Biomedical subjects

H Kawasaki

Publications and source records attributed to H Kawasaki.

At least 19 recordsLinked to original sources

PubMed1999

Effective control of Epstein-Barr virus-related hemophagocytic lymphohistiocytosis with immunochemotherapy. Histiocyte Society.

The familial form of hemophagocytic lymphohistiocytosis (HLH) is a lethal disorder. Although the prognosis for Epstein-Barr virus-associated HLH (EBV-HLH) remains uncertain, numerous reports indicate that it can also be fatal in a substantial proportion of cases. We therefore assessed the potential of immunochemotherapy with a core combination of steroids and etoposide to control EBV-HLH in 17 infants and children who met stringent diagnostic criteria for this reactive disorder of the mononuclear phagocyte system. Treatment of life-threatening emergencies was left to the discretion of participating investigators and typically included either intravenous Ig or cyclosporin A (CSA). Five patients (29%) entered complete remission during the induction phase (1 to 2 months), whereas 10 others (57%) required additional treatment to achieve this status. In 2 cases, immunochemotherapy was ineffective, prompting allogeneic bone marrow transplantation. Severe but reversible myelosuppression was a common finding; adverse late sequelae were limited to epileptic activity in one child and chronic EBV infection in 2 others. Fourteen of the 17 patients treated with immunochemotherapy have maintained their complete responses for 4+ to 39+ months (median, 15+ months), suggesting a low probability of disease recurrence. These results provide a new perspective on EBV-HLH, showing effective control (and perhaps cure) of the majority of EBV-HLH cases without bone marrow transplantation, using steroids and etoposide, with or without immunomodulatory agents.

Child↗

PubMed1999

Endogenous calcitonin gene-related peptide suppresses vasoconstriction mediated by adrenergic nerves in rat mesenteric resistance blood vessels.

The role of perivascular calcitonin gene-related peptide (CGRP)-containing nerves in the modulation of adrenergic nerve-mediated vasoconstrictions was studied in the rat perfused mesenteric vascular bed. A frequency-dependent vasoconstriction induced by periarterial nerve stimulation (1-6 Hz) of the bed was significantly potentiated by perfusion of 1 microM CGRP-(8-37) (CGRP receptor antagonist) or to a similar extent after treatment with 500 nM capsaicin. In the preparations treated with capsaicin, CGRP-(8-37) caused a small potentiation of periarterial nerve stimulation-induced vasoconstriction. Exogenous CGRP (0.1-1 nM) concentration-dependently attenuated the augmented vasoconstriction in response to periarterial nerve stimulation after treatment with capsaicin. However, exogenous CGRP (1 nM) did not attenuate the periarterial nerve stimulation-induced vasoconstriction in the bed untreated with capsaicin. These results suggest that endogenous CGRP, which is released from CGRP-containing nerves, suppresses the adrenergic nerve function involved in mechanisms regulating the tone of resistant blood vessels.

Animals↗

PubMed1999

Participation of histamine H1 and H2 receptors in passive cutaneous anaphylaxis-induced scratching behavior in ICR mice.

Scratching behavior associated with passive cutaneous anaphylaxis was examined and compared to that induced by compound 48/80 or histamine in ICR mice. Elicitation of passive cutaneous anaphylaxis, and intradermal injections of compound 48/80, histamine or serotonin induced both scratching behavior and vascular permeability increase in ICR mice. In mast cell-deficient WBB6F1-W/Wv mice, although histamine induced scratching behavior and vascular permeability increase, passive cutaneous anaphylaxis was not observed. Cetirizine and terfenadine significantly inhibited the scratching behavior and vascular permeability increase caused by passive cutaneous anaphylaxis, compound 48/80 and histamine. The histamine H1 receptor antagonists inhibited the vascular permeability increase almost completely, whereas they failed to abolish the scratching behavior. Famotidine and ranitidine significantly inhibited the scratching behavior caused by histamine. The histamine H2 receptor antagonists did not affect the vascular permeability increase caused by histamine. The combination of cetirizine and ranitidine abolished the histamine-induced scratching behavior. The combination, however, failed to potentiate the inhibition of passive cutaneous anaphylaxis-induced scratching behavior significantly. The results indicated that histamine induces scratching behavior in ICR mice through both histamine H1 and H2 receptors, and that histamine plays a major role in passive cutaneous anaphylaxis-induced scratching behavior. Histamine might also play an important role in compound 48/80-induced scratching behavior.

