TLRs activate NFkB, AP-1, and IRF transcription factors to induce the expression of inflammatory cytokines and type I interferons. A key feature of TLR signaling is the ability to induce inflammatory cytokine gene expression extremely rapidly following TLR stimulation. This is accomplished by signaling pathways using several mechanisms to activate transcription factors that are already present in the cell prior to TLR stimulation, but are kept in an inactive state. These signaling pathways use all of the following mechanisms EXCEPT: Induced ubiquitination leading to protein degradation Induced ubiquitination inducing protein–protein interactions Induced phosphorylation leading to nuclear translocation Induced phosphorylation leading to kinase activation Induced phosphorylation preventing protein degradation

TLRs activate NFkB, AP-1, and IRF transcription factors to induce the expression of inflammatory cytokines and type I interferons. A key feature of TLR signaling is the ability to induce inflammatory cytokine gene expression extremely rapidly following TLR stimulation. This is accomplished by signaling pathways using several mechanisms to activate transcription factors that are already present in the cell prior to TLR stimulation, but are kept in an inactive state. These signaling pathways use all of the following mechanisms EXCEPT: Induced ubiquitination leading to protein degradation Induced ubiquitination inducing protein–protein interactions Induced phosphorylation leading to nuclear translocation Induced phosphorylation leading to kinase activation Induced phosphorylation preventing protein degradation

Biology 2e

2nd Edition

ISBN:9781947172517

Author:Matthew Douglas, Jung Choi, Mary Ann Clark

Publisher:Matthew Douglas, Jung Choi, Mary Ann Clark

Chapter9: Cell Communication

Section: Chapter Questions

Problem 13RQ: A scientist observes a mutation in the transmembrane region of EGFR that eliminates its ability to...

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Once an activated signaling pathway has elicited the proper changes in target gene expression, the pathway must be inactivated. Otherwise, pathological consequences may result, as exemplified by persistent growth factor initiated signaling in many cancers. Many signaling pathways possess intrinsic negative feedback by which a downstream event in a pathway turns off an upstream event. Describe the negative feedback that down-regulates signals induced by (a) erythropoietin and (b) TGF-β.
Put the following steps for the outline of the growth factor signaling pathway in order: Map Kinase Kinase is Phosphorylated Proteins involved in gene transcription are activated Growth factor binds to its receptor in the cytoplasmic membrane Receptor recruits adaptor protein and GEF Autophosphorylation of tyrosine residues on the receptor Structural change of the receptor activates Tyrosine Kinase Map Kinase Kinase Kinase is phosphorylated Ras, a small GTPase, is activated by the exchange of GTP for GDP Map Kinase is Phosphorylated Map Kinase enters the nucleus
Binding of TGF-β to its receptors can elicit a variety of responses in different cell types. For example, TGF-β induces plasminogen activator inhibitor 1 in epithelial cells and specific immunoglobulins in B cells. In both cell types, Smad3 is activated. Given the conservation of the signaling pathway, what accounts for the diversity of the response to TGF-β in various cell types?
Some viruses have mechanisms to down-regulate MHC class I protein expression on the surface of cells in which the virus is replicating. This immune evasion strategy might prevent effector CD8 cytotoxic T cells from recognizing and killing the virus-infected cells. Would this immune evasion strategy also prevent the initial activation of virus-specific CD8 T cells? Yes, because no viral peptide:MHC class I complexes would form to activate CD8 T cells. No, because dendritic cells would take up infected cells and cross-present viral peptides to activate CD8 T cells. No, because some presentation of MHC class I complexes with viral peptides would occur before the virus could down-regulate all the surface MHC class I protein. Yes, because this immune evasion strategy would also function in dendritic cells, even if the virus doesn’t replicate in dendritic cells. No, because the type I interferon response induced by the virus infection will up-regulate MHC class I expression and override the…
When T cells are activated by recognizing peptide:MHC complexes on dendritic cells in the lymph node, they up-regulate the receptor CD69. For T cells expressing a given T-cell receptor, the initial strength of the T-cell receptor signal can be modulated by varying the number of peptide:MHC complexes on the dendritic cells, or by varying the affinity with which the T cell-receptor binds to the peptide:MHC complexes. As a result, T cells stimulated with stronger T-cell receptor signals will maintain high expression of CD69 for one or two days longer that if those same T cells were stimulated with weaker T-cell receptor signals. Therefore, T cells stimulated with weaker T-cell receptor signals are likely to: Die by apoptosis Undergo more rounds of proliferation that T cells stimulated with stronger T-cell receptor signals Migrate to the B-cell zones of the lymph node Have reduced effector functions, such as cytokine production Egress from the lymph node 1–2 days earlier than T cells…
Why is the signaling pathway that activates NF-κB considered to be relatively irreversible compared with cytokine or RTK signaling pathways?
which of hthe following would result in a persisting proliferation response to growth factor receptor activation after the ligand is no longer binding to its rceptor kinase? 1. Both a mutation that blocks the GTPas activity of Ras and a mutation that blocks the exchange of GDP with GTP would cause the response to persist. 2. a mutation that blocks the GTPas activity of Ras 3. neither a mutation that blocks the GTPas activity of Ras nor a mutation that blocks the exchange of GDP with GTP would cause the response to persist 4. a mutatiaon that blocks the exchange of GDP with GTP
TLR-4 recognizes bacterial lipopolysaccharide in association with the host accessory proteins MD-2 and CD14. Stimulation of the nucleic acid sensing TLRs that reside in endosomal membranes induces the production of a different cytokine response than is produced by stimulation of the plasma membrane TLRs. In part, this distinction is based on the different adapter proteins used by the nucleic acid sensing TLRs, leading to the activation of IRF factors. The cytokine response following stimulation of nucleic acid-sensing TLRs is characterized by production of: The antiviral cytokine, type I interferon TNF-a, which induces increased vascular permeability Antimicrobial peptides by macrophages Chemokines that recruit neutrophils The inflammatory complement fragments, C3a and C5a
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The first JAK kinase inhibitor to be developed, tofacitinib, inhibits JAK1 and JAK3. These two JAK kinases are required for the signaling pathways induced by multiple cytokines, including all of the receptors that share the cytokine receptor common gamma chain (gc; includes the receptors for IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21), all of the receptors that share gp130 (includes the receptor for IL-6), the receptors for GM-CSF, IL-12, and IL-23, and both type I and type II (i.e., IFN-g) interferon receptors. Tofacitinib has recently been shown to be effective in the treatment of severe rheumatoid arthritis, an autoimmune disease characterized by inflammation of the joints with prominent inflammatory cell infiltrates, autoantibodies, and eventual cartilage and bone destruction. A likely explanation for the therapeutic benefits of tofacitinib in this disease is: Its ability to inhibit the T cell functions that eventually lead to other disease symptoms Its ability to prevent T cell…