Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0024141 (systemic lupus erythematosus)
 44,322 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Ku (p70/p80) autoantigen consists of two phosphoproteins of molecular mass approximately 70,000 and 80,000 forming a macromolecular complex that binds DNA. Autoantibodies from a patient with systemic lupus erythematosus were used to isolate cDNA clones encoding the human approximately 70-kDa Ku antigen (p70) from a lambda gt11 expression library. The deduced amino acid sequence of p70 consisted of 609 amino acid residues and was confirmed by partial amino acid sequencing. The protein contains two acidic domains of 61 residues (31% Glu + Asp) and 19 residues (53% Glu + Asp) that are similar in size and charge to those found in a number of proteins involved in transcriptional activation. The 61-residue acidic region is rich in serine, raising the possibility that its charge might be modulated by phosphorylation. The predicted amino acid sequence also contains two regions with periodic repeats of either leucine alone, or leucine alternating with serine every seventh position. The latter repeat displays sequence and secondary structural similarities with the "leucine zipper" regions of the c-myc and v-myc oncogene products. The p70 antigen does not appear to have extensive sequence homology with the 80-kDa Ku autoantigen based on analysis of RNA blots and immunological criteria. A major antigenic determinant or determinants recognized by human autoantibodies is located near a leucine repeat on the carboxyl-terminal 190 amino acid residues of p70.
 ...
PMID:Molecular cloning of cDNA encoding the p70 (Ku) lupus autoantigen. 246 42

The Ku autoantigen is a heterodimer of 70- and 80-kD proteins recognized by autoantibodies from patients with systemic lupus erythematosus and related diseases that is the DNA-binding component of a DNA-dependent protein kinase. The catalytic activity of DNA-dependent protein kinase is carried by a 350-kD subunit (p350). In light of the recently described role of Ku in repairing double-strand DNA breaks, we investigated the regulation of Ku and p350 levels in neutrophils, a terminally differentiated cell type destined to undergo apoptosis. Since the appearance of double-strand DNA breaks is characteristic of apoptosis, we were interested in the possibility that Ku might oppose programmed cell death. Analysis of peripheral blood cells by flow cytometry using anti-Ku and anti-p350 monoclonal antibodies revealed that neutrophils were unstained, whereas resting (G0) lymphocytes were positive. The absence of Ku in mature neutrophils was confirmed by Western blotting and enzyme-linked immunosorbent assay for Ku antigen. In contrast, the human promyelocytic leukemia line, HL-60, which undergoes differentiation toward neutrophils after dimethylsulfoxide treatment, was positive for Ku and p350. In view of the short lifespan of neutrophils and the prolonged half-life of Ku and p350 (> 5 d), these data suggested that Ku was actively degraded during myeloid differentiation. Analysis of HL-60 cells by flow cytometry revealed that Ku staining was bimodal. Cells in G1/G0, S, or G2/M were all stained positively, whereas cells with a subdiploid DNA content characteristic of apoptosis were Ku negative. Similar results were obtained with phytohemagglutin-stimulated human lymphocytes. These data suggest that the Ku antigen is actively degraded in both myeloid cells destined to undergo apoptosis and apoptotic lymphocytes, raising the possibility that degradation of Ku may help to prevent the inappropriate repair of fragmented nuclear DNA during apoptosis.
 ...
PMID:Absence of autoantigen Ku in mature human neutrophils and human promyelocytic leukemia line (HL-60) cells and lymphocytes undergoing apoptosis. 775 97

Hypoxia is known to induce extravasation of lymphocytes and leukocytes during ischemic injury and increase the metastatic potential of malignant lymphoid cells. We have recently identified a new adhesion molecule, hypoxia-activated ligand-1/13 (HAL-1/13), that mediates the hypoxia-induced increases in lymphocyte and neutrophil adhesion to endothelium and hypoxia-mediated invasion of endothelial cell monolayers by tumor cells. In this report, we used expression cloning to identify this molecule as the lupus antigen and DNA-dependent protein kinase-associated nuclear protein, Ku80. The HAL-1/13-Ku80 antigen is present on the surface of leukemic and solid tumor cell lines, including T and B lymphomas, myeloid leukemias, neuroblastoma, rhabdomyosarcoma, and breast carcinoma cells. Transfection and ectopic expression of HAL-1/13-Ku80 on (murine) NIH/3T3 fibroblasts confers the ability of these normally nonadhesive cells to bind to a variety of human lymphoid cell lines. This adhesion can be specifically blocked by HAL-1/13 or Ku80-neutralizing antibodies. Loss of expression variants of these transfectants simultaneously lost their adhesive properties toward human lymphoid cells. Hypoxic exposure of tumor cell lines resulted in upregulation of HAL-1/13-Ku80 expression at the cell surface, mediated by redistribution of the antigen from the nucleus. These studies indicate that the HAL-1/13-Ku80 molecule may mediate, in part, the hypoxia-induced adhesion of lymphocytes, leukocytes, and tumor cells.
 ...
PMID:Hypoxia-activated ligand HAL-1/13 is lupus autoantigen Ku80 and mediates lymphoid cell adhesion in vitro. 1124 7

