kidney and promotes M2 macrophages polarization

Acute kidney injury (AKI) is an increasingly common disorder that is strongly linked to short- and long-term morbidity and mortality. During AKI process, macrophages, one of the important immune response cells, can polarize into M1 and M2 subtype from M0 subtype. It is well-known that M1 macrophages play a pro inflammatory role while M2 macrophages play an anti-inflammatory role. Glycoprotein non-metastatic melanoma protein b (Gpnmb) is a glycosylated transmembrane protein highly expressed in numerous cells, including osteoblasts, dendritic cells and macrophages. Gpnmb serves as a negative regulator of inflammation in macrophages and has a protective effect on injuries. In acute kidney injury, the macrophage has been shown diverse roles depending on different phenotype. This study provided gene expression and protein expression evidence that Gpnmb was highly expressed in M2 macrophages in the damaged areas of kidney after ischemia-reperfusion injury. Then, we successful isolated and culture mouse bone marrow-derived macrophages (BMMφ) and found that Gpnmb showed different expression levels in M0, M1 and M2 BMMφ: lowest in M1, highest in M2. After knocking down Gpnmb with si-Gpnmb, BMMφ M2 polarization and secretion of anti-inflammatory cytokines IL-10 and TGF-β were inhibited, while M1 polarization and secretion of proinflammatory cytokines IL-1β and TNF-α were promoted. Moreover, IL-4-STAT6 pathway was involved in the promotion of M2 polarization by Gpnmb. Taken together, Gpnmb may serve as a potential biomarker of AKI and play a protective role against the AKI by modulating the polarization of macrophage.

GPNMB promotes proliferation of developing eosinophils.

Glycoprotein non-metastatic melanoma protein B (GPNMB) is a type I transmembrane protein that is expressed in a wide variety of cell types, including haematopoietic lineages. We previously demonstrated that GPNMB is one of the most highly expressed genes at an early and intermediate stage of eosinophil development. We herein examined GPNMB expression and its possible functional effect using cord blood (CB) CD34+ haematopoietic stem cells differentiating toward eosinophils during a 24-day culture period. Western blot and confocal microscopy analyses showed that GPNMB reached its highest levels at day 12 with most GPNMB-positive cells also expressing major basic protein 1 (MBP1), an eosinophil granule protein. GPNMB declined thereafter, but was still present at an appreciable level at day 24, the time when CB eosinophils most abundantly expressed MBP1 and were thus considered fully differentiated. When the developing CB cells were cultured in the presence of a blocking anti-GPNMB antibody, cell proliferation was significantly reduced. In agreement, ectopic expression of GPNMB in heterologous cells resulted in a significant increase in cell proliferation, while small interfering RNA of GPNMB inhibited the GPNMB-mediated proliferation. Thus, GPNMB is expressed in a temporal manner during eosinophil development and delivers a proliferative signal upon activation.

GPNMB ameliorates mutant TDP‐43‐induced motor neuron cell death

Glycoprotein nonmetastatic melanoma protein B (GPNMB) aggregates are observed in the spinal cord of amyotrophic lateral sclerosis (ALS) patients, but the detailed localization is still unclear. Mutations of transactive response DNA binding protein 43kDa (TDP-43) are associated with neurodegenerative diseases including ALS. In this study, we evaluated the localization of GPNMB aggregates in the spinal cord of ALS patients and the effect of GPNMB against mutant TDP-43 induced motor neuron cell death. GPNMB aggregates were not localized in the glial fibrillary acidic protein (GFAP)-positive astrocyte and ionized calcium binding adaptor molecule-1 (Iba1)-positive microglia. GPNMB aggregates were localized in the microtubule-associated protein 2 (MAP-2)-positive neuron and neurofilament H non-phosphorylated (SMI-32)-positive neuron, and these were co-localized with TDP-43 aggregates in the spinal cord of ALS patients. Mock or TDP-43 (WT, M337V, and A315T) plasmids were transfected into mouse motor neuron cells (NSC34). The expression level of GPNMB was increased by transfection of mutant TDP-43 plasmids. Recombinant GPNMB ameliorated motor neuron cell death induced by transfection of mutant TDP-43 plasmids and serum-free stress. Furthermore, the expression of phosphorylated ERK1/2 and phosphorylated Akt were decreased by this stress, and these expressions were increased by recombinant GPNMB. These results indicate that GPNMB has protective effects against mutant TDP-43 stress via activating the ERK1/2 and Akt pathways, and GPNMB may be a therapeutic target for TDP-43 proteinopathy in familial and sporadic ALS. © 2016 Wiley Periodicals, Inc.

