Molecular basis of selective IgG2 deficiency. The mutated membrane-bound form of gamma2 heavy chain caused complete IGG2 deficiency in two Japanese siblings

Patients with IgG2 deficiency have recurrent sinopulmonary infections caused by Pneumococcus and Hemophilus. Hereditary and selective IgG2 deficiency was suspected in two Japanese siblings whose serum IgG2 levels were under detection limits, while other serum levels of immunoglobulin subclasses were within normal ranges. Expression level of spontaneous germline Cgamma2 transcript was normal, but that of the spontaneous mature Cgamma2 transcript was greatly decreased in the patients' PBMCs, suggesting the presence of a defect at or after the class switch to Cgamma2. We sequenced the Cgamma2 gene region, and in both patients a homozygous one-base insertion (1793insG) was present in exon 4 of the Cgamma2 gene, just upstream from the alternative splice site for M exons. The mutant membrane-bound gamma2 heavy chain loses the transmembrane domain and the evolutionarily conserved cytoplasmic domain. Considering several lines of evidence showing that intact expression of the membrane-bound heavy chain is essential for a normal response of B cells and production of secreted immunoglobulin in mice, we concluded that 1793insG is responsible for selective and complete IgG2 deficiency in these two siblings. This is the first documentation of a mutation in human selective IgG2 deficiency.

Serum IgE level is negatively correlated with the ability of peripheral mononuclear cells to produce interferon gamma (IFNgamma): evidence of reduced expression of IFNgamma mRNA in atopic patients

BACKGROUND

In patients with atopic diseases such as bronchial asthma and atopic dermatitis, an elevated serum IgE level is common. Several studies showed that interleukin-4(IL-4) and interferon-gamma (IFNgamma) are important for regulation of IgE production.

OBJECTIVES

The study was designed to examine the pathogenesis of an elevated serum IgE level at the production levels of TH1-type and TH2-type cytokines.

METHODS

The production of interleukin-2 (IL-2), IL-4, interleukin-5 (IL-5) and IFNgamma by peripheral blood mononuclear cells (PBMCs) stimulated with phytohemagglutinin (PHA) was analysed in 20 individuals with various serum IgE levels. The amount of IFNgamma mRNA in the stimulated PBMCs was analysed using a quantitative polymerase chain reaction method.

RESULTS

Cytokine production was analysed simply as a function of serum IgE level. The serum IgE level was negatively correlated with the amount of IFNgamma secreted by PBMCs (n = 20, R = -0.724, P<0.005) when logarithmically transformed data were analysed, but were not or were only weakly correlated with those of IL-4, IL-2, or IL-5 secreted by these cells (n = 20). For investigation of the cause of reduced IFNgamma production in individuals whose serum IgE level are high, the amount of IFNgamma mRNA was determined. The levels of IFNgamma mRNA expression in the stimulated PBMCs correlated well with the amount of IFNgamma secreted by the PBMCs (n = 8, R = 0.947, P < 0.001).

CONCLUSIONS

Reduced IFNgamma production ability due to reduced IFNgamma mRNA expression in PBMCs is associated with an elevated serum IgE level in atopic patients.

Identification of Dermatophagoides farinae-2-derived peptides and class II HLA molecules recognized by T cells from atopic individuals

Der f2, the group 2 allergen of Dermatophagoides farinae, is one of the major inhalation allergens in Japan. Using the mixture of a panel of overlapping synthetic peptides that spread over the entire Der f2 molecule, we found that polyclonal Der f2-specific short-term T cell lines prepared from peripheral blood mononuclear cells of 5 individuals allergic to Der f who carry most of the common HLA haplotypes seen in the Japanese population can respond mainly to 7 different peptides. Distribution of the T cell epitopes on Der f2 was not identical with that on Der p2. Five of 7 peptides stimulated T cells of more than 2 donors, regardless of HLA types. Inhibition patterns by anti-HLA class II mAbs were heterogenous in proliferative responses of each cell line, three were mainly inhibited by anti-HLA-DR mAb, and the others were inhibited by anti-HLA-DQ mAb. One of these T cell lines, SM, of which the proliferative response was partially inhibited by anti-HLA-DQ mAb, was cloned. Indeed, the T cell clone SM4.6 was restricted by DQ6 molecules encoded for by an HLA-DRB1*1502-DRB5*0102-DQA1*0103-DQB1*0601 haplotype. These results indicate that patients' T cells recognize Der f2 in association with a variety of HLA-DR or HLA-DQ as antigen-presenting molecules. Thus, although some peptides do have a more potent T cell stimulatory activity than others, the TCR ligands formed with the Der f2 molecule are highly heterogeneous, a factor also noted in Der f1-specific T cell lines in our previous study.

