Natural (ghrelin) and synthetic (hexarelin) GH secretagogues stimulate H9c2 cardiomyocyte cell proliferation

Recent experimental data demonstrate cardiovascular effects of the GH secretagogues (GHSs) hexarelin and ghrelin, the proposed natural ligand for the GHS receptor. Moreover, specific cardiac binding sites for GHSs have been suggested. The aim of the present study was to investigate if the natural ligand ghrelin and synthetic GHS peptide hexarelin and analogues have direct effects on the cardiomyocyte cell line, H9c2. Hexarelin stimulated thymidine incorporation in a dose-dependent manner with significant responses at 3 micro M (147+/-3% of control, P<0.01) and elicited maximal effects at concentrations around 30 micro M. This activity was seen already after 12 h of incubation with a maximal effect after 18 h (176+/-9% of control, P<0.01). Ghrelin also had a significant stimulatory effect on thymidine incorporation (129+/-2% of control at 3 micro M and 18 h, P<0.05). The stimulatory effect on thymidine incorporation of hexarelin, Tyr-Ala-hexarelin, EP80317 and ghrelin was specific and no stimulatory effect was observed with the truncated GH-releasing peptide EP51389 or the non-peptidyl GHS MK-0677. In competitive binding studies, (125)I-labeled Tyr-Ala-hexarelin was used as radioligand and competition curves showed displacement with hexarelin, Tyr-Ala-hexarelin, EP80317 and ghrelin, whereas MK-0677 and EP51389 produced very little displacement at 1 micro M concentration, adding further support for an alternative subtype binding site in the heart compared with the pituitary. In conclusion, we have demonstrated a dose-dependent and specific stimulation of cardiomyocyte thymidine incorporation by natural and synthetic GHS analogues, suggesting increased cell proliferation and binding of GHS to H9c2 cardiomyocyte cell membranes. These findings support potential peripheral effects of GHS on the cardiovascular system independent of an increased GH secretion.

"Tolerosomes" are produced by intestinal epithelial cells

The development of immunological tolerance to orally fed antigens depends on the sampling, processing and transportation events followed in the intestinal epithelium. We present here a description of a "tolerosome": a supra-molecular, exosome-like structure assembled in and released from the small intestinal epithelial cell. The tolerosome is a approximately 40 nm large vesicular structure that carries MHC class II (MHC II) with bound antigenic peptides sampled from the gut lumen. Tolerosomes isolated from serum shortly after antigen feeding or from an in vitro pulsed intestinal epithelial cell line are fully capable of inducing antigen specific tolerance in naive recipient animals. Purified tolerosomes represent a structure by which fed antigens can be efficiently presented to the immune system. Removal of the tolerosomes from serum by ultracentrifugation or absorption of MHC II results in abrogated tolerance development.

An improved nicotinic pharmacophore and a stereoselective CoMFA-model for nicotinic agonists acting at the central nicotinic acetylcholine receptors labelled by

A study of a series of compounds with agonistic effect at the alpha4beta2 nicotinic acetylcholine receptors resulted in an improved pharmacophore model as well as a CoMFA model. The pharmacophore was composed of three pharmacophoric elements: (1) a site point (a) corresponding to a protonated nitrogen atom, (2) a site point (b) corresponding to an electronegative atom capable of forming a hydrogen bond, and (3) the centre of a heteroaromatic ring or a C=O bond (c). The pharmacophoric elements were related by the following parameters: (a-b) 7.3-8.0 A, (a-c) 6.5-7.4 A, and the angle between the two distance vectors (delta bac) 30.4-35.8 degrees. In addition to this, a stereoselective CoMFA model was developed, which showed good predictability even for compound classes not present in the training set.

Ro 52kD autoantibodies are detected in a subset of ANA-negative sera

To define Ro 52kD, Ro 60kD, and La specificities of autoantibodies within ANA-negative sera, samples from 64 ANA-negative but SSA positive patients undergoing investigation due to suspected CTD were analysed, using recombinant antigens and synthetic peptides by immunoblotting and ELISA. The sera were selected from 4025 sera submitted for routine ANA analysis. Antibodies to Ro or La were detected in 42/64 sera (65%). Anti-Ro 52kD antibodies occurred most frequently and were present in 42/64 sera (65%). This was the only specificity of autoantibody detected in 18 sera. No patient had only anti-La or anti-Ro 60 antibodies. In total 18.64 patients (28%) had Ro 60 antibodies and 14/64 had anti-La antibodies (21%). Eight patients had antibodies reacting with all three antigens. We used the same set of sera to test the antigenicity of different regions of Ro 52kD represented by deletion clones and peptides derived from the Ro 52kD sequence. Out of 30 sera reacting with a recombinant deletion clone encompassing as residues 136-227, 12 sera reacted with a peptide corresponding to a 200-239. Some sera gave a low positive OD value with a peptide of a 176-196. Based on the results of this study in which we demonstrate Ro 52kD autoantibodies in 65% of selected ANA negative sera and define an autocephitope within the Ro 52kD protein composed of the leucine zipper domain, we suggest that testing for Ro 52kD antibodies could be included in an extended investigation of ANA negative patients with suspected connective tissue disease.

Key residues revealed in a major conformational epitope of the U1-70K protein

Epitopes depending on three-dimensional folding of proteins have during recent years been acknowledged to be main targets for many autoantibodies. However, a detailed resolution of conformation-dependent epitopes has to date not been achieved in spite of its importance for understanding the complex interaction between an autoantigen and the immune system. In analysis of immunodominant epitopes of the U1-70K protein, the major autoantigen recognized by human ribonucleoprotein (RNP)-positive sera, we have used diversely mutated recombinant Drosophila melanogaster 70K proteins as antigens in assays for human anti-RNP antibodies. Thus, the contribution of individual amino acids to antigenicity could be assayed with the overall structure of the major antigenic domain preserved, and analysis of how antigenicity can be reconstituted rather than obliterated was enabled. Our results reveal that amino acid residue 125 is situated at a crucial position for recognition by human anti-RNP autoantibodies and that flanking residues at positions 119-126 also appear to be of utmost importance for recognition. These results are discussed in relation to structural models of RNA-binding domains, and tertiary structure modeling indicates that the residues 119-126 are situated at easily accessible positions in the end of an alpha-helix in the RNA binding region. This study identifies a major conformation-dependent epitope of the U1-70K protein and demonstrates the significance of individual amino acids in conformational epitopes. Using this model, we believe it will be possible to analyze other immunodominant regions in which protein conformation has a strong impact.