Glycoprotein nonmetastatic melanoma protein B (GPNMB) promotes the progression of brain glioblastoma via Na+/K+-ATPase

Glycoprotein nonmetastatic melanoma protein B (GPNMB), which is involved in invasion and metastasis, was found to be overexpressed in various cancers. High levels of GPNMB and Na+/K+-ATPase α subunits are associated with a poor prognosis in glioblastoma patients. We showed that GPNMB interacts with Na+/K+-ATPase α subunits to activate PI3K/Akt and MEK/ERK pathways. However, it remains unclear whether the interaction of GPNMB and Na+/K+-ATPase α subunits is involves in progression of glioma. The tumor size induced by the injection of glioma GL261 cells was larger in transgenic mice overexpressing GPNMB when compared with wild-type mice. Additionally, the interaction of GPNMB and Na+/K+-ATPase α subunits was identified in the murine glioma model and in the tumors of glioblastoma patients. Ouabain, a Na+/K+-ATPase inhibitor, suppressed the glioma growth induced by the injection of glioma cells in the transgenic mice overexpressing GPNMB and blocked the GPNMB-induced migration of glioma cells. These findings indicate that GPNMB promotes glioma growth via Na+/K+-ATPase α subunits. Thus, the interaction between GPNMB and Na+, K+-ATPase α subunits represents a novel therapeutic target for the treatment of brain glioblastomas.

Adverse left ventricular remodeling by glycoprotein nonmetastatic melanoma protein B in myocardial infarction.

Cardiac diseases are the leading cause of death. Available treatment approaches are not sufficient to reverse persistent cardiac damage after injury; thus, the search for new therapeutic targets is essential. Our microarray-based screening in rat hearts 24 h after myocardial infarction (MI) yielded glycoprotein nonmetastatic melanoma protein B (GPNMB), which is known to be involved in inflammation and fibrosis after tissue injury. However, its role in the heart was elusive. We found increased cardiac expression levels of GPNMB in rats and mice after MI. Analysis of DBA/2J mice, which lack functional GPNMB due to a spontaneous point mutation, showed that systemic GPNMB deficiency was associated with preserved cardiac function and less left ventricular dilation after MI compared with DBA/2J mice with reconstituted GPNMB expression. These improvements were associated with decreased expression of matrix metalloproteinase 9, the cardiac stress genes for natriuretic peptides (atrial natriuretic peptide and brain natriuretic peptide), and β-myosin heavy chain after MI. Moreover, GPNMB deficiency attenuated the dilated cardiomyopathy in muscle lim protein knockout mice but could not prevent cardiac hypertrophy induced by isoprenaline infusion. This is the first experimental study to show that GPNMB adversely influences myocardial remodeling.-Järve, A., Mühlstedt, S., Qadri, F., Nickl, B., Schulz, H., Hübner, N., Özcelik, C., Bader, M. Adverse left ventricular remodeling by glycoprotein nonmetastatic melanoma protein B in myocardial infarction.

Ocular Albinism Type 1 Regulates Melanogenesis in Mouse Melanocytes.

