29 research outputs found
Activation of the STAT3/Acute Phase Response Factor Transcription Factor by Interleukin-5
The receptor for interleukin-5 (IL-5R) is composed of a
unique a chain (IL-5Ra) expressed on eosinophils and
basophils, associated with a bc subunit, which is shared
by the receptors for IL-3 and granulocyte macrophagecolony
stimulating factor. One of the molecular events
activated via the IL-5R is the JAK/STAT signaling pathway.
Recent reports have shown that IL-5 induces tyrosine
phosphorylation of JAK2 followed by the subsequent
cell type-specific activation of either STAT1a or
STAT5. To identify additional STAT proteins activated
by IL-5, we co-transfected the IL-5R with STAT cDNAs in
COS cells. We found that IL-5 induces binding of STAT3
to the intercellular adhesion molecule-1 pIRE, and activates
STAT3-dependent transcription. Moreover, endogenous
STAT3 was tyrosine phosphorylated and activated
in human IL-5-stimulated BaF3 cells ectopically
expressing the human IL-5R (BaF3/IL5R). These data
imply that multiple STAT proteins are involved in gene
regulation by IL-5 in a cell type-specific manner. We
further demonstrate using C-terminal truncations of the
aand bc subunits of the IL-5R that the membrane-proximal
regions of both subunits are required for STAT
activation. Interestingly, a bc receptor mutant lacking
intracellular tyrosine residues is able to mediate STAT3
activation, suggesting that tyrosine phosphorylation of
the bc receptor is not essential for STAT3 activation
A Composite C/EBP Binding Site Is Essential for the Activity of the Promoter of the IL-3/IL-5/Granulocyte-Macrophage Colony-Stimulating Factor Receptor ßc Gene
The common ß-chain (ßc) is the main signaling component of the heterodimeric receptors for IL-3, IL-5, and GM-CSF and is
primarily expressed on myeloid cells. The proximal ßc promoter is regulated by GGAA binding proteins, including PU.1, a
hemopoietic specific member of the Ets family. However, it is not likely that PU.1 alone accounts for the myeloid-restricted
expression of the ßc subunit. Here we describe the identification of a C/EBP binding enhancer that is located 2 kb upstream of
the transcription start site. The enhancer contains two elements that bind C/EBPa and -ß in U937 cells, while C/EBPe is also
bound in extracts of HL-60 cells. Importantly, deletion of the enhancer or mutation of either of one of the C/EBP sites results in
a complete loss of promoter activity in cell lines as well as in primary cells, showing the importance of C/EBP members inßc gene
activation. We further show that PU.1 has to cooperate with C/EBP proteins to induce bc transcription. Since the ßc is already
expressed on CD341 cells, these results demonstrate that both C/EBP and PU.1 are not only important for the myeloid-specific
gene regulation at later stages of myeloid differentiation
Multiple tyrosine residues in the intracellular domain of the common ß subunit of the interleukin 5 receptor are involved in activation of STAT5
Abstract In contrast to the general model of cytokine-induced
JAK/STAT signaling, tyrosine phosphorylation of the IL-5R ß
chain seems to be dispensable for STAT activation in cells
overexpressing exogenous STAT proteins. In this study we
expressed IL-5 receptor mutants in 293 cells and studied IL-5-
induced endogenous STAT-dependent transcription. Our results
indicate that: (a) tyrosine phosphorylation of the IL-5R ß chain
is required for endogenous STAT5 activation, (b) multiple
tyrosine residues are phosphorylated upon IL-5 stimulation,
including Tyr^(577) , Tyr^(612) , Tyr^(695) , and Tyr^(750) , and (c) Tyr^(612) ,
Tyr^(695) , and Tyr^(750) are all capable of inducing activation of
STAT5, demonstrating a high level of functional redundancy
within the IL-5R ß chain
Activation of 12-O-Tetradecanoylphorbol-13-acetate Response Element- and Dyad Symmetry Element-dependent Transcription by Interleukin-5 Is Mediated by Jun N-terminal Kinase/Stress-activated Protein Kinase Kinases
Interleukin-5 (IL-5) is one of the major regulators of
eosinophilic granulocytes in vivo. IL-5 exerts its pleiotropic
effects by binding to the IL-5 receptor, which is
composed of an IL-5-specific a chain and a common bc
chain shared with the receptors for IL-3 and granulocyte-
macrophage colony-stimulating factor. Previous
studies have shown that binding of IL-5 to its receptor
triggers the activation of multiple signaling cascades,
including the Ras/mitogen-activated protein kinase, the
phosphatidyl -3`-kinase, and the Janus kinase/signal
transducer and activator of transcription pathways.
