Signaling and internalisation function of the B cell antigen receptor complex.
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Amino Acid Sequence↗
Biomedical subjects
K M Kim
Publications and source records attributed to K M Kim.
Positive and negative signals transduced through surface immunoglobulins in human B cells.
Cross-linking of surface IgM and surface IgD by anti-IgM antibodies and anti-IgD antibodies, respectively, showed different effects on the growth of normal human peripheral blood B cells and the human B lymphoma cell line, B104. Only cross-linking of surface IgM transduced signals that inhibited cell division of peripheral blood B cells and B104 cells at the G2/M interphase. In B104 cells, the inhibition of cell division was followed by rapid B104 cell death. The negative signals were inhibited by cyclosporin A and FK-506 at lower concentrations than those that inhibited proliferation of the B cells. Anti-IgM antibody-induced B104 cell death was dependent on Ca2+ influx and macromolecular synthesis. B104 cells treated with anti-IgM antibodies showed neither DNA fragmentation or morphology of apoptosis but showed DNA single-strand breaks and morphology of necrosis. Nicotinamide inhibited anti-IgM antibody-induced B104 cell death and the involvement of poly(adenosine diphosphate-ribosyl)ation was suggested in the process of the B104 cell death. With regard to the intracellular mechanisms responsible for the different signals, however, no qualitative difference was detected in putative signal transducers, including tyrosine phosphorylated protein, phosphatidyl inositol turnover, Ca2+ influx, activation of protein kinase C, and messenger ribonucleic acid expression of c-fos and Egr-1 when surface IgM and surface IgD were crosslinked. Further investigations of the mechanisms responsible for the different signals transduced through surface IgM and surface IgD will provide better understanding of immunodeficiencies and autoimmune diseases.
B-Lymphocytes↗
Mechanisms involved in the inhibition of growth of a human B lymphoma cell line, B104, by anti-MHC class II antibodies.
The mechanisms involved in the inhibition of growth of a human B lymphoma cell line, B104, by anti-MHC class II antibodies (Ab) were compared with those in anti-IgM Ab-induced B104 growth inhibition. Two anti-MHC class II Ab, L227 and 2.06, inhibited the growth of B104 cells, although 2.06, but not L227, needed to be further cross-linked with a goat anti-mouse IgG Ab (GAM) to show the effect. L227 induced an increase in intracellular free Ca2+ concentration ([Ca2+]i) from the intracellular pool and little or no protein tyrosine phosphorylation, phosphatidyl inositol turnover, or expression of Egr-1 mRNA, whereas 2.06 plus GAM induced an increase in [Ca2+]i from both the intracellular and, in particular, the extracellular pools. The inhibition of B104 cell growth induced by anti-MHC class II Ab was Ca(2+)-independent and not inhibited by actinomycin D or cyclosporin A, and cell cycle arrest at the G2/M interphase was not observed. These features are very different from those observed in B104 cell death induced by anti-IgM Ab. Neither DNA fragmentation nor the morphology of apoptosis was observed. These findings demonstrate that cross-linking of MHC class II molecules transduced the negative signals through intracellular mechanisms different from those present in the cross-linking of surface IgM.
Antibodies, Monoclonal↗
Graft-versus-host disease--clinical and pathological analysis of 11 biopsy proven cases.