[Successful use of propofol for anesthesia for plasty of eyelids in epidermolysis bullosa]

A 21-year-old male with recessive dystrophic epidermolysis, required anesthesia for plastic surgery of eyelids. We took special care for the attachment of monitoring equipment and placing an intravenous cannula. Anesthesia was induced by intravenous propofol 1 mg.kg-1 and maintained with local injection of 1.0% lidocaine and continuous infusion of propofol 3-4 mg.kg-1.hr-1. Tracheal intubation was not performed and oxygen was given through a nasal cannula and spontaneous breathing was maintained throughout the anesthetic management. Respiratory condition was monitored by measuring Spo2 and end-tidal CO2 by capnography obtained from the nasal cannula. Operation was performed successfully and he was discharged without any major complications.

Two Japanese siblings with Bloom syndrome gene mutation and B-cell lymphoma

Bloom syndrome (BS) is a rare autosomal recessive genetic disorder characterized by lupus-like erythematous telangiectasia of the face, sun sensitivity, infertility and stunted growth. Upper respiratory tract and gastrointestinal infections are commonly associated with the decreased immunoglobulin levels found in BS patients. Chromosomal abnormalities are hallmarks of the disorder, and high frequencies of sister chromatid exchanges and quadriradial configurations in lymphocytes and fibroblasts are virtually diagnostic. Recently, the causative gene for BS (BLM) has been identified. We encountered and defined a family with a nonsense mutation in BLM. The brother and sister were homozygous for the mutation and both developed B-cell malignant lymphoma in their twenties. These findings indicate the importance of prenatal diagnosis and the detection of BS carriers based on molecular genetic analysis.

Management of malignant lymphoma in two siblings with Bloom's syndrome

Treatment of the malignant neoplasms which develop in patients with chromosome fragile syndrome, such as Bloom's syndrome (BS), requires extremely careful planning of the chemotherapy regime because of the excessive chemosensitivity of patients with such syndromes. Two siblings with BS developed B cell-type non-Hodgkin's lymphoma in the third decade of their lives. In both cases a 3-bp homozygous deletion of the BLM gene was detected. Since the lymphoma of the older brother was nasopharyngeal in origin, he was administrated radiation therapy as the primary treatment. However, hepatic metastasis was detected and this was the cause of his death. A 9-bp deletion in exon 7 of the p53 gene was detected in the metastatic lymphoma. His younger sister developed a lymphoma of abdominal lymph node in origin. She received a half dose of the drugs used in the acute lymphoblastic leukemia treatment without radiation, and twenty months after the diagnosis of her lymphoma she continues to be in complete remission and free of treatment complications. The p53 gene mutation was not detected in her lymphoma. These results suggest that radiation therapy and the radiation dose for the treatment for lymphoma in patients with BS should be carefully considered.

Heat shock-induced excessive relaxation of DNA in Escherichia coli mutants lacking the histone-like protein HU

Plasmid DNA in exponentially growing Escherichia coli immediately relaxes after heat shock but the relaxed DNA re-supercoils rapidly, the despite continued presence of the heat shock conditions. We have now obtained genetic evidence indicating that the histone-like protein HU of E. coli is required for this re-supercoiling of DNA. Plasmid DNA in a hupA-hupB double gene-disruption mutant relaxed excessively after heat shock, while the relaxation of DNA in a himA-himD double gene-disruption mutant and in an hns insertion mutant was transient, thereby indicating that HU protein, but not IHF or H-NS proteins, is required for the re-supercoiling of DNA. Exposure of the hupA-hupB double mutant to a temperature of 50 degrees C led to both excessive relaxation of DNA and to a decrease in viable cell number but temperatures lower than 46 degrees C did not lead to these events. Based on these results, we propose that HU protein maintains the negative supercoiling of DNA during thermal stress and contributes to cellular thermotolerance in E. coli.

