Angiotensin II-induced cardiomyocyte hypertrophy in vitro is TAK1-dependent and Smad2/3-independent

Cardiac hypertrophy occurs as an adaptation to hypertension but a sustained hypertrophic response can ultimately lead to heart failure. Angiotensin-II (Ang II) is released following hemodynamic overload and stimulates a cardiac hypertrophic response. AngII also increases expression of the regulatory cytokine, transforming growth factor-β1 (TGFβ1), which is also implicated in the cardiac hypertrophic response and can stimulate activation of Smad2/3 as well as TGFβ-activated kinase 1 (TAK1) signaling mediators. To better understand the downstream signaling events in cardiac hypertrophy, we therefore investigated activation of Smad2/3 and TAK1 signaling pathways in response to Ang II and TGFβ1 using primary neonatal rat cardiomyocytes to model cardiac hypertrophic responses. Small interfering RNA (siRNA) knockdown of Smad 2/3 or TAK1 protein or addition of the TGFβ type I receptor inhibitor, SB431542, were used to investigate the role of downstream mediators of TGFβ signaling in the hypertrophic response. Our data revealed that TGFβ1 stimulation leads to cardiomyocyte hypertrophic phenotypes that were indistinguishable from those occurring in response to Ang II. In addition, inhibition of the TGFβ1 type receptor abolished Ang II-induced hypertrophic changes. Furthermore, the hypertrophic response was also prevented following siRNA knockdown of TAK1 protein, but was unaffected by knockdown of Smad2/3 proteins. We conclude that Ang II-induced cardiomyocyte hypertrophy in vitro occurs in a TAK1-dependent, but Smad-independent, manner.     

The A-kinase anchoring protein (AKAP)-Lbc-signaling complex mediates alpha1 adrenergic receptor-induced cardiomyocyte hypertrophy

In response to various pathological stresses, the heart undergoes a pathological remodeling process that is associated with cardiomyocyte hypertrophy. Because cardiac hypertrophy can progress to heart failure, a major cause of lethality worldwide, the intracellular signaling pathways that control cardiomyocyte growth have been the subject of intensive investigation. It has been known for more than a decade that the small molecular weight GTPase RhoA is involved in the signaling pathways leading to cardiomyocyte hypertrophy. Although some of the hypertrophic pathways activated by RhoA have now been identified, the identity of the exchange factors that modulate its activity in cardiomyocytes is currently unknown. In this study, we show that AKAP-Lbc, an A-kinase anchoring protein (AKAP) with an intrinsic Rho-specific guanine nucleotide exchange factor activity, is critical for activating RhoA and transducing hypertrophic signals downstream of alpha1-adrenergic receptors (ARs). In particular, our results indicate that suppression of AKAP-Lbc expression by infecting rat neonatal ventricular cardiomyocytes with lentiviruses encoding AKAP-Lbc-specific short hairpin RNAs strongly reduces both alpha1-AR-mediated RhoA activation and hypertrophic responses. Interestingly, alpha1-ARs promote AKAP-Lbc activation via a pathway that requires the alpha subunit of the heterotrimeric G protein G12. These findings identify AKAP-Lbc as the first Rho-guanine nucleotide exchange factor (GEF) involved in the signaling pathways leading to cardiomyocytes hypertrophy.     

Interleukin-18 attracts plasmacytoid dendritic cells (DC2s) and promotes Th1 induction by DC2s through IL-18 receptor expression

In vivo evidence suggests that interleukin-18 (IL-18) shapes the development of adaptive immunity toward T-helper cell type 1 (Th1) responses. Monocyte-derived dendritic cells 1 (DC1s) preferentially induce a Th1 response, while plasmacytoid DC-derived DC2s have been linked to a Th2 response. We analyzed the role of IL-18 during the initiation phase of a Th response in vitro to elucidate the basis of these in vivo observations. IL-18 was constitutively released from DC1s, but not DC2s. Neutralization of IL-18 in coculture experiments of DC1s with allogeneic naive T lymphocytes did not alter the Th1/Th2 phenotype, while anti-IL-12 efficiently down-regulated the Th1 response. Unexpectedly, IL-18 receptor (IL-18R) alpha and beta chains were expressed on DC2 lineage. IL-18R expression was functional, as IL-18 induced chemotaxis in plasmacytoid DCs (pre-DC2s) and enhanced the allostimulatory capacity of IL-3-differentiated DC2s. Pre-DC2s exposed to IL-18 skewed the development of Th cells toward Th1 in coculture experiments of DC2s and allogeneic naive T cells, which was inhibited by IL-12 p70 neutralization. IL-18 might have a profound role during the initiation phase of an immune response by recruiting pre-DC2s and modulating the function of DC2s.     

