A microscale method for depleting cross-reactive anti-antibodies used in indirect immunofluorescence microscopy.
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Animals↗
Biomedical subjects
E K Chan
Publications and source records attributed to E K Chan.
Structure, expression and chromosomal localization of human p80-coilin gene.
Coiled bodies (CBs) are non-capsular nuclear bodies with a diameter of 0.3-1 micron and appear to be composed of coiled fibrils. Human autoantibodies to CBs recognize an 80-kD nuclear protein highly enriched in CBs, and this protein has been named p80-coilin. CBs are known to assemble and disassemble during the cell cycle, with the highest number of CBs occurring at mid to late G1 where p80-coilin is assembled into several small nuclear body-like structures. In S and G2 phases, CBs become larger and their number decreases and often they are undetectable during mitosis. Using a human autoantibody as a probe for expression cloning, we initially isolated a partial cDNA encoding p80-coilin. In this report, the 5' end of the complete cDNA for p80-coilin was obtained using the 5'-RACE (rapid amplification of cDNA ends) methodology. The size of the reconstructed full-length cDNA corresponds to the 2.7-kb mRNA detected in Northern blot analysis. The complete p80-coilin protein consists of 576 amino acids with a predicted molecular mass of 62,608. A putative p80-coilin pseudogene was also detected during the rescreening of p80-coilin cDNA. To confirm the validity of the cDNA sequence, three overlapping genomic DNA clones representing the human p80-coilin gene were selected for further analysis. The complete gene for p80-coilin contains 7 exons spanning approximately 25kb. Sequence analysis of exons 1 and 2 in genomic DNA clones confirmed the accuracy of the 5' cDNA sequence derived from the 5'-RACE procedure. Furthermore, the human p80-coilin gene was localized to chromosome 17q22-23 by fluorescence in situ hybridization.
Amino Acid Sequence↗
Human 60-kDa SS-A/Ro ribonucleoprotein autoantigen gene (SSA2) localized to 1q31 by fluorescence in situ hybridization.
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Autoantigens↗
Autoantibody responses to the "native" 52-kDa SS-A/Ro protein in neonatal lupus syndromes, systemic lupus erythematosus, and Sjogren's syndrome.
Abs to the 52-kDa SS-A/Ro protein are found in high prevalence in patients with Sjogren's syndrome (SS) and mothers whose children have the neonatal lupus syndrome (NLS). This study further defines the specificity of this response. By ELISA, 97% of 59 mothers of offspring with NLS had Abs to the 52-kDa recombinant protein compared with 80% in 132 non-NLS sera with anti-SS-A/Ro Abs (p < 0.004). Antigenic regions on the 52-kDa protein were evaluated by immunoprecipitation of [35S]-radiolabeled in vitro translation products. Ninety-five percent of 99 sera that contained anti-52-kDa Abs by ELISA reacted with a large fragment spanning amino acids (aa) 1-291. Two antigenic regions were identified, aa169-291 containing the leucine zipper that was recognized by 83% of the anti-52-kDa sera tested and aa1-78 containing the zinc finger domains that was recognized by only half the sera. No sera immunoprecipitated this N-terminal fragment exclusively. Recognition of one or both regions was not unique to any clinical subset of patients; however, a greater number of sera from patients with SS contained both specificities, whereas asymptomatic mothers whose children had NLS comprised the only clinical group in which the majority recognized the central region of the molecule. Reactivity with both epitopes was demonstrated significantly more often in sera with high titers of Abs to the 60-kDa rSS-A/Ro protein by ELISA in association with the anti-52-kDa response compared with anti-52-kDa responses associated with low titers of anti-60-kDa Abs (p < 0.04). Eighty-one percent of 16 sera that recognized the N-terminal epitope were from patients with the combination of HLA-DRB1*0301, DQA1*0501, and DQB1*0201 alleles, compared with 30% of 10 that recognized only the central epitope (p < 0.02). In summary, this study demonstrates that there are at least two antigenic determinants on the 52-kDa SS-A/Ro protein, one "immunodominant" and the other recognized by a more "restricted" subset of anti-52-kDa SS-A/Ro Abs.
Autoantibodies↗
Is the coiled body involved in nucleolar functions?