Animals↗

PubMed1999

CC chemokine receptors, CCR-1 and CCR-3, are potentially involved in antigen-presenting cell function of human peripheral blood monocyte-derived dendritic cells.

We examined the potential involvement of two CC chemokine receptors (CCRs), CCR-1 and CCR-3, in the functional activation of granulocyte-macrophage colony-stimulating factor (GM-CSF) plus interleukin-4 (IL-4)-generated human peripheral blood monocyte-derived immature dendritic cells (DCs). Flow cytometric analysis showed that CCR-1, CCR-3, CCR-5, and CXC chemokine receptor (CXCR)-4 were expressed on the cell surface of monocyte-derived DCs. Treatment with a monoclonal antibody (MoAb) to either CCR-1 or CCR-3 but not MoAbs to CCR-5 and CXCR-4 abolished chemotactic migration of monocyte-derived DCs. The DCs treated with either the anti-CCR-1 MoAb or anti-CCR-3 MoAb were less efficient than untreated DCs in proliferation of allogeneic T cells (TCs) and TC-derived secretion of interferon-gamma (IFN-gamma). The homotypic aggregation of DCs and heterotypic aggregation of DCs with TCs were suppressed by the anti-CCR-1 MoAb or anti-CCR-3 MoAb. These results indicate that CCR-1 and CCR-3 specifically regulate interaction of TCs and DCs in the process of antigen presentation.

Antibodies, Monoclonal↗

PubMed1999

Serum matrix metalloproteinase-1 in patients with chronic viral hepatitis.

BACKGROUND AND AIMS: Previously we found that serum matrix metalloproteinase (MMP)-1 activity decreased with progression of chronic liver disease. Our objectives in the present study were to observe the change in the serum MMP-1 protein concentration using recently developed specific enzyme immunoassays for MMP-1 and MMP-1 complexed with tissue inhibitor of metalloproteinases (TIMP)-1 and to elucidate the clinical usefulness of the serum MMP-1 test in chronic viral hepatitis. We measured the serum concentrations of MMP-1 and MMP-1/TIMP-1 complex using these immunoassays in 64 patients with histologically characterized chronic viral hepatitis. RESULTS: Serum MMP-1 concentration was inversely related to the histological severity of chronic hepatitis (P< 0.0001). It was closely associated with the histological degree of periportal necrosis (P< 0.0001), intralobular necrosis (P< 0.005), portal inflammation (P<0.0001) and liver fibrosis (P< 0.05). The serum concentration of MMP-1/TIMP-1 complex was also related to the histological severity of chronic hepatitis (P< 0.0001). It was associated with the degree of portal inflammation (P< 0.05), but not with the degree of periportal necrosis, intralobular necrosis or liver fibrosis. As serum MMP-1 level was closely associated with the histological degree of necroinflammation, we examined the ability of the serum MMP-1 test to differentiate active and inactive forms of hepatitis with a receiver operating curve. The results were compared with those of serum procollagen type III N-peptide (PIIINP) test. We found that the serum MMP-1 test was superior to the serum PIIINP test in assessing liver necroinflammation. CONCLUSIONS: In addition to the previously reported changes in enzyme activity, MMP-1 proteins in serum decreased during histological progression of chronic hepatitis. The serum MMP-1 test may be useful clinically to differentiate active and inactive types of hepatitis in patients with chronic viral hepatitis.

Biomarkers↗

PubMed1999

Inhibition of hepatocellular carcinoma by glycyrrhizin in diethylnitrosamine-treated mice.

