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Crystal structures of oligomeric forms of the IP-10/CXCL10 chemokine.

We have determined the structure of wild-type IP-10 from three crystal forms. The crystals provide eight separate models of the IP-10 chain, all differing substantially from a monomeric IP-10 variant examined previously by NMR spectroscopy. In each crystal form, IP-10 chains form conventional beta sheet dimers, which, in turn, form a distinct tetrameric assembly. The M form tetramer is reminiscent of platelet factor 4, whereas the T and H forms feature a novel twelve-stranded beta sheet. Analytical ultracentrifugation indicates that, in free solution, IP-10 exists in a monomer-dimer equilibrium with a dissociation constant of 9 microM. We propose that the tetrameric structures may represent species promoted by the binding of glycosaminoglycans. The binding sites for several IP-10-neutralizing mAbs have also been mapped.

Amino Acid Sequence↗

IPS-1, an adaptor triggering RIG-I- and Mda5-mediated type I interferon induction.

Type I interferons are central mediators for antiviral responses. Using high-throughput functional screening of interferon inducers, we have identified here a molecule we call interferon-beta promoter stimulator 1 (IPS-1). Overexpression of IPS-1 induced type I interferon and interferon-inducible genes through activation of IRF3, IRF7 and NF-kappaB transcription factors. TBK1 and IKKi protein kinases were required for the IPS-1-mediated interferon induction. IPS-1 contained an N-terminal CARD-like structure that mediated interaction with the CARD of RIG-I and Mda5, which are cytoplasmic RNA helicases that sense viral infection. 'Knockdown' of IPS-1 by small interfering RNA blocked interferon induction by virus infection. Thus, IPS-1 is an adaptor involved in RIG-I- and Mda5-mediated antiviral immune responses.

Adaptor Proteins, Signal Transducing↗

Distinction between relaxations induced via prostanoid EP(4) and IP(1) receptors in pig and rabbit blood vessels.

1. Our study shows that the prostacyclin analogues AFP-07 and cicaprost are moderately potent agonists for prostanoid EP(4) receptors, in addition to being highly potent IP(1) receptor agonists. Both activities were demonstrated on piglet and rabbit saphenous veins, which are established EP(4) preparations. 2. On piglet saphenous vein, PGE(2) was 6.1, 24, 96, 138, 168 and 285 times respectively more potent than AFP-07, cicaprost, PGI(2), iloprost, carbacyclin and TEI-9063 in causing relaxation. Another prostacyclin analogue taprostene did not induce maximum relaxation (21 - 74%), and did not oppose the action of PGE(2). The EP(4) receptor antagonist AH 23848 (30 microM) blocked relaxant responses to PGE(2) (dose ratio=8.6+/-1.3, s.e.mean) to a greater extent than cicaprost (4.9+/-0.7) and AFP-07 (3.8+/-0.8), had variable effects on TEI-9063-induced relaxation (3.7+/-1.5), and had no effect on taprostene responses (<2.0). 3. On rabbit saphenous vein, AH 23848 blocked the relaxant actions of PGE(2), AFP-07, cicaprost, iloprost and carbacyclin to similar extents. 4. AFP-07, cicaprost and TEI-9063 showed high IP(1) relaxant potency on piglet carotid artery, rabbit mesenteric artery and guinea-pig aorta, with AFP-07 confirmed as the most potent IP(1) agonist reported to date. AH 23848 did not block cicaprost-induced relaxation of piglet carotid artery. EP(3) contractile systems in these preparations can confound IP(1) agonist potency estimations. 5. Caution is urged when using AFP-07 and cicaprost to characterize IP(1) receptors in the presence of EP(4) receptors. Taprostene may be a lead to a highly selective IP(1) receptor agonist.

Alprostadil↗

Early post-transplant urinary IP-10 expression after kidney transplantation is predictive of short- and long-term graft function.