A convenient method for genotyping of human O6-methylguanine-DNA methyltransferase polymorphism

O6-methylguanine-DNA methyltransferase (MGMT) is one of the DNA repair enzymes in mammals. We previously screened the variant alleles for the MGMT gene in the general population, and found three variants (V1, V2, V3), two of which caused amino acid substitutions (Leu84Phe for V1, and Trp65Cys for V2). In order to accelerate the ecogenetic and pharmacogenetic studies on MGMT polymorphism, we therefore developed a new PCR-based RFLP method for genotyping. The present method has some advantages over the initial PCR-single strand conformation polymorphism (SSCP) method, particularly regarding its simplicity, rapidity and specificity.

Evidence of apoptotic procedure in deafferented striatum after cortical injury in young adult rats

In denervated striatum after excitotoxic cortical lesion in young adult rats, apoptotic cells, though quite few, were observed by TUNEL 2 weeks after surgery. Also, prominent expressions of p53 were observed at the same time. These data indicate that apoptotic procedure may be involved in the denervation-induced degeneration even in young adults.

Inhibition of interferon-gamma production from lymphocytes stimulated with food antigens by a beta 2-agonist, procaterol, in patients with food-sensitive atopic dermatitis

Procaterol hydrochloride is a relatively new beta 2-selective agonist with a unique carbostyril nucleus. In this study, procaterol dose-dependently inhibited IFN-gamma production of peripheral blood mononuclear cells stimulated with ovalbumin in patients with hen's egg-sensitive atopic dermatitis, without inhibition of proliferative responses of peripheral blood mononuclear cells. Our results suggest that procaterol also has an effect as an immunomodulator, in addition to its effect as a beta 2-selective agonist.

Tissue and subcellular distributions, and characterization of rat brain protein phosphatase 2A containing a 72-kDa delta/B" subunit

A 74-kDa delta/B" subunit was isolated by heparin-Sepharose column chromatography from human erythrocyte protein phosphatase 2A (PP2A) consisting of a 34-kDa catalytic subunit (alpha/C) and 63- and 74-kDa regulatory subunits (beta/A and delta/B") in a ratio of 1:1:1. The purified delta/B" was used as an immunogen in mice, to prepare specific antisera against delta/B". Immunoblot analyses with the antisera detected an immunoreactive 72-kDa protein in the cytosol from various rat tissues including erythrocytes, brain, lung, testis, adrenal gland, heart, spleen, kidney, and liver. The 72-kDa protein was highly abundant in brain and was distributed evenly in cerebral cortex, cerebellum, and brain stem. The 72-kDa protein was also detected in mitochondria and microsome fractions. An immunoreactive 68-kDa protein was detected mainly in nuclear and microsome fractions. The 72-kDa protein from rat brain cytosol copurified with phosphorylated H2B histone phosphatase activity during successive chromatographies on DEAE-Toyopearl, AH-Sepharose, Sephadex G-150, H1 histone-Toyopearl, TSK DEAE-5PW, protamine-Toyopearl, and TSK G3000SW columns. The purified enzyme migrated as a single protein band on nondenaturing PAGE and as three protein bands of 34, 63, and 72 kDa in a ratio of 1:1:1 on SDS-PAGE. The molecular weight of the enzyme was estimated to be 170,000 from the s20,W value of 7.2 +/- 0.3 S and the Stokes radius of 5.5 +/- 0.1 nm. The rat brain enzyme was classified as PP2A, based on the following properties; (1) an IC50 for okadaic acid of 10(-9) M; (2) its preferential dephosphorylation of the a subunit of phosphorylase kinase; (3) its insensitivity to protein inhibitor 2; and (4) its heterotrimeric subunit structure. The Km value and the molecular activity of the enzyme for phosphorylated H2B histone were 72.3 +/- 0.3 microM and 192 +/- 2 mol Pi released/min/mol enzyme, respectively, and were comparable to those of human erythrocyte PP2A (alpha1 beta1 delta1/ CAB"). The 72-kDa subunit in the purified rat brain PP2A was phosphorylated in vitro by cAMP-dependent protein kinase.

