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*
Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD 20814;
Department of Cellular Injury, Walter Reed Army Institute of Research, Silver Spring, MD 20910;
Department of Medicine, Washington Hospital Center, Washington, DC 20010; and
Department of Medicine, Wake Forest University School of Medicine, Winston-Salem, NC 27257
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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IL-2 is a growth factor for both T and B lymphocytes that is
exclusively produced by T cells. IL-2 gene expression is
regulated by the cooperative binding of discrete transcription factors
on the IL-2 promoter/enhancer and is predominantly
controlled at the transcriptional level. AP-1, NF-AT, and NF-
B bind
at distinct sites on the IL-2 promoter and interact to regulate
IL-2 transcriptional initiation in normal T cells
(8, 9, 10). There is evidence that transcriptional repression
of the IL-2 gene is associated with T cell anergy (9, 10, 11),
and recently, it was reported that in anergic cells the -180 site of
the IL-2 promoter binds cAMP-responsive element binding protein
(CREB)/cAMP-responsive element modulator (CREM) and not AP-1
(12).
CREB, CREM, inducible cAMP early repressor, and activating transcription factor-1 are members of the cAMP-responsive NFs and exhibit a high degree of sequence homology. One common feature is the basic domain/leucine zipper motifs, which bind an 8-bp regulatory palindromic DNA sequence (cAMP-responsive elements (CREs)). These NFs are activated following phosphorylation by several protein kinases in response to different signaling routes, including protein kinase A, protein kinase C, ribosomal S6 kinase pp90rsk, mitogen- and stress-activated kinase, mitogen-activated protein kinase-activated protein kinase-2, and Ca2+/ calmodulin-dependent kinase IV. Phosphorylation of Ser133 in CREB and Ser117 in CREM acts as a molecular switch, because it regulates the ability of these factors to interact with the ubiquitously expressed coactivators CREB binding protein (CBP) and p300 that form a bridge with the basal transcriptional machinery (13, 14).
The structure of CREB and CREM consists of the transcriptional activation domain (Q1, P box, Q2) and the DNA binding/dimerization domain (bZip region). Both the CREB and CREM genes encode multiple isoforms. For CREM, these mechanisms include alternative splicing, alternative initiation codon, and the presence of an intronic alternative promoter. CREB isoforms act as transcription activators, whereas CREM isoforms can act as either activators or repressors. CREM isoforms containing only the P box or the Q2 domain act as repressors (13, 14).
SLE T cells produce decreased amounts of IL-2 following antigenic stimulation in vitro (1, 2, 5, 15). Here, we show that the decreased production of IL-2 is the result of active IL-2 gene transcriptional repression mediated by the binding of phosphorylated CREM (p-CREM) to the -180 site of the IL-2 promoter.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Thirty SLE patients (29 women and 1 man) were studied. All subjects fulfilled at least 4 of the 11 revised criteria of the American College of Rheumatology for the Classification of SLE (16). The age of the patients ranged from 21–74 yr (mean ± SD, 42.9 ± 13.4). Six of the patients were Caucasian, and 24 were African-Americans. Disease activity (17) was quantified by the SLE disease activity index (SLEDAI) score (mean ± SD, 5.4 ± 4.5). Ten patients had been treated with prednisone, but they had taken no steroid for 24 h before venipuncture. Ten subjects were treated with hydroxychloroquine, three patients with prednisone and azathioprine, and three with cyclophosphamide and dexamethasone. The remainder were receiving no treatment. Seven additional patients (six women and one man), five with rheumatoid arthritis, one with Sjogren’s syndrome, and one with dermatomyositis, served as the disease control group. The age range was similar to that in the SLE group (mean ± SD, 45 ± 3.5). Twenty normal volunteers (normal control group; mean age ± SD, 32 ± 4.2) served as controls.