Coiled bodies (CBs) are structural constituents observed in nuclei of most eukaryotic cells. They usually occur in the nucleoplasm as well as in contact with the nucleolar surface. In this work we studied the hepatocyte nuclei of hibernating dormice in order to investigate possible modifications of CBs along the seasonal cycle. CBs were abundant during hibernation and rapidly disappeared upon arousal from hibernation. Moreover, CBs were frequently found to be integrated into the nucleolar body. Immunocytochemical analyses showed that CBs contain nucleoplasmic as well as nucleolar RNA-processing factors, suggesting an "ambiguous" role for this organelle in the nuclear functions.
Animals↗
Immunocytochemical characterization of human NOR-90 (upstream binding factor) and associated antigens reactive with autoimmune sera. Two MR forms of NOR-90/hUBF autoantigens.
The 90-kDa nucleolus organizer region autoantigen (NOR-90) was previously shown to be identical to the human upstream binding factor (hUBF) and composed of two Mr forms. In this study, thirteen human anti-NOR-90/hUBF autoimmune sera were used to further characterize NOR-90/hUBF and its associated autoantigens. Nucleolar and nucleoplasmic staining of interphase cells and NOR staining in mitosis were observed with all sera by immunofluorescence. All sera showed equal reactivity with both high and low Mr forms in Western blotting and immunoprecipitation, suggesting that the cellular content and distribution for both Mr forms were approximately equal. Using extracts of [35S]methionine- and [32P]orthophosphate-labeled cells, phosphorylated and nonphosphorylated NOR-90/hUBF were identified for both Mr forms and these two populations were recognized by human autoantibodies. In immunoprecipitation analyses, the nonphosphorylated population was readily extracted while the phosphorylated population was tightly bound. Clinical data were available for 8 patients in whom anti-NOR-90/hUBF autoantibodies were present. They had diverse diagnoses including SLE, rheumatoid arthritis and malignancies. Although only one patient was diagnosed as scleroderma, Raynaud's phenomenon was observed in 4 of the 8 patients. Interestingly, one NOR-90/hUBF serum was shown to contain additional antibodies to RNA polymerases I and II.
Adult↗
Isolation and function of human and pig islets.
This report confirms reproducible methods to isolate and assess viability and function of pig and human islets. We processed 10 pig and five human pancreata. The pancreata were digested by a modification of Ricordi's automated method for islet isolation. The number of islet equivalents (150 microns diameter islets) was 335,190 +/- 79,345 islets per pig pancreas (5,146 +/- 1,274 islets/g pig pancreas) and 323,630 +/- 147,810 per human pancreas (6,252 +/- 2,572 islets/g human pancreas). The majority of islets were in the range of 50-200 microns diameter, and 20% of the islet population had a size distribution of 200 microns diameter in both porcine and human models. The purity of the final preparations exceeded 90%. The secretory response of perifused islets showed a biphasic insulin release pattern in both species. Perifused fresh pig islets released 2.5 pmol/L islet-1 min-1 at 2.0 mM glucose and 6.2 pmol/L islet-1 min-1 at 16.7 mM glucose. After 7 days culture at 37 degrees C, human islets released 1.32 pmol/L islet-1 min-1 at 2.0 mM and 12.24 pmol/L islet-1 min-1 at 16.7 mM. These results indicate that this procedure is useful to obtain pure, large, and functional islets from pig and human pancreata.
Adult↗
Relationship between maternal and neonatal levels of antibodies to 48 kDa SSB(La), 52 kDa SSA(Ro), and 60 kDa SSA(Ro) in pregnancies complicated by congenital heart block.
OBJECTIVE: Since there is suggestive but, to date, indirect evidence that maternal anti-SSA(Ro) and SSB(La) antibodies are pathogenic in congenital heart block (CHB), we explored the hypothesis that binding to fetal tissues would result in selective depletion of autoantibodies from the neonatal circulation. METHODS: Maternal and umbilical cord levels of anti-48 kDa SSB(La), anti-52 kDa SSA(Ro) and anti-60 kDa SSA(Ro) antibodies were measured by ELISA and immunoprecipitation at parturition in 15 pregnancies complicated by CHB. A control group consisted of 13 pregnancies in which the mother was known to have antibodies to either SSA(Ro) and/or SSB(La) and the children did not have CHB. RESULTS: The ratios of maternal to cord serum levels of anti-48 SSB(La), anti-52 SSA(Ro) and anti-60 kDa SSA(Ro) antibodies ranged from 0.71 to 2.38 in both affected and unaffected pregnancies. The mean ratio obtained for each of the 3 autoantibodies was not significantly different between the 2 groups. Moreover these ratios did not significantly differ from the mean ratios obtained for total IgG levels in either group. CONCLUSION: These data demonstrate that maternal antibodies to all components of the SSA(Ro) SSB(La) system are efficiently transported across the placenta and are not selectively depleted in the circulation of neonates with CHB.
