Cross-linking of the B-cell antigen receptor (BCR) induces tyrosine phosphorylation of Shc, which is believed to lead to the activation of Ras. Previous work has shown that tyrosine-phosphorylated Shc forms complexes with another adapter... more
Cross-linking of the B-cell antigen receptor (BCR) induces tyrosine phosphorylation of Shc, which is believed to lead to the activation of Ras. Previous work has shown that tyrosine-phosphorylated Shc forms complexes with another adapter protein, Grb2, and the Ras guanine nucleotide exchange factor SOS. Here, we demonstrate that phosphorylation of Shc by the hematopoietic cell-specific tyrosine kinase Syk induces binding
Research Interests: Membrane Proteins, Signal Transduction, Biological Sciences, Molecular and cellular biology, Humans, and 13 moreSequence alignment, Mice, Animals, Proteins, Phosphotyrosine, B Lymphocytes, Amino Acid Sequence, Protein Binding, Binding Site, Gtp Binding Proteins, Tyrosine Kinase, Tyrosine Phosphorylation, and B cell antigen receptor (BCR)
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Cross-linking of the B cell AgR results in activation of mature B cells and tolerization of immature B cells. The initial signaling events stimulated by membrane immunoglobulin (mIg) cross-linking are tyrosine phosphorylation of a number... more
Cross-linking of the B cell AgR results in activation of mature B cells and tolerization of immature B cells. The initial signaling events stimulated by membrane immunoglobulin (mIg) cross-linking are tyrosine phosphorylation of a number of proteins. Among the targets of mIg-induced tyrosine phosphorylation are the tyrosine kinases encoded by the lyn, blk, fyn, and syk genes, the mIg-associated proteins MB-1 and Ig-beta, phospholipase C-gamma 1 and -gamma 2, as well as many unidentified proteins. In this report we show that mIg cross-linking also regulates phosphatidylinositol 3-kinase (PtdIns 3-kinase), an enzyme that phosphorylates inositol phospholipids and plays a key role in mediating the effects of tyrosine kinases on growth control in fibroblasts. Cross-linking mIg on B lymphocytes greatly increased the amount of PtdIns 3-kinase activity which could be immunoprecipitated with anti-phosphotyrosine (anti-tyr(P) antibodies. This response was observed after mIg cross-linking in m...
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In general, a long-lasting immune response to viruses is achieved when they are infectious and replication competent. In the mouse, the neutralizing antibody response to Friend murine leukemia virus is contributed by an allelic form of... more
In general, a long-lasting immune response to viruses is achieved when they are infectious and replication competent. In the mouse, the neutralizing antibody response to Friend murine leukemia virus is contributed by an allelic form of the enzyme Apobec3 (abbreviated A3). This is counterintuitive because A3 directly controls viremia before the onset of adaptive antiviral immune responses. It suggests that A3 also affects the antibody response directly. Here, we studied the relative size of cell populations of the adaptive immune system as a function of A3 activity. We created a transgenic mouse that expresses all seven human A3 enzymes and compared it to WT and mouse A3-deficient mice. A3 enzymes decreased the number of marginal zone B cells, but not the number of follicular B or T cells. When mouse A3 was knocked out, the retroelement hitchhiker-1 and sialyl transferases encoded by genes close to it were overexpressed three and two orders of magnitude, respectively. We suggest that A3 shifts the balance, from the fast antibody response mediated by marginal zone B cells with little affinity maturation, to a more sustained germinal center B-cell response, which drives affinity maturation and, thereby, a better neutralizing response.