Lymphocyte isolation and stimulation conditions
Heparinized peripheral venous blood was obtained from the study
subjects. PBMC were separated from RBC on Lymphoprep gradient (Nycomed
Pharma, Oslo, Norway), and T cells were separated subsequently by
magnetic depletion of non-T cells, as recommended by the manufacturer
(MACS Pan T cell isolation kit, Mitenyi Biotec, Auburn, CA). Briefly,
non-T cells (B cells, monocytes, NK cells, dendritic cells, early
erythroid cells, platelets, and basophils) from PBMC were indirectly
magnetically labeled using a cocktail of hapten-conjugated CD11b, CD16,
CD19, CD36, and CD56 Abs and MACS microbeads coupled to an
anti-hapten mAb. The magnetically labeled cells were depleted by
retaining them on a MACS column in the magnetic field of MidiMACS. The
purified T cells were >95% positive for CD3 as tested using flow
cytometry. Where mentioned, stimulation of T cells was performed using
4 µl/ml anti-CD3
(OKT3) and 10 µl/ml anti-CD28, or 10
ng/ml PMA and 0.5 µg/ml ionomycin.
Antibodies
Anti-phospho-CREB mAb, anti-p300 mAb, and anti-mouse CBP were purchased from Upstate Biotechnology (Lake Placid, NY). Anti-phospho-CREM and anti-CREB as well as the goat anti-rabbit and goat anti-mouse HRP-conjugated mAbs were purchased from Santa Cruz Biotechnology (Santa Cruz, CA).
Preparation of nuclear extracts, EMSA, immunoblotting, and immunoprecipitation
At least 5 million T cells were used for preparation of extracts as previously described (16). The dsDNA probe of the -180 site (-164 to -189 bp) on the IL-2 promoter used was 5'-catccattcagtcagtctttgggggt-3' in shift and supershift assays as previously described (18). Nuclear and cytoplasmic extracts were separated electrophoretically and used in immunoblotting and immunoprecipitation studies as previously described (19). Ten micrograms of cytoplasmic and nuclear extracts were used for the immunoblotting experiments.
Transfection and luciferase assays
Freshly isolated normal T cells were rested overnight in medium
containing 10% FCS and PHA (1 µg/ml). Plasmids encoding two tandem
-180 sites on the IL-2 promoter, the IL-2 promoter (from -575 to +57
bp; a gift from Dr. A. Rao), and CREM
(a gift from Dr.
Sassone-Corsi) were used for the transfection. T cells (5 x
106) were transiently transfected by
electroporation at 250 mV and 950 µF in 0.25 ml of complete medium.
After 20 h, T cells were stimulated as described above, and
cytoplasmic extracts were prepared using a luciferase assay kit
(Promega, Madison, WI). Briefly, cells were resuspended in lysis buffer
with 0.01 M DTT and incubated at room temperature for 15 min. After a
brief centrifugation 30 µl of the supernatant was used with 100 µl
of luciferase assay reagent. Luminescence was measured immediately for
30 s using a Luminometer (Sunnyvale, CA). Transfection efficiency
was established in all samples by cotransfection with a plasmid
encoding 
-galactosidase. The luciferase activity was normalized
using the -galactosidase readings.
Quantitative determination of IL-2
PBMC from SLE patients (n = 12) and control subjects (n = 9) were incubated for 24 h in the presence of 1 µg/ml PHA. IL-2 secretion was measured in culture supernatants by ELISA (R&D Systems, Minneapolis, MN).
Data analysis
Analysis of the OD of the CREB/CREM band was performed using QuantityOne software (Bio-Rad, Hercules, CA) after background subtraction from each band. Data were evaluated for statistical significance by Student’s t test. IL-2 levels were treated geometrically and geometric means (x/÷ the anti-log of the SD of the log values) are given.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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SLE T cells display diverse cellular and cytokine aberrations
(1, 5), including decreased production of IL-2 following
antigenic stimulation in vitro (1, 2, 3, 15). The reported
presence of p50-p50 homodimers and the reduction or the absence of
p50-p65 heterodimers of NF-B in the nuclear extracts of stimulated
SLE T cells suggested that decreased production of IL-2 is the result
of defective transcriptional regulation (20). To determine
whether other factors directly contribute to impaired IL-2 production
by SLE T cells, we studied the nuclear proteins that bind to the -180
site (-164 to -189 bp) of the IL-2 promoter
(12).
