Glycoprotein Nonmetastatic Melanoma Protein B Research Articles

Glycoprotein nonmetastatic melanoma protein B (GPNMB) as a novel neuroprotective factor in cerebral ischemia–reperfusion injury

Glycoprotein nonmetastatic melanoma protein B (GPNMB) is a type I transmembrane protein reported to have neuroprotective effects in the neurodegenerative disease amyotrophic lateral sclerosis (ALS). We investigated whether GPNMB is also neuroprotective against brain ischemia–reperfusion injury (IRI). Focal ischemia/reperfusion injury was induced via filament middle cerebral artery occlusion (MCAO) for 2h, followed by reperfusion upon withdrawal of the filament. We assessed the neuroprotective effects of GPNMB using transgenic (Tg) mice which over expressing GPNMB or recombinant GPNMB which has the sequence of human extracellular GPNMB. The results showed that GPNMB was up-regulated after IRI, and that genomic over-expression of GPNMB significantly ameliorated infarct volume. Next, we investigated the protective mechanisms of GPNMB via Western blotting and immunohistochemistry (IHC). Phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1/2), and protein kinase B (Akt), were increased in the GPNMB Tg group according to Western blotting data. IHC analysis showed that GPNMB was expressed not only in neurons, but also in astrocytes, produced labeling patterns similar to that in human brain ischemia. Furthermore, recombinant GPNMB also decreased infarction volume. These results indicate that GPNMB protected neurons against IRI, and phosphor-Akt and phosphor-ERK might be a part of the protective mechanisms, and that the neuroprotective effect of GPNMB was seemingly induced by the extracellular sequence of GPNMB.In conclusion, these findings indicate that GPNMB has neuroprotective effects against IRI, via phosphorylation of ERK1/2 and Akt, suggesting that GPNMB may be a therapeutic target for ischemia–reperfusion injuries.

PS13 - 2. Glycoprotein Nonmetastatic Melanoma protein B (GPNMB) is induced in obese macrophages as a result of lysosomal stress

It has been extensively described that low-grade inflammatory condition plays a crucial role in the genesis and development of diseases in metabolic syndrome. Furthermore, macrophage infiltration in the adipose compartment increases the local level of inflammatory cytokines that cause insulin resistance and inhibition of adipocyte differentiation.

GPNMB enhances bone regeneration by promoting angiogenesis and osteogenesis: Potential role for tissue engineering bone

Bone regeneration is a coordinated process involving the connection between blood vessels and bone cells. Glycoprotein non-metastatic melanoma protein B (GPNMB) is known to be vital in bone formation. However, the effect of GPNMB on bone regeneration and the underlying molecular mechanism are still undefined. Fibroblast growth factor receptor (FGFR)-mediating signaling is pivotal in bone formation and angiogenesis. Therefore, we assessed GPNMB function as a communicating molecule between osteoblasts and angiogenesis, and the possible correlation with FGFR-1 signaling. Recombinant GPNMB dose-dependently increased the differentiation of human bone marrow stromal cells (hBMSCs) into osteoblasts, as well as the mRNA levels of osteoblasts marker alkaline phosphatase (ALP) and osteocalcin (OCN). Furthermore, these increases depended on the activation of FGFR-1 signaling, as pretreatment with FGFR-1 siRNA or its inhibitor SU5402 dramatically dampened GPNMB-induced osteogenesis. Additionally, GPNMB triggered dose-dependently the proliferation and migration of human umbilical vein endothelial cells (hUVECs), FGFR-1 phosphorylation, as well as capillary tube and vessels formation in vitro and in vivo. Blocking FGFR-1 signaling dampened GPNMB-induced angiogenic activity. Following construction of a rodent cranial defect model, scaffolds delivering GPNMB resulted in an evident increase in blood vessels and new bone formation; however, combined delivery of GPNMB and SU5402 abated these increase in defect sites. Taken together, these results suggest that GPNMB stimulates bone regeneration by inducing osteogenesis and angiogenesis via regulating FGFR-1 signaling. Consequently, our findings will clarify a new explanation about how GPNMB induces bone repair, and provide a potential target for bone regeneration therapeutics and bone engineering.