Here we describe that IL-5 activates the serine/threonine
protein kinase Jun N-terminal kinase/stress-activated
protein kinase (JNK/SAPK) pathway. We show
that IL-5 activates TPA response element (TRE)-dependent
transcription in transfection experiments. TRE activation
by IL-5 is mediated by a region of the bc (577-
581) that is also responsible for activation of JNK/SAPK
and for activation of dyad symmetry element (DSE)-dependent
transcription. Dominant-negative SAPK or
ERK kinase-1 was used to demonstrate that JNK/SAPK
activation is necessary for induction of DSE- and TREdependent
transcription by IL-5, whereas extracellular
signal-regulated kinase 2 was not essential for TRE- and
DSE-dependent transcription. By contrast, IL-5-induced
activation of the tyrosine kinase Janus kinase 2 seems to
be a prerequisite for TRE- and DSE-dependent transcription.
Taken together, we show for the first time
that IL-5 activates kinases of the JNK/SAPK family, and
that this activation is linked to IL-5-induced TRE- and
DSE-dependent transcription
Differential Activation of Functionally Distinct STAT5 Proteins by IL-5 and GM-CSF During Eosinophil and Neutrophil Differentiation from Human CD34^+ Hematopoietic Stem Cells
Interleukin-5 (IL-5) and granulocyte macrophage-colony
stimulating factor (GM-CSF) are important
cytokines for the proliferation, differentiation, and acti-vation
of myeloid lineages. The JAK/STAT pathway is
one of the signaling pathways implicated in mediating
biological responses induced by these cytokines. Previous
studies have demonstrated that these cytokines predomi-nantly
activate an 80 kDa STAT5 isoform in mature
granulocytes. To better understand the role of STAT pro-teins
during growth and differentiation of granulocytes,
we evaluated differentiation of human CD34^+ hematopoi-etic
stem cells ex vivo toward eosinophils and neutrophils.
Bandshift experiments showed that in an early stage of
both differentiation pathways (14 days), the 94 kDa
STAT5B protein was activated by both IL-5 (eosino-phil
lineage) and GM-CSF (neutrophil lineage). How-ever,
during maturation of both lineages (days 21 and
28), increased expression of a functionally distinct 80
kDa STAT5 isoform was observed, resulting in het-erodimer
DNA-binding complexes containing both the
94 and 80 kDa STAT5 proteins. The finding that
functionally distinct isoforms of STAT5 are activated
during the early and late differentiation stages of
granulocytes suggests that they might be involved in
regulating different biological functions in these cells
An AP-1 site in the promoter of the human IL-5RK gene is necessary for promoter activity in eosinophilic HL60 cells
Interleukin-5 (IL-5) plays a crucial role in the
proliferation, differentiation and activation of eosinophils. The
IL-5 receptor is composed of an IL-5-specific a subunit, which is
expressed by eosinophils and basophils, and a ßc-subunit shared
with the receptors for IL-3 and GM-CSF. We identified an AP-1
element which is important for IL-5Ra promoter activity in
eosinophilic HL60 cells. The AP-1 site and the previously
identified EOS1 site cooperate, since single mutation of either of
the sites decreased promoter activity. We show that the AP-1 site
of the IL-5Ra promoter binds multiple proteins, including cJun,
CREB, and CREM
STAT3ß, a Splice Variant of Transcription Factor STAT3, Is a Dominant Negative Regulator of Transcription
The 89-kDa STAT3 protein is a latent transcription
factor which is activated in response to cytokines (interleukin
(IL)-5 and -6) and growth factors (epidermal
growth factor). Binding of IL-5 to its specific receptor
activates JAK2 which leads to the tyrosine phosphorylation
of STAT3 proteins. Here we report the cloning of a
