title: Control of myoblast fusion by a guanine nucleotide exchange factor, loner, and its effector ARF6.
abstract: Myoblast fusion is essential for the formation and regeneration of skeletal muscle. In a genetic screen for regulators of muscle development in Drosophila, we discovered a gene encoding a guanine nucleotide exchange factor, called loner, which is required for myoblast fusion. Loner localizes to subcellular sites of fusion and acts downstream of cell surface fusion receptors by recruiting the small GTPase ARF6 and stimulating guanine nucleotide exchange. Accordingly, a dominant-negative ARF6 disrupts myoblast fusion in Drosophila embryos and in mammalian myoblasts in culture, mimicking the fusion defects caused by loss of Loner. Loner and ARF6, which also control the proper membrane localization of another small GTPase, Rac, are key components of a cellular apparatus required for myoblast fusion and muscle development. In muscle cells, this fusigenic mechanism is coupled to fusion receptors; in other fusion-competent cell types it may be triggered by different upstream signals.
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D001483:Base Sequence / Q000235:genetics; D002459:Cell Fusion; D002478:Cells, Cultured; D003593:Cytoplasm / Q000235:genetics / Q000378:metabolism; D018076:DNA, Complementary / Q000032:analysis / Q000235:genetics; D029721:Drosophila Proteins / Q000235:genetics / Q000302:isolation & purification*; D004331:Drosophila melanogaster / Q000166:cytology / Q000196:embryology* / Q000201:enzymology; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000235:genetics; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000302:isolation & purification*; D051379:Mice; D008969:Molecular Sequence Data; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000201:enzymology; D018482:Muscle, Skeletal / Q000166:cytology / Q000196:embryology* / Q000201:enzymology; D009154:Mutation / Q000235:genetics; D032446:Myoblasts / Q000166:cytology / Q000201:enzymology*; D017434:Protein Structure, Tertiary / Q000235:genetics; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D000089982:ADP-Ribosylation Factor 6; D018076:DNA, Complementary; D029721:Drosophila Proteins; D020662:Guanine Nucleotide Exchange Factors; D011956:Receptors, Cell Surface; C478493:Siz protein, Drosophila; D020727:ADP-Ribosylation Factors; C000715727:Arf6 protein, mouse; D020744:rac GTP-Binding Proteins