Graft-versus-host disease (GVHD) is a life threatening complication that may occur following allogenic bone marrow transplantation (BMT) in the patients with aplastic anemia, leukemia or genetic immunodeficiency. It has been known that GVHD occurs approximately 70% of recipients of BMT in western countries but no definite incidence has been reported in Korea. In our St. Mary's Hospital, GVHD occurs in about 30% of BMT recipients. Histopathologically the acute phase skin shows diffuse lymphocytic infiltrates in the upper dermis with extensive exocytosis. Scattered throughout the epidermis are many degenerated keratinocytes, which are often associated with one or more satellite lymphocytes (satellite cell necrosis). In the chronic phase, acanthosis, eosinophilic keratinocytes resembling colloid bodies and mononuclear cell infiltrates in the upper dermis are noted. We reviewed 5 cases of acute GVHD and 6 cases of chronic GVHD. All patients received allogenic BMT from Jan. 1, 1992 to July 1, 1993. Ten patients were male and one was female. The mean age was 34 (20-70). The pathologic diagnosis was 3 cases of CML, 2 of ALL, 2 of AML (FAB M2), 2 of aplastic anemia, 1 of CLL and 1 of AML (FAB M5). The interval from BMT to GVHD varied from 14 days to 4 years (median 220 days). The skin and GI tract were involved in all eleven cases. Ten cases were histologically proven by skin biopsies, and two cases by salivary gland and colonic biopsies, respectively. The histological findings of the skin, salivary gland and colonic biopsieds were described. Immunohistochemical stain of the skin was done using CD4, CD8, HLA DR and Leu 7 antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Cloning of the human glycine transporter type 1: molecular and pharmacological characterization of novel isoform variants and chromosomal localization of the gene in the human and mouse genomes.
We report the molecular cloning of a cDNA encoding a high affinity human glycine transporter. An open reading frame of 1914 nucleotides encodes a 638-amino acid protein that transports glycine in a Na+/Cl(-)-dependent manner. In common with other Na+/Cl(-)-dependent transporters, it possesses 12 putative transmembrane domains, according to its hydropathicity profile. This protein is the human homologue of a glycine transporter previously isolated from rat [glycine transporter type 1b (GlyT-1b)]. In addition to the human GlyT-1b, we also characterized a novel functional isoform produced by alternative splicing. This isoform, GlyT-1c, which is distinct from GlyT-2 recently characterized in rat, contains an additional exon encoding 54 amino acids in the amino-terminal part of GlyT-1b and is mainly expressed in brain. These two isoforms are products of the same gene and are localized on human chromosome 1p31.3, as well as on mouse chromosome 4, close to the locus for the spontaneous mouse neuromuscular mutation clasper. When expressed in COS-7 cells, both the human GlyT-1b and GlyT-1c display a time- and dose-dependent uptake of glycine, which is abolished when either Na+ or Cl- is substituted with other ions. For both GlyT-1b and GlyT-1c the affinities for glycine are similar, with Km values of 70-90 microM, and this uptake is inhibited by sarcosine with similar potencies. In addition to the three transporter isoforms present in the human genome, i.e., GlyT-1a, GlyT-1b, and GlyT-1c, point-mutated variants, which appear to be totally devoid of glycine uptake activity when expressed in COS-7 cells, were obtained by polymerase chain reaction amplification of mRNA from human substantia nigra. These variants point to regions of the glycine transporter that might be important in the processing or transport function of this protein.
Amino Acid Sequence↗
Molecular mimicry of the antigen receptor signalling motif by transmembrane proteins of the Epstein-Barr virus and the bovine leukaemia virus.
BACKGROUND: Many transmembrane proteins of eukaryotic cells have only a short cytoplasmic tail of 10 - 100 amino acids, which has no obvious catalytic function. These tails are thought to be involved either in signal transduction or in the association of transmembrane proteins with the cytoskeleton. We have previously identified, in the cytoplasmic tails of components of B and T lymphocyte antigen receptors, an amino-acid motif that is required for signalling. The same motif is also found in the cytoplasmic tails of two viral proteins: the latent membrane protein, LMP2A, of Epstein Barr virus and the envelope protein, gp30, of bovine leukaemia virus. Interestingly, both viruses can activate infected B lymphocytes to proliferate, as does signalling by the B-cell receptor. RESULTS: In this study, we show that the cytoplasmic tails of the two viral proteins, and the cytoplasmic tail of the B-cell receptor immunoglobulin-alpha chain, when linked to CD8 in chimeric transmembrane proteins, can transduce signals in B cells. Cross-linking of these chimeric receptors activates B-cell protein tyrosine kinases and results in calcium mobilization. Furthermore, these cytoplasmic sequences are also protein tyrosine kinase substrates and may interact with cytosolic proteins carrying SH2 protein-protein interaction domains. CONCLUSION: Our findings suggest that viral transmembrane proteins can mimic the antigen-induced stimulation of the B-cell antigen receptor and thus can influence the activation and/or survival of infected B lymphocytes.