Interleukin-6 (B-cell stimulatory factor 2)-dependent growth of a Lennert's lymphoma-derived T-cell line (KT-3)

A T lymphoma cell line (KT-3) established from a patient with Lennert's lymphoma showed macrophage-dependent growth. Macrophage-derived factors were able to replace the macrophage functions. Experiments using a variety of cytokines demonstrated that KT-3 proliferated in response to recombinant interleukin-2 (rIL-2), rIL-4, or rIL-6 but did not proliferate in response to rIL-1 alpha, rIL-1 beta, rIL-3, recombinant granulocyte colony-stimulating factor (rG-CSF), rGM-CSF, recombinant interferon-alpha (rIFN-alpha), rIFN-gamma, recombinant tumor necrosis factor (rTNF-alpha), or native IFN-beta. Polyclonal rabbit anti-IL-6 antibody almost completely neutralized the activities of macrophage- derived factors or IL-6 but not IL-2 or IL-4. Scatchard plot analysis demonstrated that KT-3 cells indeed express IL-6 receptors. The results indicate that the macrophage-derived factor that supports the growth of KT-3 is IL-6 and suggest that macrophage-derived IL-6 may play an important role in the histopathogenesis of Lennert's lymphoma.     

IRF7 activation by Epstein–Barr virus latent membrane protein 1 requires localization at activation sites and TRAF6, but not TRAF2 or TRAF3

Epstein–Barr virus (EBV) latent infection membrane protein 1 (LMP1), a constitutively aggregated and activated pseudoreceptor, activates IFN regulatory factor 7 (IRF7) through RIP1. We now report that the LMP1 cytoplasmic carboxyl terminal amino acids 379–386 bound IRF7 and activated IRF7. IRF7 activation required TRAF6 and RIP1, but not TRAF2 or TRAF3. LMP1 Y₃₈₄YD₃₈₆, which are required for TRADD and RIP1 binding and for NF-κB activation, were not required for IRF7 binding, but were required for IRF7 activation, implicating signaling through TRADD and RIP1 in IRF7 activation. Association with active LMP1 signaling complexes was also critical for IRF7 activation because (i) a dominant-negative IRF7 bound to LMP1, blocked IRF7 association and activation, but did not inhibit LMP1 induced NF-κB or TBK1 or Sendai virus-mediated IFN stimulated response element activation; and (ii) two different LMP1 transmembrane domain mutants, which fail to aggregate, each bound IRF7 and prevented LMP1 from binding and activating IRF7 in the same cell, but did not prevent NF-κB activation. Thus, efficient IRF7 activation required association with LMP1 CTAR2 in proximity to LMP1 CTAR2 mediated kinase activation sites.     

Interleukin-1, Interleukin-2, Interleukin-4, Interleukin-6, Tumor Necrosis Factor α, and Interferon-γ Levels in Sera from Patients With Scleroderma

Objective. To determine whether interleukin-lα (IL-1α), IL-1β, IL-2, IL-4, interferon-γ (IFNγ), IL-6, and tumor necrosis factor α (TNFα) are detected more frequently in sera from scleroderma patients than in sera from controls. Methods. Serum concentrations of these cytokines were measured in 78 scleroderma patients and 73 controls, using enzyme-linked immunosorbent assay, radioimmunoassay, and bioassay techniques. Results. IL-2, IL-4, and IL-6 were each detected more frequently in sera from scleroderma patients than in sera from controls. TNFα and IL-1α were found with equal frequency in patient and control sera. IL-1β and IFNγ were not detected in any sera. Conclusion. IL-2, IL-4, and IL-6 may be among the cytokines that contribute to the disease process in scleroderma patients. To our knowledge, this is the first report of elevated serum IL-4 levels in human disease.     