Hydrogen peroxide induced responses of cat tracheal smooth muscle cells

1. The effects of hydrogen peroxide (H2O2) (10(-6)-10(-3) M) on membrane potential, membrane currents, intracellular calcium concentration, resting muscle tone and contractions elicited by electrical field stimulation (EFS) and carbachol were examined in cat tracheal strips and isolated smooth muscle cells. 2. H2O2 (10(-4) and 10(-5) M) enhanced the amplitude of contractions and excitatory junction potentials (e.j.p.) evoked by EFS without changing muscle tone and resting membrane potential of the tracheal smooth muscle, and enhanced the contraction induced by carbachol (10(-3) M). At an increased concentration (10(-3) M), H2O2 elevated resting muscle tone and marginally hyperpolarized the membrane in the majority of the cells. 3. In 51 out of 56 cells examined, H2O2 (10(-6)-10(-3) M) elicited an outward current at a holding potential of -40 mV and enhanced the frequency of the spontaneous transient outward current (STOC). In 20 cells the outward current was preceded by a small inward current. In the other cells, H2O2 elicited only an inward current or did not affect the background current. 4. In Ca2+ free solution the action of H2O2 on the resting muscle tone, STOCs, background current and on the current induced by ramp depolarization was significantly reduced. 5. H2O2 (10(-4) M) increased the intracellular ionized calcium concentration both in the absence and presence of external Ca2+. However, the effect developed faster and was of a higher amplitude in the presence of external Ca2+. 6. These results suggest that H2O2 increases intracellular Ca2+, with a subsequent augmentation of stimulation-evoked contractions, and enhances Ca2+ and voltage-sensitive potassium conductance.

Genetic changes induced by heterocyclic amines

Clarification of the mutational fingerprints of HCAs offers a promising approach in the investigation of the role of heterocyclic amines (HCAs) in human carcinogenesis. We analyzed mutations in the tumor related genes of tumors induced by HCAs, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), which mainly yield DNA-adducts of C8-guanine. The G-->T transversion at codon 13-2nd position in Ha-ras was predominantly observed in mouse forestomach and rat Zymbal gland tumors induced by MeIQ. In contrast, various types of mutation were detected in the ras family genes of rat Zymbal gland tumors induced by IQ; the presence of a methyl group at position 4 of imidazo[4,5-f]quinoline gave rise to a remarkable difference in the mutational fingerprint. Apc mutations were detected in PhIP- and IQ-induced rat colon tumors, with incidences of 50% (4/8) and 15% (2/13), respectively. All five mutations detected in the four PhIP-induced tumors consisted of a guanine deletion from the 5'-GGGA-3' sequence, in contrast with T to C and C to T mutations in IQ-induced tumors. Four of these five mutations shared seven common nucleotides, -GTGGGAT- surrounding the guanine; indicating that PhIP leaves a characteristic mutational fingerprint in Apc. Colon tumors induced by PhIP were also found to have mutations in their microsatellite sequences, and similar results were detected in mammary gland tumors induced by PhIP, contrasting with no mutations in IQ-induced colon tumors and a very low frequency of mutations in 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumors. Although the mechanisms involved in the induction of microsatellite mutations are not known yet, microsatellite mutations which can also be detected in sporadic human tumors, including colon and breast tumors, were indicated to be a characteristic of PhIP. Mammary tumors induced by PhIP showed loss of heterozygocity (LOH) at the distal part of chromosome 10, which shows synteny with the distal part of human chromosome 17, where LOH frequently occurs in human breast cancer. In conclusion, each heterocyclic amine leave a mutational fingerprint which is specific to each compound. Since the tumor-related genes involved in PhIP-induced tumors have characteristics in common with those in human cancers, further detailed analysis will provide us with useful information on mutational fingerprints, and on the possible contribution of PhIP to human colon cancer.

