Novel small GTPase M-Ras participates in reorganization of actin cytoskeleton

• Published in: Oncogene Vol. 15; no. 20; pp. 2409 - 2417
• Main Authors: MATSUMOTO, K, ASANO, T, ENDO, T
• Format: Journal Article
• Language: English
• Published: Basingstoke Nature Publishing 13.11.1997; Nature Publishing Group
• Subjects: 3T3 Cells - metabolism; 3T3 Cells - ultrastructure; Actin; Actins - metabolism; Amino Acid Sequence; Animals; Base Sequence; Biological and medical sciences; Cell differentiation; Cell Line; Cell membranes; Cell physiology; Cell transformation and carcinogenesis. Action of oncogenes and antioncogenes; Cloning, Molecular; Cytoskeleton; Cytoskeleton - metabolism; Cytoskeleton - ultrastructure; DNA, Complementary - genetics; Epitopes; Fibroblasts; Fundamental and applied biological sciences. Psychology; Genes; GTP Phosphohydrolases - genetics; GTP Phosphohydrolases - physiology; Guanosine triphosphatases; Guanosine triphosphate; Guanosine Triphosphate - physiology; Mice; Microinjection; Microinjections; Molecular and cellular biology; Molecular Sequence Data; Monomeric GTP-Binding Proteins; Muscle, Skeletal - enzymology; Musculoskeletal system; Mutagenesis, Site-Directed; Organ Specificity; Ras protein; Rats; Sequence Alignment; Sequence Homology, Amino Acid; Skeletal muscle; Species Specificity; Subcellular Fractions - chemistry; Transfection; GTP; Nucleotide sequence; Enzyme; Triphosphoric monoester hydrolases; Rodentia; Contractile protein; dGTPase; Homology; Esterases; Gene expression; Binding protein; Vertebrata; Mammalia; Cell line; Microinjection; Enzymatic activity; Gene; Mouse; Actin; Hydrolases; Cytoskeleton; Multigene family; Mutation; G protein
• ISSN: 0950-9232; 1476-5594
• DOI: 10.1038/sj.onc.1201416

During an attempt to elucidate regulatory mechanisms of skeletal muscle cell differentiation, we cloned cDNAs encoding a novel small GTPase from cDNA libraries of the mouse skeletal muscle cell line C2 and rat brain. It was designated as M-Ras due to the structural similarity to Ras family proteins. M-Ras contained conserved motifs for GDP/GTP-binding and GTPase activities, whereas it varied from the other Ras family proteins at several amino acids within the extended effector domain. From the C-terminal sequence, M-Ras is presumed to be anchored to the cell membrane with a geranylgeranyl group in combination with a polybasic region. Bacterially expressed recombinant M-Ras exerted the GTP-binding and GTPase activities. A mutant M-RasG22V was unable to hydrolyze bound GTP, indicating that it serves as a constitutively active form. Epitope-tagging experiments showed that M-Ras was concentrated on certain plasma membrane-associated structures. Transfection of M-Ras cDNA and microinjection of the M-RasG22V protein into fibroblasts induced formation of the peripheral microspikes. In addition, the actin stress fibers disappeared and instead numerous actin foci were formed in the injected cells. The transfected cells eventually exhibited dendritic appearances with microspikes. Consequently, M-Ras is likely to participate in reorganization of the actin cytoskeleton.