Glycyrrhizin (GL) is widely used in Japan as a therapeutic agent for chronic active liver diseases. However, its action on hepatocarcinogenesis remains to be elucidated. To clarify its effect, mice treated with diethylnitrosamine (NDEA) with or without GL were analyzed. Five-week-old male BALB/c mice were divided into two groups, GL (n=50) and C (n=47). Mice in the GL group intramuscularly received 2 mg of GL 3 days a week, and mice in the C group received the same volume of saline in the same way. After 2 weeks, the mice were treated with an i.p. injection of 75 mg/kg body wt of NDEA weekly for 3 weeks and 100 mg/kg body wt of NDEA weekly for the following 3 weeks. Thirty additional mice that did not receive NDEA treatment were divided into two groups, GC (n=15) and SC (n=15). They received GL or saline, respectively. Mice in the 4 groups were killed every 5 weeks after the last injection of NDEA from 7 weeks to 32 weeks. Liver function tests such as AST and albumin were significantly improved in the GL group compared with the C group (P < 0.05, each). Although liver nodules appeared in the C group at 22 weeks, they were not observed until 32 weeks in the GL group. At 32 weeks, the mean number of liver tumors, composed of adenoma and hepatocellular carcinoma (HCC), in the GL group was 0.71, which was significantly decreased compared with 1.64 of the C group (P < 0.05). The mean number of HCC in the GL group was 0.29/liver, which was lower than 0.82/liver in the C group (P < 0.05). The incidence rate of HCC at 32 weeks was 64% in the C group and 21% in the GL group (P < 0.05, C versus GL group). Our results suggest that GL treatment inhibits the occurrence of HCC.

Adenoma↗

PubMed1998

Contribution of GABA(A)-mediated conductances to anoxia-induced depolarization.

CA1 pyramids were studied intracellularly in rat hippocampal slices to establish the contribution of excitatory amino acid (EAA) and GABA(A) receptors to the depolarizations induced by brief (< 10 min) anoxic episodes. An increase of the amplitude of the depolarizations evoked by successive anoxic episodes occurred with KCl (n=4 cells), not with K-acetate-filled (n=3) recording electrodes. Moreover, with K-acetate-filled electrodes the anoxic depolarization amplitude was reduced, but not abolished by EAA receptor antagonists (n=14). The residual anoxic depolarizations were blocked by a GABA(A) receptor antagonist (n=5) and decreased by the carbonic anhydrase inhibitor acetazolamide (n=4). We conclude that the anoxic depolarizations generated by CA1 pyramids are caused by the activation of EAA along with GABA(A) receptors leading to an increased membrane conductance to both Cl- and HCO3-.

Animals↗

PubMed1998

A family of cAMP-binding proteins that directly activate Rap1.

cAMP (3',5' cyclic adenosine monophosphate) is a second messenger that in eukaryotic cells induces physiological responses ranging from growth, differentiation, and gene expression to secretion and neurotransmission. Most of these effects have been attributed to the binding of cAMP to cAMP-dependent protein kinase A (PKA). Here, a family of cAMP-binding proteins that are differentially distributed in the mammalian brain and body organs and that exhibit both cAMP-binding and guanine nucleotide exchange factor (GEF) domains is reported. These cAMP-regulated GEFs (cAMP-GEFs) bind cAMP and selectively activate the Ras superfamily guanine nucleotide binding protein Rap1A in a cAMP-dependent but PKA-independent manner. Our findings suggest the need to reformulate concepts of cAMP-mediated signaling to include direct coupling to Ras superfamily signaling.

1-Methyl-3-isobutylxanthine↗

PubMed1998

Reaction mechanism of fluoroacetate dehalogenase from Moraxella sp. B.

