Signal Transduction Gomperts, Bastien D; Kramer, ljsbrand M; Tatham, Peter E. R
2002, 2002-03-08
eBook
Signal Transduction is a well-illustrated, coherent look at cellular signaling processes. Beginning with the basics, it explains how cells respond to external cues, hormones, growth factors, ...cytokines, cell surfaces, etc., and then shows how these inputs are integrated and coordinated. The extensive color artwork provides the reader with a clearer comprehension of key topics, and margin notes are incorporated to highlight milestones in the evolution of signal transduction. This book serves as an invaluable resource for advanced undergraduates, graduate researchers, and established scientists working in cell biology, pharmacology, immunology, and related fields.
The prodromal phase of dementia with Lewy bodies (DLB) includes (1) mild cognitive impairment (MCI), (2) delirium-onset, and (3) psychiatric-onset presentations. The purpose of our review is to ...determine whether there is sufficient information yet available to justify development of diagnostic criteria for each of these. Our goal is to achieve evidence-based recommendations for the recognition of DLB at a predementia, symptomatic stage. We propose operationalized diagnostic criteria for probable and possible mild cognitive impairment with Lewy bodies, which are intended for use in research settings pending validation for use in clinical practice. They are compatible with current criteria for other prodromal neurodegenerative disorders including Alzheimer and Parkinson disease. Although there is still insufficient evidence to propose formal criteria for delirium-onset and psychiatric-onset presentations of DLB, we feel that it is important to characterize them, raising the index of diagnostic suspicion and prioritizing them for further investigation.
Airways are exposed to myriad environmental and damaging agents such as reactive oxygen species (ROS), which also have physiological roles as signaling molecules that regulate stem cell function. ...However, the functional significance of both steady and dynamically changing ROS levels in different stem cell populations, as well as downstream mechanisms that integrate ROS sensing into decisions regarding stem cell homeostasis, are unclear. Here, we show in mouse and human airway basal stem cells (ABSCs) that intracellular flux from low to moderate ROS levels is required for stem cell self-renewal and proliferation. Changing ROS levels activate Nrf2, which activates the Notch pathway to stimulate ABSC self-renewal and an antioxidant program that scavenges intracellular ROS, returning overall ROS levels to a low state to maintain homeostatic balance. This redox-mediated regulation of lung stem cell function has significant implications for stem cell biology, repair of lung injuries, and diseases such as cancer.
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•ROS level flux regulates self-renewal of mouse and human airway basal stem cells•ROS flux signals through Nrf2 to regulate the canonical Notch pathway•Notch regulates airway basal stem cell self-renewal•Control of ROS flux by Nrf2 is critical for preserving airway stem cell homeostasis
Paul et al. show that dynamic changes in the levels of reactive oxygen species activate Notch signaling to control proliferation and self-renewal of airway basal stem cells.
Interaction of ligands with 'Ca2+-mobilizing' receptors is thought to result in the generation of two second messengers, inositol trisphosphate and diacylglycerol, from a common substrate, ...phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) (refs 1, 2), a component of plasma membranes. It is not known how the occupation of such receptors is translated into the activation of the catalytic unit polyphosphoinositide (PPI) phosphodiesterase, and then to cellular activation, but our recent experiments suggest that GTP regulatory proteins may be involved. In mast cells, non-hydrolysable analogues of GTP introduced and then trapped in the cytosol are able to substitute for external ligands in inducing exocytosis, a well-defined Ca2+-dependent process, suggesting that guanine nucleotide regulatory proteins may act by stimulating the catalytic activity of the PPI phosphodiesterase. We now provide evidence that mast cell secretion is inhibited by internalized neomycin, a compound known to interact with PPI. We also show that the PPI phosphodiesterase of human neutrophil plasma membranes can be activated simply by adding GTP analogues in the presence of concentrations of Ca2+ that pertain in unstimulated cells. These findings strongly support the idea that the coupling factor linking receptor and PPI phosphodiesterase is a guanine nucleotide binding protein analogous to those involved in the activation and inhibition of adenylate cyclase.
We applied recombinant forms of the Rho-related small guanosine triphosphatases (GTPases) Rac2 and Cdc42/G25K to permeabilized mast cells to test their ability to regulate exocytotic secretion. Mast ...cells permeabilized with streptolysin-O leak soluble (cytosol) proteins over a period of 5 min and become refractory to stimulation by Ca2+ and guanosine triphosphate (GTP)gammaS over about 20-30 min. This loss of sensitivity is likely to be due to loss of key regulatory proteins that are normally tethered at intracellular locations. Exogenous proteins that retard this loss of sensitivity to stimulation may be similar, if not identical, to those secretory regulators that are lost. Recombinant Rac and Cdc42/G25K, preactivated by binding GTPgammaS, retard the loss of sensitivity (run-down) and, more importantly, enable secretion to be stimulated by Ca2+ alone. Investigation of the concentration dependence of each of these two GTPases applied individually to the permeabilized cells, and of Cdc42/G25K applied in the presence of an optimal concentration of Rac2, has provided evidence for a shared effector pathway and also a second effector pathway activated by Cdc42/G25K alone. Dominant negative mutant (N17) forms of Rac2 and Cdc42/G25K inhibit secretion induced by Ca2+ and GTPgammaS. Our data suggest that Rac2 and Cdc42 should be considered as candidates for GE, GTPases that mediate exocytosis in cells of hematopoeitic origin.