心房颤动犬心房肌细胞三磷酸肌醇1型和2型受体的分布及表达

目的探讨心房颤动(房颤)时犬心房肌细胞三磷酸肌醇1型受体(IP3R1)和三磷酸肌醇2型受体(IP3R2)的表达及分布的改变。方法选择10只杂种犬,分为正常对照组和房颤起搏器组,每组5只。房颤起搏器组用起搏器进行房颤式快速起搏,起搏频率(500±20)次/min,术后观察24周。正常对照组不置入起搏器。24周后取出心脏,用RT-PCR、荧光免疫组织化学和Western blot技术检测犬心房肌细胞IP3R1、IP3R2在mRNA表达水平,蛋白水平的表达和分布。结果房颤起搏器组犬心房肌细胞IP3R1、IP3R2在mRNA和蛋白水平的表达明显高于正常对照组(P<0.05),IP3R1主要在细胞质内表达,IP3R2除了在细胞质内表达增加外,在心房肌细胞闰盘、细胞膜和细胞核膜分布均显著增加。结论房颤时犬心房肌细胞IP3R1和IP3R2的表达上调及功能增强,IP3R2是与心房肌细胞内钙信号调控的主要受体,可能也参与细胞缝隙连接之间的钙信号传递过程。     

Interleukin-2 inhibits FMS-like tyrosine kinase 3 receptor ligand (flt3L)-dependent development and function of conventional and plasmacytoid dendritic cells

Steady-state development of plasmacytoid dendritic cells (pDCs) and conventional dendritic cells (cDCs) requires the ligand for FMS-like tyrosine kinase 3 receptor (flt3L), but little is known about how other cytokines may also control this process. In this study, we show that IL-2 inhibits the development of both pDCs and cDCs from bone marrow cells under flt3L stimulation, by acting on lineage(-) flt3(+) precursors. This inhibition of DC development by IL-2 requires IL-2Rα and IL2Rβ. IL-2Rα is specifically expressed in one stage of the DC precursor: the monocyte and DC progenitors (MDPs). Furthermore, more MDPs are found in flt3L-stimulated bone marrow cultures when IL-2 is present, suggesting that IL-2 may be inhibiting DC development at the MDP stage. Consistent with our in vitro findings, we observe that nonobese diabetic (NOD) mice, which express less IL-2 compared with diabetes-resistant NOD.Idd3/5 mice, have more splenic pDCs. Additionally, DCs developed in vitro in the presence of flt3L and IL-2 display reduced ability to stimulate T-cell proliferation compared with DCs developed in the presence of flt3L alone. Although the addition of IL-2 does not increase the apoptosis of DCs during their development, DCs developed in the presence of IL-2 are more prone to apoptosis upon interaction with T cells. Together our data show that IL-2 can inhibit both the development and the function of DCs. This pathway may have implications for the loss of immune tolerance: Reduced IL-2 signaling may lead to increased DC number and T-cell stimulatory capacity.     

The variants in PTPRB,TRAF3IP3, and DISC1 genes were associated with Graves’ disease in the Chinese population

Previously, a case series study was conducted on our part in which 5 patients with Graves’ disease (GD) were collected from a 3-generation family to screen for susceptibility genes responsible for GD. The single nucleotide variants of Microtubule-associated protein 7 domain containing 2 c. 452C > T, p. Ala151Val, Solute carrier family 1 member 7 c. 1204C > T, p. Arg402Cys, tumor necrosis factor receptor-associated factor 3 interacting protein 3 (TRAF3IP3) c. 209A > T, p. Asn70Ile, protein tyrosine phosphatase receptor type B (PTPRB) c. 3472A > G, p. Ser1158Gly, Phosphoinositide-3-kinase regulatory subunit 3 c. 121C > T, p. Pro41Ser, disrupted in schizophrenia 1 (DISC1), c. 1591G > C p. Gly531Arg were associated with the familial GD. We then further confirmed these variants and investigated whether other mutations render susceptibility to GD. The case-control study collected patients with sporadic GD or no GD family history. A snapshot program was used for genotyping the selected SNPs in 235 GD patients (GD group 1) and 284 healthy patients (control group). Furthermore, another 184 GD patients were recruited (GD group 2) to sequence the specified exons of these genes. The sequenced data was compared with Chinese Millionome Database (CMDB). Several variants of PTPRB, phosphoinositide-3-kinase regulatory subunit 3, TRAF3IP3, and DISC1 were found in GD group 2 but not in CMDB. Moreover, the allele frequency of SNP rs2076150 (TRAF3IP3) and rs2492367 DISC1 in GD group 2 was significantly higher than that of in CMDB (all P < .05). When the control group or CMDB was set as a reference group, a significantly higher frequency in alter allele C of SNP rs186466118 PTPRB was observed in GD group 1 and GD group (constituted by GD group 1 and GD group 2). Equally importantly, there was a correlation between the allele C of SNP rs186466118 and the increased risk of GD susceptibility (all P < .05). PTPRB, TRAF3IP3, and DISC1 may be susceptibility genes for GD, and more variants of PTPRB, TRAF3IP3, and DISC1 were found in GD patients.     