First, we performed EMSAs using an oligonucleotide that spans from
-164 to -189 bp (-180 site) on the IL-2 promoter using
nuclear extracts from unstimulated T cells from patients with SLE
(n = 30), the disease control group (n
= 7), (rheumatoid arthritis, n = 5; dermatomyositis,
n = 1; Sjogren’s syndrome, n = 1), and
normal individuals (n = 20). We observed significantly
increased binding of nuclear extracts from unstimulated SLE T cells to
the -180 site. By contrast, binding from normal individuals and
disease control patients was minimal or undetectable. To determine the
composition of the shifted bands, we used Abs directed against
phosphorylated CREB (p-CREB) and p-CREM in EMSA. Unexpectedly, nuclear
extracts from 28 of 30 (93%) SLE patients displayed increased binding
of p-CREM. In some extracts (10 of 30, 33%), p-CREB binding was also
detected (Fig. 1
a). Minimal
p-CREB and no p-CREM binding were detected in extracts from
unstimulated disease control and normal T cells (Fig. 1b).
While unlabeled oligonucleotides completely inhibited the binding of
SLE T cell nuclear extracts (Fig. 1c), irrelevant
oligonucleotides failed to do so (data not shown), indicating binding
specificity.
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d). Maximal intensity was reached by 6 h in both
normal subjects and SLE patients and decreased thereafter (Fig. 1e). Unlabeled -180 oligonucleotide inhibited p-CREB and
p-CREM binding, demonstrating binding specificity (Fig. 1f).
In contrast, activated SLE T cells displayed two patterns of binding:
either p-CREM alone or a mixture of p-CREB (30% of the band density)
and p-CREM (60% of the band density). On the average, binding by
nuclear extracts of activated SLE T cells was 5-fold less than that in
unstimulated nuclear extracts (Fig. 1, d and g).
Moreover, using anti-AP-1 Abs in EMSA, we failed to detect any AP-1
binding (10) (Fig. 1f). Finally, we examined
binding of nuclear extracts from SLE and normal T cells that had been
previously rested for 18 h and subsequently stimulated as
described above. Although in stimulated and unstimulated normal T cells
we detected binding patterns similar to those in the unrested cells, in
unstimulated SLE T cells we observed decreased p-CREM binding, which
was still higher than that in normal T cells. p-CREM binding of nuclear
extracts from rested stimulated SLE T cells was still decreased (data
not shown).
Together, these experiments clearly demonstrate that p-CREM alone or
p-CREM and p-CREB (in which p-CREM contributes the most) bind the -180
site of the IL-2 promoter in SLE T cells, whereas in control T cells
this represents almost exclusively a p-CREB binding site. p-CREM and
p-CREB binding in all studied SLE subjects and normal subjects is shown
in Table I.
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To determine whether increased binding of p-CREM or p-CREM/p-CREB
identified in EMSA correlates with protein expression, we quantified
immunoblots of nuclear extracts from SLE, rheumatoid arthritis, and
normal T cells. SLE nuclear extracts immunoblotted with anti-p-CREM
and anti-p-CREB Abs revealed the presence of p-CREM and p-CREB in
all SLE subjects studied (Fig. 2b; n = 10 of
10, 100% for p-CREM; n = 9 of 10, 90% for p-CREB). By
contrast, nuclear extracts form unstimulated normal T cells expressed
minimal, but detectable, amounts of only p-CREB. When cells were
activated by PMA and ionomycin, p-CREB, but not p-CREM, was detected in
the nuclear extracts (Fig. 2a). Similar results were
obtained following stimulation with anti-CD3 and anti-CD28 Abs
(data not shown). Cytoplasmic extracts from unstimulated SLE T cells (9
of 10) displayed minimal amounts of CREB and p-CREB, but no p-CREM
(Fig. 2b). The cytoplasmic extracts from T cells from
rheumatoid arthritis patients (n = 2) and normal
subjects (n = 7) expressed CREB (9, 10),
but no p-CREB and p-CREM (Fig. 2a). Nuclear extracts from
stimulated cells from SLE patients displayed decreased amounts of
p-CREB and p-CREM compared with unstimulated cells (Fig. 2c). Thus, elevated protein levels of nuclear p-CREM protein
are associated with the increased p-CREM DNA binding observed in
EMSA.