The early identification of renal transplant recipients at enhanced risk of developing acute and subclinical rejection would allow individualized adjustment of immunosuppression before functional graft injury occurs and would exclude these patients from drug-weaning studies. Protein and reverse transcriptase-polymerase chain reaction-based analyses of candidate markers in urine open the opportunity to closely monitor kidney-transplanted patients non-invasively. The chemokine interferon-inducible protein 10 (IP-10; CXCL10) might be an interesting candidate to uncover ongoing immune processes within the graft. Urine samples from kidney-transplanted recipients were retrospectively analyzed for IP-10 mRNA and protein expression. IP-10 levels were correlated with the incidence of acute rejection episodes proven by histology and long-term graft function assessed by the glomerular filtration rate 6 months post transplantation. IP-10 expression in urine identified patients with ongoing acute rejection episodes several days before a biopsy was indicated by rising serum creatinine levels. Most importantly, elevated levels of urinary IP-10 protein within the first four postoperative weeks were predictive of graft function at 6 months even in the absence of acute rejection. These data reveal a correlation between elevated IP-10 expression in urine at early time points post-transplantation and intragraft immune activation that leads to acute rejection and compromised long-term graft function.

Adult↗

Effect of inositol hexaphosphate (IP(6)) on human normal and leukaemic haematopoietic cells.

Inositol hexaphosphate (IP(6)), a naturally polyphosphorylated carbohydrate, has been reported to have significant in vivo and in vitro anticancer activity against numerous tumours, such as colon, prostate, breast, liver and rhabdomyosarcomas. To confirm this activity in haematological malignancies and to characterize some of the mechanisms of IP(6) action, we analysed its effects on human leukaemic cell lines and fresh chronic myelogenous leukaemia (CML) progenitor cells using a combined cellular and molecular approach. IP(6) had a dose-dependent cytotoxic effect on all of the evaluated cell lines, with accumulation in the G2M phase in two out of five cell lines tested. At the molecular level, cDNA microarray analysis after IP(6) exposure showed an extensive downmodulation of genes involved in transcription and cell cycle regulation and a coherent upregulation of cell cycle inhibitors. Furthermore, IP(6) treatment of fresh leukaemic samples of bone marrow CD34+ CML progenitor cells significantly inhibited granulocyte-macrophage colony-forming unit (CFU-GM) formation (P = 0.0062) in comparison to normal bone marrow specimens, which were not affected. No differentiating effect on HL60 cells was observed. Taken together, our results confirm the antiproliferative activity of IP(6) and suggest that it may have a specific antitumour effect also in chronic myeloid leukaemias, via active gene modulation.

Cell Cycle↗

Epidermal interferon-gamma inducible protein-10 (IP-10) and monokine induced by gamma-interferon (Mig) but not IL-8 mRNA expression is associated with epidermotropism in cutaneous T cell lymphomas.

Epidermal infiltration by neoplastic CD4+ T cells is a characteristic histologic feature of early stage mycosis fungoides, the most common type of cutaneous T cell lymphoma (CTCL). The mechanisms involved in epidermotropism are unknown. It has been suggested that the CXC chemokines IL-8 and interferon-gamma inducible protein 10 (IP-10) may play a role, but evidence that these chemokines are produced within the epidermis in epidermotropic CTCL is lacking. In this study skin biopsies from 17 CTCL patients, including 12 mycosis fungoides, four pleomorphic CTCL, and one CD8+ CTCL, were investigated for epidermal IL-8 and IP-10 mRNA expression by RNA in situ hybridization. In addition, the expression of monokine induced by gamma-interferon (Mig) mRNA, a CXC chemokine closely related to IP-10, was studied as well. The expression of IL-8 receptors A and B (CXCR1 and CXCR2, respectively) was investigated by immunohistochemistry. The results were correlated with the number and phenotype of epidermotropic T cells. Epidermal expression of IP-10 and Mig mRNA was detected in 10 of 11 and seven of 11 epidermotropic CTCL, respectively, but not in five nonepidermotropic CTCL biopsies or normal human skin. Epidermal IP-10 and Mig mRNA expression correlated with epidermal infiltration of CD4+ T cells, but not of CD8+ T cells. IL-8 mRNA was demonstrated in the epidermis of only two of 15 CTCL biopsies, and was associated, in both cases, with accumulation of neutrophils. Consistently, immunostaining of the (intraepidermal) T cells with antibodies against CXCR1 and CXCR2 was not observed. In conclusion, the results of this study indicate that IP-10, and to a lesser extent Mig, but not IL-8 is involved in the preferential infiltration of neoplastic CD4+ T cells in CTCL.