BRCA2 germline mutations in Japanese breast cancer families

Germline mutations of BRCA2 were examined in 20 Japanese breast cancer families without BRCA1 mutations, including one demonstrating cancer development in a male. Three different mutations, resulting in truncation of the BRCA2 protein, were detected in 3 different families. They were 9474insA (exon 24, termination at codon 3110), C8729A (exon 20, S2834 ter) and 982del4 (exon 9, termination at codon 275). The 982del4 mutation was detected in the family with a case of male breast cancer. Age at onset was young, with a range of 28-43 years, in the 2 female breast cancer families with truncation mutations. One probable missense mutation, A10462G (13412V), was further detected in 2 families, although cosegregation of this allele with the breast cancer phenotype was not complete. The rate of BRCA2 mutations in Japanese families was suggested to be almost the same as in Western countries, and larger than it is the case for BRCA1.

Establishment of a new cell line from a patient with hairy cell leukemia-Japanese variant

A cell line, JHC-2, was established from the peripheral blood of a patient with hairy cell leukemia (HCL)-Japanese variant. The JHC-2 cells have cytologic features similar to those of the original tumor cells. They displayed hairy cytoplasmic projections by phase contrast and scanning electron microscopy. The tartrate-resistant acid phosphatase reaction was weakly positive. The immunophenotype of the JHC-2 cells was CD5-, CD10-, CD11c+/-, CD19+, CD21+, CD23+, CD24-, CD25+/-, CD38- and FMC-7+. The expression of surface immunoglobulin (IgG, kappa) and the configuration of Ig gene rearrangements in the JHC-2 cells were identical to those in the original leukemic cells, and the JHC-2 cells displayed trisomy 9 on cytogenetic examination. Southern blot analysis for the Epstein-Barr virus (EBV) genome showed that the JHC-2 cells contained the EBV genome, although the freshly isolated leukemic cells did not. These results indicate that the JHC-2 cell line is an EBV spontaneously transformed B cell line originating from HCL cells.

Polyclonal B-cell lymphocytosis with features resembling hairy cell leukemia-Japanese variant

Polyclonal B lymphocytosis was found in four patients having clinical and hematologic features resembling those of hairy cell leukemia (HCL). All four patients were women between 37 and 67 years of age. Three patients had splenomegaly. Lymphadenopthy was absent or slight. Persistent lymphocytosis was seen in all the patients, and anemia and/or thrombopenia was observed in three of the patients. Abnormal lymphocytes have long microvilli and prominent membranous ruffles on their surfaces. Bone marrow aspirates and biopsy specimens showed increased numbers of abnormal lymphocytes with round nuclei and abundant pale cytoplasm. Although these findings were similar to those of HCL, studies of Ig gene rearrangements and expression showed the polyclonal proliferation of B cells. We called this new disease hairy B-cell lymphoproliferative disorder (HBLD). All four patients exhibited a polyclonal increase in serum IgG. The morphology of the cells in HBLD was more similar to that of leukemia cells of a variant form of HCL (HCL-Japanese variant) than to typical HCL cells. The surface IgG+, CD5-, CD11c+, CD22+, CD24-, CD25- phenotype and the weak tartrate-resistant acid phosphatase activity in the cells were identical to those of HCL cells of the Japanese variant. Our findings suggest that the B cells in HBLD are the nonmalignant counterpart of leukemic B cells in HCL-Japanese variant.

Reduced expression of the interferon-gamma messenger RNA in IgG2 deficiency

The specific defect that causes IgG2 deficiency, which is one of the primary immunodeficiencies, is unknown. Recently, it was shown that interferon-gamma (IFN-gamma) induces synthesis of human germline C gamma 2 transcripts. In the authors' previous study and the present one, peripheral blood lymphocytes (PBLs) of all five tested patients with IgG2 deficiency failed to produce enough IFN-gamma when stimulated with phytohaemagglutinin or concanavalin A although they produced a sufficient amount of interleukin-2 (IL-2). The low level of IgG2 production in pokeweed mitogen-stimulated PBLs of four tested patients was improved by the addition of recombinant IFN-gamma. In this study, the amount of IFN-gamma messenger RNA showed various degrees of reduction in all five tested patients. Sequence analysis of the IFN-gamma coding regions and flanking regions revealed neither a point mutation nor a deletion for any of the patients. Thus the results suggest that the reduced expression of IFN-gamma messenger RNA may play an important role in the IgG2 deficiency of these patients.

