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1.
Signal regulation by family conspiracy 总被引:6,自引:0,他引:6
The signal regulating proteins (SIRPs) are a family of ubiquitously expressed transmembrane glycoproteins composed of two
subgroups: SIRPα and SIRPβ, containing more than ten members. SIRPα has been shown to inhibit signalling through a variety of receptors including receptor tyrosine kinases and cytokine receptors.
This function involves protein tyrosine kinases and is dependent on immunoreceptor tyrosine-based inhibition motifs which
recruit key protein tyrosine phosphatases to the membrane. Negative regulation by SIRPα may also involve its ligand, CD47, in a bi-directional signalling mechanism. The SIRPβ subtype has no cytoplasmic domain but instead associates with at least one other transmembrane protein (DAP-12, or KARAP).
DAP-12 possesses immunoreceptor tyrosine-based activation motifs within its cytoplasmic domain that are thought to link SIRPβ to activating machinery. SIRPα and SIRPβ thus have complementary roles in signal regulation and may conspire to tune the response to a stimulus.
Received 6 July 2000; revised 2 August 2000; accepted 5 August 2000 相似文献
2.
Llorca O 《Cellular and molecular life sciences : CMLS》2008,65(9):1302-1310
In mammals, the mannose receptor family consists of four members, Endo180, DEC-205, phospholipase A2 receptor and the mannose receptor. The extracellular domains of all these receptors contain a similar arrangement of domains
in which an Nterminal cysteine-rich domain is followed by a single fibronectin type II domain and eight or ten C-type lectin-like
domains. This review focuses on the threedimensional structure of the receptors in the mannose receptor family and its functional
implication. Recent research has revealed that several members of this family can exist in at least two configurations: an
extended conformation with the N-terminal cysteinerich domain pointing outwards from the cell membrane and a bent conformation
where the N-terminal domains fold back to interact with C-type lectin-like domains at the middle of the structure. Conformational
transitions between these two states seem to regulate the interaction of these receptors with ligands and their oligomerization.
Received 25 October 2007; received after revision 23 November 2007; accepted 7 December 2007 相似文献
3.
Summary Studies have implicated Ca++ in the actions of ethanol at many biochemical levels. Calcium as a major intracellular messenger in the central nervous system is involved in many processes, including protein phosphorylation enzyme activation and secretion of hormones and neurotransmitters. The control of intracellular calcium, therefore, represents a major step by which neuronal cells regulate their activities. The present review focuses on three primary areas which influence intracellular calcium levels; voltage-dependent Ca++ channels, receptor-mediated inositol phospholipid hydrolysis, and Ca++/Mg++-ATPase, the high affinity membrane Ca++ pump.Current research suggests that a subtype of the voltage-dependent Ca++ channel, the dihydropyridine-sensitive Ca++ channel, is uniquely sensitive to acute and chronic ethanol treatment. Acute exposure inhibits, while chronic ethanol exposure increases45Ca++-influx and [3H]dihydropyridine receptor binding sites. In addition, acute and chronic exposure to ethanol inhibits, then increases Ca++/Mg++-ATPase activity in neuronal membranes. Changes in Ca++ channel and Ca++/Mg++-ATPase activity following chronic ethanol may occur as an adaptation process to increase Ca++ availability for intracellular processes. Since receptor-dependent inositol phospholipid hydrolysis is enhanced after chronic ethanol treatment, subsequent activation of protein kinase-C may also be involved in the adaptation process and may indicate increased coupling for receptor-dependent changes in Ca++/Mg++-ATPase activity.The increased sensitivity of three Ca++-dependent processes suggest that adaptation to chronic ethanol exposure may involve coupling of one or more of these processes to receptor-mediated events. 相似文献
4.
Signalling in viral entry 总被引:9,自引:0,他引:9
Greber UF 《Cellular and molecular life sciences : CMLS》2002,59(4):608-626
Viral infections are serious battles between pathogens and hosts. They can result in cell death, elimination of the virus
or latent infection keeping both cells and pathogens alive. The outcome of an infection is often determined by cell signalling.