Antigens, CD↗

Intercellular adhesion molecule-I (ICAM-I, CD54) deficiency segregates the unique pathophysiological requirements for generating idiopathic pneumonia syndrome (IPS) versus graft-versus-host disease following allogeneic murine bone marrow transplantation.

Following allogeneic bone marrow transplantation (alloBMT), idiopathic pneumonia syndrome (IPS) and graft-versus-host disease (GVHD) caused by donor cell alloreactivity remain major obstacles to a successful outcome. Intercellular adhesion molecule-1 (ICAM-1) is an adhesion molecule that is involved in regulating lymphohematopoietic cell migration and facilitating T-cell responses. To determine whether ICAM-1 expression in the host would affect IPS or GVHD tissue injury responses, ICAM-1(-/-) mice were compared with ICAM-1(+/+) controls. ICAM-1(-/-) recipients did not exhibit the manifestations of IPS injury such as an increase in lung weights nor decreased lung function. The influx of T cells, macrophages, and neutrophils was dramatically dampened as was the production of the inflammatory cytokines interferon-gamma and tumor necrosis factor alpha and the chemokines monocyte chemotactic protein 1, macrophage inflammatory protein 1alpha (MIP-1alpha), MIP-1beta, and lymphotactin, normally upregulated in the lung during IPS. In contrast, systemic levels of these mediators were unaffected and GVHD-induced lesions in the liver and colon did not differ in severity regardless of ICAM-1 expression. GVHD-mediated mortality was accelerated in ICAM-1(-/-) recipients at doses of allogeneic spleen cells that are otherwise not uniformally lethal. These data implicate ICAM-1 as playing a critical role in the generation of IPS; therefore, ICAM-1 may be a discerning element, segregating IPS from GVHD injury post-alloBMT.

Animals↗

CXCR3 and heparin binding sites of the chemokine IP-10 (CXCL10).

The chemokine IP-10 (interferon-inducible protein of 10 kDa, CXCL10) binds the G protein-coupled receptor CXCR3, which is found mainly on activated T cells and NK cells, and plays an important role in Th1-type inflammatory diseases. IP-10 also binds to glycosaminoglycans (GAGs), an interaction thought to be important for its sequestration on endothelial and other cells. In this study, we performed an extensive mutational analysis to identify the CXCR3 and heparin binding sites of murine IP-10. The mutants were characterized for heparin binding, CXCR3 binding, and the ability to induce chemotaxis, Ca(2+) flux, and CXCR3 internalization. Double mutations neutralizing adjacent basic residues at the C terminus did not lead to a significant reduction in heparin binding, indicating that the main heparin binding site of IP-10 is not along the C-terminal alpha helix. Alanine exchange of Arg-22 had the largest effect on heparin binding, with residues Arg-20, Ile-24, Lys-26, Lys-46, and Lys-47 further contributing to heparin binding. A charge change mutation of Arg-22 resulted in further reduction in heparin binding. The N-terminal residue Arg-8, preceding the first cysteine, was critical for CXCR3 signaling. Mutations of charged and uncharged residues in the loop regions of residues 20-24 and 46-47, which caused reduced heparin binding, also resulted in reduced CXCR3 binding and signaling. CXCR3 expressing GAG-deficient Chinese hamster ovary cells revealed that GAG binding was not required for IP-10 binding and signaling through CXCR3, which suggests that the CXCR3 and heparin binding sites of IP-10 are partially overlapping.

Amino Acid Sequence↗

Detection of a gamma interferon-induced protein IP-10 in psoriatic plaques.

The pathologic features of psoriatic plaques are inflammation and increased epidermal turnover. IP-10, a cytokine the expression of which is induced by gamma-interferon, is a member of a family of soluble mediators with inflammatory and growth-promoting activities. IP-10 protein was detected in keratinocytes and the dermal infiltrate from active psoriatic plaques using an affinity-purified rabbit anti-IP-10 antibody in immunoperoxidase studies. Successful treatment of active plaques decreased IP-10 expression in plaques. These results were corroborated by Northern blot analysis with an IP-10 cDNA probe. We have previously detected activated T cells and HLA-DR keratinocytes in active psoriatic plaques. Since IP-10 is detected in delayed cellular immune responses, the present study further points to the role of ongoing cellular immune responses in the pathogenesis of psoriasis.