Improving the nicotinic pharmacophore with a series of (Isoxazole)methylene-1-azacyclic compounds: synthesis, structure-activity relationship, and molecular modeling

A series of (isoxazole)methylene-1-azacyclic compounds was prepared. The compounds were tested for affinity to central nicotinic acetylcholine receptors (nAChRs) and central muscarinic receptors. The compounds covered a broad range of affinities for the nAChRs (IC(50) = 0.32 to >1000 nM), with selectivities for the nAChRs over the muscarinic receptors in the range of 3-183. The high-affinity compound (Z)-26 (3-(4-methyl-5-isoxazolyl)methylene-1-azabicyclo[2.2. 2]octane, IC(50) = 3.2 nM) having only one energy minimum was used as the reference structure in a computational study. This ligand has enabled definition of an important distance parameter, and the existence of this parameter was supported by showing that other potent nicotinic ligands (for example, nicotine and epibatidine) fit the model.

Antibodies given orally in the neonatal period can affect the immune response for two generations: evidence for active maternal influence on the newborn's immune system

Two day old Wistar rats were tube fed with 1 or 10 micrograms of a mouse IgG1 monoclonal anti-idiotypic (a-Id) antibody that was directed against an anti-Escherichia coli-K13 capsular polysaccharide antibody. A control group was given 10 micrograms of an unrelated control antibody. Six weeks after the administration of antibodies, the rats were intestinally colonised with an ovalbumin (OVA)-producing E. coli O6K13 strain. At 8 weeks of age, the male rats (first generation) and the offsprings of the female rats (second generation), were parenterally immunised with OVA and dead wild type E. coli O6K13, and the immune response was followed. In the rats of the first generation, there were no major differences between the groups in the immune response to the bacterium. However, the offspring of the neonatally a-Id administered rats had a profoundly affected immune response to the idiotypically connected antigen K13, but also to other antigens on the bacteria. Thus, a-Id treatment in the first generation gave, in the second generation, a greatly enhanced serum antibody response to the spatially related antigens OVA and O6 LPS, as well as to the idiotypically connected antigen K13. Concurrently, the in vitro spleen cell proliferative response to both OVA and the wild type bacterium was lowered. Overall, greater effects were seen with the higher dose of a-Id. In conclusion, our results demonstrate that by giving monoclonal antibodies idiotypically connected to a single bacterial component to neonatal rats, one profoundly influence the immune response also to other-spatially related-bacterial antigens in their offsprings.

Autoantibody profiles in canine ANA-positive sera investigated by immunoblot and ELISA

Canine systemic lupus erythematosus (SLE) has a similar disease expression as human SLE, but the serological characterisation of the canine disease is as yet incomplete. In the present study, we examined the specificity of antinuclear antibodies (ANA) in indirect immunofluorescence (IIF) positive canine sera. Sixty-four canine IIF ANA positive sera were characterised using HeLa cell nuclear extract immunoblots and recombinant U1-70K ELISA. We compared these results with a previously shown concordance between indirect immunofluorescence and immunodiffusion in canine SLE serological diagnosis. One canine serum reacting with Sm proteins was observed, and five canine sera presented anti-RNP autoantibodies against the antigens 70K, A, C, and/or B/B'. The autoantigen most frequently recognised was a 43 kDa nuclear protein, previously described as hnRNP G. This prominent canine autoantigen was missing in the commercially available extract designed for immunodiffusion testing of human sera. Other prominent canine autoantigens were found not to be identical with the principal human ones, thus making present human test systems deficient for the use in canine systemic connective disease diagnosis. The development of antigenic extract designed for canine autoimmune autoantigens is necessary in order to make immunodiffusion a useful method in canine diagnosis. The anti-RNP positive canine sera were examined in more detail and we found that the human major antigenic region of the most prominent RNP antigen, the U1-70K protein, also is targeted by canine autoantibodies. Thus, the response against the RNP antigen seems to be conserved between man and dog.

The Zn2+ binding domain of the human Ro 52 kDa protein is a target for conformation-dependent autoantibodies

The Ro 52 kDa protein was originally identified using autoimmune sera directed against the Ro/SS-A antigen, also known as Ro ribonucleoprotein particles (Ro RNPs). In most human cells these consist of one of four small human cytoplasmic (hY) RNA molecules complexed with the Ro 60 kDa protein. This protein interacts directly with the hY RNAs, whereas the Ro 52 kDa protein is thought to associate via protein-protein interactions. The Ro RNPs are present in all mammalian cells, but their intracellular location and function remain unclear. The primary structure shows that the Ro 52 kDa protein is a member of a small family of proteins sharing two features, a leucine zipper region and an aminoterminal cysteine-histidine rich region with two different putative zinc finger motifs. To study if the Ro 52 kDa protein actually binds Zn2+, both the full-length Ro 52 kDa clone and various subclones were expressed as recombinant proteins and assayed for Zn2+ binding in vitro. A fragment containing the first cysteine-histidine cluster at residues 14-54 and other larger overlapping fragments were found to bind Zn2+. In this report we also demonstrate that the Zn2+ binding domain is a target for conformation-dependent anti-Ro 52 kDa autoantibodies. The antigenicity is dramatically increased by the same reducing conditions that promote Zn2+ binding. This is in contrast to the previously described immunodominant Ro 52 kDa domain.