Antibodies, Antinuclear↗
Cytochemical and immunocytochemical characterization of nuclear bodies during hibernation.
Brown adipose tissue and liver of hibernating, arousing and euthermic individuals of the dormouse Muscardinus avellanarius were studies using ultrastructural cytochemistry and immunocytochemistry with the aim to investigate possible fine structural modifications of the cell nucleus during the seasonal cycle. The general morphology of brown adipocyte and hepatocyte nuclei was similar in the three experimental groups. However, three nuclear structural constituents were identified only in hibernating individuals: coiled bodies (CBs) and amorphous bodies (ABs) were observed in hepatocytes and, together with bundles of nucleoplasmic fibrils (NF), were present in brown adipocytes of hibernating dormice. In arousing animals only some structural constituents suggestive of poorly structured CBs were found. The latter showed the same immunocytochemical features as CBs of hibernating individuals, suggesting that they are disappearing CBs. A possible involvement of CBs in storing and/or processing RNA which must be rapidly and abundantly released upon arousal is discussed. ABs similarly to CBs contain RNA and nucleoplasmic ribonucleoproteins (RNPs) and could also be involved in mRNA pathways. NF do not contain nucleic acids or RNPs and seem to be composed of protein-aceous material; their functional role in the nuclear metabolism of hibernating brown adipocytes remains unclear.
Adipocytes↗
Transient negative effect of dithizone on dynamic insulin secretion of isolated islets in SA rats.
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Animals↗
Molecular characterization of two human autoantigens: unique cDNAs encoding 95- and 160-kD proteins of a putative family in the Golgi complex.
Serum autoantibodies from a patient with autoantibodies directed against the Golgi complex were used to screen clones from a HepG2 lambda Zap cDNA library. Three related clones, designated SY2, SY10, and SY11, encoding two distinct polypeptides were purified for further analysis. Antibodies affinity purified by adsorption to the lambda Zap-cloned recombinant proteins and antibodies from NZW rabbits immunized with purified recombinant proteins reproduced Golgi staining and bound two different proteins, 95 and 160 kD, from whole cell extracts. The SY11 protein was provisionally named golgin-95 and the SY2/SY10 protein was named golgin-160. The deduced amino acid sequence of the cDNA clone of SY2 and SY11 represented 58.7- and 70-kD proteins of 568 and 620 amino acids. The in vitro translation products of SY2 and SY11 cDNAs migrated in SDS-PAGE at 65 and 95 kD, respectively. The in vitro translated proteins were immunoprecipitated by human anti-Golgi serum or immune rabbit serum, but not by normal human serum or preimmune rabbit serum. Features of the cDNA suggested that SY11 was a full-length clone encoding golgin-95 but SY2 and SY10 together encoded a partial sequence of golgin-160. Analysis of the SY11 recombinant protein identified a leucine zipper spanning positions 419-455, a glutamic acid-rich tract spanning positions 322-333, and a proline-rich tract spanning positions 67-73. A search of the SwissProt data bank indicated sequence similarity of SY11 to human restin, the heavy chain of kinesin, and the heavy chain of myosin. SY2 shared sequence similarity with the heavy chain of myosin, the USO1 transport protein from yeast, and the 150-kD cytoplasmic dynein-associated polypeptide. Sequence analysis demonstrated that golgin-95 and golgin-160 share 43% sequence similarity and, therefore, may be functionally related proteins.
Amino Acid Sequence↗
Immunocytochemical analysis of the coiled body in the cell cycle and during cell proliferation.