Journal Article↗
The role of G protein in muscarinic depolarization near resting potential in cultured hippocampal neurons.
Cultured neurons from the CA1 and CA3 regions of the rat hippocampus were studied by using the whole-cell version of patch clamp. Application of acetylcholine (5-10 microM) or muscarine (20 microM) to a neuron with a holding potential of approximately -70 mV produced a slow inward current. This inward current was inhibited by atropine (1-2 microM). Loading the cell with GTP gamma S caused a change in the muscarinic response. In the control cells the muscarine-induced inward current recovered by 89%. On the other hand, in the GTP gamma S-loaded cells the inward current recovered by only 30%, indicating some irreversibility. Pertussis toxin treatment did not change the muscarine-induced slow inward current. Loading the cells with cyclic AMP (100 microM) plus IBMX (1 mM) (an inhibitor of phosphodiesterase) did not occlude the effect of muscarine. We conclude that the slow inward current is mediated through a pertussis toxin-insensitive G protein, and that cyclic AMP is not a part of the signal transduction cascade. The finding that the GTP gamma S-loaded cells did not show complete irreversibility was discussed in relation to the results of Benson et al. (J. Physiol., 404 (1988) 479-496), which showed that there are two ionic mechanisms responsible for the muscarine-induced depolarization. Occasionally cells were encountered, in which muscarine (or acetylcholine) evoked a large and rapid inward current, followed by the usual slow inward current. The time course of this rapid response was not affected by GTP gamma S.
Acetylcholine↗
Differential signaling through the Ig-alpha and Ig-beta components of the B cell antigen receptor.
The B cell antigen receptor is a complex containing the antigen-binding immunoglobulin molecules and the Ig-alpha/Ig-beta heterodimer which presumably connects the B cell antigen receptor to intracellular signaling components. To analyze the functional properties of the cytoplasmic parts of the B cell antigen receptor, we used the K46 B lymphoma line (IgG2a, kappa) to express chimeric molecules composed of the extracellular and transmembrane part of the CD8 alpha molecule and the cytoplasmic sequence of either the Ig-alpha (CD8 alpha/Ig-alpha), the Ig-beta (CD8 alpha/Ig-beta) protein or the membrane-bound gamma 2a heavy chain (CD8 alpha/gamma 2a). From these three types of chimeric molecules only (CD8 alpha/Ig-alpha and CD8 alpha/Ig-beta, but not CD8 alpha/gamma 2a, could transduce signals, thus providing the first evidence that the cytoplasmic tail of Ig-alpha and Ig-beta have a signaling capacity. After cross-linking with anti-CD8 alpha antibodies, both molecules induced a similar increase in intracellular free calcium ion and in MAP kinase phosphorylation. Protein tyrosine kinases, however, were strongly activated via the CD8 alpha/Ig-alpha and only marginally via the CD8 alpha/Ig-beta molecule. This suggests that the Ig-alpha and Ig-beta proteins have distinct roles during signal transduction through the B cell antigen receptor.
Amino Acid Sequence↗
Cyclosporin A and FK506 block the negative signaling mediated by surface IgM cross-linking in normal human mature B cells.
