Microphthalmia transcription factor regulates the expression of the novel osteoclast factor GPNMB

Institute for Molecular Biosciences, Co-operative Research Centre for Chronic Inflammatory Diseases, The University of Queensland, St. Lucia, QLD 4072, Australia.
Gene (Impact Factor: 2.14). 05/2008; 413(1-2):32-41. DOI: 10.1016/j.gene.2008.01.014
Source: PubMed


Microphthalmia transcription factor (MITF) regulates bone homeostasis by inducing expression of critical genes associated with osteoclast function. Gpnmb is a macrophage-enriched gene that has also been shown to be expressed in osteoblasts. Here, we have shown gpnmb to be highly induced in maturing murine osteoclasts. Microarray expression profile analysis identified gpnmb as a potential target of MITF in RAW264.7 cells, subclone C4 (RAW/C4), that overexpress this transcription factor. Electrophoretic mobility shift assays identified a MITF-binding site (M-box) in the gpnmb promoter that is conserved in different mammalian species. Anti-MITF antibody supershifted the DNA-MITF complex for the promoter site while MITF binding was abolished by mutation of this site. The gpnmb promoter was transactivated by co-expression of MITF in reporter gene assays while mutation of the gpnmb M-box prevented MITF transactivation. The induction of gpnmb expression during osteoclastogenesis was shown to exhibit similar kinetics to the known MITF targets, acp5 and clcn7. GPNMB expressed in RAW/C4 cells exhibited distinct subcellular distribution at different stages of osteoclast differentiation. At days 5 and 7, GPNMB protein co-localised with the osteoclast/macrophage lysosomal/endocytic marker MAC-3/LAMP-2, suggesting that GPNMB resides in the endocytic pathway of mature macrophages and is possibly targeted to the plasma membrane of bone-resorbing osteoclasts. The inclusion of gpnmb in the MITF regulon suggests a role for GPNMB in mature osteoclast function.

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Available from: Allison R Pettit, Jan 05, 2015
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    • "required for the differentiation and function of osteoblasts (Selim et al., 2003; Abdelmagid et al., 2008) and osteoclasts (Ripoll et al., 2008; Sheng et al., 2008), inhibition of T-cell activation (Chung et al., 2007, 2009), and invasion and metastasis by several cancers (Onaga et al., 2003; Rich et al., 2003; Kuan et al., 2006; Tse et al., 2006; Rose et al., 2007; Williams et al., 2010). GPNMB expression significantly increases with disease progression in the spinal cords of patients with ALS and in transgenic mice that serve as a model of ALS (Tanaka et al., 2012). "
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    ABSTRACT: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by progressive loss of motor neurons and subsequent muscular atrophy. The quality of life of patients with ALS is significantly improved by ameliorating muscular symptoms. We previously reported that glycoprotein nonmetastatic melanoma protein B (GPNMB; osteoactivin) might serve as a target for ALS therapy. In the present study, superoxide dismutase 1/glycine residue 93 changed to alanine (SOD1(G93A) ) transgenic mice were used as a model of ALS. Expression of the C-terminal fragment of GPNMB was increased in the skeletal muscles of SOD1(G93A) mice and patients with sporadic ALS. SOD1(G93A) /GPNMB transgenic mice were generated to determine whether GPNMB expression ameliorates muscular symptoms. The weight and cross-sectional area of the gastrocnemius muscle, number and cross-sectional area of myofibers, and denervation of neuromuscular junctions were ameliorated in SOD1(G93A) /GPNMB vs. SOD1(G93A) mice. Furthermore, direct injection of a GPNMB expression plasmid into the gastrocnemius muscle of SOD1(G93A) mice increased the numbers of myofibers and prevented myofiber atrophy. These findings suggest that GPNMB directly affects skeletal muscle and prevents muscular pathology in SOD1(G93A) mice and may therefore serve as a target for therapy of ALS. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.
    Full-text · Article · Jul 2015 · Journal of Neuroscience Research
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    • "The pathological roles of GPNMB in cancer tissues include inducing invasion, suppressing the immune system, causing angiogenesis, and enhancing cell adhesion (Maric et al., 2013). GPNMB is also implicated in differentiation and functioning of osteoclasts (Ripoll et al., 2008) and osteoblasts (Abdelmagid et al., 2008), impairment of T-cell activation (Chung et al., 2007), and regulation of degeneration/regeneration of extracellular matrix in skeletal muscles (Ogawa et al., 2005). In addition, GPNMB helps regulate the invasion and metastasis of several cancers , including uveal melanoma (Williams et al., 2010), glioma (Rich et al., 2003), breast cancer (Rose et al., 2007), hepatocellular carcinoma (Onaga et al., 2003), and cutaneous melanoma (Tse et al., 2006). "
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    ABSTRACT: 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. Focal ischemia/reperfusion injury was induced via filament middle cerebral artery occlusion for 2 h, 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 ischemia reperfusion injury, and that genomic over-expression of GPNMB significantly ameliorated infarct volume. Next, we investigated the protective mechanisms of GPNMB via western blotting and immunohistochemistry. 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. Immunohistochemistry analysis showed that GPNMB was expressed not only in neurons, but also in astrocytes, produced labelling patterns similar to that in human brain ischemia. Furthermore, recombinant GPNMB also decreased the infarction volume. These results indicate that GPNMB protected neurons against ischemia reperfusion injury, 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 ischemia reperfusion injury, via phosphorylation of ERK1/2 and Akt, suggesting that GPNMB may be a therapeutic target for ischemia reperfusion injuries.
    Full-text · Article · Jul 2014 · Neuroscience
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    • "In addition, GPNMB is abundantly expressed in differentiated osteoclasts73 and was found to play an important role in mediating cell fusion to produce multi-nucleated osteoclasts.59 GPNMB has been shown to physically associate with β1 or β3 containing integrin complexes in osteoclasts and to be an important mediator of osteoclast differentiation/fusion. "
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    ABSTRACT: Molecularly targeted therapies are rapidly growing with respect to their clinical development and impact on cancer treatment due to their highly selective anti-tumor action. However, many aggressive cancers such as triple-negative breast cancer (TNBC) currently lack well-defined therapeutic targets against which such agents can be developed. The identification of tumor-associated antigens and the generation of antibody drug-conjugates represent an emerging area of intense interest and growth in the field of cancer therapeutics. Glycoprotein non-metastatic b (GPNMB) has recently been identified as a gene that is over-expressed in numerous cancers, including TNBC, and often correlates with the metastatic phenotype. In breast cancer, GPNMB expression in the tumor epithelium is associated with a reduction in disease-free and overall survival. Based on these findings, glembatumumab vedotin (CDX-011), an antibody-drug conjugate that selectively targets GPNMB, is currently being investigated in clinical trials for patients with metastatic breast cancer and unresectable melanoma. This review discusses the physiological and potential pathological roles of GPNMB in normal and cancer tissues, respectively, and details the clinical advances and challenges in targeting GPNMB-expressing malignancies.
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