Ro/SS-A and La/SS-B antibody level variation in patients with Sjögren's syndrome and systemic lupus erythematosus

To examine both possible correlations between anti-Ro/SS-A and anti-La/SS-B levels and their correlation with clinical disease activity in patients with Sjögren's syndrome (SS) or systemic lupus erythematosus (SLE), an ELISA was developed using purified recombinant Ro 60 kDa, Ro 52 kDa and La antigens. The ELISA was used for testing sequential serum samples from 16 patients with either SS or SLE. The patients were followed for periods between 15 and 128 months, and 3-15 serum samples per patient were analysed and compared with clinically apparent disease activity at the time of sampling in 14 patients. A temporal correlation of antibody levels to Ro and La antigens was found, and antibodies to different epitopes of the Ro 60 kDa protein showed parallel variation in seven of eight patients tested. Co-variation of autoantibody levels and disease activity was found in 11 of 14 patients. In seven of these 11 patients the anti-Ro and anti-La levels were stable and changes in disease activity were minimal during the observation period. In the other four of these 11, changes in disease activity were noted, with an associated change in autoantibody levels. The results suggest that the serological response to Ro and La antigens, as well as to different epitopes of the Ro 60 kDa protein, is antigen driven and regulated by common mechanisms, and indicate a correlation of Ro and La antibodies with pathogenic events.

Intracellular localisation of the Ro 52kD auto-antigen in HeLa cells visualised with green fluorescent protein chimeras

Autoantibodies to the Ro/SSA and La/SSB antigens are found in patients with Sjogren's syndrome and systemic lupus erythematosus. The Ro/SSA autoantigen consists of a 52 kD and a 60 kD protein, complexed with one of four small RNA molecules. The La protein can associate with the complex. The Ro/SSA autoantigens are present in all mammalian cells, but their intracellular location is subject of controversy and their function remains unclear. To study the intracellular sorting and targeting of Ro 52 kD we have constructed expression plasmids encoding fusion proteins between the full-length Ro 52 kD protein as well as Ro 52 kD fragments and the green fluorescent protein (GFP) from the jelly fish, Aequorea Victoria. The subcellular distribution of the GFP-Ro 52 kD fusion proteins was investigated in transient expression experiments using transfected HeLa cells. The GFP-full-length Ro 52 kD fusion protein was accumulated in the cytoplasm and excluded from the nucleus. When GFP was fused with the La protein, the fluorescence was located in the nucleus. Clones coding for Ro 52 kD fragments containing the hydrophilic central part of the Ro 52 kD protein gave the same intracellular location and type of cytoplasmic speckles as the full-length Ro 52 kD protein. In contrast, both amino terminal and carboxy terminal fragments were uniformly distributed throughout the cell just like the GFP protein itself. These observations indicated a cytoplasmic location of the Ro 52 kD protein and demonstrated the crucial role of the hydrophilic domain in restricting the Ro 52 kD protein to this intracellular compartment.

Autoepitope-mapping of the U1-70K protein with human-Drosophila chimeric proteins

The 70K protein is the major autoantigen for anti-RNP autoantibodies directed against the U1 small nuclear ribonucleoprotein complex particle. The U1-70K protein has been epitope-mapped by various groups, and a major antigenic region of about 70 amino acids has been found which overlaps with the RNA binding motif. Attempts to map the major antigenic region further with smaller cloned fragments or with peptides have been hampered by total loss of, or strongly reduced, antigenicity. Thus the major antigenic region is composed of conformational epitopes and a detailed analysis of particular epitopes has not been possible. In the present work, we examine the antigenicity of chimeric proteins assembled from the highly conserved Drosophila melanogaster 70K proteins grafted with human 70K segments. With this approach, the effects on antigenicity of exchanging particular segments can be assayed with the overall structure of the major antigenic domain kept relatively constant. Our results, supported by depletion experiments, show that residues 99-128 from the human protein are essential for recognition by both human and canine anti-RNP autoantibodies. These residues have to be presented in a manner that allows correct conformational interaction between the different protein domains.

Thrombomucin, a novel cell surface protein that defines thrombocytes and multipotent hematopoietic progenitors

MEP21 is an avian antigen specifically expressed on the surface of Myb-Ets-transformed multipotent hematopoietic precursors (MEPs) and of normal thrombocytes. Using nanoelectrospray tandem mass spectrometry, we have sequenced and subsequently cloned the MEP21 cDNA and named the gene thrombomucin as it encodes a 571-amino acid protein with an extracellular domain typical of the mucin family of proteoglycans. Thrombomucin is distantly related to CD34, the best characterized and most used human hematopoietic stem cell marker. It is also highly homologous in its transmembrane/intracellular domain to podocalyxinlike protein-1, a rabbit cell surface glycoprotein of kidney podocytes. Single cell analysis of yolk sac cells from 3-d-old chick embryos revealed that thrombomucin is expressed on the surface of both lineage-restricted and multipotent progenitors. In the bone marrow, thrombomucin is also expressed on mono- and multipotent progenitors, showing an overlapping but distinct expression pattern from that of the receptor-type stem cell marker c-kit. These observations strengthen the notion that the Myb-Ets oncoprotein can induce the proliferation of thrombomucin-positive hematopoietic progenitors that have retained the capacity to differentiate along multiple lineages. They also suggest that thrombomucin and CD34 form a family of stem cell-specific proteins with possibly overlapping functions in early hematopoietic progenitors.

Human anti-RNP sera contain both human-specific and cross-reactive anti-70K autoantibodies

The U1 snRNP (small nuclear ribonucleoprotein complex) associated 70K protein is the main autoantigen for the anti-RNP autoantibodies which are directed against the U1 snRNP particle. The major antigenic region of the 70K protein has by various laboratories been mapped to an RNA binding domain required for the 70K-U1 snRNA interaction. We have used recombinant proteins comprising this region from the human and the Drosophila melanogaster 70K proteins to examine the species specificity of the human anti-70K autoantibodies found in 42 patient sera. Most, but not all, anti-70K positive sera in this cross-sectional sample contained both human 70K specific anti-bodies and Drosophila 70K reactive antibodies. Results of a longitudinal follow-up of 14 patients indicated that the cross-reactive anti-70K antibodies developed secondarily to the establishment of a species-specific anti-70K reaction. In a fraction of the patient sera this broadening of the response never occurred. Taken together, the data in this study support the hypothesis that the endogenous human 70K protein is the immunogen driving the production of anti-70K autoantibodies.