Coiled bodies (CBs) are small, round structures found in the nucleoplasm of most eukaryotic cells. Human autoantibodies to a 80-kDa protein, p80-coilin, are immunohistologic markers for CBs. A polyclonal rabbit antiserum (R288) raised against recombinant p80-coilin was shown to have similar immunochemical properties as human autoantibodies and was used to analyze the expression of p80-coilin-associated CBs in cell cultures synchronized by double thymidine block, nocodazole arrest, serum starvation, or hormonal deprivation. By employing thymidine block and nocodazole arrest of HeLa cells, CBs were observed in immunofluorescent studies to be largest in size in the S and G2 phases of the cell cycle. These large CBs might have coalesced into one or two such structures per cell from smaller and more numerous CBs of three to eight per cell during the mid G1 phase of the cell cycle. No CB-like structures were observed in mitosis and early G1. However, immunoblotting analyses showed that the total amount of p80-coilin remained approximately the same throughout the cell cycle. When HeLa cells were separated into soluble and particulate fractions, p80-coilin was detected predominantly in the soluble fraction in mitosis and early G1, whereas it was present predominantly in the particulate fraction in late G1, S, and G2 when structurally distinct CBs were observed. In the analysis of CBs in two experimental models of cell proliferation (reversal of 3T3 serum starvation and FRTL-5 thyrotropin deprivation), proliferating cells contained larger, brighter, and more numerous CBs as well as a > 2-fold increase in the total amount of p80-coilin compared to that in quiescent cells. The expression of p80-coilin in quiescent cells induced to proliferate and the cyclic formation and breakdown of CBs might be consistent with the notion that CBs may be specialized centers related to the maturation of mRNA, but this evidence is indirect and needs further definitive study.
Autoantigens↗
Isolated congenital heart block. Long-term outcome of mothers and characterization of the immune response to SS-A/Ro and to SS-B/La.
OBJECTIVE: To study the long-term outcome of mothers of children with isolated congenital heart block (CHB) and to characterize the maternal autoantibody response to SS-A/Ro and SS-B/La. METHODS: A retrospective clinical study of 33 mothers a mean of 11.2 years (SD 9.2 years, range 0-32 years) after the delivery of their first child with CHB. A clinical and immunologic study of 31 of these mothers, compared with 89 healthy mothers, 45 mothers with systemic lupus erythematosus (SLE), and 19 mothers with primary Sjögren's syndrome (SS), all of whom had healthy children. The specificity of the autoantibody responses to SS-A/Ro and SS-B/La was studied by enzyme-linked immunosorbent assays using purified human recombinant antigens and affinity-purified antigens. RESULTS: By the time of the analysis, 2 (6%) of the 33 mothers of CHB children had died and 6 (18%) had met the criteria for SLE. As a group, mothers of CHB children had clinical and immunologic characteristics more closely related to primary SS than to SLE or any other connective tissue disease. The predominant autoantibody response was to the SS-A/Ro antigens, notably to the 52-kd SS-A/Ro protein (prevalence 97%). Compared with controls with SLE, mothers of CHB children had higher titers of antibodies to recombinant 52-kd and 60-kd SS-A/Ro proteins and to the affinity-purified SS-A/Ro antigen (P < 0.05, P < 0.01, and P < 0.001, respectively). Compared with controls with primary SS, the autoantibody responses were similar. CONCLUSION: The predominant autoimmune disorder in mothers of children with CHB is subclinical primary SS. Antibodies to SS-A/Ro appear to be a prerequisite for the development of CHB.
Adolescent↗
Characterization of antinuclear autoantibodies present in the serum from nonobese diabetic (NOD) mice.
The nonobese diabetic (NOD) mouse develops insulin-dependent type 1 diabetes in response to autoantibodies and T-cell attack directed against pancreatic islet cell antigens. Sera obtained from nondiabetic and diabetic female mice demonstrated a 1.4-fold increase in IgG levels when compared to BALB/c control animals. Nondiabetic and diabetic male mice had a 2.1- and 3-fold increase, respectively, in serum IgG levels over that of control mice. Seven of 11 non-diabetic and 7/10 diabetic sera from female NOD mice contained antibody to cytoplasmic or nuclear components of HEp-2 cells. Cytoplasmic staining revealed reaction against cytoskeletal and midbody structures. Punctate nuclear staining patterns with HEp-2 cells showed antibody reaction to the centriole, mitotic chromosomes, and nuclear rim. On the other hand, sera from BALB/c mice were negative for antibody staining of HEp-2 cells. Confirmation of the autoantibody nature of the NOD sera was obtained by antibody staining of nuclear structures from the mouse 3T3 fibroblast cell line, and by staining of salivary gland tissue sections. The nuclear and cytoplasmic staining patterns of diabetic NOD sera were reminiscent of the autoantibody staining patterns observed in Sjögren's syndrome and other inflammatory autoimmune connective tissue diseases.