Interleukin-1α, interleukin-2, and soluble interleukin-2 receptors in polymyositis

Cell-mediated immunity has been implicated in the pathogenesis of polymyositis (PM). We conducted a prospective study in which serum levels of soluble interleukin-2 receptors (IL-2R), IL-1α, and IL-2 were correlated with creatine kinase (CK) levels and clinical disease activity. Cytokines and IL-2R were quantitated in 133 serum samples from 14 patients by use of an enzyme-linked immunosorbent assay. In patients with acute PM (9 patients), soluble IL-2R and IL-1α levels were elevated initially, but declined rapidly with therapy. A significant linear relationship was found between soluble IL-2R levels and CK levels. IL-2 was initially detectable in only 3 patients, and it disappeared with therapy in all 3. The levels of cytokines and IL-2R were consistently normal in patients with inactive PM (2 patients). In patients with chronic PM (3 patients), the cytokines and soluble IL-2R levels were normal despite persistently abnormal CK levels and/or muscle weakness. Cellular IL-2R levels correlated positively with serum levels of soluble IL-2R. Our studies substantiate a pathogenic role for cellular immunity in PM, with the finding of activation of lymphocytes. The finding of increased levels of IL-1α demonstrates for the first time that there is monocyte activation in PM. Persistent elevation of CK levels after normalization of the levels of cytokines and IL-2R may be prognostic of impending chronic disease. Serum soluble IL-2R appear to be a sensitive indicator of improvement or exacerbation of disease activity in patients with PM.     

Targeted expression of the inositol 1,4,5-triphosphate receptor (IP3R) ligand-binding domain releases Ca2+ via endogenous IP3R channels

Virtually all functions of a cell are influenced by cytoplasmic [Ca(2+)] increases. Inositol 1,4,5-trisphosphate receptor (IP(3)R) channels, located in the endoplasmic reticulum (ER), release Ca(2+) in response to binding of the second messenger, IP(3).IP(3)Rs thus are part of the information chain interpreting external signals and transforming them into cytoplasmic Ca(2+) transients. IP(3)Rs function as tetramers, each unit comprising an N-terminal ligand-binding domain (LBD) and a C-terminal channel domain linked by a long regulatory region. It is not yet understood how the binding of IP(3) to the LBD regulates the gating properties of the channel. Here, we use the expression of IP(3) binding protein domains tethered to the surface of the endoplasmic reticulum (ER) to show that the all-helical domain of the IP(3)R LBD is capable of depleting the ER Ca(2+) pools by opening the endogenous IP(3)Rs, even without IP(3) binding. This effect requires the domain to be within 50 A of the ER membrane and is impaired by the presence of the N-terminal inhibitory segment on the LBD. These findings raise the possibility that the helical domain of the LBD functions as an effector module possibly interacting with the channel domain, thereby being part of the gating mechanisms by which the IP(3)-induced conformational change within the LBD regulates Ca(2+) release.     

High-density lipoprotein (HDL) promotes angiogenesis via S1P3-dependent VEGFR2 activation

High-density lipoprotein (HDL) has previously been shown to promote angiogenesis. However, the mechanisms by which HDL enhances the formation of blood vessels remain to be defined. To address this, the effects of HDL on the proliferation, transwell migration and tube formation of human umbilical vein endothelial cells were investigated. By examining the abundance and phosphorylation (i.e., activation) of the vascular endothelial growth factor receptor VEGFR2 and modulating the activity of the sphingosine-1 phosphate receptors S1P1–3 and VEGFR2, we characterized mechanisms controlling angiogenic responses in response to HDL exposure. Here, we report that HDL dose-dependently increased endothelial proliferation, migration and tube formation. These events were in association with increased VEGFR2 abundance and rapid VEGFR2 phosphorylation at Tyr1054/Tyr1059 and Tyr1175 residues in response to HDL. Blockade of VEGFR2 activation by the VEGFR2 inhibitor SU1498 markedly abrogated the pro-angiogenic capacity of HDL. Moreover, the S1P3 inhibitor suramin prevented VEGFR2 expression and abolished endothelial migration and tube formation, while the S1P1 agonist CYM-5442 and the S1P2 inhibitor JTE-013 had no effect. Last, the role of S1P3 was further confirmed in regulation of S1P-induced endothelial proliferation, migration and tube formation via up-regulation and activation of VEGFR2. Together, these findings argue that HDL promotes angiogenesis via S1P3-dependent up-regulation and activation of VEGFR2 and also suggest that the S1P–S1P3–VEGFR2 signaling cascades as a novel target for HDL-modulating therapy implicated in vascular remodeling and functional recovery in atherosclerotic diseases such as myocardial infarction and ischemic stroke.     