Cross-linking of surface IgM (sIgM) or sIgD by anti-IgM Ab or anti-IgD Ab, respectively, induced DNA synthesis in peripheral blood B cells (PBL-B). Cell division, determined by the increase in the number of M phase cells, was also induced when PBL-B were stimulated with anti-IgD Ab plus IL-4 or Staphylococcus aureus Cowan I (SAC), but far less by stimulation with anti-IgM Ab plus IL-4. Anti-IgM Ab did not suppress the DNA synthesis induced by SAC or anti-IgD Ab plus IL-4, but it did suppress the cell division induced by them. Thus, sIgM cross-linking generates both positive and negative signaling to B-cell proliferation. Cyclosporin A (CSA) and FK506 suppressed DNA synthesis and cell division at relatively high concentrations. On the other hand, CSA and FK506 at lower concentrations blocked the anti-IgM Ab-generated inhibition of cell division without affecting DNA synthesis. Low concentrations of CSA did not affect the cell division induced by anti-IgD Ab plus IL-4 but did increase the cell division induced by SAC or anti-IgM Ab plus IL-4, suggesting that stimulation with SAC, as well as with anti-IgM Ab plus IL-4, generates both positive and negative signals to cell division, whereas sIgD lacks the ability to transduce negative signaling.
Antibodies, Anti-Idiotypic↗
The alterations of cellular metabolism in the contralateral testis following spermatic cord torsion in rats.
Cellular metabolic study was performed on the contralateral testis after torsion to delineate early testicular changes. In 9-week-old Sprague-Dawley rats the left testicle was rotated and fixed to the scrotum for 3, 8 and 24 hours in 3 groups (I, II and III). Each group was divided into 3 subgroups (a, b and c) by the length of detorsion of 0, 4 hours and 14 days. We measured adenosine triphosphate, total adenosine nucleotides and adenylate energy charge of the contralateral testis by high performance liquid chromatography. Compared to controls, no subgroups showed differences in the histological parameters. Also in subgroups Ia, Ib, Ic and IIa none of the metabolic parameters were significantly altered. However, subgroups IIb and IIc, and group III and its subgroups showed significantly decreased levels of all metabolic parameters. Therefore, it appears that unilateral testicular torsion (greater than 8 hours) and detorsion affect the contralateral testicular metabolism without gross histological changes in rats, and these changes seem to be reversible in terms of cellular recoverability because the maximally decreased level of adenylate energy charge among all subgroups is only 13% compared to controls. These findings suggest that some systemic mechanisms rather than an immunological or local inflammatory process is involved in this early period after torsion.
Adenine Nucleotides↗
Signalling function of the B-cell antigen receptors.
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Animals↗
Urodynamic evaluation in pediatric neurogenic bladder.
Urodynamic evaluation in pediatric neurogenic bladder is prerequisite for accurate prediction of prognosis and selection of appropriate treatment modality. We classified normal, hyperreflexic and areflexic bladders by cystometry. Hyperreflexic bladder was subdivided into two groups with or without detrusor sphincter dyssynergia and areflexic bladder into low pressure and high pressure. Among 36 patients with myelodysplasia on whom we performed a videourodynamic study vesicoureteral reflux was found in three of 7 patients with hyperreflexia with detrusor sphincter dyssynergia, two of 6 patients with hyperreflexia without detrusor sphincter dyssynergia and five of 10 patients with areflexia with high pressure. Low pressure areflexic bladder didn't show vesicoureteral reflux. When we evaluated 39 pediatric neurogenic bladder patients with a mean 25.5 follow-up months period, upper tract deterioration was improved and normal findings persisted in all the compliant patients to treatment. In the noncompliant group initial abnormal upper tract findings persisted or aggravated, especially in hyperreflexic bladder with dyssynergia and high pressure areflexic bladder. One of the three hyperreflexic bladders with dyssynergia and two of six high pressure areflexic bladders received augmented cystoplasty. These data show that urodynamic evaluation in pediatric neurogenic bladder provides excellent criteria for selecting high risk groups in pediatric neurogenic bladder.