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Macrophage Fc g receptors (Fc g Rs) mediate the uptake and destruction of antibody-coated vi- ruses, bacteria, and parasites. We examined Fc g R signaling and phagocytic function in bone marrow-derived macrophages from mutant mice lacking... more
Macrophage Fc g receptors (Fc g Rs) mediate the uptake and destruction of antibody-coated vi- ruses, bacteria, and parasites. We examined Fc g R signaling and phagocytic function in bone marrow-derived macrophages from mutant mice lacking the major Src family kinases ex- pressed in these cells, Hck, Fgr, and Lyn. Many Fc g R-induced functional responses and signal- ing events
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Summary Receptors on macrophages for the Fc region of IgG (Fc g R) mediate a number of responses important for host immunity. Signaling events necessary for these responses are likely initi- ated by the activation of Src-family and... more
Summary Receptors on macrophages for the Fc region of IgG (Fc g R) mediate a number of responses important for host immunity. Signaling events necessary for these responses are likely initi- ated by the activation of Src-family and Syk-family tyrosine kinases after Fc g R cross-linking. Macrophages derived from Syk-deficient (Syk 2 ) mice were defective in phagocytosis of parti-
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Bacterial lipopolysaccharide (LPS) elic- its responses by macrophages that help the body repel infections. Recent evidence indicates that phosphatidylinositol 3-kinase (PI 3-kinase) may mediate some of these responses. Here, we show that... more
Bacterial lipopolysaccharide (LPS) elic- its responses by macrophages that help the body repel infections. Recent evidence indicates that phosphatidylinositol 3-kinase (PI 3-kinase) may mediate some of these responses. Here, we show that exposing macrophages to LPS rapidly in- creased membrane-associated PI 3-kinase activity and also elevated p70 S6 kinase activity. Inhibitors of PI 3-kinase or the mammalian target of rapamy-
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AVID (Angiography Versus Intravascular ultrasound-Directed stent placement) is a multicenter, randomized controlled trial designed to assess the effect of intravascular ultrasound (IVUS)-directed stent placement on the 12-month rate of... more
AVID (Angiography Versus Intravascular ultrasound-Directed stent placement) is a multicenter, randomized controlled trial designed to assess the effect of intravascular ultrasound (IVUS)-directed stent placement on the 12-month rate of target lesion revascularization (TLR). After elective coronary stent placement and an optimal angiographic result (<10% stenosis), 800 patients were randomized to Angiography- or IVUS-directed therapy. Blinded IVUS was performed in the Angiography group without further therapy. In the IVUS group, IVUS criteria for optimal stent placement (<10% area stenosis, apposition, and absence of dissection) were applied. Final minimum stent area was 6.90+/-2.43 mm(2) in the Angiography group and 7.55+/-2.82 mm(2) in the IVUS group (P=0.001). In the IVUS group, only 37% with inadequate expansion (<90%) received further therapy. The 12-month TLR rate was 12.0% in the Angiography group and 8.1% in the IVUS group (P=0.08, 95% confidence level [CI], [-8.3% t...
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Myocardial Ischemia/Infarction Enhancing Quality of Care for Acute Myocardial Infarction: Shifting the Focus of Improvement From Key Indicators to Process of Care and Tool Use The American College of Cardiology Acute Myocardial Infarction Guidelines Applied in Practice Project in Michigan: Flint ...more
The antigen receptor of B lymphocytes (BCR) plays important roles in virtually every stage in the development, inactivation, or activation of B cells. The BCR is a complex of membrane immunoglobulin (mIg) and a heterodimer of two... more
The antigen receptor of B lymphocytes (BCR) plays important roles in virtually every stage in the development, inactivation, or activation of B cells. The BCR is a complex of membrane immunoglobulin (mIg) and a heterodimer of two transmembrane polypeptides called Ig-alpha and Ig-beta. Site directed mutation of the mu immunoglobulin heavy chain has demonstrated that the mu transmembrane domain plays a key role in the assembly of mIgM with Ig-alpha/Ig-beta. In addition, there is a strong correlation between the ability of various mutant mIgM molecules to associate with Ig-alpha/Ig-beta and their ability to induce signal transduction reactions such as protein tyrosine phosphorylation and phosphoinositide breakdown. The cytoplasmic domains of Ig-alpha and Ig-beta share a region of limited homology with each other and with components of the T cell antigen receptor and of the Fc receptor. The presence of regions of the cytoplasmic domains of Ig-alpha or Ig-beta including this conserved amino acid sequence motif is sufficient to confer signaling function on chimeric transmembrane proteins. Both Ig-alpha and Ig-beta chimeras are capable of inducing all of the BCR signaling events tested. Based on these and related observations, we propose that the motifs act to initiate the BCR signaling reactions by binding and activating tyrosine kinases. Among the important events mediated by BCR signaling is induced expression of a series of genes referred to as early response genes. In B cells these include transcription factors and at least one component that regulates signaling events. One of these genes, c-myc, appears to play an important role in mediating apoptosis in B cells stimulated via the BCR complex.