Bilateral breast tumors, malignant phyllodes tumor and invasive lobular carcinoma in a 46,XX/46,XY mosaic female with family history of breast cancer

Bilateral breast tumors, a malignant phyllodes tumor in the right breast and an invasive lobular carcinoma in the left breast, occurred in a 47-year-old woman with 46XX/46XY mosaic karyotype in her peripheral blood lymphocytes and intersex external genitalia. Postmortem examination revealed bilateral ovotestis. Three of the patient's sisters also had breast cancer. In situ hybridization with a Y-specific probe revealed Y-chromosome-specific signal in both tumors, suggesting that the clonal origin of tumors in this patient was Y-containing cells. Androgen-receptor polymorphism also revealed a monoallelic X chromosome pattern in the recurrent phyllodes tumor tissue taken at autopsy, in addition to loss of heterozygosity demonstrated at locus TP53. The slippage of the CA repeats in the tumor was also shown at the loci of D5S82 and D11S527. The mechanistic basis for the occurrence of bilateral malignant tumors of the breast, XX/XY mosaicism, and familial clustering of breast cancer is still unknown. The present study, however, suggests that the sex chromosome abnormality may have modified the cancer phenotype in a manner similar to breast cancer in Klinefelter's syndrome (though phenotypically male) and the Y chromosome may have promoted cell growth.

Preferential potentiation by hypotonic cell swelling of muscarinic cation current in guinea pig ileum

The effects of hypotonic cell swelling (HCS) on muscarinic receptor-activated cationic current in guinea pig ileal smooth muscle were investigated by the whole cell patch-clamp technique. With nystatin-perforated recording, reduced external tonicity from 312 to 262 mosM caused cell swelling but hardly affected the membrane currents activated by depolarization, such as outward-rectifying K and voltage-dependent Ca currents. In contrast, the inward current evoked by carbachol at -60 mV was greatly increased (approximately 50%) by the same extent of hypotonicity. This effect is likely to occur through potentiation of nonselective cation channels coupled to the muscarinic receptor (mNSCCs) and probably does not involve elevated intracellular Ca2+ concentration ([Ca2+]i), since neither removal of external Ca2+ nor [Ca2+]i buffering with 10 mM 1,2-bis-(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid significantly affected the results. Furthermore, the time course and degree of this potentiation closely matched those of video-microscopically monitored HCS. These results support the view that mechanosensitive modulation may be a powerful mechanism to regulate mNSCCs activity in gut smooth muscle, together with membrane potential and [Ca2+]i.

Increase in negative supercoiling of plasmid DNA in Escherichia coli exposed to cold shock

Negative supercoiling of plasmid DNA in Escherichia coli cells can decrease transiently when exposed to heat shock. The effect of cold shock on DNA supercoiling was examined, and analysis by agarose gel electrophoresis in the presence of chloroquine revealed that negative supercoiling of plasmid DNA in cells increased when cells were exposed to cold shock. This increase was transient and was nil when the cells were pretreated with nalidixic acid, an inhibitor of DNA gyrase. In a mutant deficient in expression of HU protein, the increase in negative supercoiling of DNA by cold shock is less apparent than in wild-type cells. It is proposed that DNA gyrase and HU protein have a role in the DNA supercoiling reaction seen with cold shock.

Identification of autophosphorylation sites in c-Yes purified from rat liver plasma membranes

c-Yes was purified 322-fold from a rat liver plasma membrane fraction to a single 60-kDa band on SDS-PAGE. The purified protein contained essentially no phosphotyrosine residues and was autophosphorylated with Mg2+. ATP exclusively at tyrosine residues with a concomitant increase in the protein-tyrosine kinase activity. The autophosphorylated c-Yes was extensively digested by trypsin and the resultant two major phosphopeptides, peptides I and II, were purified by HPLC on a reversed-phase C-18 column. The amino acid sequence of peptide I was determined to be LIEDNEYTAR, which is identical with the sequence from Leu-418 through Arg-427 of mouse c-Yes, indicating that one of the autophosphorylation sites corresponds to Tyr-424 of the mouse c-Yes. After partial determination of the N-terminal sequence of 10 amino acid residues of peptide II, the 230 bp sequence of rat cDNA that encodes the N-terminal 76 amino acid residues of c-Yes covering peptide II, was determined. From the predicted amino acid sequence, the sequence of peptide II was assumed to be from Tyr-16 through Lys-46, YTPENPTEPVNTSAGHYGVEHATAATTSSTK. The purified c-Yes phosphorylated the tyrosine residue of synthetic peptides covering Tyr-32 and its surrounding sequence but did not phosphorylate peptides covering Tyr-16 and its surrounding sequence, suggesting that the other autophosphorylation site is Tyr-32.