Blotting, Northern↗

IP-10, a -C-X-C- chemokine, elicits a potent thymus-dependent antitumor response in vivo.

IP-10 is a member of the -C-X-C-chemokine superfamily of proinflammatory cytokines whose secretion is induced by interferon gamma (IFN-gamma) and lipopolysaccharide (LPS). To date no function has been described for IP-10. We have genetically engineered tumor cells to secrete high levels of murine IP-10 and demonstrate that while IP-10 has no effect on the growth of these tumor cells in culture, it elicits a powerful host-mediated antitumor effect in vivo. The IP-10 antitumor response is T lymphocyte dependent, non-cell autonomous, and appears to be mediated by the recruitment of an inflammatory infiltrate composed of lymphocytes, neutrophils, and monocytes. These results document an important biologic property of IP-10 and raise the possibility that some of the T cell-directed effects of IFN-gamma and LPS may be mediated by this chemokine.

Animals↗

Prostacyclin-IP signaling and prostaglandin E2-EP2/EP4 signaling both mediate joint inflammation in mouse collagen-induced arthritis.

Prostaglandin (PG)I2 (prostacyclin [PGI]) and PGE2 are abundantly present in the synovial fluid of rheumatoid arthritis (RA) patients. Although the role of PGE2 in RA has been well studied, how much PGI2 contributes to RA is little known. To examine this issue, we backcrossed mice lacking the PGI receptor (IP) to the DBA/1J strain and subjected them to collagen-induced arthritis (CIA). IP-deficient (IP-/-) mice exhibited significant reduction in arthritic scores compared with wild-type (WT) mice, despite anti-collagen antibody production and complement activation similar to WT mice. IP-/- mice also showed significant reduction in contents of proinflammatory cytokines, such as interleukin (IL)-6 in arthritic paws. Consistently, the addition of an IP agonist to cultured synovial fibroblasts significantly enhanced IL-6 production and induced expression of other arthritis-related genes. On the other hand, loss or inhibition of each PGE receptor subtype alone did not affect elicitation of inflammation in CIA. However, a partial but significant suppression of CIA was achieved by the combined inhibition of EP2 and EP4. Our results show significant roles of both PGI2-IP and PGE2-EP2/EP4 signaling in the development of CIA, and suggest that inhibition of PGE2 synthesis alone may not be sufficient for suppression of RA symptoms.

Animals↗

Essential role of IPS-1 in innate immune responses against RNA viruses.

IFN-beta promoter stimulator (IPS)-1 was recently identified as an adapter for retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (Mda5), which recognize distinct RNA viruses. Here we show the critical role of IPS-1 in antiviral responses in vivo. IPS-1-deficient mice showed severe defects in both RIG-I- and Mda5-mediated induction of type I interferon and inflammatory cytokines and were susceptible to RNA virus infection. RNA virus-induced interferon regulatory factor-3 and nuclear factor kappaB activation was also impaired in IPS-1-deficient cells. IPS-1, however, was not essential for the responses to either DNA virus or double-stranded B-DNA. Thus, IPS-1 is the sole adapter in both RIG-I and Mda5 signaling that mediates effective responses against a variety of RNA viruses.

Adaptor Proteins, Signal Transducing↗

Increased IFN-gamma protein in bronchoalveolar lavage fluid of anti-IP-10 antibody-treated F344 rats following Sendai viral infection.

A previous study showed that virus-resistant F344 rats had higher levels of interferon-gamma (IFN-gamma)-inducible protein 10 (IP-10) than did virus-susceptible BN rats early after Sendai viral infection. The initial goal of this study was to determine if an early high expression of IP-10 in F344 rats contributes to their resistance to virus-induced airway injury. Infected F344 rats were treated with anti-IP-10 rabbit serum or normal rabbit serum. Results indicated that blocking of IP-10 protein did not significantly change the resistance of F344 rats. However, we observed that neutralization of IP-10 increased IFN-gamma protein in bronchoalveolar lavage (BAL) fluid of F344 rats 7 days after inoculation compared with rats that received normal rabbit serum. The pulmonary IFN-gamma mRNA abundance remained comparable. This effect was not caused by fluctuation of the viral titer in the lung. This interesting phenomenon suggests that expression of IFN-gamma protein can be modulated by treatment with anti-IP-10 antibody at the posttranscriptional or translational level in this model.