Adolescent↗
Regulation of cell division of mature B cells by ionomycin and phorbol ester.
The growth of a human B lymphoma cell line B104, an experimental model for mature B cells, was inhibited by ionomycin but not 12-O-tetradecanoylphorbol-13-acetate (TPA). Ionomycin inhibited B104 cells from entering into the M phase of the cell cycle without affecting DNA synthesis. The inhibition of cell division of B104 cells by ionomycin occurred within 24 h after stimulation. Because such a mode of action resembles that of anti-IgM antibodies, signals transduced by Ca2+ may be responsible for the inhibition of cell division of B104 cells by anti-IgM antibodies. Indeed, EGTA suppressed the inhibition of cell division of B104 cells caused not only by ionomycin, but also by anti-IgM antibody. Although TPA itself did not have any ability to promote the growth of B104 cells, it could cancel the inhibition of cell division of B104 cells by ionomycin and increase the proportion of B104 cells entering into the M phase of the cell cycle. Staphylococcus aureus Cowan I causes the greatest proliferation of normal human peripheral blood B cells during the period from 48 to 72 h after stimulation. When ionomycin was added to S. aureus Cowan I-stimulated peripheral blood B cells at 48 h of culture, it inhibited cell division during this period without affecting DNA synthesis. In the presence of TPA, this activity of ionomycin was suppressed, and the proportion of M-phase cells increased. These results suggest that cell division of mature B cells is regulated by the signals mediated by Ca2+ and protein kinase C in a mode quite different from that of regulation of DNA synthesis.
B-Lymphocytes↗
Anti-IgM antibody-induced cell death in a human B lymphoma cell line, B104, represents a novel programmed cell death.
We investigated the mechanisms of anti-IgM antibody-induced cell death in a recently established human surface IgM+ IgD+ B lymphoma cell line, B104, the growth of which is irreversibly inhibited by anti-IgM antibody but not by anti-IgD antibody, and compared it with the cell death of T cells via TCR/CD3 complex and with the cell death of a murine anti-IgM antibody-sensitive B lymphoma cell line, WEHI-231. The rapid time course of B104 cell death and its requirements for de novo macromolecular synthesis and Ca2+ influx suggest that anti-IgM antibody-induced B104 cell death is an active Ca(2+)-dependent programmed cell death. Moreover, cyclosporin A rescued B104 cells from this lethal signal, via surface IgM, suggesting that the intracellular mechanisms involved are quite similar to those of T cell death. DNA fragmentation, which has been reported in TCR/CD3 complex-mediated T cell death, apoptosis, was not involved in the B104 cell death process, but the possible involvement of DNA single-strand breaks was suggested. Observations under light microscopy and transmission electron microscopy indicated that the morphologic features of dying B104 cells resembled necrosis rather than apoptosis. B104 cell death was shown to be quite distinct from that of WEHI-231 in cell death kinetics, the mode of cell death, and the response to cyclosporin A. These data collectively indicate that the death of B104 cells resulting from surface IgM cross-linking represents a hitherto undefined mode of programmed cell death.
Antibodies, Anti-Idiotypic↗
Anti-IgM but not anti-IgD antibodies inhibit cell division of normal human mature B cells.
Insolubilized anti-IgD antibody markedly increased DNA synthesis in and cell division of normal peripheral blood B cells (PBL-B) when used in combination with IL-4. Anti-IgM antibodies also induced DNA synthesis of PBL-B, but their ability to induce cell division was less than that of anti-IgD antibodies even when used in combination with IL-4. Moreover, anti-IgM antibodies inhibited cell division of PBL-B stimulated with insolubilized anti-IgD antibody plus IL-4 without affecting DNA synthesis. Anti-IgM antibodies also inhibited Staphylococcus aureus Cowan I-induced cell division of PBL-B without affecting DNA synthesis. These results indicate that cross-linkage of surface IgM (sIgM) in mature B cells generates negative signals to inhibit cell division of mature B cells. Because anti-IgD antibodies did not inhibit cell division at all, the role of sIgD in the regulation of cell division of mature B cells may be quite different from that of sIgM. IFN-alpha/beta promoted cell division of PBL-B stimulated with insolubilized anti-IgD antibody plus IL-4. They also counteracted the inhibitory effect of anti-IgM antibody on cell division of PBL-B.
