Activated but not resting T cells or thymocytes express colony‐stimulating factor 1 mRNA without co‐expressing c‐<i>fms</i> mRNA

Self Cite

Stimulation of highly purified primary T lymphocytes through CD2 and CD28 adhesion molecules induces a long-term proliferation, dependent on persistent autocrine secretion of interleukin 2 (IL-2), high and prolonged expression of inducible CD25/IL-2 receptor ␣ chain (IL-2R␣), and secretion of growth factors such as the granulocyte-macrophage colony-stimulating factor (GM-CSF). CD28 costimulation appears to activate cytokine gene expression through conserved B-related CD28 response (CD28RE) or cytokine 1 (CK-1) elements in addition to canonical NF-Bbinding sites. In this report, we assess: 1) the evolution of the expression, over an 8-day time period, of the Rel/NF-B family of proteins in costimulated versus TcR/CD3-stimulated primary T cells; 2) the impact of changes on the in vitro occupancy of GM-CSF B and CK-1, as well as IL-2R␣ B sites; and 3) the differential regulation of newly synthesized p65 and c-Rel by IB proteins. We show that CD2؉CD28 stimulation specifically induces, at maximal T cell proliferation phase, sustained nuclear overexpression of NFKB2 p52 and c-Rel subunits which might rely on long-lasting processing of p100 precursor for p52 and increased neosynthesis of c-Rel. This up-regulation correlates with sustained occupancy of GM-CSF B and CK-1 elements by both proteins. Conversely, these subunits do not appear to bind to the IL-2R␣ B site. Costimulation, but not TcR/CD3 stimulation, appears supported by sustained down-regulation of both IB␣ and -␤ regulators. Furthermore, contrary to p65, c-Rel appears to display little affinity for p105, p100 and IB␣ regulators.

Section: Induction Of Rel Proteins In Primary Human T Lymphocytes Stimentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Temporal and Subunit-specific Modulations of the Rel/NF-κB Transcription Factors Through CD28 Costimulation

Kahn-Perlès¹,

Lipcey²,

Lécine³

et al. 1997

Self Cite

“…Stimulation of human primary T lymphocytes with CD2ϩCD28 mAbs induces sustained cell proliferation, IL-2 secretion, and high IL-2 receptor ␣ chain (IL-2R␣) expression (42,49,50). Moreover, actively dividing cells ultimately reverse to quiescence about 2 weeks after initial triggering and then survive for several days.…”

Section: Sp1 Expression Is Modified In Dividing T Lymphocytes-mentioning

confidence: 99%

Sp1 Transcriptional Activity Is Up-regulated by Phosphatase 2A in Dividing T Lymphocytes

Lacroix

Lipcey

Imbert

et al. 2002

We have followed Sp1 expression in primary human T lymphocytes induced, via CD2 plus CD28 costimulation, to sustained proliferation and subsequent return to quiescence. Binding of Sp1 to wheat germ agglutinin lectin was not modified following activation, indicating that the overall glycosylation of the protein was unchanged. Sp1 underwent, instead, a major dephosphorylation that correlated with cyclin A expression and, thus, with cell cycle progression. A similar change was observed in T cells that re-entered cell cycle following secondary interleukin-2 stimulation, as well as in serum-induced proliferating NIH/3T3 fibroblasts. Phosphatase 2A (PP2A) appears involved because 1) treatment of dividing cells with okadaic acid or cantharidin inhibited Sp1 dephosphorylation and 2) PP2A dephosphorylated Sp1 in vitro and strongly interacted with Sp1 in vivo. Sp1 dephosphorylation is likely to increase its transcriptional activity because PP2A overexpression potentiated Sp1 site-driven chloramphenicol acetyltransferase expression in dividing Kit225 T cells and okadaic acid reversed this effect. This increase might be mediated by a stronger affinity of dephosphorylated Sp1 for DNA, as illustrated by the reduced DNA occupancy by hyperphosphorylated Sp factors from cantharidin-or nocodazole-treated cells. Finally, Sp1 dephosphorylation appears to occur throughout cell cycle except for mitosis, a likely common feature to all cycling cells.Sp1 is the founding member of a multigene family of transcription factors including Sp1, Sp2, Sp3, Sp4 (see Refs. 1-3 for reviews), and Sp5 proteins (4, 5). Both Sp1 and Sp3 are abundant and ubiquitous, whereas Sp4 is mainly expressed in neuronal tissues and Sp5 exhibits a dynamic and highly restricted expression pattern during embryogenesis. This protein family shares three highly conserved zinc finger DNA binding motifs that recognize GC or GT/CACC boxes present in many promoters. Sp1 was first viewed as a constitutive transcriptional activator regulating basal expression of many cellular and viral genes. However, it is now established that Sp1 activity is modulated in response to numerous signals and that this factor plays a critical role in cell growth and differentiation. Sp1 mediates the induction of dihydrofolate reductase (6) and thymidine kinase (7) genes associated with DNA synthesis and is therefore intricately linked to growth/cell cycle progression. In line with this, the ectopic expression of truncated Sp1 prolongs the S phase and reduces the growth rate (8). Conversely, Sp1 mediates cell division arrest by up-regulating the expression of genes coding for negative regulators of the cell cycle such as p2lWaf1/Cip1 , in p53-dependent growth control (9) or p53-independent pathway of terminal differentiation (10 -12).Sp1's manifold roles can be reconciled if one integrates the multiple time-ordered regulations to which this factor is itself submitted. First, Sp1 is a direct target of numerous cell cycle regulators, which activate or repress its activity. For instance, cyclin A (13...

“…T cell proliferation is also influenced by co-stimulatory signals delivered by CD28 (17) and by mitogens contained in serum, which is indispensable for T cell propagation in vitro (18). The capacity of co-stimulatory signals to up-regulate IL-2R␣ transcription has been reported (19).…”

Section: Engagement Of T Cell Receptors (Tcrs)mentioning

confidence: 99%

Interdependence of cdk2 Activation and Interleukin-2Rα Accumulation in T Cells

Mohapatra

Pledger

2001

We have shown previously that serum promotes T cell proliferation by acting with T cell receptor (TCR) agonists to efficiently down-regulate p27 Kip1 and activate cdk2-containing complexes. In the studies described here, the effect of serum on the expression of the ␣ subunit of the interleukin-2 receptor (IL-2R␣) was examined. We found that serum was required for maximal and sustained IL-2R␣ protein expression and consequent IL-2 signaling in TCR-activated splenocytes. Serum had no effect on IL-2R␣ mRNA levels and thus modulates IL-2R␣ expression post-transcriptionally. Unlike wild-type splenocytes, splenocytes exhibiting serum-independent cdk2 activation due to loss of p27 Kip1 efficiently expressed IL-2R␣ in serum-deficient medium. Conversely, serum did not promote IL-2R␣ accumulation in conditions in which cdk2 activity was blocked. These findings demonstrate that cdk2 activation is necessary and sufficient for IL-2R␣ accumulation in TCR-stimulated splenocytes. On the other hand, IL-2 signaling was required (at least in part) for cdk2 activation in these cells. Thus, cdk2 activation, IL-2R␣ expression, and IL-2 signaling are interdependent events, and we suggest that this feed-forward regulatory loop plays a key role in T cell mitogenesis.