Autoantibody repertoire to Ro/SSA and La/SSB antigens in patients with primary and secondary Sjögren's syndrome

Autoimmune diseases are characterized serologically by the presence of antibodies to specific autoantigens. Antibodies to the two antigens Ro/SSA and La/SSB are found in patients with primary (pSS) and secondary Sjögren's syndrome (sSS). To explore if differences in the fine specificity of these autoantibodies could be distinguished in sera from patients with primary (n = 17) and secondary (n = 20) Sjögren's syndrome, sera were analysed by immunoblotting and ELISA using recombinant antigens and synthetic peptides. Minor differences were detected when the frequencies of the Ro 60 kD, Ro 52 kD and La autoantibody specificities to full-length proteins in the pSS and sSS groups were compared. However, when reactivity to different parts of the Ro 60 kD antigen was analysed, including recombinant fragments encompassing amino acid (aa) 1-134, aa 181-320 and aa 397-525, only two sera, both from pSS patients, reacted to the aminoterminal fragment aa 1-134, and 3/4 sera that reacted with the carboxyterminal aa 397-525 fragment derived from sSS patients. Of all the anti-Ro 60 kD positive sera, 80% reacted with the middle fragment encompassing aa residues 181-320. The fine specificity of the autoantibodies reacting with this 181-320 aa region was further mapped with synthetic peptides, and a peptide (VSLVCEKLCNEKLLKKARIH) recognized by 8 out of 16 sera from both pSS and sSS patients was identified.

Nuclear colocalization of the Ro 60 kDa autoantigen and a subset of U snRNP domains

The Ro 60 kDa protein is an RNA binding molecule present both in the cytoplasm and in the nucleus. Cytoplasmic Ro 60 kDa is complexed to other proteins and to certain RNAs denoted hYRNAs. This RNA-protein complex is also known as the Ro/SSA antigen recognized by sera from patients with certain autoimmune disorders. Components interacting with the nuclear Ro 60 kDa protein fraction in mammalian cells have not been identified. To look for an association with previously known nuclear structures, rabbit antisera to the amino- and carboxy-terminal parts of the Ro 60 kDa protein were used in immunomorphological studies on HeLa cells. A strong speckled nuclear pattern and a weak cytoplasmic staining were detected. Double immunofluorescence staining with affinity purified anti-Ro 60 kDa antibodies and monoclonal antibodies recognizing the Sm and RNP antigens of the U snRNPs, displayed colocalization. Another U snRNP containing nuclear compartment, the coiled bodies, did not contain any Ro 60 kDa protein. Cells infected with a toga virus demonstrated redistribution of both U snRNP antigens and the Ro 60 kDa protein with retained colocalization. These results indicate a role for the nuclear fraction of the Ro 60 kDa protein in RNA processing.

U2-snRNP B" protein gene is an early growth-inducible gene

In this work we isolated mouse U2-snRNP-specific b" clones and analysed the expression of the mouse U2-snRNP-specific b" and U1-snRNP-specific 70K genes in NIH-3T3 fibroblasts. Stimulation of growth-arrested NIH-3T3 cells with serum was found to evoke a rapid increase in the amount of cytoplasmic b" and 70K mRNAs. These increases in mRNA did not require de novo protein synthesis. Moreover, the inhibition of protein synthesis by cycloheximide caused a superinduction in the amounts of the U1-snRNP-specific 70K transcripts. We also found that c-Ha-rasVal12 oncogene-transformed NIH-3T3 cells have higher levels of the b" and 70K mRNAs than the normal 3T3 cells. These data imply that the b" and 70K are early growth response genes, and their enhanced expression might be of significance in the processing of pre-mRNAs into mature mRNAs.

Single-view screening mammography: psychological, endocrine and immunological effects of recalling for a complete three-view examination

To investigate influences of a recall due to inconclusive findings on screening mammography, 45 women were examined with psychological ('mood' and 'coping'), endocrine and immunological tests immediately after complete mammography (first interview), 2-3 days after the initial screening mammography, and 3 weeks after the women had been informed of normal findings (second interview). The mood score in the first interview was significantly lower than in the second. No differences were found in the endocrine and immunological tests. The recall for complete mammography provoked a significant short-term emotional reaction not reflected in changes in the endocrine and immune functions.

MRL/lpr mice produce anti-Ro 52,000 MW antibodies: detection, analysis of specificity and site of production

MRL/lpr mice are studied as one of the animal models of the human autoimmune disease Sjögren's syndrome. The mice develop inflammatory exocrinopathy resembling that of patients with Sjögren's syndrome. To investigate if MRL/lpr mice produce the anti-Ro/SS-A and anti-La/SS-B autoantibodies common to Sjögren's syndrome patients, mouse sera were tested in ELISA and Western blot with recombinant Ro 60,000 MW, Ro 52,000 MW and La antigen. Thirty per cent of mice aged 4 months and 5% of mice aged 2 months produced antibodies to human Ro 52,000 MW. Antibodies to Ro 60,000 MW and La were found in a low percentage of the older mice but not at all in the younger mice. Immunohistological staining of mouse organ sections demonstrated anti-Ro 52,000 MW-producing cells in spleen, lymph nodes and salivary glands of seropositive animals. These findings provide further evidence for the usefulness of the MRL/lpr mouse as a model for Sjögren's syndrome.

Identification of antigenic regions of the human 52kD Ro/SS-A protein recognized by patient sera

Patients with several different connective tissue diseases including Sjögren's syndrome and systemic lupus erythematosus produce autoantibodies reacting with a 52kD protein component of the Ro/SS-A antigen. Antibody recognition of recombinant Ro 52kD proteins encoded by both full-length and deletion clones was analysed by immunoblotting with patient sera. An antigenic region recognized by all anti-Ro 52kD positive sera was found in the middle part of the protein. By further mapping of residues 136-292 with overlapping clones, at lest two independent epitopes within the domain were detected. This part of the protein contains a leucine zipper motif and shows structural similarities with a predicted coiled-coil region involved in protein dimer formation. In addition, one fifth of the sera reacted weakly with another antigenic region located in the amino-terminal part of the protein containing two putative zinc fingers. These results demonstrate the presence of an immunodominant region but also heterogeneity in the human autoimmune response to the 52kD protein moiety of the Ro/SS-A antigen.