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Activation of macrophages by bacterial lipopolysaccharide (LPS) induces transcription of genes that encode for proinflammatory regulators of the immune response. Previous work has suggested that activation of the transcription factor... more
Activation of macrophages by bacterial lipopolysaccharide (LPS) induces transcription of genes that encode for proinflammatory regulators of the immune response. Previous work has suggested that activation of the transcription factor activator protein 1 (AP-1) is one LPS-induced event that mediates this response. Consistent with this notion, we found that LPS stimulated AP-1-mediated transcription of a transfected reporter gene in the murine macrophage cell line RAW 264.7. As AP-1 activity is regulated in part by activation of the c-Jun N-terminal kinase (JNK), which phosphorylates and subsequently increases the transcriptional activity of c-Jun, we examined whether LPS treatment of macrophages resulted in activation of this kinase. LPS treatment of RAW 264.7 cells, murine bone marrow-derived macrophages, and the human monocyte cell line THP-1 resulted in rapid activation of the p46 and p54 isoforms of JNK. Treatment with wild-type and rough mutant forms of LPS and synthetic lipid A resulted in JNK activation, while pretreatment with the tyrosine kinase inhibitor herbimycin A inhibited this response. Binding of LPS-LPS binding protein (LBP) complexes to CD14, a surface receptor that mediates many LPS responses, was found to be crucial, as pretreatment of THP-1 cells with the monoclonal antibody 60b, which blocks this binding, inhibited JNK activation. These results suggest that LPS activation of JNK in monocyte/macrophage cells is a CD14- and protein tyrosine phosphorylation-dependent event that may mediate the early activation of AP-1 in regulating LPS-triggered gene induction.
Research Interests: Immune response, Kinetics, Enzyme Inhibitors, Macrophages, Multidisciplinary, and 19 moreLipopolysaccharide, Cell line, Humans, Escherichia coli, Mice, Animals, Quinones, Transcription Factor, Salmonella, Lipopolysaccharides, Tyrosine Kinase Inhibitor, Monocytes, Transfection, Monoclonal Antibody, Recombinant Proteins, Protein Binding, Lipid A, Benzoquinones, and Tyrosine Phosphorylation
Research Interests: Immunology, Nature, Dendritic Cells, Signal Transduction, Inflammatory Bowel Disease, and 14 moreHumans, Mice, Animals, Dendritic cell, Splenomegaly, Ankylosing Spondylitis, Colitis, T lymphocytes, Population expansion, Homeostasis, Cysteine endopeptidases, DNA binding proteins, Lymphatic Diseases, and Crohn Disease
Signalling by membrane immunoglobulin, the B-lymphocyte antigen receptor, regulates B-cell maturation and activation. Crosslinking of membrane immunoglobulin by antigen or by anti-immunoglobulin antibodies inactivates immature B cells,... more
Signalling by membrane immunoglobulin, the B-lymphocyte antigen receptor, regulates B-cell maturation and activation. Crosslinking of membrane immunoglobulin by antigen or by anti-immunoglobulin antibodies inactivates immature B cells, eliminating many of the B cells capable of producing auto-antibodies. By contrast, crosslinking of membrane immunoglobulin promotes activation of mature B cells for clonal expansion and antibody production against foreign antigens. Crosslinking membrane IgM on the immature B-cell line WEHI-231 induces growth arrest. This response may be analogous to the deletion or inactivation of immature B cells that is induced by antigen or anti-IgM antibodies. Membrane immunoglobulin crosslinking stimulates phosphoinositide hydrolysis, which leads to increases in intracellular calcium and activation of protein kinase C. The induced phosphoinositide breakdown is important for inhibiting WEHI-231 growth (ref. 7 and D. Page, M.R.G., K. Fahey, L. Matsuuchi and A.L.D., manuscript submitted for publication), but may not be sufficient, as agents that elevate calcium and activate protein kinase C cause only partial growth arrest. We now show that in both mature splenic B cells and the immature B-cell line WEHI-231 crosslinking membrane immunoglobulin also stimulates phosphorylation of protein tyrosine, a reaction that has been implicated as a key regulator of cell growth. Most of these phosphorylations were not a consequence of the phosphoinositide pathway. Thus, tyrosine phosphorylation is a second mode of transmembrane signalling by membrane immunoglobulin.