Animals↗
Molecular biology of autoantigens and new insights into autoimmunity.
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Antibody Formation↗
La autoantigen enhances and corrects aberrant translation of poliovirus RNA in reticulocyte lysate.
Translation initiation on poliovirus RNA occurs by internal binding of ribosomes to a sequence within the 5' untranslated region. We have previously characterized a HeLa cell protein, p52, that binds to a fragment of the poliovirus 5' untranslated region (K. Meerovitch, J. Pelletier, and N. Sonenberg, Genes Dev. 3:1026-1034, 1989). Here we report the purification of the HeLa p52. Protein microsequencing identified p52 as La autoantigen. The La protein is a human antigen that is recognized by antibodies from patients with autoimmune disorders such as systemic lupus erythematosus and Sjögren's syndrome. We show that the La protein stimulates translation of poliovirus RNA, but not brome mosaic virus, tobacco mosaic virus, and alfalfa mosaic virus 4 RNA, translation in a reticulocyte lysate. In addition, La corrects aberrant translation of poliovirus RNA in a reticulocyte lysate. Subcellular immunolocalization showed that La protein is mainly nuclear, but after poliovirus infection, La is redistributed to the cytoplasm. Our results suggest that La protein is involved in poliovirus internal initiation of translation and might function through a similar mechanism in the translation of cellular mRNAs.
Amino Acid Sequence↗
Autoantibodies in viral hepatitis-related hepatocellular carcinoma.
Patients with hepatocellular carcinoma (HCC) develop autoantibodies to nuclear and nucleolar antigens (ANAs) which can be readily detected by immunofluorescence on cell substrates. The frequency of ANAs in HCC is 31% (57/184). The identity of three autoantigens was established as: NOR-90, nucleolus organizer region (doublet) polypeptides involved in RNA polymerase I transcription; fibrillarin, a component of nucleolar U3 RNP involved in pre-ribosomal RNA processing, and nucleophosmin/protein B23, a nucleolar protein involved in ribosome maturation and cell proliferation. Changes in ANAs were observed in some patients during transition from chronic liver disease to HCC and were manifested as seroconversion from ANA-negative to ANA-positive status by an increase in titers and changes in ANA specificities. Serum from a patient during this transition period was used to isolate a cDNA clone encoding a novel nuclear protein with structural motifs characteristic of a family of splicing factors. These observations support the notion that ANA responses in HCC might be driven by intracellular events related to transformation from the stage of chronic injury to the stage of malignancy. Changes in ANA profiles which were observed to precede clinically diagnosed HCC in some patients might be early markers of transformation.
Autoantibodies↗
Novel nuclear autoantigen with splicing factor motifs identified with antibody from hepatocellular carcinoma.
A patient with liver cirrhosis who progressed to hepatocellular carcinoma was found to develop novel antinuclear antibodies. The serum was used to isolate full-length cDNA clones encoding related proteins of 530 amino acids (representative clone HCC1.4) and 524 amino acids (representative clone HCC1.3). Affinity-purified antibodies eluted from recombinant proteins recognized a 64-kD nuclear protein in Western blotting and decorated the nucleoplasm in a speckled-network fashion in immunofluorescence, colocalizing with antibodies to pre-mRNA splicing factor SC35 and uridine-rich small nuclear RNAs. The deduced amino acid sequence contained an arginine/serine-rich (RS) domain and three-ribonucleoprotein consensus sequence domains, two classes of motifs present in several splicing factors. A repeating octapeptide of Arg-Ser-Arg-Ser-Arg(Lys)-Glu(Asp)-Arg-Lys(Arg) was present in RS region of HCC1. This octapeptide sequence called RS-ERK motif was also found in splicing factors U2AF 35- and 65-kD proteins and 70-kD U1 small nuclear ribonucleoprotein. The molecular features and immunolocalization data suggest that the HCC1 autoantigen may be associated with splicing activities and are consistent with observations that autoantibody responses frequently target molecules involved in important cellular biosynthetic functions.
Amino Acid Sequence↗