Influx of extracellular calcium mediates 1,25-dihydroxyvitamin D3-dependent transcaltachia (the rapid stimulation of duodenal Ca2+ transport)

We investigated the role of extracellular Ca2+ in 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] rapid stimulation of intestinal Ca2+ transport (termed transcaltachia) in the perfused duodenal of vitamin D-replete chicks. The carboxylic ionophore ionomycin (2 microM) was found to stimulate 45Ca2+ transport from the lumen to the vascular effluent to the same extent as physiological levels of 1,25-(OH)2D3. The increase in duodenal 45Ca2+ transport caused by 1,25-(OH)2D3 was dependent on the presence of medium Ca2+, since it was abolished by prior addition of EGTA and was restored upon the addition of Ca2+. Depolarization of the basal lateral membrane of intestinal epithelial cells with 70 mM K+ caused a rapid increase in 45Ca2+ transport (30% above control values within 2 min and 250% after 20 min of vascular perfusion). The rise was also abolished by prior addition of EGTA. Intracellular calcium concentrations ([Ca2+]i) were measured in isolated duodenal cells from vitamin D-replete chicks using the fluorescent dye fura 2. A 1-min incubation with physiological concentrations of 1,25-(OH)2D3 (130 pM) caused an increase in [Ca2+]i from a basal level of 168 +/- 23 nM to 363 +/- 44 nM. Pretreatment of intestinal epithelial cells with the protein kinase-C activator tetradeconyl-phorbol acetate (100 nM) or the adenylate cyclase activator forskolin (10 microM), both shown to induce acute stimulation of intestinal 45Ca2+ transport in the perfused duodenum, also mimicked the stimulatory effect of 1,25-(OH)2D3 on [Ca2+]i. The increase in [Ca2+]i elicited by the 1,25-(OH)2D3 was due to Ca2+ influx from the extracellular medium, since it was blocked by the Ca2+ chelator EGTA (5 mM) and the Ca2+ channel antagonist nifedipine (1 microM). These results suggest that the acute effects of 1,25-(OH)2D3 on duodenal 45Ca2+ transport are triggered by the influx of Ca2+ through voltage-operated Ca2+ channels and that both protein kinase-C and protein kinase-A play an important role in mediating or modulating 1,25-(OH)2D3 effects on transcaltachia.     

Distinct localization and function of (1,4,5)IP(3) receptor subtypes and the (1,3,4,5)IP(4) receptor GAP1(IP4BP) in highly purified human platelet membranes

Platelet activation is associated with an increase of cytosolic Ca(++) levels. The (1,4,5)IP(3) receptors [(1,4,5)IP(3)R] are known to mediate Ca(++) release from intracellular stores of many cell types. Currently there are at least 3 distinct subtypes of (1,4, 5)IP(3)R-type I, type II, and type III-with suggestions of distinct roles in Ca(++) elevation. Specific receptors for (1,3,4,5)IP(4) belonging to the GAP1 family have also been described though their involvement with Ca(++) regulation is controversial. In this study we report that platelets contain all 3 subtypes of (1,4,5)IP(3)R but in different amounts. Type I and type II receptors are predominant. In studies using highly purified platelet plasma (PM) and intracellular membranes (IM) we report a distinct localization of these receptors. The PM fractions were found to contain the type III (1,4,5)IP(3)R and GAP1(IP4BP) in contrast to IM, which contained type I (1,4,5)IP(3)R. The type II receptor exhibited a dual distribution. In studies examining the labeling of surface proteins with biotin in intact platelets only the type III (1,4,5)IP(3)R was significantly labeled. Immunogold studies of ultracryosections of human platelets showed significantly more labeling of the PM with the type III receptor antibodies than with type I receptor antibodies. Ca(++) flux studies were carried out with the PM to demonstrate in vitro function of inositol phosphate receptors. Ca(++) release activities were present with both (1,4,5)IP(3) and (1, 3,4,5)IP(4) (EC(50) = 1.3 and 0.8 micromol/L, respectively). Discrimination of the Ca(++)-releasing activities was demonstrated with cyclic adenosine monophosphate (cAMP)-dependent protein kinase (cAMP-PK) specifically inhibiting (1,4,5)IP(3) but not (1,3,4, 5)IP(4)-induced Ca(++) flux. In experiments with both PM and intact platelets, the (1,4,5)IP(3)Rs but not GAP1(IP4BP) were found to be substrates of cAMP-PK and cGMP-PK. Thus the Ca(++) flux property of (1,3,4,5)IP(4) is insensitive to cAMP-PK. These studies suggest distinct roles for the (1,4,5)IP(3)R subtypes in Ca(++) movements, with the type III receptor and GAP1(IP4BP) associated with cation entry in human platelets and the type I receptor involved with Ca(++) release from intracellular stores.     