Antibodies, Anti-Idiotypic↗
Acute hemodynamic and endocrinological effects of partial fetal bladder obstruction.
The pathophysiology of fetal urinary obstruction has not been elucidated. Using a unique, reproducible and easily reversible animal preparation, we studied the acute hemodynamic and endocrinological responses to partial fetal bladder obstruction in 16 ovine fetuses at 115 days of gestation (term 147 days). After partial obstruction blood pressure and renal weight increased significantly for at least 72 hours. Renal blood flow trended upwards, particularly from 24 to 72 hours, although this change was not statistically significant. Plasma renin activity was significantly increased during the first 24 hours after obstruction but it returned to baseline thereafter. Plasma cortisol or catecholamine concentrations remained unchanged. The time course and pattern of hemodynamic changes in this fetal sheep preparation of partial urinary obstruction differ significantly from those reported in other preparations.
Animals↗
Tyrosine phosphorylation of IgM- and IgD-associated molecules of a human B lymphoma cell line B104.
We investigated tyrosine phosphorylation and structural properties of the IgM-associated molecules in comparison with IgD-associated molecules in a recently established human surface IgM+, IgD+ B lymphoma cell line, B104, the growth of which was irreversibly inhibited by anti-IgM mAbs but not by anti-IgD mAbs. Tyrosine kinase activity and tyrosine phosphorylated proteins were detected in anti-IgM and anti-IgD immunoprecipitates from digitonin lysates of B104 cells with the use of an in vitro kinase assay followed by a re-immunoprecipitation experiment with anti-phosphotyrosine mAbs. Tyrosine phosphorylated proteins of 74, 58-44, 41, and 39 kDa were detected in anti-IgM immunoprecipitates, whereas tyrosine phosphorylated proteins of 74, 58-44, and 39 kDa, but not 41 kDa, were detected in anti-IgD immunoprecipitates. Crosslinking of surface IgM and surface IgD stimulated rapid tyrosine phosphorylation of different sets of proteins which included tyrosine-phosphorylated proteins of the same or similar molecular weights as those detected in the anti-IgM and anti-IgD immunoprecipitates respectively. After deglycosylation by N-glycosidase, both the IgM- and IgD-associated phosphoproteins (pp58-pp39) gave rise to the same three bands of 29, 27, and 26 kDa. Proteolytic peptide mapping of these three deglycosylated proteins showed that the primary structures of the IgM- and IgD-associated molecules are identical, suggesting that the IgM- and IgD-associated phosphoproteins (pp58-pp39) are the products of the same or closely related genes. One of the products, pp41, may be associated with IgM, but not with IgD, although the same gene product may be associated with IgD in a different glycosylation pattern.
Antibodies, Anti-Idiotypic↗
Differences in the effects of divorce on major depression in men and women.
OBJECTIVE: The authors examined the relationship between marital disruption and major depressive episodes. METHOD: The analyses were based on longitudinal, community-based data from the New Haven Epidemiologic Catchment Area (ECA) program on respondents 18-60 years old. The presence and history of major depression was assessed by using the National Institute of Mental Health Diagnostic Interview Schedule. RESULTS: Martial disruption was associated with higher prevalence rates of major depression in both men and women, but only men had a greater risk of a first-onset major depression. Differences between men and women in rates of major depression were observed only among married subjects. CONCLUSIONS: These findings suggest that the relationship between marital disruption and major depressive episode differs for men and women. They also provide further evidence that differences between men and women in rates of depression vary by marital status.
Adolescent↗