To investigate whether ocular albinism type 1 (OA1) is differentially expressed in the skin of mice with different coat colors and to determine its correlation with coat color establishment in mouse, the expression patterns and tissue distribution characterization of OA1 in the skin of mice with different coat colors were qualitatively and quantitatively analyzed by real-time quantitative PCR (qRT-PCR), immunofluorescence staining and Western blot. The qRT-PCR analysis revealed that OA1 mRNA was expressed in all mice skin samples tested, with the highest expression level in brown skin, a moderate expression level in black skin and the lowest expression level in gray skin. Positive OA1 protein bands were also detected in all skin samples by Western blot analysis. The relative expression levels of OA1 protein in both black and brown skin were significantly higher than that in gray skin, but there was no significant difference between black and brown mice. Immunofluorescence assays revealed that OA1 was mainly expressed in the hair follicle matrix, the inner and outer root sheath in the skin tissues with different coat colors. To get further insight into the important role of OA1 in the melanocytes’ pigmentation, we transfected the OA1 into mouse melanocytes and then detected the relative expression levels of pigmentation-related gene. Simultaneously, we tested the melanin content of melanocytes. As a result, the overexpression of OA1 significantly increased the expression levels of microphthalmia-associated transcription factor (MITF), tyrosinase (TYR), tyrosinase-related protein 1 (TRP1) and premelanosome protein (PMEL). However, the tyrosinase-related protein 2 (TRP2) level was attenuated. By contrast, the level of glycoprotein non-metastatic melanoma protein b (GPNMB) was unaffected by OA1 overexpression. Furthermore, we observed a significant increase in melanin content in mouse melanocyte transfected OA1. Therefore, we propose that OA1 may participate in the formation of coat color by regulating the level of MITF and the number, size, motility and maturation of melanosome.

Elevation of glycoprotein nonmetastatic melanoma protein B in type 1 Gaucher disease patients and mouse models.

Gaucher disease is caused by inherited deficiency of lysosomal glucocerebrosidase. Proteome analysis of laser‐dissected splenic Gaucher cells revealed increased amounts of glycoprotein nonmetastatic melanoma protein B (gpNMB). Plasma gpNMB was also elevated, correlating with chitotriosidase and CCL18, which are established markers for human Gaucher cells. In Gaucher mice, gpNMB is also produced by Gaucher cells. Correction of glucocerebrosidase deficiency in mice by gene transfer or pharmacological substrate reduction reverses gpNMB abnormalities. In conclusion, gpNMB acts as a marker for glucosylceramide‐laden macrophages in man and mouse and gpNMB should be considered as candidate biomarker for Gaucher disease in treatment monitoring.

The novel monoclonal antibody 9F5 reveals expression of a fragment of GPNMB/osteoactivin processed by furin-like protease(s) in a subpopulation of microglia in neonatal rat brain.

To differentiate subtypes of microglia (MG), we developed a novel monoclonal antibody, 9F5, against one subtype (type 1) of rat primary MG. The 9F5 showed high selectivity for this cell type in Western blot and immunocytochemical analyses and no cross‐reaction with rat peritoneal macrophages (Mφ). We identified the antigen molecule for 9F5: the 50‐ to 70‐kDa fragments of rat glycoprotein nonmetastatic melanoma protein B (GPNMB)/osteoactivin, which started at Lys170. In addition, 9F5 immunoreactivity with GPNMB depended on the activity of furin‐like protease(s). More important, rat type 1 MG expressed the GPNMB fragments, but type 2 MG and Mφ did not, although all these cells expressed mRNA and the full‐length protein for GPNMB. These results suggest that 9F5 reactivity with MG depends greatly on cleavage of GPNMB and that type 1 MG, in contrast to type 2 MG and Mφ, may have furin‐like protease(s) for GPNMB cleavage. In neonatal rat brain, amoeboid 9F5+ MG were observed in specific brain areas including forebrain subventricular zone, corpus callosum, and retina. Double‐immunοstaining with 9F5 antibody and anti‐Iba1 antibody, which reacts with MG throughout the CNS, revealed that 9F5+ MG were a portion of Iba1+ MG, suggesting that MG subtype(s) exist in vivo. We propose that 9F5 is a useful tool to discriminate between rat type 1 MG and other subtypes of MG/Mφ and to reveal the role of the GPNMB fragments during developing brain. GLIA 2016;64:1938–1961

Glycoprotein non-metastaticmelanoma protein B promotes glioma motility and angiogenesis through the Wnt/β-catenin signaling pathway.

