T-cell activation signals and human T-cell leukemia virus type I-encoded p40x protein activate the mouse granulocyte-macrophage colony-stimulating factor gene through a common DNA element.

Abstract

Activation of T cells by an antigen, a mitogen, or a combination of a phorbol ester ) and a calcium ionophore (A23187) leads to induction of a set of lymphokine genes. Treatment of human T-cell leukemia line Jurkat by a mitogen or p4OX, a transactivator protein encoded by human T-cell leukemia virus type I, activates many transfected lymphokine genes in a transient transfection assay. To study the mechanism of lymphokine gene induction, we examined the effects of mitogen stimulation and p4OX on the gene for the mouse granulocyte-macrophage colony-stimulating factor (GM-CSF) in Jurkat cells. Deletion and mutation analyses showed that the 5'-flanking region of the gene for the GM-CSF is composed of two types of regulatory elements. One sequence, located at positions -95 to -73, determines response to stimulation by either TPA-A23187 or p4OX. This region contains conserved lymphokine element 2, which appears in the gene for interleukin 3 (IL-3) and is followed by a GC-rich stretch. This GC-rich stretch alone specifies inducible response to p4oX but not to TPA-A23187. Another sequence, located at positions -113 to -96 upstream of a TATA-like sequence, mediates inducible response to p49X but not to TPA-A23187. This sequence includes conserved lymphokine element 1, which appears in several lymphokine-cytokine genes, such as those for IL-3, G-CSF, and IL-2. We previously showed that the simian virus 40 early region promoter was also induced by a mitogen or p4OX in Jurkat cells. Deletion analysis showed that the minimum regions required for stimulation by both signals are identical. These results, which indicate that p40X stimulates transcription of the gene for the GM-CSF or the simian virus 40 early region promoter through the same DNA element or an overlapping DNA element required for induction by a mitogen, lend further support to the notion that p4,X can exert its function by activating a component(s) of the T-cell signal transduction pathway which is activated by an antigen or a mitogen.Expression of many eucaryotic genes is regulated by hormones, growth factors, or other stimuli that interact with specific receptors to induce various intracellular processes.Activation of protein kinase C and increase of Ca"+ mobilization are used as signal transduction processes in many different types of cells (2, 26). When T cells are exposed to antigens, the T-cell antigen receptor-CD3 complex transduces the extracellular stimulus across the plasma membrane, generating intracellular signals. These signals activate phosphoinositide turnover, leading to production of diacylglycerol, which activates protein kinase C, and inositol trisphosphate, which results in increased Ca 2 mobilization or influx or both (42). Signal transduction events further downstream trigger a series of biochemical reactions in the nucleus which result in production of a battery of lymphokines. These can then mediate numerous effector functions to help coordinate the immune and inflammatory responses (20). Nuclear oncogenes, such as c-fos and c-myc, and th...

Induction of Murine Macrophage Growth by Oxidized Low Density Lipoprotein Is Mediated by Granulocyte Macrophage Colony-stimulating Factor

“…Phorbol 12-myristate 13-acetate and A23187 (a calcium ionophore) are reported to increase GM-CSF mRNA levels through activation of PKC in human Jurkat T cell line (54). The recent report from this laboratory demonstrated that Ox-LDL initiated an increase in intracellular Ca 2ϩ and subsequent activation of PKC within 10 min after incubation with macrophages (19).…”

Sites of Action of Protein Kinase C and Phosphatidylinositol 3-Kinase Are Distinct in Oxidized Low Density Lipoprotein-induced Macrophage Proliferation

“…Extensive studies using Tlymphocytes showed that GM-CSF induction following PKC activation is mainly regulated at a transcriptional level (26) and several cis-acting elements that regulate GM-CSF gene expression were identified (27). Moreover, T-lymphocytes were shown to express and release GM-CSF in response to PKC activators, such as phorbol 12-myristate 13-acetate and A23187 (a calcium ionophore) (28 -31).…”

Granulocyte/macrophage Colony-stimulating Factor Plays an Essential Role in Oxidized Low Density Lipoprotein-induced Macrophage Proliferation

“…This notion was supported by a following report. Phorbol 12-myristate 13-acetate (PMA) and A23187 (a calcium ionophore) were reported to increase GM-CSF mRNA levels through activation of PKC in a human Jurkat T cell line (27).…”