Identification of microRNAs changed in the neonatal lungs in response to hyperoxia exposure

Bronchopulmonary dysplasia (BPD) is a multifactorial chronic lung disease of premature infants. BPD can be attributed to the dysregulation of normal lung development due to ventilation and oxygen toxicity, resulting in pathologic complications of impaired alveolarization and vascularization. MicroRNAs (miRNA) are small noncoding RNAs that regulate gene expression posttranscriptionally and are implicated in diverse biological processes and diseases. The objectives of this study are to identify the changed miRNAs and their target genes in neonatal rat lungs in response to hyperoxia exposure. Using miRNA microarray and real-time PCR analyses, we found downregulation of five miRNAs, miR-342, miR-335, miR-150, miR-126*, and miR-151*, and upregulation of two miRNAs, miR-21 and miR-34a. Some of these miRNAs had the highest expression during embryonic and early postnatal development. DNA microarray analysis yielded several genes with conserved binding sites for these altered miRNAs. Glycoprotein nonmetastatic melanoma protein b (GPNMB) was experimentally verified as a target of miR-150. In summary, we identified seven miRNAs that were changed in hyperoxia-exposed neonatal lungs. These results provide a basis for deciphering the mechanisms involved in the spatial and temporal regulation of proteins that contribute to the pathogenesis of BPD.

The potential of GPNMB as novel neuroprotective factor in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is an incurable and fatal neurodegenerative disease characterized by the loss of motor neurons. Despite substantial research, the causes of ALS remain unclear. Glycoprotein nonmetastatic melanoma protein B (GPNMB) was identified as an ALS-related factor using DNA microarray analysis with mutant superoxide dismutase (SOD1G93A) mice. GPNMB was greatly induced in the spinal cords of ALS patients and a mouse model as the disease progressed. It was especially expressed in motor neurons and astrocytes. In an NSC34 cell line, glycosylation of GPNMB was inhibited by interaction with SOD1G93A, increasing motor neuron vulnerability, whereas extracellular fragments of GPNMB secreted from activated astrocytes attenuated the neurotoxicity of SOD1G93A in neural cells. Furthermore, GPNMB expression was substantial in the sera of sporadic ALS patients than that of other diseased patients. This study suggests that GPNMB can be a target for therapeutic intervention for suppressing motor neuron degeneration in ALS.

The transport of non-surfactant based paclitaxel loaded magnetic nanoparticles across the blood brain barrier in a rat model

There is much interest in utilizing the intrinsic properties of magnetic nanoparticles (MNPs) for the theranostic approaches in medicine. With an aim to develop a potential therapeutics for glioma treatment, efficacy of aqueous dispersible paclitaxel loaded MNPs (Pac-MNPs) were studied in glioblastoma cell line (U-87). The identified potential receptor, glycoprotein non-metastatic melanoma protein B (GPNMB) overexpressed by glioblastoma cells, was actively targeted using GPNMB conjugated Pac-MNPs in U-87 cells. As blood brain barrier (BBB) is the primary impediment in the treatment of glioblastoma, therefore, an attempt was taken to evaluate the biodistribution and brain uptake of Pac-MNPs in rats. The bioavailability of Pac-MNPs illustrated a prolonged blood circulation in vivo, which demonstrated the presence of significant amounts of drug in rat brain tissues as compared to native paclitaxel. Further, the transmission electron microscopy (TEM) study revealed significant accumulation of the Pac-MNPs in the brain tissues. Being an effective contrast enhancement agent for magnetic resonance imaging (MRI) at tissue levels, the MNPs devoid of any surfactant demonstrated enhanced contrast effect in liver and brain imaging. Hence, the significant prevalence of drugs in the rat brain tissues, in vitro targeting potentiality as well as the augmented contrast effect elicit the non-invasive assessment and theranostic applications of MNPs for brain tumor therapy.

