Role of N-terminal sequences of the tyrosine kinase sf-Stk in transformation of rodent fibroblasts by variants of Friend spleen focus-forming virus

• Published in: International journal of cancer Vol. 131; no. 5; pp. 1083 - 1094
• Main Authors: Umehara, Daigo, Kawamura, Maki, Odahara, Yuka, Watanabe, Shinya, Hanson, Charlotte, Ruscetti, Sandra, Nishigaki, Kazuo
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01-09-2012; Wiley-Blackwell; Wiley Subscription Services, Inc
• Subjects: Amino Acid Sequence; Amino acids; Anemia - etiology; Anemia - metabolism; Anemia - pathology; Animals; Biological and medical sciences; Blotting, Western; Cancer; Cell Transformation, Neoplastic - metabolism; Cell Transformation, Neoplastic - pathology; Cells, Cultured; env; erythroleukemia; Fibroblasts - metabolism; Fibroblasts - pathology; Fibroblasts - virology; Glycoproteins; Hematologic and hematopoietic diseases; Humans; Kinases; Leukemia, Experimental - genetics; Leukemia, Experimental - metabolism; Leukemia, Experimental - virology; Leukemias. Malignant lymphomas. Malignant reticulosis. Myelofibrosis; Medical research; Medical sciences; Mice; Molecular Sequence Data; Mutagenesis, Site-Directed; Mutation; Mutation - genetics; pathogenesis; Phosphorylation; Plasmids - genetics; Polycythemia - etiology; Polycythemia - metabolism; Polycythemia - pathology; Protein Structure, Tertiary; Receptor Protein-Tyrosine Kinases - genetics; Receptor Protein-Tyrosine Kinases - metabolism; Retroviridae Infections - genetics; Retroviridae Infections - metabolism; Retroviridae Infections - virology; retrovirus; Sequence Homology, Amino Acid; sf-Stk; Signal Transduction; Spleen; Spleen Focus-Forming Viruses - genetics; transformation; Tumor Virus Infections - genetics; Tumor Virus Infections - metabolism; Tumor Virus Infections - virology; Tumors; tyrosine kinase; Viral Envelope Proteins - genetics; Viral Envelope Proteins - metabolism; Viruses; Genetic variability; Pathogenesis; tyrosine kinase; Myeloproliferative syndrome; Retrovirus; Cancerology; N terminal-Sequence; Protein-tyrosine kinase; Erythroleukemia; Spleen; sf-Stk; Enzyme; Transferases; Acute; Rodentia; Retroviridae; Genotype; Malignant hemopathy; env; transformation; Variant; Virus; Vertebrata; Mammalia; M6 acute myelocytic leukemia; Animal; Fibroblast; Cancer
• ISSN: 0020-7136; 1097-0215
• DOI: 10.1002/ijc.27330

Infection of erythroid cells by Friend spleen focus‐forming virus (SFFV) leads to acute erythroid hyperplasia in mice, due to expression of its unique envelope glycoprotein, gp55. Erythroid cells expressing SFFV gp55 proliferate in the absence of their normal regulator, erythropoietin, because of the interaction among the viral envelope protein, the erythropoietin receptor, and a short form of the receptor tyrosine kinase Stk (sf‐Stk). This leads to constitutive activation of several signal transduction pathways. Our previous studies showed that sf‐Stk interacts with SFFV gp55, forming disulfide‐linked complexes. This covalent interaction, along with other noncovalent interactions with SFFV‐gp55, results in constitutive tyrosine phosphorylation of sf‐Stk and rodent fibroblast transformation. Here, we determined the precise amino acid region within sf‐Stk that contributes to fibroblast transformation by the polycythemia‐inducing (SFFV‐P) and the anemia‐inducing (SFFV‐A) strains of SFFV. Sf‐Stk deletion mutants showed different transforming abilities in fibroblasts infected with SFFV‐P and SFFV‐A, although the N‐terminal extracellular domain of sf‐Stk was essential for fibroblast transformation by both viruses. Point mutations of sf‐Stk indicated that cysteine 19 was critical for fibroblast transformation by SFFV‐P, although all four cysteines (8, 19, 37 and 42) appeared to be important for fibroblast transformation by both SFFV‐P and SFFV‐A. Mutation of sf‐Stk cysteine 19 abolished its ability to form dimers with SFFV‐P and SFFV‐A gp55. These results suggest that the interaction between sf‐Stk and the envelope proteins of the polycythemia‐ and anemia‐inducing variants of SFFV is architecturally different.