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CREB binding protein (CBP) and p300 are known to bind p-CREB,
resulting in the formation of heteromeric activator complexes that
contribute to efficient and specific initiation of transcription
(13, 14). To determine whether the p-CREM detected in SLE
T cells is functional by virtue of its binding to CBP and/or p300, we
immunoprecipitated nuclear extracts from SLE and normal T cells with
anti-p300 and anti-CBP Abs. Immunoprecipitation of p300 in
nuclear extracts from unstimulated SLE T cells (n = 3)
revealed a p-CREM-p300 complex, whereas in nuclear extracts from
unstimulated normal T cells (n = 4) such complexes were
barely detectable in all samples examined (Fig. 3). In the same SLE samples, p-CREB
coprecipitated with p300 (Fig. 3). Also, immunoprecipitation of CBP
from nuclear extracts from unstimulated SLE T cells (n
= 2) revealed p-CREM-CBP complexes in both samples and p-CREB-CBP
complexes in one of two samples, whereas normal unstimulated T cells
did not reveal any p-CREB or p-CREM-CBP complexes (data not shown).
Thus, p-CREM in SLE T cells interacts with both CBP and p300
coactivators, forming complexes that would be expected to modulate
transcription.
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To determine whether p-CREM binding to the -180 site modifies the
transcriptional regulation of the IL-2 promoter, we
initially quantified IL-2 production following mitogenic stimulation in
vitro. PBMC from SLE subjects and normal controls were stimulated with
PHA (1 µg/ml) for 24 h, and secreted IL-2 in supernatants was
quantified by ELISA. Compared with controls, the amount of IL-2
secreted by SLE cells was 4-fold lower (p <
0.001; Fig. 4a). Analysis of T
cell nuclear extracts from these SLE subjects by EMSA revealed
increased amounts of p-CREM and p-CREB in 12 (100%) and five (42%)
specimens, respectively. Particularly notable was the observation that
nuclei with only p-CREM binding by EMSA were derived from the four SLE
subjects whose cells produced the lowest amounts of IL-2 (Fig. 4b). When analyzed by immunoblotting and
immunoprecipitation, these nuclear extracts possessed abundant amounts
of p-CREM that formed heteromeric complexes with CBP and p300.
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a, stimulation of transfected
normal T cells with PMA and ionomycin for 6 h induced a mean
2.8-fold increase in luciferase activity compared with that in
stimulated normal T cells transfected with pGL2
alone (n = 4; range, 1.8–3.7). By contrast,
stimulation of SLE T cells resulted in a mean 1.1-fold increase in
luciferase activity (n = 4; range, 0.2–1.2;
p < 0.05 compared with normal stimulated T cells). To
establish that CREM indeed suppresses the transcriptional activity
driven by the -180 site, we cotransfected normal T cells with a
construct encoding CREM and then added PMA and ionomycin for 6
h. Indeed, cotransfection of CREM resulted in a 1.8-fold decrease
(65% decrease) in luciferase activity compared with that in stimulated
T cells that were transfected with the construct driven by the two
-180 sites alone (p < 0.004). The luciferase
activity in unstimulated normal and SLE T cells followed a similar
pattern (Fig. 5a).
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. As shown in Fig. 5b, normal T
cells stimulated with PMA and ionomycin induced a mean 23.5-fold
increase in luciferase activity compared with that in unstimulated
cells. Cotransfection of the cells with CREM resulted in a mean 50%
decrease in luciferase activity (n = 4;
p < 0.001 compared with that in stimulated normal T
cells transfected with IL-2 alone). Unstimulated normal T cells that
were transfected with both the IL-2 promoter and CREM constructs
also displayed a mean 50% decrease in luciferase activity compared
with that in normal unstimulated T cells that were transfected with the
IL-2 promoter construct alone. p-CREM DNA binding and protein levels are not affected by disease activity or medication and are persistent after 3 mo of follow-up
We analyzed the relationship among SLE disease activity, treatment
modalities, and p-CREM binding by EMSA or p-CREM protein content by
immunoblotting. We failed to detect any significant differences in
p-CREM binding (Table II) or protein
levels among patients with active (SLEDAI > 4; n =
12) or inactive disease (SLEDAI < 4; n = 11).