PS15 - 77. GPNMB is induced by adipose tissue macrophage during obesity and contributes to adipose tissue inflammation

Obesity goes hand in hand with low grade inflammation, which is an essential contributor to insulin resistance. This inflammation is orchestrated by a variety of cell types and their released soluble factors. A typical feature observed in obese adipose tissue is the formation of socalled crown like structures, which consist of recruited inflammatory macrophages surrounding non viable adipocytes. Glycoprotein non-metastatic melanoma protein B (GPNMB) is a transmembrane glycoprotein expressed by several cell types including macrophages.

Novel Kidney Injury Biomarkers

New biomarkers are currently under development for acute kidney injury and chronic kidney disease. Panels of validated biomarkers are most likely to be required to obtain information that will help in delineating acute versus chronic disease, the pathogenetic nature of the process, the severity, and the capacity for reversibility. Glycoprotein non-metastatic melanoma protein-b, a protein associated with regulation of inflammation and autophagy, is in an intermediate stage of development as a kidney injury biomarker.

ADAM10 Releases a Soluble Form of the GPNMB/Osteoactivin Extracellular Domain with Angiogenic Properties

BackgroundGlycoprotein non-metastatic melanoma protein B (GPNMB)/Osteoactivin (OA) is a transmembrane protein expressed in approximately 40–75% of breast cancers. GPNMB/OA promotes the migration, invasion and metastasis of breast cancer cells; it is commonly expressed in basal/triple-negative breast tumors and is associated with shorter recurrence-free and overall survival times in patients with breast cancer. Thus, GPNMB/OA represents an attractive target for therapeutic intervention in breast cancer; however, little is known about the functions of GPNMB/OA within the primary tumor microenvironment.Methodology/Principal FindingsWe have employed mouse and human breast cancer cells to investigate the effects of GPNMB/OA on tumor growth and angiogenesis. GPNMB/OA-expressing tumors display elevated endothelial recruitment and reduced apoptosis when compared to vector control-derived tumors. Primary human breast cancers characterized by high vascular density also display elevated levels of GPNMB/OA when compared to those with low vascular density. Using immunoblot and ELISA assays, we demonstrate the GPNMB/OA ectodomain is shed from the surface of breast cancer cells. Transient siRNA-mediated knockdown studies of known sheddases identified ADAM10 as the protease responsible for GPNMB/OA processing. Finally, we demonstrate that the shed extracellular domain (ECD) of GPNMB/OA can promote endothelial migration in vitro.Conclusions/SignificanceGPNMB/OA expression promotes tumor growth, which is associated with enhanced endothelial recruitment. We identify ADAM10 as a sheddase capable of releasing the GPNMB/OA ectodomain from the surface of breast cancer cells, which induces endothelial cell migration. Thus, ectodomain shedding may serve as a novel mechanism by which GPNMB/OA promotes angiogenesis in breast cancer.

Glycoprotein nonmetastatic melanoma protein b, a melanocytic cell marker, is a melanosome‐specific and proteolytically released protein

Melanosomes are organelles specialized for the production of melanin pigment and are specifically produced by melanocytic cells. More than 150 pigmentation-related genes have been identified, including glycoprotein nonmetastatic melanoma protein b (GPNMB). A recent proteomics analysis revealed that GPNMB is localized in melanosomes, and GPNMB is a membrane-bound glycoprotein that shows high homology with a well-known melanosomal structural protein, Pmel17/gp100. In this study, we show that GPNMB is expressed in melanocytes of normal human skin, as well as in human melanoma cells. GPNMB is heavily glycosylated and is enriched in mature (stage III and IV) melanosomes in contrast to MART-1 and Pmel17, which are abundant in early (stage I and II) melanosomes. MART-1 and Pmel17 play critical roles in the maturation of early melanosomes; thus, we speculate that GPNMB might be important in the functions of late melanosomes, possibly their transport and/or transfer to keratinocytes. We also demonstrate that a secreted form of GPNMB is released by ectodomain shedding from the largely Golgi-modified form of GPNMB and that the PKC and Ca(2+) intracellular signaling pathways regulate that shedding. We conclude that GPNMB is a melanosomal protein that is released by proteolytic ectodomain shedding and might be a useful and specific histological marker of melanocytic cells.