IgM and IgG subclass distribution of human anti-Ro/SSA 60 kDa autoantibodies

The Ro/SSA and La/SSB antigens are common targets for autoantibodies found in the sera of patients with Sjögren's syndrome and SLE. The anti-Ro/SSA and anti-La/SSB antibodies often appear together but are not cross-reactive. This paper describes the humoral autoimmune response to the Ro/SSA 60 kDa protein moiety with respect to the presence of IgM and IgG1-4 antibodies. IgM antibodies to the Ro 60 kDa protein coexisted with IgG anti-Ro 60 kDa antibodies in nearly half of the sera. A similar fraction also contained IgM anti-La/SSB antibodies. The frequency of sera with IgM antibodies of both specificities was that expected from random overlap. A predominating IgG1 anti-Ro 60 kDa response was found in all patients, but anti-Ro 60 kDa antibodies of the other IgG subclasses were present also in a high number of sera. This is in contrast to the reported IgG subclass distribution of anti-La/SSB antibodies. Mapping of IgM and IgG1-4 antibody recognition of different parts of the Ro 60 kDa protein was also performed. IgM and IgG1-4 antibodies of all sera reacted with the central part of the Ro 60 kDa protein, encompassing amino acid residues 181-320.

IgG and IgM anti-snRNP reactivity in sequentially obtained serum samples from patients with connective tissue diseases

Sequentially obtained serum samples from 30 patients with connective tissue disease positive for antibody to ribonucleoprotein (RNP) were examined to determine the specificities of IgG and IgM antibodies to snRNP during the disease course using immunoblotting of nuclear extracts. The antibody patterns were correlated with disease activity. The patterns of antibody to snRNP of individual patients were mainly stable during the study but changes in levels of antibody to snRNP were seen corresponding to changes in clinical activity. These results indicate that increased reactivity of serum IgM antibodies against the B/B' proteins seems to precede a clinically evident exacerbation of disease whereas IgG antibody reactivity to the 70 K protein peaks at the time of a disease flare.

Clinical manifestations and anti-(U1)snRNP antibodies: a prospective study of 29 anti-RNP antibody positive patients

Twenty-nine anti-RNP positive patients were followed prospectively with a mean observation time of 65 months (29-120 months). The clinical course was correlated to the presence of IgM and IgG anti-(U1)snRNP antibodies as revealed by immunoblotting from sequentially obtained sera. There was a striking dissociation between the fluctuating course, with the appearance of new manifestations followed by remissions, and the stability of the anti-snRNP antibody specificities where an appearance or a disappearance of anti-snRNP specificities was a rare phenomenon. The main epitope recognized by the IgG antibodies was the 70 kDa protein and of the IgM antibodies the B/B' proteins. No shift from the IgM to the IgG isotype was observed. The presence of IgG anti-70 kDa and IgM anti-B/B' antibodies was highly associated with presence of arthralgias, Raynaud's phenomenon and arthritis. Further, an association was noted between the combined presence of IgG anti-70 kDa, anti-A and anti-C antibodies and IgM anti-B/B' and puffy hands, myositis, pulmonary fibrosis and sclerodactyly, i.e. all manifestations of mixed connective tissue disease (MCTD). On the contrary, serositis as often seen in SLE was correlated to the presence of IgG anti-B/B' antibodies. Thus the longitudinal analysis of the correlation between anti-snRNP antibody specificities and clinical manifestations support the concept of MCTD as a distinct entity.

6-Hydroxy-3-n-propyl-2,3,4,5-tetrahydro-1H-3-benzazepine and analogs: new centrally acting 5-HT1A receptor agonists

The ring-closed phenylethylamine analogue 6-hydroxy-3-n-propyl-2,3,4,5-tetrahydro-1H-3-benzazepine (1) is a 5-HT1A receptor agonist of moderate potency, according to both in vivo biochemical data and in vitro binding data. The active compounds of this series also induce the 5-HT behavioral syndrome. Molecular modeling studies were performed with molecular mechanics calculations, and a tentative explanation for the relatively low potency of these serotonergic benzazepines is provided.

Conformational analysis of dopamine D-2 receptor antagonists of the benzamide series in relation to a recently proposed D-2 receptor-interaction model

Conformational analysis using molecular mechanics calculations (MM2(87)) has been performed for four different types of benzamides which display high affinity for the dopamine D-2 receptor. In order to elucidate the conformation of the receptor-bound molecules, a previously described dopamine D-2 receptor-interaction model has been employed. We conclude that all four types of benzamides accommodated in the proposed receptor-interaction model are in low-energy conformations. An acyclic amide side chain is concluded to adopt an extended conformation in the receptor-bound benzamide. A phenylpyrrole analogue of the benzamides could similarly be fitted to the model. Using the receptor-interaction model, the enantioselectivity of benzamides with an N-ethyl-2-pyrrolidinylmethyl side chain could be rationalized in terms of different conformational energies of the receptor-bound enantiomers. Two different receptor sites for N-alkyl substituents are suggested.

Identification of antigenic regions of the human Ro 60 kDa protein using recombinant antigen and synthetic peptides

Autoantibodies reacting with the human Ro 60 kDa protein are present in anti-Ro/SS-A positive sera from patients with several different connective tissue diseases including Sjögren's syndrome and systemic lupus erythematosus. To investigate the humoral immune response to this protein, the pattern of antibody recognition of recombinant Ro 60 kDa proteins encoded by both full-length and deletion clones was analysed by immunoblotting. An antigenic region recognized by nearly all anti-Ro 60 kDa positive sera was found to reside in the middle part of the protein. In addition, some sera reacted with two other antigenic regions located in the amino-terminal and carboxyl-terminal part of the protein. For further mapping, overlapping peptides covering the most frequently recognized region of the protein were synthesized by solid-phase methods and used as antigens in ELISA. Three major patterns of reactivity to Ro 60 kDa peptides were found. These results not only indicate the presence of an immunodominant region but also heterogeneity in the autoimmune human response to the Ro 60 kDa antigen.