Fluoroacetate dehalogenase (EC 3.8.1.3) catalyzes the dehalogenation of fluoroacetate and other haloacetates. The amino acid sequence of fluoroacetate dehalogenase from Moraxella sp. B is similar to that of haloalkane dehalogenase (EC 3.8.1.5) from Xanthobacter autotrophicus GJ10 in the regions around Asp-105 and His-272, which correspond to the active site nucleophile Asp-124 and the base catalyst His-289 of the haloalkane dehalogenase, respectively (Krooshof, G. H., Kwant, E. M., Damborský, J., Koca, J., and Janssen, D. B. (1997) Biochemistry 36, 9571-9580). After multiple turnovers of the fluoroacetate dehalogenase reaction in H218O, the enzyme was digested with trypsin, and the molecular masses of the peptide fragments formed were measured by ion-spray mass spectrometry. Two 18O atoms were shown to be incorporated into the octapeptide, Phe-99-Arg-106. Tandem mass spectrometric analysis of this peptide revealed that Asp-105 was labeled with two 18O atoms. These results indicate that Asp-105 acts as a nucleophile to attack the alpha-carbon of the substrate, leading to the formation of an ester intermediate, which is subsequently hydrolyzed by the nucleophilic attack of a water molecule on the carbonyl carbon atom. A His-272 --> Asn mutant (H272N) showed no activity with either fluoroacetate or chloroacetate. However, ion-spray mass spectrometry revealed that the H272N mutant enzyme was covalently alkylated with the substrate. The reaction of the H272N mutant enzyme with [14C]chloroacetate also showed the incorporation of radioactivity into the enzyme. These results suggest that His-272 probably acts as a base catalyst for the hydrolysis of the covalent ester intermediate.

Acetates↗

PubMed1998

Inhibition of apoptosis by survivin predicts shorter survival rates in colorectal cancer.

Deregulated inhibition of apoptosis (programmed cell death) may facilitate the insurgence of neoplasia, but whether it also influences the outcome of common cancers has remained controversial. In this study, we investigated the expression of a novel inhibitor of apoptosis, survivin, in colorectal cancer and its relationship with tumor cell apoptosis and overall prognosis. By immunohistochemistry, survivin was expressed in 91 of 171 (53.2%) cases of colorectal carcinomas of histological stages 0 to IV. In contrast, normal colon epithelium did not express survivin. Although survivin expression did not correlate with p53 abnormalities (46.5% versus 58.0%; P = 0.18), survivin-positive cases were strongly associated with bcl-2 expression (72.5% versus 27.4%; P < 0.0001) and reduced apoptotic index (0.76% +/- 0.39% versus 1.17% +/- 0.62%; P < 0.0001). Expression of survivin alone in bcl-2-negative (discordant) cases also resulted in reduced apoptotic index (0.82% +/- 0.57% versus 1.16% +/- 0.66%; P = 0.0046). When analyzed for prognostic significance, patients with low apoptotic index (< 0.97%) had worse survival rates than the group with high apoptosis (P < 0.001), and a multivariate Cox proportional hazard model identified reduced apoptosis as an independent predictive factor for overall survival (P < 0.0001). These data demonstrate that apoptosis inhibition by survivin, alone or in cooperation with bcl-2, is an important predictive/prognostic parameter of poor outcome in colorectal carcinoma and identify survivin as a new diagnostic/therapeutic target in cancer.

Adult↗

PubMed1998

Molecular characterization of guanosine kinase gene from a facultative alkalophile, Exiguobacterium aurantiacum ATCC 35652.

Guanosine kinase activity was identified in an alkalophile, Exiguobacterium aurantiacum ATCC 35652, and the gsk gene encoding it was isolated as a homologous fragment of the Brevibacterium acetylicum gsk. The cloned chromosomal fragment contained an open reading frame which encodes a polypeptide of 308 amino acids with a molecular mass of 33349 Da. The Ex. aurantiacum Gsk shows strong sequence similarity to B. acetylicum Gsk, but possesses five additional amino acids at the C-terminus. An Mr 39200 protein synthesized in Escherichia coli harboring plasmids carrying Ex. aurantiacum gsk was purified and characterized. A 0.9 kb transcript revealed by Northern blot analysis and the presence of a factor-independent terminator structure suggest that Ex. aurantiacum gsk is monocistronic, although B. acetylicum gsk has been shown to be bicistronic. The striking alterations in the 3'-untranslated region resulted in a different gene organization.