cDNA encoding a variant of the transcription factor
STAT3 (named STAT3b) which was isolated by screening
an eosinophil cDNA library. Compared to wild-type
STAT3, STAT3b lacks an internal domain of 50 base
pairs located near the C terminus. This splice product is
a naturally occurring isoform of STAT3 and encodes a
80-kDa protein. We found by reconstitution of the human
IL-5R in COS cells that like STAT3, STAT3bis phosphorylated
on tyrosine and binds to the pIRE from the
ICAM-1 promoter after IL-5 stimulation. However,
STAT3b fails to activate a pIRE containing promoter in
transient transfection assays. Instead, co-expression of
STAT3binhibits the transactivation potential of STAT3.
These results suggests that STAT3b functions as a negative
regulator of transcription
The effect of iterative model reconstruction on coronary artery calcium quantification
Coronary artery calcium (CAC) scoring with computed tomography (CT) is an established tool for quantifying calcified atherosclerotic plaque burden. Despite the widespread use of novel image reconstruction techniques in CT, the effect of iterative model reconstruction on CAC score remains unclear. We sought to assess the impact of iterative model based reconstruction (IMR) on coronary artery calcium quantification as compared to the standard filtered back projection (FBP) algorithm and hybrid iterative reconstruction (HIR). In addition, we aimed to simulate the impact of iterative reconstruction techniques on calcium scoring based risk stratification of a larger asymptomatic population. We studied 63 individuals who underwent CAC scoring. Images were reconstructed with FBP, HIR and IMR and CAC scores were measured. We estimated the cardiovascular risk reclassification rate of IMR versus HIR and FBP in a larger asymptomatic population (n = 504). The median CAC scores were 147.7 (IQR 9.6-582.9), 107.0 (IQR 5.9-526.6) and 115.1 (IQR 9.3-508.3) for FBP, HIR and IMR, respectively. The HIR and IMR resulted in lower CAC scores as compared to FBP (both p < 0.001), however there was no difference between HIR and IMR (p = 0.855). The CAC score decreased by 7.2 % in HIR and 7.3 % in IMR as compared to FBP, resulting in a risk reclassification rate of 2.4 % for both HIR and IMR. The utilization of IMR for CAC scoring reduces the measured calcium quantity. However, the CAC score based risk stratification demonstrated modest reclassification in IMR and HIR versus FBP
Recommended from our members
Minimum Information about a Biosynthetic Gene cluster
A wide variety of enzymatic pathways that produce specialized metabolites in bacteria, fungi and plants are known to be encoded in biosynthetic gene clusters. Information about these clusters, pathways and metabolites is currently dispersed throughout the literature, making it difficult to exploit. To facilitate consistent and systematic deposition and retrieval of data on biosynthetic gene clusters, we propose the Minimum Information about a Biosynthetic Gene cluster (MIBiG) data standard.Chemistry and Chemical Biolog
Case report. Removing a penoscrotal ring after scrotal infusion Case report. Het verwijderen van een penoscrotale ring na scrotuminfusie
A patient visited our emergency room with a red, swollen scrotum and a penoscrotal ring after scrotal infusion with saline. Scrotum inflation or scrotum infusion is an unusual sexual activity in which one injects the scrotum with physiological saline solution, air, or other kind of gas. Because of the edematous scrotum this ring was, even after a few days not removable by the patient himself. This industrial penoscrotal ring was removed with hydraulic tools of the fire department without any damage to the skin