Moreover, treatment did not significantly alter p-CREM binding. When T
cells from the same SLE subjects (n = 7) were analyzed
3–4 mo later, neither p-CREM binding nor nuclear p-CREM protein levels
were significantly different. Taken together, p-CREM binding to the
-180 site on the IL-2 promoter as well as its nuclear
protein content appear to be significantly increased compared with
control values and are independent of disease activity (Table II) and
mode of therapy.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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in response to antigenic
challenge in vitro, this has raised the possibility that SLE T
cells may be anergic (1, 22, 23). This impaired
cellular immunity contributes to the higher frequency of severe,
often life-threatening infections in this disorder (6, 7). Recently, it has been learned that T cell anergy is characterized in part by enhanced binding of p-CREM/p-CREB to the -180 site of the IL-2 promoter/enhancer (12). To establish whether diminished IL-2 production by SLE T cells is the result of reduced IL-2 transcriptional activation due to increased p-CREM binding to the -180 site in SLE T cells, we studied the T cells of a cross-section of SLE subjects with a spectrum of disease activity. Here, we demonstrate that unstimulated SLE T cells exhibit markedly increased nuclear binding to the -180 site of the IL-2 promoter compared with either normal or disease controls by EMSA. Importantly, this enhanced binding activity is the result of the transcriptional repressor, p-CREM, or of p-CREM/p-CREB complexes. Increased p-CREM binding is associated with accumulation of nuclear p-CREM, which can form heteromeric complexes with both CBP and p300 coactivators (12, 14). By contrast, p-CREB binding to the -180 site of the IL-2 promoter is under-represented, particularly when one compares p-CREB binding in activated T cells from normal or disease controls. In part, this is likely to reflect the disproportionate increase in nuclear p-CREM, although other, as yet unidentified mechanisms may also be operative that limit p-CREB content. Nevertheless, like p-CREM, p-CREB can form heteromeric complexes with both CBP and p300 coactivators. p-CREM may mediate transcriptional repression of IL-2-luciferase activity, possibly through its formation of heteromeric complexes with CBP and p300 (24, 25), resulting in diminished production of IL-2.
Certain CREM isoforms suppress the transcription activity of particular
genes (13). At this point we do not know whether the CREM
that we have observed to be increased in SLE T cells belongs to one of
these isoforms, but because cotransfection in normal T cells with an
inhibitory isoform (CREM) resulted in decreased luciferase activity,
we suspect that CREM in SLE represents an inhibitory isoform. It is
possible, though, that the increased levels of CREM sequester the
transcription coactivators CBP and p300 (Fig. 3), thereby making them
unavailable to CREB or other transcription factors. Sequestration of
the coactivators would prevent the formation of bridging complexes
necessary for recruitment of the transcriptional machinery and could
lead indirectly to decreased transactivation of the IL-2
promoter. Indeed, it has been shown that overexpression of CREB
inhibits AP-1- and NF-B-mediated gene transcription by competing for
the limited amounts of the coactivators CBP and p300 (25, 26). Finally, it is possible that p-CREM exhibits higher DNA
binding affinity than p-CREB, resulting in occupation of the -180 site
in SLE and subsequent repression of the IL-2 transcription.
Regulation of IL-2 transcription is complex, and its
decreased transcription in SLE T cells is probably multifactorial.
Previously, we reported decreased NF-B (20) and AP-1
(27) activity in SLE T cells, two more factors that are
also involved in transcription of the IL-2 gene. It is
possible that decreased IL-2 production by SLE T cells reflects an
integrated effect of diminished activators (e.g., NF-B) and
excessive expression of repressors (e.g., p-CREM).
The mechanism responsible for increased expression of CREM in SLE T
cells remains unknown. It is fascinating that the same cells display
decreased levels of certain molecules (e.g., TCR 
-chain and p65 Rel
A protein), but increased levels of others (e.g., CD40 ligand and
c-myc proto-oncogene) (4). The pathways
responsible for the phosphorylation of CREM in SLE T cells are also not
known. The phosphorylation pattern of various cytosolic SLE T cell
proteins is aberrant (19), and the activities of protein
kinase A isozymes I and II (28, 29) and C
(30) that phosphorylate CREB on
Ser133 are decreased. The complete
characterization of pathways involved in the phosphorylation of CREM
may decipher its role in the transcriptional regulation of SLE T cell
genes. Also, it is unclear at this point why the levels of p-CREM
decrease in SLE T cells following stimulation.