The major part of mast cell actin is Triton-soluble and behaves as a monomer in the DNase I inhibition assay. Thus, actin exists predominantly in monomeric or short filament form, though filamentous ...actin is clearly apparent in the cortical region after rhodamine-phalloidin (RP) staining. The minimum actin content is estimated to be ∼2.5 μ g/106 cells (cytosolic concentration ∼110 μM. After permeabilization of mast cells by the bacterial cytolysin streptolysin-O, ∼60% of the Triton-soluble actin leaks out within 10 min. However, the staining of the cortical region by RP remains undiminished, and the cells are still capable of exocytosis when stimulated by GTP-γ-S together with Ca2+. In the presence of cytochalasin E the requirement for Ca2+ is decreased, indicating that disassembly of the cytoskeleton may be a prerequisite for exocytosis. This disassembly is likely to be controlled by Ca2+-dependent actin regulatory proteins; their presence is indicated by a Ca2+-dependent inhibition of polymerization of extraneous pyrene-G-actin by a Triton extract of mast cells. The effect of cytochalasin E on secretion is similar to that of phorbol myristate acetate, an activator of protein kinase C; both agents enhance the apparent affinity for Ca2+ and cause variable extents of Ca2+-independent secretion. Exposing the permeabilized cells to increasing concentrations of Ca2+ caused a progressive decrease in F-actin levels as measured by flow cytometry of RP-stained cells. In this respect, both cytochalasin E and phorbol ester mimicked the effects of calcium. GTP-γ-S was not required for the Ca2+-dependent cortical disassembly. Thus, since conditions have not yet been identified where secretion can occur in its absence, cortical disassembly may be essential (though it is not sufficient) for exocytosis to occur.
Widespread experience indicates that application of suboptimal concentrations of stimulating ligands (secretagogues) to secretory cells elicits submaximal extents of secretion. Similarly, for ...permeabilized secretory cells, the extent of secretion is related to the concentration of applied intracellular effectors. We investigated the relationship between the extent of secretion from mast cells (assessed as the release of hexosaminidase) and the degranulation (exocytosis) responses of individual cells. For permeabilized mast cells stimulated by the effector combination Ca2+ plus GTP-γ-S and for intact cells stimulated by the Ca2+ ionophore ionomycin, we found that exocytosis has the characteristics of an all-or-none process at the level of the individual cell. With a suboptimal stimulus, the population comprised only totally degranulated cells and fully replete cells. In contrast, a suboptimal concentration of compound 48/80 applied to intact cells induced a partial degree of degranulation. This was determined by observing the morphological changes accompanying degranulation by light and electron microscopy and also as a reduction in the intensity of light scattered at 90°, indicative of a change in the cell-refractive index. These results may be explained by the existence of a threshold sensitivity to the combined effectors that is set at the level of individual cells and not at the granule level. We used flow cytometry to establish the relationship between the extent of degranulation in individual rat peritoneal mast cells and the extent of secretion in the population (measured as the percentage release of total hexosaminidase). For comparison, secretion was also elicited by applying the Ca2+ ionophore ionomycin or compound 48/80 to intact cells. For permeabilized cells and also for intact cells stimulated with the ionophore, levels of stimulation that generate partial secretion gave rise to bimodal frequency distributions of 90° light scatter. In contrast, a partial stimulus to secretion by compound 48/80 resulted in a single population of partially degranulated cells, the degree of degranulation varying across the cell population. The difference between the all-or-none responses of the permeabilized or ionophore-treated cells and the graded responses of cells activated by compound 48/80 is likely to stem from differences in the effective calcium stimulus. Whereas cells stimulated with receptor-directed agonists can undergo transient and localized Ca2+ changes, a homogeneous and persistent stimulus is sensed at every potential exocytotic site in the permeabilized cells.
CXC chemokines in angiogenesis Strieter, Robert M.; Burdick, Marie D.; Gomperts, Brigitte N. ...
Cytokine & growth factor reviews,
12/2005, Letnik:
16, Številka:
6
Journal Article
Recenzirano
Odprti dostop
CXC chemokines display pleiotropic effects in immunity, regulating angiogenesis, and mediating organ-specific metastases of cancer. In the context of angiogenesis, CXC chemokines are a unique family ...of cytokines, known for their ability to behave in a disparate manner in the regulation of angiogenesis. Members that contain the ‘ELR’ motif are potent promoters of angiogenesis, and mediate their angiogenic activity via binding and activating CXCR2 on endothelium. In contrast, members, in general, those are inducible by interferons and lack the ELR motif (ELR
−) are potent inhibitors of angiogenesis, and bind to CXCR3 on endothelium. This review will discuss the biology of these angiogenic and angiostatic CXC chemokines and discuss their disparate angiogenic activity in the context of a variety of disorders.
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