Amino Acid Sequence↗

PubMed1998

Purification of native p94, a muscle-specific calpain, and characterization of its autolysis.

p94, a skeletal muscle-specific calpain, has attracted much attention because its gene is responsible for limb-girdle muscular dystrophy type 2A. p94, however, has not been characterized at the protein and enzyme levels, owing to its very rapid autolysis. In the present study, a purification procedure for p94 was first established by using a recombinant inactive p94 expressed in COS cells in which the active site cysteine residue was changed to serine [p94(C129S)]. The isolation of native p94 from rabbit skeletal muscle by the established method with conventional procedures was extremely difficult because p94 became highly unstable in a crude extract on the addition of NaCl for separation. Purification of native p94 was possible with an antibody-affinity column but only as an inactive enzyme; p94(C129S) was purified as a homodimer. Characterization of p94, especially autolysis, was performed with partly purified native p94 and p94(C129S). The autolysis of p94, which consisted at least partly of an intermolecular reaction, proceeded in three consecutive steps; 60 and 58 kDa fragments were produced as intermediates before a stable 55 kDa fragment appeared. Autolysis of p94 was regarded as a degradative step rather than for the activation of the enzyme. All the autolysis cleavage sites were located in the p94-specific insertion sequence 1 region, which explains why p94 is unstable compared with the other calpains. The autolysis sites in p94 clearly showed a different specificity relative to the autolytic and proteolytic cleavage sites of the ubiquitous mu- and m-calpains, in its preference for residues at the P3 to P1' sites, indicating a distinct substrate specificity and function for the muscle enzyme.

Amino Acid Sequence↗

PubMed1998

A Rap guanine nucleotide exchange factor enriched highly in the basal ganglia.

Ras proteins, key regulators of growth, differentiation, and malignant transformation, recently have been implicated in synaptic function and region-specific learning and memory functions in the brain. Rap proteins, members of the Ras small G protein superfamily, can inhibit Ras signaling through the Ras/Raf-1/mitogen-activated protein (MAP) kinase pathway or, through B-Raf, can activate MAP kinase. Rap and Ras proteins both can be activated through guanine nucleotide exchange factors (GEFs). Many Ras GEFs, but to date only one Rap GEF, have been identified. We now report the cloning of a brain-enriched gene, CalDAG-GEFI, which has substrate specificity for Rap1A, dual binding domains for calcium (Ca2+) and diacylglycerol (DAG), and enriched expression in brain basal ganglia pathways and their axon-terminal regions. Expression of CalDAG-GEFI activates Rap1A and inhibits Ras-dependent activation of the Erk/MAP kinase cascade in 293T cells. Ca2+ ionophore and phorbol ester strongly and additively enhance this Rap1A activation. By contrast, CalDAG-GEFII, a second CalDAG-GEF family member that we cloned and found identical to RasGRP [Ebinu, J. O., Bottorff, D. A., Chan, E. Y. W., Stang, S. L., Dunn, R. J. & Stone, J. C. (1998) Science 280, 1082-1088], exhibits a different brain expression pattern and fails to activate Rap1A, but activates H-Ras, R-Ras, and the Erk/MAP kinase cascade under Ca2+ and DAG modulation. We propose that CalDAG-GEF proteins have a critical neuronal function in determining the relative activation of Ras and Rap1 signaling induced by Ca2+ and DAG mobilization. The expression of CalDAG-GEFI and CalDAG-GEFII in hematopoietic organs suggests that such control may have broad significance in Ras/Rap regulation of normal and malignant states.

Amino Acid Sequence↗

PubMed1998

Multiple actions of the novel anticonvulsant drug topiramate in the rat subiculum in vitro.