Genome-wide scans of SLE patients have revealed multiple disease susceptibility loci, some of which are shared by various cohorts of patients (31, 32). The CREB gene maps in the 2q33–35 region of the human genome, whereas CREM appears to localize to the 10p11.2 band (33). Although these loci have not been identified in these genome scans as disease susceptibility loci for SLE in the studied cohorts, it is possible that genes located in the identified SLE susceptibility loci could affect the expression and function of CREM and CREB. Transgenic mice expressing a dominant negative form of CREB display markedly decreased IL-2 production, G1 cell-cycle arrest, and subsequent apoptotic death (34).
Taken together, our data demonstrate that p-CREM acts as a repressor of the IL-2 promoter in SLE T cells. Additional studies are needed to understand the mechanisms that lead to the increased levels of p-CREM in SLE and whether it interacts with other positive transcription factors that bind to the IL-2 promoter.
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Acknowledgments |
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Footnotes |
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2 Address correspondence and reprint requests to Dr. George C. Tsokos, Walter Reed Army Institute of Research, Robert Grant Road, Building 503, Room 1A32, Silver Spring, MD 20910-7500.
3 Abbreviations used in this paper: SLE, systemic lupus erythematosus; CREB, cAMP-responsive element binding protein; CREM, cAMP-responsive element modulator; CBP, CREB binding protein; p-CREM, phosphorylated CREM; p-CREB, phosphorylated CREB; SLEDAI, SLE disease activity index.
Received for publication September 6, 2000. Accepted for publication January 3, 2000.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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B activity in T lymphocytes from patients with systemic lupus erythematosus is associated with decreased p65-RelA protein expression. J. Immunol. 163:1682.B mediated transcription. J. Immunol. 159:5450.[Abstract]
and RI transcripts and proteins in systemic lupus erythematosus T lymphocytes. J. Immunol. 162:5639.-subunit in systemic lupus erythematosus T lymphocytes. J. Immunol. 165:2830.This article has been cited by other articles:
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  M. Ahlmann, G. Varga, K. Sturm, R. Lippe, K. Benedyk, D. Viemann, T. Scholzen, J. Ehrchen, F. U. Muller, M. Seidl, et al. The Cyclic AMP Response Element Modulator {alpha} Suppresses CD86 Expression and APC Function J. Immunol., April 1, 2009; 182(7): 4167 - 4174. [Abstract] [Full Text] [PDF]
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K. Sunahori, Y.-T. Juang, and G. C. Tsokos Methylation Status of CpG Islands Flanking a cAMP Response Element Motif on the Protein Phosphatase 2Ac{alpha} Promoter Determines CREB Binding and Activity J. Immunol., February 1, 2009; 182(3): 1500 - 1508. [Abstract] [Full Text] [PDF]
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V. C. Kyttaris, Y. Wang, Y.-T. Juang, A. Weinstein, and G. C. Tsokos Increased Levels of NF-ATc2 Differentially Regulate CD154 and IL-2 Genes in T Cells from Patients with Systemic Lupus Erythematosus J. Immunol., February 1, 2007; 178(3): 1960 - 1966. [Abstract] [Full Text] [PDF]
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K. Tenbrock, Y.-T. Juang, N. Leukert, J. Roth, and G. C. Tsokos The Transcriptional Repressor cAMP Response Element Modulator {alpha} Interacts with Histone Deacetylase 1 to Repress Promoter Activity J. Immunol., November 1, 2006; 177(9): 6159 - 6164. [Abstract] [Full Text] [PDF]
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K. Tenbrock, V. C. Kyttaris, M. Ahlmann, J. M. Ehrchen, M. Tolnay, H. Melkonyan, C. Mawrin, J. Roth, C. Sorg, Y.-T. Juang, et al. The Cyclic AMP Response Element Modulator Regulates Transcription of the TCR {zeta}-Chain J. Immunol., November 1, 2005; 175(9): 5975 - 5980. [Abstract] [Full Text] [PDF]
