The mechanisms underlying the engulfment of apoptotic corpses, which is involved in development, cellular homeostasis, and autoimmunity, remain largely unknown in mammals. MEGF10 is a mammalian ortholog of nematode CED-1, a transmembrane protein involved in engulfment of apoptotic corpses. MEGF10-expressing cells display an irregular, mosaic-like pattern of MEGF10, causing cells to tightly adhere to coated glass dishes. This restricted cell motility caused cells to adopt a flat appearance. In the present study, we observed that these cells formed unusually large vacuoles, the formation of which we linked to the cytoplasmic domain of MEGF10. While investigating the signaling pathway and trafficking of MEGF10, we identified an interaction between MEGF10 and clathrin assembly protein complex 2 medium chain (AP50), a component of clathrin-coated pits. In cells co-expressing MEGF10 and AP50, MEGF10 and AP50 colocalized and mirrored the adhesion pattern of MEGF10. LC-MS/MS and immunoblot analyses revealed that the MEGF10 associated with AP2 alpha and beta subunits in addition to associating with AP50 and beta-actin, and that MEGF10 was ubiquitinated and tyrosine phosphorylated. Moreover, we observed that MEGF10 mRNA expression is primarily restricted to the brain, with robust expression in the stellate cells of the cerebellum. Elucidating the trafficking and regulatory machinery of MEGF10 will guide us in having a deeper understanding of the mechanisms involved in clearing apoptotic cells.
"Multiple EGF-like domain 10 (MEGF10), a type I transmembrane protein consisting of 17 EGF-like domains in the extracellular region, is known as a mammalian ortholog of nematode CED-1  . MEGF10 is predominantly expressed in the brain and skeletal muscle   . MEGF10 acts as a phagocytic receptor for amyloid b-peptide (Ab42) clearance  and apoptotic cell engulfment  . "
[Show abstract][Hide abstract] ABSTRACT: MEGF10 is known to function as a myogenic regulator of satellite cells in skeletal muscle. Mutations in MEGF10 gene cause a congenital myopathy called early onset myopathy, areflexia, respiratory distress and dysphagia (EMARDD). Despite its biological importance in muscle physiology, transcriptional regulation of the MEGF10 gene is unknown. Here, we characterized the 5' flanking region of the human MEGF10 gene and showed that the role of myogenic basic helix-loop-helix factor (bHLH) myogenin in MEGF10 transcription in muscle cells. Myogenin was found to share a similar expression pattern with MEGF10 during muscle regeneration and to increase the promoter activity of the MEGF10 gene in C2C12 cells. Overexpression of myogenin led to upregulation of MEGF10 mRNA in C2C12 cells. Site-directed mutagenesis assays revealed that the conserved E-box element at the region -114/-108 serves as a myogenin-binding motif. Promoter enzyme immunoassays and chromatin immunoprecipitation analysis showed direct interaction between myogenin and the myogenin-binding motif in the MEGF10 promoter. Taken together, these results indicate that myogenin is a positive regulator in transcriptional regulation of MEGF10 in skeletal muscle.
Biochemical and Biophysical Research Communications 07/2014; 450(4). DOI:10.1016/j.bbrc.2014.07.061 · 2.30 Impact Factor
"Among these are a number that are involved in the development of bone and teeth, for example IL11, encoding an interleukin involved in the development of craniofacial bones and teeth and the closure of the cranial sutures , and LRP1, encoding a low-density lipoprotein receptor-related protein also involved in chondrocyte differentiation . In addition, three of the 16 genes have roles in apoptosis; UNC5B , MEGF10  and PPP1R15A, which encodes a regulator of protein phosphatase 1 [36,37]. Furthermore, NF-κBIE is down-regulated in three and up-regulated in one cell line. "
[Show abstract][Hide abstract] ABSTRACT: Comparisons of the genomes of Neandertals and Denisovans with present-day human genomes have suggested that the gene RUNX2, which encodes a transcription factor, may have been positively selected during early human evolution. Here, we overexpress RUNX2 in ten human cell lines and identify genes that are directly or indirectly affected by RUNX2 expression. We find a number of genes not previously known to be affected by RUNX2 expression, in particular BIRC3, genes encoded on the mitochondrial genome, and several genes involved in bone and tooth formation. These genes are likely to provide inroads into pathways affected by RUNX2 and potentially by the evolutionary changes that affected RUNX2 in modern humans.
PLoS ONE 12/2013; 8(12):e83218. DOI:10.1371/journal.pone.0083218 · 3.23 Impact Factor
"This sequence is present in the phylogenetically and functionally related Caenorhabditis elegans protein ced-1 (Zhou et al., 2001), but not in the mammalian ortholog MEGF10 (Nagase et al., 2001; Suzuki and Nakayama, 2007). Moreover, AGAP007256 encodes the motifs NPxY and YxxL, which in D. melanogaster draper, C. elegans ced-1 and mammalian MEGF10 have been shown to be phosphorylated during protein activation (Freeman et al., 2003; Suzuki and Nakayama, 2007). Throughout the rest of this paper, AGAP007256 is referred to as draper. "
[Show abstract][Hide abstract] ABSTRACT: Insects fight infection using a variety of signaling pathways and immune effector proteins. In Drosophila melanogaster, three members of the Nimrod gene family (draper, nimC1 and eater) bind bacteria, and this binding leads to phagocytosis by hemocytes. The Nimrod gene family has since been identified in other insects, but their function in non-drosophilids remains unknown. The purpose of this study was to identify the members of the Nimrod gene family in the malaria mosquito, Anopheles gambiae, and to assess their role in immunity. We identified and sequenced three members of this gene family, herein named draper, nimrod and eater, which are the orthologs of D. melanogaster draper, nimB2 and eater, respectively. The three genes are preferentially expressed in hemocytes and their peak developmental expression is in pupae and young adults. Infection induces the transcriptional upregulation of all three genes, but the magnitude of this upregulation becomes more attenuated as mosquitoes become older. RNAi-based knockdown of eater, but not draper or nimrod, decreased a mosquito's ability to kill Escherichia coli in the hemocoel. Knockdown of draper, eater, or any combination of Nimrod family genes rendered mosquitoes more likely to die from Staphylococcus epidermidis. Finally, knockdown of Nimrod family genes did not impact mRNA levels of the antimicrobial peptides defensin (def1), cecropin (cecA) or gambicin (gam1), but eater knockdown led to a decrease in mRNA levels of nitric oxide synthase. Together, these data show that members of the A. gambiae Nimrod gene family are positive regulators of the mosquito antibacterial response.
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