Animals↗

Molecular analysis of the genetic defect in a large cohort of IP patients and identification of novel NEMO mutations interfering with NF-kappaB activation.

Incontinentia Pigmenti (IP) is an X-linked genodermatosis that is lethal for males and present in females with abnormal skin pigmentation and high variable clinical signs, including retinal detachment, anodontia, alopecia, nail dystrophy and nervous system defects. The NF-kappaB essential modulator (NEMO) gene, responsible for IP, encodes the regulatory subunit of the IkappaB kinase (IKK) complex required for nuclear factor kappaB (NF-kappaB) activation. We analyzed the NEMO gene in 122 IP patients and identified mutations in 83 (36 familiar and 47 sporadic cases). The recurrent NEMO exon 4-10 deletion that is the major cause of the disease was present in 73 females (59.8%). In addition 10 point alterations (8.2% of females) were identified: three frameshift, three nonsense, three missense and one in-frame deletion of a single amino acid. We measured the effects of these NEMO point-mutations on NF-kappaB signaling in nemo(-/-) deficient murine pre-B cells. A mutation in the N-terminal domain, required for IKK assembly, reduced but did not abolish NF-kappaB activation following lipopolysaccharide stimulation. Mutations that disrupt the C-terminal domain, required for the recruitment of upstream factors, showed lower or no NF-kappaB activation. A phenotype score based on clinical features of our IP patients was applied for summarizing disease severity. The score did not correlate with mutation type or domain affected indicating that other factors influence the severity of IP. Such a factor is likely to be X-inactivation. Indeed, 64% of our patients have extremely skewed X-inactivation pattern (>/=80 : 20). Overall IP pathogenesis thus depends on a combination of X-inactivation and protein domain that recruit upstream factors and activate NF-kappaB.

Animals↗

High intercontinental migration rates and population admixture in the sapstain fungus Ophiostoma ips.

Ophiostoma ips is a common fungal associate of various conifer-infesting bark beetles in their native ranges and has been introduced into non-native pine plantations in the Southern Hemisphere. In this study, we used 10 microsatellite markers to investigate the population biology of O. ips in native (Cuba, France, Morocco and USA) and non-native (Australia, Chile and South Africa) areas to characterize host specificity, reproductive behaviour, and the potential origin as well as patterns of spread of the fungus and its insect vectors. The markers resolved a total of 41 alleles and 75 haplotypes. Higher genetic diversity was found in the native populations than in the introduced populations. Based on the origin of the insect vectors, the populations of O. ips in Australia would be expected to reflect a North American origin, and those in Chile and South Africa to reflect a European origin. However, most alleles observed in the native European population were also found in the native North American population; only the allele frequencies among the populations varied. This admixture made it impossible to confirm the origin of the introduced Southern Hemisphere (SH) populations of O. ips. There was also no evidence for specificity of the fungus to particular bark beetle vectors or hosts. Although O. ips is thought to be mainly self-fertilizing, evidence for recombination was found in the four native populations surveyed. The higher genetic diversity in the North American than in the European population suggests that North America could be the possible source region of O. ips.

Alleles↗

Noninvasive detection of renal allograft inflammation by measurements of mRNA for IP-10 and CXCR3 in urine.