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S. Krishnan, J. G. Kiang, C. U. Fisher, M. P. Nambiar, H. T. Nguyen, V. C. Kyttaris, B. Chowdhury, V. Rus, and G. C. Tsokos Increased Caspase-3 Expression and Activity Contribute to Reduced CD3{zeta} Expression in Systemic Lupus Erythematosus T Cells J. Immunol., September 1, 2005; 175(5): 3417 - 3423. [Abstract] [Full Text] [PDF]
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C. E. Zielinski, S. N. Jacob, F. Bouzahzah, B. E. Ehrlich, and J. Craft Naive CD4+ T Cells from Lupus-Prone Fas-Intact MRL Mice Display TCR-Mediated Hyperproliferation Due to Intrinsic Threshold Defects in Activation J. Immunol., April 15, 2005; 174(8): 5100 - 5109. [Abstract] [Full Text] [PDF]
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V. C. Kyttaris, Y.-T. Juang, K. Tenbrock, A. Weinstein, and G. C. Tsokos Cyclic Adenosine 5'-Monophosphate Response Element Modulator Is Responsible for the Decreased Expression of c-fos and Activator Protein-1 Binding in T Cells from Patients with Systemic Lupus Erythematosus J. Immunol., September 1, 2004; 173(5): 3557 - 3563. [Abstract] [Full Text] [PDF]
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M. R. Elliott, R. A. Shanks, I. U. Khan, J. W. Brooks, P. J. Burkett, B. J. Nelson, V. Kyttaris, Y.-T. Juang, G. C. Tsokos, and G. M. Kammer Down-Regulation of IL-2 Production in T Lymphocytes by Phosphorylated Protein Kinase A-RII{beta} J. Immunol., June 15, 2004; 172(12): 7804 - 7812. [Abstract] [Full Text] [PDF]
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V C Kyttaris, Y-T Juang, and G C Tsokos Gene therapy in systemic lupus erythematosus Lupus, May 1, 2004; 13(5): 353 - 358. [Abstract] [PDF]
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S. Krishnan, D. L. Farber, and G. C. Tsokos T Cell Rewiring in Differentiation and Disease J. Immunol., October 1, 2003; 171(7): 3325 - 3331. [Full Text] [PDF]
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M. P. Nambiar, C. U. Fisher, A. Kumar, C. G. Tsokos, V. G. Warke, and G. C. Tsokos Forced Expression of the Fc Receptor {gamma}-Chain Renders Human T Cells Hyperresponsive to TCR/CD3 Stimulation J. Immunol., March 15, 2003; 170(6): 2871 - 2876. [Abstract] [Full Text] [PDF]
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K. Tenbrock, Y.-T. Juang, M. Tolnay, and G. C. Tsokos The Cyclic Adenosine 5'-Monophosphate Response Element Modulator Suppresses IL-2 Production in Stimulated T Cells by a Chromatin-Dependent Mechanism J. Immunol., March 15, 2003; 170(6): 2971 - 2976. [Abstract] [Full Text] [PDF]
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Y.-T. Juang, K. Tenbrock, M. P. Nambiar, M. F. Gourley, and G. C. Tsokos Defective Production of Functional 98-kDa Form of Elf-1 Is Responsible for the Decreased Expression of TCR {zeta}-Chain in Patients with Systemic Lupus Erythematosus J. Immunol., November 15, 2002; 169(10): 6048 - 6055. [Abstract] [Full Text] [PDF]
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K. Tenbrock, Y.-T. Juang, M. F. Gourley, M. P. Nambiar, and G. C. Tsokos Antisense Cyclic Adenosine 5'-Monophosphate Response Element Modulator Up-Regulates IL-2 in T Cells from Patients with Systemic Lupus Erythematosus J. Immunol., October 15, 2002; 169(8): 4147 - 4152. [Abstract] [Full Text] [PDF]
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Y.-T. Juang, E. E. Solomou, B. Rellahan, and G. C. Tsokos Phosphorylation and O-Linked Glycosylation of Elf-1 Leads to Its Translocation to the Nucleus and Binding to the Promoter of the TCR {zeta}-Chain J. Immunol., March 15, 2002; 168(6): 2865 - 2871. [Abstract] [Full Text] [PDF]
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D W Montgomery Prolactin production by immune cells Lupus, October 1, 2001; 10(10): 665 - 675. [Abstract] [PDF]
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E. E. Solomou, Y.-T. Juang, and G. C. Tsokos Protein Kinase C-{{theta}} Participates in the Activation of Cyclic AMP-Responsive Element-Binding Protein and Its Subsequent Binding to the -180 Site of the IL-2 Promoter in Normal Human T Lymphocytes J. Immunol., May 1, 2001; 166(9): 5665 - 5674. [Abstract] [Full Text] [PDF]
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