Recent research has hypothesized that empowerment can arise from collective action through collective self-objectification (CSO), defined as action that actualizes participants’ social identity against the power of dominant groups. Activists (N 37) described several experiences that made them feel empowered (and disempowered). Among the various explanations they offered for these feelings, the most prominent were CSO, unity, and support (or their absence). CSO was also predictive of reports of positive emotion, although unity was the best predictor of reports of further involvement. Overall, the study suggests that actualizing one’s social identity through collective action has personal as well as political significance

The Friend spleen focus-forming virus (SFFV) encodes a unique envelope glycoprotein, gp55, which allows erythroid cells to proliferate and differentiate in the absence of erythropoietin (Epo). SFFV gp55 has been shown to interact with the Epo receptor complex, causing constitutive activation of various signal-transducing molecules. When injected into adult mice, SFFV induces a rapid erythroleukemia, with susceptibility being determined by the host gene Fv-2, which was recently shown to be identical to the gene encoding the receptor tyrosine kinase Stk/Ron. Susceptible, but not resistant, mice encode not only full-length Stk but also a truncated form of the kinase, sf-Stk, which may mediate the biological effects of SFFV infection. To determine whether expression of SFFV gp55 leads to the activation of sf-Stk, we expressed sf-Stk, with or without SFFV gp55, in hematopoietic cells expressing the Epo receptor. Our data indicate that sf-Stk interacts with SFFV gp55 as well as gp55 P , the biologically active form of the viral glycoprotein, forming disulfide-linked complexes. This covalent interaction, as well as noncovalent interactions with SFFV gp55, results in constitutive tyrosine phosphorylation of sf-Stk and its association with multiple tyrosine-phosphorylated signal-transducing molecules. In contrast, neither Epo stimulation in the absence of SFFV gp55 expression nor expression of a mutant of SFFV that cannot interact with sf-Stk was able to induce tyrosine phosphorylation of sf-Stk or its association with any signal-transducing molecules. Covalent interaction of sf-Stk with SFFV gp55 and constitutive tyrosine phosphorylation of sf-Stk can also be detected in an erythroleukemia cell line derived from an SFFV-infected mouse. Our results suggest that SFFV gp55 may mediate its biological effects in vivo by interacting with and activating a truncated form of the receptor tyrosine kinase Stk.The Friend spleen focus-forming virus (SFFV) causes an acute erythroleukemia in susceptible strains of mice (for a review, see reference 37). SFFV encodes a unique envelope glycoprotein, gp55, that associates specifically with the erythropoietin receptor (EpoR) at the cell surface (4, 10, 21, 45), allowing erythroid cells to proliferate in the absence of erythropoietin (Epo), the normal regulator of erythropoiesis. Epo stimulation of the EpoR activates a number of signal transduction pathways, including the Jak-Stat, the Ras/Raf-1/mitogenactivated protein kinase (MAPK), and the phosphatidylinositol 3-kinase (PI3-kinase) pathways (for a review, see reference 46). Using the Epo-dependent erythroleukemia cell line HCD-57, we have previously demonstrated that infection with SFFV, which abrogates the Epo dependence of these cells (36), constitutively activates Stat DNA-binding activity (30); Ras (27); Raf-1, MEK, and MAPK (26); PI 3-kinase and Akt kinase (29); and protein kinase C (27).Although interaction of the SFFV envelope glycoprotein with the EpoR complex is essential for inducing the biological effects of the virus, other f...

The erythroleukemia-inducing Friend spleen focus-forming virus (SFFV) encodes a unique envelope glycoprotein which allows erythroid cells to proliferate and differentiate in the absence of erythropoietin (Epo). In an effort to understand how SFFV causes Epo independence, we have been examining erythroid cells rendered factor independent by SFFV infection for constitutive activation of signal-transducing molecules. Previous studies from our laboratory showed that various signal-transducing molecules known to be activated by Epo, including Stat proteins and components of the Raf-1/MAP kinase pathway, are constitutively activated in SFFV-infected erythroid cells in the absence of Epo. Since another signal transduction pathway involving activation of phosphatidylinositol 3-kinase (PI 3-kinase) after Epo stimulation plays an important role in erythroid cell proliferation and differentiation, we carried out studies to determine if this pathway was also activated in SFFV-infected cells in the absence of Epo. Our studies show that PI 3-kinase is constitutively activated in erythroid cells rendered factor independent by infection with SFFV and that PI 3-kinase activity, but not Epo receptor tyrosine phosphorylation, is required for the proliferation of these cells in the absence of Epo. We further show that in SFFV-infected erythroid cells grown in the absence of Epo, PI 3-kinase associates with the insulin receptor substrate (IRS)-related adapter molecules IRS-2, Gab1, and Gab2, which are constitutively tyrosine phosphorylated in SFFV-infected cells. Finally, Akt, a protein kinase that is one of the downstream effectors of PI 3-kinase, and SHIP, a lipid phosphatase that is important for Akt activation through PI 3-kinase, are both tyrosine phosphorylated in SFFV-infected cells grown in the absence of Epo. Our results indicate that induction of Epo independence by SFFV requires the activation of PI 3-kinase and suggest that constitutive activation of this kinase in SFFV-infected cells may occur primarily through interaction of PI 3-kinase with constitutively phosphorylated IRS-related adapter molecules.The proliferation and differentiation of erythroid cells are controlled by the binding of erythropoietin (Epo) to its cell surface receptor, resulting in the activation of various signal transduction pathways. The major pathways known to be activated through the Epo receptor (EpoR) are the Jak-Stat and the Ras/Raf-1/mitogen-activated protein kinase (MAPK) pathways. When Epo binds to the EpoR, the receptor-bound tyrosine kinase Jak2 becomes rapidly activated (41, 68), most likely through receptor dimerization (66), and is thought to phosphorylate itself and tyrosine residues located in the cytoplasmic region of the EpoR (17, 39). Specific phosphotyrosine residues on the receptor then serve as docking sites for Stat proteins, in particular Stat5, which become phosphorylated and translocated to the nucleus (11,21,22,30,48,49,52,65). The tyrosine-phosphorylated sites on the Epo receptor also serve as docking sites for adapter ...

We present a remodeling method for high-affinity unnatural-base DNA aptamers to augment their thermal stability and nuclease resistance, for use as drug candidates targeting specific proteins. Introducing a unique mini-hairpin DNA provides robust stability to unnatural-base DNA aptamers generated by SELEX using genetic alphabet expansion, without reducing their high affinity. By this method, >80% of the remodeled DNA aptamer targeting interferon-γ (KD of 33 pM) survived in human serum at 37 °C after 3 days under our experimental conditions, and sustainably inhibited the biological activity of interferon-γ.