Glioma is a common tumor with high mortality and poor overall survival. However, the regulatory mechanisms of glioma tumorigenesis and glioma cell motility are completely unknown. Here, we investigated the role of glycoprotein non-metastatic melanoma protein B in glioma. The expression of glycoprotein non-metastatic melanoma protein B is observed to be aberrantly regulated in glioma tissues and cells, and high levels of glycoprotein non-metastatic melanoma protein B present an inverse correlation with the survival of glioma patients. Compared with the control, glycoprotein non-metastatic melanoma protein B inhibition significantly retarded the proliferation and migration of human glioma cells. The tube formation ability of HBMECs induced by glioma cells was also remarkably reduced by glycoprotein non-metastatic melanoma protein B silencing. Increased levels of VEGF-C and TEM7 were down-regulated by the suppression of glycoprotein non-metastatic melanoma protein B in glioma cells. Additionally, the activity of MMP-2/3/9 was assessed in glioma cells using Western blotting and gelatin zymography assay; their activities were strongly decreased following the suppression of glycoprotein non-metastatic melanoma protein B. Further studies suggested that canonical Wnt/β-catenin pathway was activated, but was inactivated by glycoprotein non-metastatic melanoma protein B suppression in glioma cells. In conclusion, we demonstrate that glycoprotein non-metastatic melanoma protein B might be an inducer for glioma and could enhance matrix metalloproteinase activity through Wnt/β-catenin pathway to contribute to glioma tumorigenesis. This may represent a new understanding for malignant glioma.

Macrophage-Associated Osteoactivin/GPNMB Mediates Mesenchymal Stem Cell Survival, Proliferation, and Migration Via a CD44-Dependent Mechanism.

Although MSCs have been widely recognized to have therapeutic potential in the repair of injured or diseased tissues, it remains unclear how functional activities of mesenchymal stem cells (MSCs) are influenced by the surrounding inflammatory milieu at the site of tissue injury. Macrophages constitute an essential component of innate immunity and have been shown to exhibit a phenotypic plasticity in response to various stimuli, which play a central role in both acute inflammation and wound repair. Osteoactivin (OA)/Glycoprotein non-metastatic melanoma protein B (GPNMB), a transmembrane glycoprotein that plays a role in cell differentiation, survival, and angiogenesis. The objective of this study was to investigate the potential role of OA/GPNMB in macrophage-induced MSC function. We found that reparative M2 macrophages express significantly greater levels of OA/GPNMB than pro-inflammatory M1 macrophages. Furthermore, using loss of function and rescue studies, we demonstrated that M2 macrophages-secreted OA/GPNMB positively regulates the viability, proliferation, and migration of MSCs. More importantly, we demonstrated that OA/GPNMB acts through ERK and AKT signaling pathways in MSCs via CD44, to induce these effects. Taken together, our results provide pivotal insight into the mechanism by which OA/GPNMB contributes to the tissue reparative phenotype of M2 macrophages and positively regulates functional activities of MSCs. J. Cell. Biochem. 117: 1511-1521, 2016. © 2015 Wiley Periodicals, Inc.

No association of GPNMB rs156429 polymorphism with Parkinson’s disease, amyotrophic lateral sclerosis and multiple system atrophy in Chinese population

BackgroundThe rs156429 polymorphism in the glycoprotein nonmetastatic melanoma protein B (GPNMB) gene was found to be associated with the risk for Parkinson disease (PD) in Caucasian population by genome-wide association studies (GWAS). Recently, encoded protein, GPNMB, was identified as a novel neuro-protective factor in amyotrophic lateral sclerosis (ALS). The overlapping of clinical manifestations and pathologic characteristics among PD, ALS, and multiple system atrophy (MSA) are observed. ObjectThis study aimed at investigating the possible associations of the polymorphism and the three neurodegenerative diseases: PD, ALS and MSA in a Chinese population. MethodsAll of the subjects, including PD (n=1096), sporadic ALS (SALS) (n=876) and MSA (n=356) patients, and 829 health controls (HCs) were included. All subjects were genotyped for this polymorphism using Sequenom iPLEX Assay technology. ResultsNo differences were found in the genotype distributions and minor allele frequency of GPNMB rs156429 between PD patients and HCs, between SALS patients and HCs, between MSA patients and HCs, and between subgroups of PD, ALS and MSA patients with regard to clinical features such as sex, age of onset, presence or absence of cognitive abnormality, depression and anxiety. ConclusionLack of association identified in our study suggests that it may be premature to conclude associations between GPNMB rs156429 and SALS, PD and MSA. More studies on such an association involving a larger number of participants are needed to confirm the present findings.