A study on the contribution of the 1-phenyl substituent to the molecular electrostatic potentials of some benzazepines in relation to selective dopamine D-1 receptor activity

The molecular electrostatic potentials for a selective dopamine D-1 receptor antagonist, 7-chloro-8-hydroxy-1-phenyl-2,3,4,5-tetrahydro-1H-3-methylbenzazepine (SCH 23390 (1], and a selective dopamine D-1 receptor agonist, 7,8-dihydroxy-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine (SK&F 38393 (2], have been calculated in order to obtain an understanding of the nature of the interactions between the phenyl ring and the receptor. Analogues of 1 with conformationally constrained phenyl rings have also been studied. Based on this study, the conclusion is drawn that an important part of the interaction between the phenyl ring in the benzazepines and the receptor is due to electrostatic forces, and that the phenyl ring interacts with the same receptor site as the oxygen atom of the 8-hydroxy group.

Intranuclear localization of a new snRNP-related antigen

The intranuclear distribution of a new antigen (F78) associated with U snRNPs (small nuclear RNA-protein complexes) was compared with that of the RNP and Sm protein antigens previously identified on individual snRNP particles. Human and rat cells were double stained with human autoantisera and mouse monoclonal antibodies. The binding of the human and mouse antibodies was detected with secondary antibodies conjugated with fluorescein and rhodamine, respectively. The resulting immunofluorescence patterns were compared by digital image analysis. The F78, RNP, and Sm antigens show speckled fluorescence patterns which overlap to a great extent. The F78 pattern, however, also contains two classes of structural elements not present in the RNP pattern. Furthermore, during mitosis expression of the F78 antigen is completely suppressed from early prophase to telophase, while the RNP and Sm antigens are found evenly distributed throughout the cytoplasm of the dividing cells.

Antigenic domains on the U1 small nuclear ribonucleoprotein-associated 70K polypeptide: a comparison of regions selectively recognized by human and mouse autoantibodies and by monoclonal antibodies

Antigenic regions on the U1 small nuclear ribonucleoprotein (snRNP)-associated 70K polypeptide recognized by human and mouse autoantibodies or by monoclonal antibodies were identified and compared. Using a set of 70K fusion proteins as antigen in enzyme-linked immunosorbent assay and immunoblotting revealed that serum autoantibodies of human and of MRL/Mp mouse origin recognized a common region of the 70K polypeptide. Monoclonal anti-70K antibodies derived from a patient with mixed connective tissue disease, from an autoimmune MRL/Mp mouse, and from a BALB/c mouse immunized with purified U1 snRNP were all shown to bind to a part of the 70K polypeptide rich in charged residues and different from the region recognized by most human and MRL/Mp mouse serum autoantibodies.

Decreased activity of the heparan sulfate-modifying enzyme glucosaminyl N-deacetylase in hepatocytes from streptozotocin-diabetic rats

N-Deacetylation is the initial polymer modification step in heparan sulfate biosynthesis and a prerequisite to subsequent N- and O-sulfation. It has previously been shown that the sulfation of liver heparan sulfate is lowered in diabetes (Kjellén, L., Bielefeld, D., and Höök, M. (1983) Diabetes 32, 337-342). To investigate whether the reduced sulfation is the result of a lowered N-deacetylase activity, we have assayed this enzyme in hepatocytes from streptozotocin-diabetic rats. In addition, the activity of the glucuronosyl C5-epimerase, which catalyzes a modification reaction subsequent to N-sulfation, was measured. The deacetylase activity, expressed per microgram of cell protein, was about 40% lower in diabetic hepatocytes as compared with control cells, whereas the epimerase activity was unaffected. Recently, a approximately 110-kDa glycoprotein that carries N-sulfotransferase activity was identified as one of at least two protein components required for N-deacetylation in mouse mastocytoma tissue (Pettersson, I., Kusche, M., Unger, E., Wlad, H., Nylund, L., Lindahl, U., and Kjellén, L. (1991) J. Biol. Chem. 266, 8044-8049). We therefore investigated if the lowered N-deacetylase activity in diabetes could be ascribed to a deficiency in either one of the corresponding rat components. The results indicated that (i) the glycoprotein component is present in limiting amounts in both control and diabetic cells, (ii) diabetes results in a lowered activity of this component, and (iii) excess amounts of the additional protein(s) needed for N-deacetylase activity are present in both control and diabetic cells.

Biosynthesis of heparin. Purification of a 110-kDa mouse mastocytoma protein required for both glucosaminyl N-deacetylation and N-sulfation

The polymer modification process in the biosynthesis of heparin/heparan sulfate is initiated by N-deacetylation, followed by N-sulfation, of N-acetylglucosamine units. Chromatography of a detergent extract from mouse mastocytoma on wheat germ agglutinin-Sepharose yielded a protein fraction, eluted with 0.3 M N-acetylglucosamine, that expressed N-deacetylase activity, but only after recombination with proteins that did not bind to the lectin column. In subsequent purification of the active lectin-bound component, all assays were performed following addition of the unbound protein fraction. After two additional chromatography steps, on blue Sepharose and 3',5'-ADP-agarose, the lectin-binding N-deacetylase component had been purified about 4300-fold with an 11% yield and showed essentially a single band, corresponding to an apparent molecular weight of approximately 110,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Analysis of the purified 110-kDa protein showed that it contained, in addition to the N-deacetylase, N-sulfotransferase activity; however, the expression of N-sulfotransferase activity was independent of additional proteins. Backtracking the N-sulfotransferase through the purification scheme previously applied to the N-deacetylase showed the two enzyme activities to the N-deacetylase showed the two enzyme activities to be cofractionated in each separation step. It is proposed that the expression of glucosaminyl N-deacetylase activity depends on the concerted action of (at least) two protein components, one of which also possesses glucosaminyl N-sulfotransferase activity.