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To determine how all-cause hospitalizations within 12 months preceding an index heart failure (HF) hospitalization affect risk stratification for 30-day all-cause readmission. Early readmission of inpatients with HF is challenging to... more
To determine how all-cause hospitalizations within 12 months preceding an index heart failure (HF) hospitalization affect risk stratification for 30-day all-cause readmission. Early readmission of inpatients with HF is challenging to predict, yet this outcome is used to compare hospital performance and guide reimbursement. Most risk models do not consider the potentially important variable of prior admissions. We analyzed Medicare inpatients with HF aged 66 years or older admitted to 14 Michigan community hospitals from October 1, 2002, to March 31, 2003, and from January 1 to June 30, 2004. Clinical data were obtained from admission charts, hospitalization dates from Centers for Medicare &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp; Medicaid Services (CMS) claims, and mortality dates from the Social Security Death Index. We used mixed-effects logistic regression and reclassification indices to evaluate the ability of a CMS chart-based readmission risk model, prior admissions, and their combination to predict 30-day readmission in survivors of the index HF hospitalization. Of 1807 patients, 43 (2.4%) died during the index admission; 476 of 1764 survivors (27%) were readmitted 30 or fewer days after discharge. Adjusted for the CMS readmission model, prior admissions significantly increased the odds of 30-day readmission (1 vs 0: odds ratio, 4.67; 95% CI, 3.37-6.46; ≥2 vs 0: odds ratio, 6.49; 95% CI, 4.93-8.55; both P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;.001), improved model discrimination (c statistic, 0.61-0.74, P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;.001), and reclassified many patients (net reclassification index, 0.40; integrated discrimination index, 0.12). In Medicare inpatients with HF, prior all-cause admissions strongly increase all-cause readmission risk and markedly improve risk stratification for 30-day readmission.
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Research Interests: Cardiology, Treatment Outcome, Peer Review, Quality of Care, Process, and 17 moreHumans, Project evaluation, Female, Male, Care, Michigan, Acute Myocardial Infarction, Patient Admission, Enzyme, Aged, Myocardial Infarction, Public health systems and services research, Coronary artery bypass surgery, Pilot Projects, Expansion, Angiotensin Converting Enzyme Inhibitors, and The American
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Research Interests: Mice, DBA, Animals, Peptides, The, and 5 moreT lymphocytes, Experimental Medicine, B Lymphocytes, Epitopes, and Interphase
B cell antigen receptor (BCR) cross-linking activates both Src family and Syk tyrosine kinases, resulting in increased cellular protein-tyrosine phosphorylation and activation of several downstream signaling enzymes. To define the role of... more
B cell antigen receptor (BCR) cross-linking activates both Src family and Syk tyrosine kinases, resulting in increased cellular protein-tyrosine phosphorylation and activation of several downstream signaling enzymes. To define the role of Syk in these events, we expressed the BCR in the AtT20 mouse pituitary cell line. These nonlymphoid cells endogenously expressed the Src family kinase Fyn but not Syk. Anti-IgM stimulation of these cells failed to induce most of the signaling events that occur in B cells. BCR-expressing AtT20 transfectants were generated that also expressed Syk. Syk expression reconstituted several signaling events upon anti-IgM stimulation, including Syk phosphorylation and association with the BCR, tyrosine phosphorylation of numerous proteins including Shc, and activation of mitogen-activated protein kinase. In contrast, Syk expression did not reconstitute anti-IgM-induced inositol phosphate production. A catalytically inactive Syk mutant could associate with the BCR and become tyrosine phosphorylated but could not reconstitute downstream signaling events. Expression of the Src family kinase Lck instead of Syk also did not reconstitute signaling. Thus, wild type Syk was required to reconstitute several BCR-induced signaling events but was not sufficient to couple the BCR to the phosphoinositide signaling pathway.
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... Increases in InsPi clearly preceed inereases in InsP: and lnsP, supporting the idea that anti-IgM causes selective cleavage of PtdlnsP; and that InsP: and InsP are derived from InsPj rather than from phospholipase C action on PtdlnsP... more
... Increases in InsPi clearly preceed inereases in InsP: and lnsP, supporting the idea that anti-IgM causes selective cleavage of PtdlnsP; and that InsP: and InsP are derived from InsPj rather than from phospholipase C action on PtdlnsP or Ptdlns, respectively. Page 6. ...