We used an in vitro slice preparation to study whether and how the anticonvulsant drug topiramate (TPM, 50-500 microM) modulates the excitability of rat subicular neurons that generate action potential bursts mainly caused by voltage-dependent, Na+-electrogenesis. Subiculum is a gating structure for outputs originating from the hippocampus proper, and thus it may play a role in limbic seizures. In 28/45 neurons, TPM induced a steady hyperpolarization of the resting membrane potential (RMP) that ranged between -2 and -16 mV and was associated with a 24-62% decrease of the apparent membrane input resistance. TPM also depressed the ability of these cells to generate action potential bursts in response to brief (5-150 ms) depolarizing pulses; such an effect was characterized by an increase in the amount of intracellular depolarizing current required for eliciting action potential bursts, and it also occurred when the TPM-induced steady hyperpolarization was compensated by injecting steady depolarizing current. In addition TPM reduced by approx. 50% the regular action potential firing elicited by prolonged (350-1000 ms) depolarizing pulses (n=15 of 27 neurons). Recovery of the TPM-induced changes was not seen during washout for periods of 20-80 min (n=7). Both the steady hyperpolarization of the RMP and the input resistance decrease elicited by TPM were markedly reduced by the GABAA receptor antagonists bicuculline methiodide (10 microM; n=6) or picrotoxin (100 microM; n=2); such an effect was associated with a reduction, but not with blockade of the depressant action exerted by TPM on burst generation. Our findings indicate that TPM reduces subicular cell excitability, and modifies bursting ability and repetitive firing properties. These effects may be ascribed to actions on voltage-gated, Na+ electrogenesis and GABAA receptors. We propose that these changes in excitability may all contribute to the anticonvulsant action of TPM in limbic seizures that occur in temporal lobe epilepsy patients.

Action Potentials↗

PubMed1998

Aberrant expression of double-stranded RNA-dependent protein kinase in hepatocytes of chronic hepatitis and differentiated hepatocellular carcinoma.

We immunohistochemically analyzed the expression of double-stranded RNA-dependent protein kinase (PKR) using a monoclonal antibody, 71/10. Test samples included 64 human liver biopsies and 25 liver sections of rats inoculated with diethylnitrosamine. The PKR signals in human fatty livers and normal rat livers were minimum. Scoring signal intensity from 0-4, the average scores of chronic active (14 cases) and chronic persistent (6 cases) hepatitis associated with hepatitis virus C (HCV) were 2.8 and 2.0, respectively (P = 0.038). The stained cells were significantly more abundant in the periportal than centrilobular regions for both chronic active and persistent hepatitis (P < 0.001 each). The average score of liver cirrhosis associated with HCV was 1.9. Those scores of well-, moderately, and poorly differentiated hepatocellular carcinomas associated with HCV were 3.4, 2.1, and 0.3, respectively (P < 0.001 for each pair). Those scores of well- and poorly differentiated carcinomas associated with hepatitis virus B were 2.3 and 0.0, respectively (P < 0.001). The average score of rat carcinomas induced by diethylnitrosamine was 1.9. Morphologically, nuclei of the vast majority of PKR-positive cells looked not apoptotic. The ratio of PKR-positive cells to apoptotic cells by terminal transferase-mediated dUTP nick end labeling method was approximately 20 in hepatitis, and over 100 in well-differentiated carcinoma.

Animals↗

PubMed1998

High susceptibility of p53(+/-) knockout mice in N-butyl-N-(4-hydroxybutyl)nitrosamine urinary bladder carcinogenesis and lack of frequent mutation in residual allele.