Cloning and structural analysis of a gene encoding a mouse mastocytoma proteoglycan core protein; analysis of its evolutionary relation to three cross hybridizing regions in the mouse genome

Serglycin (SGC) is a Ser-Gly-repeat-containing protein, used as a proteoglycan core protein in the parietal yolk sac and in mast cells, where glycosaminoglycan side chains are attached to the serine residues of the repeat region. In this article, the structure of the gene SGC encoding mouse SGC is reported. The gene is divided into three exons, which are all contained within a region of approximately 13 kb. Nucleotide (nt) sequence analysis was carried out on a region of 1.2 kb upstream from the first exon. The region containing the two promoters (active in parietal yolk sac and in mast cells, respectively) was analyzed for the presence of recognition sites for known DNA-binding proteins. A number of sequences closely related to known recognition sites were found in both promoters, and one consensus octamer-binding site could be identified in the putative yolk-sac promoter. Multiple regions in the mouse genome hybridizing with DNA fragments covering the Ser-Gly repeat region have previously been described, and it has been suggested that these loci may represent other proteoglycan core proteins. Analysis of nt sequence was carried out on three out of the more than 15 of these regions present in the mouse genome. However, none of the clones analyzed was found to have any open reading frame in the region of cross-hybridization which possibly could code for a SGC protein. Instead, one of the clones was found to contain an exon encoding a highly basic protein, unrelated to SGC. Hence, no evidence was found for a multigene family of Ser-Gly-repeat-containing proteoglycan-encoding genes.

Conformational analysis and structure-activity relationships of selective dopamine D-1 receptor agonists and antagonists of the benzazepine series

Comprehensive conformational analysis using molecular mechanics calculations (MM2(85)) has been carried out for the potent and selective dopamine D-1 receptor agonist 7,8-dihydroxy-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine (1; SK&F 38393), the antagonist 7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine (8; SCH 23390), and several analogues, including conformationally constrained ones. Calculated conformational energies have been related to pharmacological and biochemical data in an attempt to identify the biologically active conformations of 1 and 8. It is concluded that the most probable receptor-bound conformation in both cases is a chair conformation with an equatorial phenyl ring and for 8 an equatorial N-methyl group. It is suggested that the orientation of the phenyl ring in the receptor-bound molecule does not deviate in terms of dihedral angles by more than about 30 degrees from the preferred phenyl group rotamer in which the planes of two aromatic rings are essentially orthogonal.

Recombinant 70-kD protein used for determination of autoantigenic epitopes recognized by anti-RNP sera

A panel of high- and low-titre anti-RNP-positive patient sera was tested for reactivity with human snRNP proteins. The U1 snRNP-specific 70-kD peptide was found to be the most prominent RNP antigen recognized by high-titre anti-RNP sera, mainly found in patients with mixed connective tissue disease (MCTD). The reactivity with the 70-kD protein was further analysed with recombinant fusion proteins containing different segments of the protein. One major and two minor antigenic regions were found. Most patient sera, both with high- and low-titre anti-RNP antibodies, only recognized the major region. The most aminoterminal region, showing partial sequence homology with a mouse retroviral p30 gag protein, contained an epitope that was recognized by one serum only.

Human autoantibodies against the 70-kd polypeptide of U1 small nuclear RNP are associated with HLA-DR4 among connective tissue disease patients

Serum samples from patients with connective tissue disease (CTD) were characterized using a recently developed enzyme-linked immunosorbent assay for reactivity with individual specific polypeptides of U1 small nuclear ribonucleoproteins, including the U1-70-kd protein. The distribution of HLA antigens was compared in CTD patients with and in those without anti-U1-70-kd autoantibodies and in normal controls. The frequencies of HLA-DR4 and HLA-DRw53 were increased among the anti-U1-70-kd autoantibody positive CTD group compared with the frequencies in anti-U1-70-kd autoantibody negative systemic lupus erythematosus patients and compared with normal controls. We conclude that the presence of autoantibodies reactive with the anti-U1-70-kd protein antigen is associated with HLA-DR4 and HLA-DRw53.

Appearance and origin of snRNP antigens in chick erythrocyte nuclei reactivated in heterokaryons

Fusion of terminally differentiated chick erythrocytes (CE) with transcriptionally active rat myoblasts results in heterokaryons in which the CE nuclei undergo reactivation of RNA synthesis and splicing. In order to analyze the transport and assembly of small nuclear ribonucleoprotein (snRNP) particles and larger molecular complexes engaged in RNA processing, we have examined CE nuclei in heterokaryons for the presence of four U snRNP-related nuclear antigens (Sm, 70,000 Mr, F78 and M3G-cap) and for one antigen (La), associated with RNA polymerase III transcripts. Inactive erythrocyte nuclei showed low levels of Sm and F78 antigens, but the other antigens were undetectable. Immediately after fusion, the fluorescence of the pre-existing chicken Sm antigen was detected in the CEn, and then the intensity of the signal increased rapidly during reactivation. The other antigens appeared more slowly, reaching full intensity at different time points after fusion. Blocking of chick transcription did not block the appearance of Sm, 70,000 Mr, cap and La antigens but did effectively inhibit the appearance of the F78 antigen. It has previously been demonstrated that the structure recognized by this monoclonal antibody is physically associated with functional splicing complexes. Blocking of translation in heterokaryons abolished uptake of snRNPs into the chicken nuclei. Taken together, the results indicate that rat snRNP complexes were imported into the chick nuclei after assembly in the cytoplasm. For all the studied antigens, except F78, this translocation was independent of chick RNA synthesis. The appearance of the F78 antigen was totally dependent on expression of chicken genes.