Glycoprotein nonmetastatic melanoma protein B extracellular fragment shows neuroprotective effects and activates the PI3K/Akt and MEK/ERK pathways via the Na+/K+-ATPase.

Glycoprotein nonmetastatic melanoma protein B (GPNMB) plays important roles in various types of cancer and amyotrophic lateral sclerosis (ALS). The details of GPNMB function and its interacting protein have not been clarified. Therefore, to identify GPNMB binding partners on the cell membrane, we used membrane protein library/BLOTCHIP-MS technology, which enables us to analyze all cell membrane proteins as binding partners of the GPNMB extracellular fragment. As a result of a comprehensive search, we identified the alpha subunits of Na+/K+-ATPase (NKA) as a possible binding partner. We confirmed the interaction between the GPNMB extracellular fragment and NKA by immunoprecipitation and immunostaining in NSC-34 cells. Indeed, endogenous GPNMB extracellular fragment bound to and colocalized with NKA alpha subunits. Furthermore, exogenous GPNMB extracellular fragment, i.e., human recombinant GPNMB, also bound to and colocalized with NKA alpha subunits. Additionally, we found that the GPNMB extracellular fragment had neuroprotective effects and activated the phosphoinositide 3-kinase (PI3K)/Akt and mitogen-activated protein kinase (MAPK)-extracellular signal-regulated kinase (ERK) kinase (MEK)/ERK pathways via NKA. These findings indicated that NKA may act as a novel “receptor” for the GPNMB extracellular fragment, offering additional molecular targets for the treatment of GPNMB-related diseases, including various types of cancer and ALS.

Expression of glycoprotein nonmetastatic melanoma protein B in macrophages infiltrating injured mucosa is associated with the severity of experimental colitis in mice.

Glycoprotein nonmetastatic melanoma protein B (Gpnmb) is a transmembrane glycoprotein, which negatively regulates the inflammatory responses of macrophages. However, the role of Gpnmb in intestinal macrophages remains to be fully elucidated. The present study aimed to investigate the expression of Gpnmb and its effects on colonic mucosal injuries associated with dextran sulfate sodium (DSS)‑induced colitis in BALB/c mice, DBA/2J (D2) mice lacking Gpnmb and Gpnmb‑transgenic DBA/2J mice (D2‑gpnmb+). The colonic expression of Gpnmb increased with the severity of DSS‑induced colitis in BALB/c mice, and macrophages infiltrating the inflamed mucosa were found to express Gpnmb. The D2 mice lacking Gpnmb exhibited more severe DSS‑induced colitis, which was accompanied by higher levels of pro‑inflammatory cytokines, including interleukin (IL)‑1β and IL‑6, compared with the D2‑gpnmb+ mice. Following lipopolysaccharide stimulation, macrophages from the D2 mice expressed higher levels of pro‑inflammatory cytokines and lower levels of IL‑10, compared with the D2‑gpnmb+mice. In addition, in the RAW264.7 murine macrophage cell line, knockdown of Gpnmb by small interfering RNA was associated with increased production of pro‑inflammatory cytokines, which were potentially mediated by the extracellular signal‑regulated kinase (ERK) and p38 signaling pathways. The results of the present study indicated that macrophages infiltrating injured mucosa express Gpnmb, and that Gpnmb‑positive macrophages may ameliorate inflammation in the intestinal mucosa by decreasing pro‑inflammatory cytokine production via the ERK and p38 signaling pathways.