Crucial role of type 1, but not type 3, inositol 1,4,5-trisphosphate (IP(3)) receptors in IP(3)-induced Ca(2+) release, capacitative Ca(2+) entry, and proliferation of A7r5 vascular smooth muscle cells

Stimulation of G protein- or tyrosine kinase-coupled receptors regulates cell proliferation through intracellular Ca(2+) ([Ca(2+)](i)) signaling. In A7r5 cells, we confirmed that inositol 1,4,5-trisphosphate (IP(3)) mediates vasopressin (VP)-evoked Ca(2+) release from intracellular stores and showed that types 1 (IP(3)R(1)) and 3 (IP(3)R(3)) IP(3) receptors were expressed. Using antisera selective for IP(3)R(1) or IP(3)R(3) and another that interacted equally well with both subtypes, together with membranes from SF:9 cells expressing only single IP(3)R subtypes to calibrate immunoblotting, we established that A7r5 cells express 81% IP(3)R(1) and 19% IP(3)R(3). To elucidate the contributions of IP(3)R(1) and IP(3)R(3) to Ca(2+) signaling and proliferation, stable clones expressing promoter-inducible antisense cDNA fragments (-90 to +9) corresponding to the two IP(3)R subtypes were selected. Mild inhibition of IP(3)R(1) (71+/-8% of control level) slightly attenuated the IP(3)-evoked Ca(2+) release (IICR) induced by VP but significantly decreased the subsequent capacitative Ca(2+) entry (CCE) and proliferation. Moderate inhibition (34+/-6%) strongly decreased both IICR and CCE and further blocked proliferation. Complete inhibition almost abolished IICR and CCE and arrested proliferation entirely. Complete inhibition of IP(3)R(3) expression slightly attenuated IICR without affecting CCE or proliferation. In cells microinjected with a low dose of heparin, VP-induced CCE was more susceptible than IICR to mild inhibition of both IP(3)R(1) and IP(3)R(3). A high dose of heparin had a similar effect to complete inhibition of IP(3)R(1) expression: it blocked VP-evoked IICR entirely and CCE by 90%. We conclude that IP(3)R(1), but not IP(3)R(3), is crucial for IICR, CCE, and proliferation of vascular smooth muscle cells.     

Interleukin-2 (IL-2) upregulates BAG-1 gene expression through serine- rich region within IL-2 receptor beta c chain

BAG-1 is a Bci-2-binding protein which functions in protection from apoptotic cell death. Here we provide evidence for interleukin-2 (IL-2)- mediated upregulation of BAG-1 expression. In hematopoietic cell line BAF-B03 F7 cells, gene transfer mediated expression of the IL-2R beta c chain is sufficient to confer proliferation and cell survival responses to IL-2. In these IL-2R beta c-expressing cells, BAG-1 mRNA was dramatically induced by IL-2. The IL-2-mediated induction of BAG-1 expression required the activation of tyrosine kinase(s) and was sensitive to rapamycin as the induction of bcl-2 expression was. Analysis of the transfectants which express mutant IL-2R beta c chains or mutant Janus family protein tyrosine kinase Jak3 lacking the kinase domain showed that the IL-2-mediated BAG-1 gene expression required the serinerich region within the IL-2R beta c chain, but Jak3 activation was dispensable. The signaling pathway for BAG-1 gene expression thus highly resembles that for bcl-2 gene expression, strongly suggesting that their induction shares the same signaling pathway. In addition, deletion of the serine-rich region led to loss of IL-2-mediated protection from apoptotic cell death. Taken together, these studies demonstrate that the serine-rich region of the IL-2R beta c chain mediates the coordinated expression of bcl-2 and BAG-1 genes, thereby contributing to suppression of apoptosis.