178 PI3-kinase signaling modulates the induction of MHC molecules by IFN-gamma

Although it has been well documented that the biological activities of gamma interferon (IFN-gamma) are initiated through interaction with its cell surface receptor, the signal transduction mechanisms which mediate the effects of this cytokine have remained unclear. In order to facilitate a better understanding of IFN-gamma signaling, we have designed an assay using human fibroblast cell homogenates in which IFN-gamma activates the formation of the IFN-gamma activation factor (GAF) transcription complex. GAF mediates the rapid transcriptional activation of the guanylate-binding protein gene by IFN-gamma. Activation of GAF in homogenates required ATP, but not Ca2+ or GTP. Fractionation of homogenates indicated that both the pellet (18,000 x g) and the remaining cytoplasmic fraction were required for GAF activation by IFN-gamma. In intact cells and cell homogenates, the activation of GAF was prevented by the specific tyrosine kinase inhibitor genistein. Treatment of GAF-containing nuclear extracts with either monoclonal antiphosphotyrosine antibody or protein tyrosine phosphatase prevented the assembly of the transcription complex, indicating that its formation required phosphorylation of tyrosine residues. Furthermore, the tyrosine phosphatase inhibitors phenylarsine oxide and zinc chloride also inhibited GAF formation in vitro, but only if these agents were added to cell homogenates before IFN-gamma was added. The addition of either agent 5 min after IFN-gamma had no effect. These results provide the first evidence for an IFN-gamma-regulated tyrosine phosphatase/kinase signaling cascade that permits this cytokine to activate the transcription of an early-response gene.

Download Full-text

Wiskott-Aldrich Syndrome Interacting Protein Deficiency Uncovers the Role of the Co-receptor CD19 as a Generic Hub for PI3 Kinase Signaling in B Cells

Immunity ◽

10.1016/j.immuni.2015.09.004 ◽

2015 ◽

Vol 43 (4) ◽

pp. 660-673 ◽

Cited By ~ 40

Author(s):

Selina Jessica Keppler ◽

Francesca Gasparrini ◽

Marianne Burbage ◽

Shweta Aggarwal ◽

Bruno Frederico ◽

...

Keyword(s):

B Cells ◽

Pi3 Kinase ◽

Protein Deficiency ◽

Kinase Signaling ◽

Interacting Protein ◽

Wiskott Aldrich Syndrome

Download Full-text

IGFs stimulate zebrafish cell proliferation by activating MAP kinase and PI3-kinase-signaling pathways

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.2001.280.4.r1230 ◽

2001 ◽

Vol 280 (4) ◽

pp. R1230-R1239 ◽

Cited By ~ 69

Author(s):

Kasiani C. Pozios ◽

Jun Ding ◽

Brian Degger ◽

Zee Upton ◽

Cunming Duan

Keyword(s):

Cell Proliferation ◽

Protein Kinase ◽

Dna Synthesis ◽

Signaling Pathways ◽

Kinase Inhibitor ◽

Pi3 Kinase ◽

Dependent Manner ◽

Embryonic Cells ◽

Kinase Signaling ◽

Igf I

Insulin-like growth factor (IGF)-I and -II have been cloned from a number of teleost species, but their cellular actions in fish are poorly defined. In this study, we show that both IGF-I and -II stimulated zebrafish embryonic cell proliferation and DNA synthesis in a concentration-dependent manner, whereas insulin had little mitogenic activity. Affinity cross-linking and immunoblotting studies revealed the presence of IGF receptors with the characteristics of the mammalian type I IGF receptor. Competitive binding assay results indicated that the binding affinities of the zebrafish IGF-I receptors to IGF-I, IGF-II, and insulin are 1.9, 2.6, and >190 nM, indicating that IGF-I and -II bind to the IGF-I receptor(s) with approximately equal high affinity. To further investigate the cellular mechanism of IGF actions, we have studied the effects of IGFs on two major signal transduction pathways: mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3 kinase). IGFs activated MAPK in zebrafish embryonic cells in a dose-dependent manner. This activation occurred within 5 min of IGF-I stimulation and disappeared after 1 h. IGF-I also caused a concentration-dependent activation of protein kinase B, a downstream target of PI3 kinase, this activation being sustained for several hours. Inhibition of MAPK activation by the MAPK kinase inhibitor PD-98059 inhibited the IGF-I-stimulated DNA synthesis. Similarly, use of the PI3 kinase inhibitor LY-294002 also inhibited IGF-I-stimulated DNA synthesis. When both the MAPK and PI3 kinase pathways were inhibited using a combination of these compounds, the IGF-I-stimulated DNA synthesis was completely negated. These results indicate that both IGF-I and -II are potent mitogens for zebrafish embryonic cells and that activation of both the MAPK and PI3 kinase-signaling pathways is required for the mitogenic action of IGFs in zebrafish embryonic cells.

Download Full-text