In eukaryotes the non-homologous end-joining repair of double strand breaks in DNA is executed by a series of proteins that bring about the synapsis, preparation and ligation of the broken DNA ends. The mechanism of this process appears to be initiated by the obligate heterodimer (Ku70/Ku86) protein complex Ku that has affinity for DNA ends. Ku then recruits the DNA-dependent protein kinase catalytic subunit (DNA-PKcs). The three-dimensional structures of the major part of the Ku heterodimer, representing the DNA-binding core, both free and bound to DNA are known from X-ray crystallography. However, these structures lack a region of ca 190 residues from the C-terminal region (CTR) of the Ku86 subunit (also known as Lupus Ku autoantigen p86, Ku80, or XRCC5) that includes the extreme C-terminal tail that is reported to be sufficient for DNA-PKcs-binding. We have examined the structural characteristics of the Ku86CTR protein expressed in bacteria. By deletion mutagenesis and heteronuclear NMR spectroscopy we localised a globular domain consisting of residues 592-709. Constructs comprising additional residues either to the N-terminal side (residues 543-709), or the C-terminal side (residues 592-732), which includes the putative DNA-PKcs-binding motif, yielded NMR spectra consistent with these extra regions lacking ordered structure. The three-dimensional solution structure of the core globular domain of the C-terminal region of Ku86 (Ku86CTR(592-709)) has been determined using heteronuclear NMR spectroscopy and dynamical simulated annealing using structural restraints from nuclear Overhauser effect spectroscopy, and scalar and residual dipolar couplings. The polypeptide fold comprises six regions of alpha-helical secondary structure that has an overall superhelical topology remotely homologous to the MIF4G homology domain of the human nuclear cap binding protein 80 kDa subunit and the VHS domain of the Drosophila protein Hrs, though strict analysis of the structures suggests that these domains are not functionally related. Two prominent hydrophobic pockets in the gap between helices alpha2 and alpha4 suggest a potential ligand-binding characteristic for this globular domain.
 ...
PMID:The 3D solution structure of the C-terminal region of Ku86 (Ku86CTR). 1467 64

IL-2 gene expression in activated T-cells is initiated by chromatin remodeling at the IL-2 proximal promoter and conversion of a transcriptional repressor into a potent transcriptional activator. A purine-box regulator complex was purified from activated Jurkat T-cell nuclei based on sequence-specific DNA binding to the antigen receptor response element (ARRE)/nuclear factor of activated T-cells (NF-AT) target DNA sequence in the proximal IL-2 promoter. ARRE DNA-binding subunits were identified as NF90, NF45 and systemic lupus erythematosis autoantigens, Ku80 and Ku70. Monoclonal antibodies to Ku80, Ku70 and NF90 specifically inhibit constitutive and inducible ARRE DNA-binding activity in Jurkat T-cells. Ku80, Ku70 and NF90 bind specifically to the IL-2 gene promoter in vivo, as demonstrated by chromatin immunoprecipitation. Activation of Jurkat T-cells and mouse primary spleen cells induces binding of Ku80 and NF90 to the IL-2 promoter in vivo, and decreases binding of Ku70 to the IL-2 promoter in vivo, and these dynamic changes are inhibited by immunosuppressants cyclosporin A and triptolide. Dynamic changes in binding of Ku80, Ku70 and NF90 to the IL-2 proximal promoter in vivo correlate with chromatin remodeling and transcriptional initiation in activated T-cells.
 ...
PMID:Dynamic binding of Ku80, Ku70 and NF90 to the IL-2 promoter in vivo in activated T-cells. 1738 50

Ku70 (Lupus Ku autoantigen p70) is essential in nonhomologous end joining DNA double-strand break repair, and ku70(-/-) mice age prematurely because of increased genomic instability and DNA damage responses. Previously, we found that Ku70 also inhibits Bax, a key mediator of apoptosis. We hypothesized that Bax-mediated apoptosis would be enhanced in the absence of Ku70 and contribute to premature death observed in ku70(-/-) mice. Here, we show that ku70(-/-) bax(+/-) and ku70(-/-) bax(-/-) mice have better survival, especially in females, than ku70(-/-) mice, even though Bax deficiency did not decrease the incidence of lymphoma observed in a Ku70-null background. Moreover, we found that ku70(-/-) mice develop lung diseases, like emphysema and pulmonary arterial (PA) occlusion, by 3 months of age. These lung abnormalities can trigger secondary health problems such as heart failure that may account for the poor survival of ku70(-/-) mice. Importantly, Bax deficiency appeared to delay the development of emphysema. This study suggests that enhanced Bax activity exacerbates the negative impact of Ku70 deletion. Furthermore, the underlying mechanisms of emphysema and pulmonary hypertension due to PA occlusion are not well understood, and therefore ku70(-/-) and Bax-deficient ku70(-/-) mice may be useful models to study these diseases.
...
PMID:Bax deficiency extends the survival of Ku70 knockout mice that develop lung and heart diseases. 2581 3

Etiology, pathogenesis, and immunology of systemic lupus erythematosus (SLE) form a complex, still undeciphered picture that recently has been further made complicated by a new factor of morbidity: human papillomaviruses (HPVs). Indeed, a prevalence of HPV infections has been reported among SLE patients. Searching for molecular mechanisms that might underlie and explain the relationship between HPV infection and SLE, we explored the hypothesis that immune responses following HPV infection may crossreact with proteins that, when altered, associate with SLE. Analyzing HPV L1 proteins and using Epstein-Barr virus (EBV) and human retrovirus (HERV) as controls, we found a vast peptide overlap with human proteins comprehending lupus Ku autoantigen proteins p86 and p70, lupus brain antigen 1 homolog, lupus antigen expressed in neurons and muscles, natural killer cell IgG-like receptors, complement proteins C4-A and C4-B, complement receptor CD19, and others. The multitude and heterogeneity of peptide overlaps not only further support the hypothesis that crossreactivity can represent a primum movens in SLE onset, but also provide a molecular framework to the concept of SLE as "an autoimmune mosaic syndrome." Finally, once more, it emerges the need of using the principle of peptide uniqueness as a new paradigm for safe and efficacious vaccinology.
 ...
PMID:HPV and systemic lupus erythematosus: a mosaic of potential crossreactions. 2811 7