The loss of p53 functions is considered to compromise the growth-suppression machinery of the cell and facilitate neoplastic change. In humans, genetic alteration in the p53 gene is one of the most frequently observed molecular changes in tumors, including urinary bladder carcinomas. We have investigated the susceptibility of heterozygote p53 knockout mice to N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) in terms of urinary bladder tumor induction. Both p53(+/-) knockout mice and C57BL/6 original parent strain were administered 0, 0.002, 0.004, 0.0075 and 0.025% BBN in the drinking water for 20 weeks. As compared with the C57BL/6 strain, greater lesion yields were observed in knockout mice after 20 weeks of treatment. Transitional cell carcinomas were found in 9 (75%) and 12 (100%) of each 12 mice of the 0.0075 and 0.025% BBN treatment groups, respectively, whereas only 1 (11%) and 6 (67%) of each 9 of the C57BL/6 mice demonstrated tumors. Preneoplastic lesions (dysplasia) were also observed more frequently in the lower dose groups in the knockout mice than C57BL/6 mice. PCR single-strand conformation polymorphism analysis followed by DNA direct sequencing of the p53 gene (exons 5-8) extracted from bladder tumors demonstrated mutations in 3 of 11 (27.3%; exon 7) and 8 of 29 (27.6%; exons 5-8) tumors in C57BL/6 and knockout mice, respectively. There was no significant difference in the mutation rates at the residual p53 gene between the two cases. All mutations observed in knockout mice were restricted to the normal allele, and none were present in the gene-targeted null allele. In a separate experiment, 5-bromo-2'-deoxyuridine labeling indices after treatment with BBN for 2 or 4 weeks were significantly higher in knockout mice than wild-type mice. Measurement of the urinary concentration of N-butyl-N-(3-carboxypropyl)nitrosamine, a proximate carcinogenic metabolite, revealed no significant differences between knockout and original parent strain after administration of 0.0075% BBN in the drinking water for 4 weeks. In conclusion, knockout mice are distinctly more sensitive to urinary bladder carcinogenesis induced by BBN than their original parent strain, as evidenced by elevated DNA synthesis during carcinogen administration and an increased tumor yield. The high susceptibility of p53 knockout mice appeared to be related to the high level of cell proliferation rather than that of N-butyl-N-(3-carboxypropyl)nitrosamine in the urine or that of mutations at the p53 gene.

Alleles↗

PubMed1998

A new NEDD8-ligating system for cullin-4A.

NEDD8 is a ubiquitin (Ub)-like protein. Here we report a novel ubiquitinylation-related pathway for modification by NEDD8. NEDD8 was activated by an E1 (Ub-activating enzyme)-like complex, consisting of APP-BP1 and hUba3 with high respective homologies to the amino- and carboxy-terminal regions of E1 and then linked to hUbc12 (a human homolog of yeast Ub-conjugating enzyme Ubc12p). The major target protein modified by NEDD8 was found to be Hs-cullin-4A (Cul-4A), a member of the family of human cullin/Cdc53 proteins functioning as an essential component of a multifunctional Ub-protein ligase E3 complex that has a critical role in Ub-mediated proteolysis.

Amino Acid Sequence↗

PubMed1998

Interleukin-12 induces tyrosine phosphorylation of an 85-kDa protein associated with the interleukin-12 receptor beta 1 subunit.

Interleukin-12 (IL12) is a heterodimeric cytokine composed of p35 and p40 subunits and having multiple immunomodulatory effects on T cells as well as on natural killer cells. Two subunits, beta 1 and beta 2, consisting of the functional IL12 receptor complex, have been recently identified as members of the hemopoietin receptor superfamily, bearing strong homology to gp130. In the present study, we attempted to further characterize the biochemical nature of the IL12 receptor complex and to delineate IL12-triggered signal transduction pathways. To this end, we established a Jurkat transfectant (JIL12R beta 1t) highly expressing the recombinant human IL12 receptor beta 1 subunit. Using this transfectant, we identified an 85-kDa protein (p85) which is associated with the beta 1 subunit and appears to be a cell surface protein, but is distinct from the beta 2 subunit (130 kDa). p85 was also detected in PHA-activated T cells. Importantly, p85 was rapidly tyrosine phosphorylated upon stimulation of both JIL12R beta 1t cells and PHA-activated T cells with IL12. These results suggest that p85 is a component of the IL12 receptor complex and may play a significant role in mediating IL12-dependent signals.

Animals↗