Microsatellite instability in B-cell lymphoma originating from Bloom syndrome

Bloom syndrome (BS) is a rare autosomal recessive genetic disorder characterized by lupus-like erythematous telangiectasias of the face, sun sensitivity, stunted growth infertility and immunodeficiency. In addition, BS patients are highly predisposed to cancers. Although recently the causative gene of BS (BLM) was identified as a DNA helicase homologue, the function of BLM in DNA replication has not been elucidated. In this study, p53 mutation and microsatellite instability in B-cell lymphomas originating from 2 sibling BS patients were investigated. In the originally developed tumor of both patients, no p53 mutation was detected. In one patient, however, after treatment by ionizing radiation the B-cell lymphoma recurred, showing a 9-bp deletion in exon 7. In lymphoma cells and an EB-virus-transformed cell line from BS lymphocytes of this patient, microsatellite instability was also detected from the reduced length of microsatellite DNA markers, although in the other patient microsatellite instability was not detected. Thus, 2 B-cell lymphomas, despite having the same BLM mutation, showed different phenotypes in terms of p53 mutation and microsatellite instability.

Electrophysiological characterization of a motilin agonist, GM611, on rabbit duodenal smooth muscle

Effects of motilin and a newly synthesized erythromycin derivative, GM611, on membrane potential and currents of rabbit duodenal smooth muscle have been investigated by intracellular potential recording and whole cell patch-clamp technique and compared with results from contractile experiments. Motilin and GM611 (0.01-100 nM) dose dependently produced slowly sustained depolarizations (half-maximal effective dose = 0.15 and 3.9 nM for motilin and GM611, respectively) but exhibited biphasic effects on spike activities superimposed on slow waves. With small depolarizations, the number of spike discharges increased, whereas larger depolarizations markedly reduced spike amplitude. Motilin-induced (or GM611-induced) depolarization appeared to be associated with the activation of monovalent cation-selective channels, and the reduction in the spike amplitude appeared mainly to be associated with inhibition of voltage-dependent Ca2+ channels. Furthermore, data from patch-clamp experiments suggested that Ca2+ release occurred from heparin-sensitive internal stores upon stimulation of motilin receptors by these agonists. Possible implications of these electrophysiological effects in motilin- or GM611-induced tonic and phasic contractions have been discussed.

VLA-5 in the plasma cell line, FR4ds, acts as a common regulator of VLA-4 and VLA-6 in spreading induced by fibronectin and laminin

VLA-5 recognizes the GRGDSP sequence of fibronectin (FN) in the extracellular matrix (ECM). We examined the role of beta1 integrin in the spreading of the human plasma cell line, FR4ds, induced by FN and laminin (LN). We first examined the role of VLA-5 in the spreading induced by FN. Anti-alpha4 antibody induced 46.4% inhibition, whereas anti-alpha5 had no effect. A combination of anti-alpha4 and anti-alpha5 enhanced the inhibition of spreading significantly. Complementary inhibition was also demonstrated using the GRGDSP peptide plus anti-alpha4 and the GRGDNP peptide of LN plus anti-alpha4. The results suggested that VLA-5 is a regulator of VLA-4 and that it is involved in the recognition of GRGDNP. We then examined the role of VLA-5 in the spreading induced by LN. Anti-alpha6 induced 53.1% inhibition. Anti-alpha5 alone had no effect. A combination of alpha5 and anti-alpha6, however, significantly enhanced the inhibition of spreading. The combination of GRGDSP plus anti-alpha6 and GRGDNP plus anti-alpha6 resulted in complete inhibition. These results suggested that VLA-5 participates in the recognition of LN cooperatively with VLA-6 and that VLA-5 is a common regulator of VLA-4 and the LN receptor, VLA-6.