BACKGROUND: We explored the hypothesis that measurements of mRNA encoding interferon-inducible protein-10 (IP-10) or the chemokine receptor CXCR3 in urinary cells offer a noninvasive means of elucidating cellular traffic causing acute rejection of human renal allografts. METHODS: We obtained 63 urine specimens from 58 renal allograft recipients who underwent 63 allograft biopsies to resolve the basis for graft dysfunction, and 27 additional urine samples from 24 other patients with stable allograft function. Twenty-seven of the 63 biopsies were classified as acute rejection, 20 as other, and 16 as chronic allograft nephropathy. We measured the levels of transcripts for IP-10 and CXCR3, and a constitutively expressed gene 18S rRNA in the urine specimens and correlated transcript levels with renal allograft diagnosis. RESULTS: mRNA levels of IP-10 (P < 0.0001) or CXCR3 (P < 0.0001) but not the levels of 18S rRNA (P= 0.56) predicted intragraft cellular traffic causing acute rejection. Receiver-operating characteristic curve analysis demonstrated that acute rejection can be predicted with a sensitivity of 100% and a specificity of 78% using the (log-transformed) cutoff value of 9.11 copies of IP-10, and with a sensitivity of 63% and a specificity of 83% using the cutoff value of 11.59 copies of CXCR3. Immunohistologic analysis of allograft biopsies showed exuberant expression of IP-10 and CXCR3 during acute rejection whereas both were absent in grafts with stable function. CONCLUSION: Our investigation demonstrates that intragraft cellular events associated with acute rejection of human renal allografts can be noninvasively identified by measurements of mRNA for IP-10 and CXCR3 in urinary cells.

Adult↗

TGF-beta-induced Ca(2+) influx involves the type III IP(3) receptor and regulates actin cytoskeleton.

Ca(2+) influx has been postulated to modulate the signaling pathway of transforming growth factor-beta (TGF-beta); however, the underlying mechanism and functional significance of TGF-beta-induced stimulation of Ca(2+) influx are unclear. We show here that TGF-beta stimulates Ca(2+) influx in mesangial cells without Ca(2+) release. The influx of Ca(2+) is prevented by pharmacological inhibitors of inositol 1,4,5-trisphosphate receptors (IP(3)R) as well as specific antibodies to type III IP(3)R (IP(3)RIII) but not to type I IP(3)R (IP(3)RI). TGF-beta enhances plasma membrane localization of IP(3)RIII, whereas the sarcoplasmic-endoplasmic reticulum Ca(2+)-ATPase (SERCA) preferentially translocates to the nucleus. Untreated mesangial cells exhibit actin filamentous protrusions on the cell surface, and treatment with TGF-beta dramatically reduces this pattern. The alterations in the actin cytoskeleton by TGF-beta are dependent on TGF-beta-induced Ca(2+) influx. These studies identify a novel pathway by which TGF-beta regulates Ca(2+) influx and induces cytoskeletal alterations.

Actins↗

Novel biochemical and functional insights into nuclear Ca(2+) transport through IP(3)Rs and RyRs in osteoblasts.

We report the first biochemical and functional characterization of inositol trisphosphate receptors (IP(3)Rs) and ryanodine receptors (RyRs) in the nuclear membrane of bone-forming (MC3T3-E1) osteoblasts. Intact nuclei fluoresced intensely with anti-RyR (Ab(34)) and anti-IP(3)R (Ab(40)) antisera in a typically peripheral nuclear membrane pattern. Isolated nuclear membranes were next subjected to SDS-PAGE and blotted with isoform-specific anti-receptor antisera, notably Ab(40), anti-RyR-1, anti-RyR-2 (Ab(129)), and anti-RyR-3 (Ab(180)). Only anti-RyR-1 and Ab(40) showed bands corresponding, respectively, to full-length RyR-1 ( approximately 500 kDa) and IP(3)R-1 (approximately 250 kDa). Band intensity was reduced by just approximately 20% after brief tryptic proteolysis of intact nuclei; this confirmed that isolated nuclear membranes were mostly free of endoplasmic reticular contaminants. Finally, the nucleoplasmic Ca(2+) concentration ([Ca(2+)](np)) was measured in single nuclei by using fura-dextran. The nuclear envelope was initially loaded with Ca(2+) via Ca(2+)-ATPase activation (1 mM ATP and approximately 100 nM Ca(2+)). Adequate Ca(2+) loading was next confirmed by imaging the nuclear envelope (and nucleoplasm). Exposure of Ca(2+)-loaded nuclei to IP(3) or cADP ribose resulted in a rapid and sustained [Ca(2+)](np) elevation. Taken together, the results provide complementary evidence for nucleoplasmic Ca(2+) influx in osteoblasts through nuclear membrane-resident IP(3)Rs and RyRs. Our findings may conceivably explain the direct regulation of osteoblastic gene expression by hormones that use the IP(3)-Ca(2+) pathway.

3T3 Cells↗