Primary structure of a mouse mastocytoma proteoglycan core protein

The complete nucleotide sequence of a mouse mastocytoma proteoglycan core protein mRNA was determined. The mRNA, estimated to contain 1.1 kb, encodes a protein with an Mr of 16715. A 21-amino acid-residue region of the protein is composed of alternating serine and glycine residues. Southern-blot analysis of mouse genomic DNA with cDNA containing sequences corresponding to the Ser-Gly repeat region revealed more than 15 gene fragments. Hybridization with a probe corresponding to the N-terminal portion of the core protein identified two fragments, and cDNA covering the C-terminal part of the core protein and the 3' untranslated part of the mRNA hybridized to a single fragment. Antibodies against the core protein, obtained after immunization of rabbits with a fusion protein, reacted with both chondroitin sulphate proteoglycans and heparin proteoglycans produced by the tumour. In immunoblotting of a microsomal fraction from the mastocytoma, the antiserum recognized a single protein (Mr 17,000), which probably represents the core protein before glycosylation.

Demonstration of an amino terminal La epitope recognized by human anti-La sera

In order to study the antigenic properties of the La protein we have isolated a 1650 base pair (bp)-long human cDNA encoding an anti-La reactive protein. Restriction enzyme analysis and DNA sequencing was used to compare this clone with two published but inconsistent partial sequences. Our clone extends about 220 bp further towards the 5' end than the two clones previously studied and includes a putative initiation codon. When introduced into an expression vector, stable fusion proteins were made both from the initial clone and from two deletion clones. The recombinant proteins were tested by immunoblotting against a panel of anti-La sera. All reacted with the fusion protein produced by the 1650-bp clone. About half of the anti-La sera showed reactivity against the recombinant protein from the shortest deletion clone. This indicates the presence of an epitope in the amino terminal part of the La protein, encoded by sequences not present in previously published clones.

Enzyme-linked immunosorbent assay using isolated (U) small nuclear ribonucleoprotein polypeptides as antigens to investigate the clinical significance of autoantibodies to these polypeptides

In order to investigate the clinical significance of autoantibodies to individual U small nuclear ribonucleoprotein (snRNP) polypeptides, an enzyme-linked immunosorbent assay (ELISA) using isolated 68K, A, B/B', and D polypeptides from purified U1 snRNP was developed. The ELISA levels of IgG antibodies were positively correlated with results of immunoblotting and hemagglutination. In patients positive for antibodies to ribonucleoprotein, IgG anti-68K reactivity was associated with active mixed connective tissue disease, and in particular with myositis and esophageal hypomotility. IgG B/B' and D polypeptide reactivities were associated with systemic lupus erythematosus and renal disorder. Raynaud's phenomenon was infrequent in patients with high IgG B/B' and D polypeptide reactivities. Pleuritis/pericarditis was associated with the IgG B/B' polypeptide reactivities. In longitudinal studies, ELISA levels of IgG antibodies against these polypeptides changed in parallel with disease activity.

Human autoantibody secreted by immortalized lymphocyte cell line against the 68K polypeptide of the U1 small nuclear ribonucleoprotein

Autoantibody of an immortalized human lymphocyte cell line, Su-2E4, derived from peripheral lymphocytes of a patient with mixed connective tissue disease, showed specific binding of the 68K polypeptide of U1 small nuclear RNP (snRNP) and immunoprecipitation of U1 RNA. The reaction patterns of Su-2E4 and a murine monoclonal anti-(U1)snRNP line, 2.73, and results of a competition assay with the 2 antibodies suggest similar, but not necessarily identical, epitope recognition.

Multiple antigen recognition by individual human monoclonal antibodies of rheumatic disease patient origin

We tested by Western blot several thousand antibody-secreting human cell lines immortalized by hybridoma fusion or Epstein-Barr virus transformation of peripheral blood lymphocytes from patients with systemic lupus erythematosus or mixed connective tissue disease. The blots utilized total human Jurkat cell extract as the antigen. More than 20% of these established lines produced antibodies which recognized multiple bands on the blots, frequently 50 bands or more. Experiments were performed to rule out the possibility of the bands being the result of mixed cell populations or nonspecific antibody-antigen binding. Cloning of these cell lines failed to alter the Western blot patterns produced, indicating that the populations were monoclonal. Antibody eluted from a number of the different single blot bands showed the same ability to reproduce the multiple band pattern, thus revealing the presence of only one antibody. Western blots performed in the presence of specific and nonspecific inhibitors demonstrated the ability of the antibody to specifically recognize and bind to certain antigens. Binding did not result from indiscriminate sticking of IgM molecules to the nitrocellulose paper. The patterns of multiple antigen recognition were not due to antigen degradation. Additionally, enzyme linked immunosorbant assays revealed binding of the monoclonal antibodies to specific antigens, and the antibodies failed to recognize commonly crossreactive antigens such as DNA, histone, poly-L-lysine, glycophorin, and serum glycoproteins. The patterns of multiple antigen binding to a large number of polypeptides are therefore due to single antibodies, and the binding is specific.

Structure-activity relationships for apomorphine congeners. Conformational energies vs. biological activities

A series of apomorphine congeners has been studied with respect to their ability to mimic the structural requirements of the dopamine pharmacophore in the potent and stereoselective dopamine receptor agonist (R)-apomorphine. Conformational energies of the mimicking structures calculated by molecular mechanics (MMP2) correlate well with the observed biological activities.

The use of immunoblotting and immunoprecipitation of (U) small nuclear ribonucleoproteins in the analysis of sera of patients with mixed connective tissue disease and systemic lupus erythematosus. A cross-sectional, longitudinal study

Antibodies to ribonucleoproteins (RNP) and to the Sm antigen in sera from patients with mixed connective tissue disease (MCTD) and systemic lupus erythematosus were studied using the techniques of immunoblotting and immunoprecipitation of U small nuclear RNPs. A cross-sectional study indicated that antibodies reacting with a 68K protein were associated with anti-RNP specificity in MCTD, but rarely occurred in systemic lupus erythematosus patients' sera. A longitudinal study demonstrated the persistence of MCTD blotting patterns over many years, and the subsequent disappearance of those specificities in sera from patients who were in prolonged remission.