Viruses deliver genomes and proteins with signalling potential into target cells and thereby alter the metabolism of the host.
Virus interactions with cell surface receptors can elicit two types of signals, conformational changes of viral particles,
and intracellular signals triggering specific cellular reactions. Responses by cells include stimulation of innate and adaptive
immunity, growth, proliferation, survival and apoptosis. In addition, virus-activated cell signalling boosts viral entry and
gene delivery, as recently shown for adenoviruses and adeno-associated viruses. This review illustrates that multiple activation
of host cells during viral entry profoundly impacts the elaborate relationship between hosts and viral pathogens.
Received 13 September 2001; received after revision 23 October 2001; accepted 16 November 2001 相似文献
5.
K. Watanabe E. F. Williams J. S. Law W. L. West 《Cellular and molecular life sciences : CMLS》1979,35(11):1487-1489
Summary Vinblastine selectively inhibits the activation of brain cyclic AMP phosphodiesterase activity by Ca++-protein activator (50% inhibition by 2×10–5 M). This inhibitory effect was reversed by excessive amounts of the activator, whereas large quantities of Ca++ caused only a slight suppression of the vinblastine effect. This result of vinblastine suggests a new site of its action and also suggests the possible role of protein activator, phosphodiesterase proteins or cyclic nucleotides in the previously known effects of vinblastine in vivo and in vitro.Our thanks to Drs A. R. Rhoads, C. B. Klee and R. A. Fergusson for analyzing PA preparations by gel electrophoresis and gel electrofocusing, and to Drs A. A. Suran and D. Soifer for their valuable critiques to this work. This work was partly supported by Biochemical Research Support Grant No. 5SO7RRO5361 to K.W. and Graduate Training Grant No. 5TO2GMO500002 to W.L.W. from NIH. 相似文献
6.
Izaurralde E 《Cellular and molecular life sciences : CMLS》2001,58(8):1105-1112
The distinguishing feature of eukaryotic cells is the segregation of RNA biogenesis and DNA replication in the nucleus, separate
from the cytoplasmic machinery for protein synthesis. As a consequence, messenger RNAs (mRNAs) and all cytoplasmic RNAs from
nuclear origin need to be transported from their site of synthesis in the nucleus to their final cytoplasmic destination.
Nuclear export occurs through nuclear pore complexes (NPCs) and is mediated by saturable transport receptors, which shuttle
between the nucleus and cytoplasm. The past years have seen great progress in the characterization of the mRNA export pathway
and the identification of proteins involved in this process. A novel family of nuclear export receptors (the NXF family),
distinct from the well-characterized family of importin β-like proteins, has been implicated in the export of mRNA to the cytoplasm.
Received 23 January 2001; received after revision 12 April 2001; accepted 12 April 2001 相似文献
7.
One of the central elements of excitation-contraction coupling, the voltage-sensing dihydropyridine receptor, is believed
to exist as a high-molecular-mass complex in the triad junction. Although freeze-fracture electron microscopical analysis
suggests a tetrad complex, no direct biochemical evidence exists demonstrating the actual size of the native membrane complex.
Using a combination of various two-dimensional gel electrophoresis techniques, we show here that the principal α
1-subunit of the dihydropyridine receptor and its auxiliary α
2-subunit form a triad complex of approximately 2800 kDa under native conditions. Established Ca2+-ATPase tetramers and calsequestrin monomers were employed for the internal standardization of the gel systems used. Thus,
the large voltage-sensing complex appears to be tightly associated, since it does not disintegrate during subcellular fractionation
and native electrophoresis procedures. Our findings support the cell biological hypothesis that native dihydropyridine receptor
units form a tetrad structure within the transverse tubules.
Received 10 October 2000; revised 28 November 2000; accepted 4 January 2001 相似文献
8.
Summary Total plasma Mg++ and Ca++, Mg++ in erythrocytes as well as protein-bound plasma Mg++ were investigated in wild and hatchery-reared smolts. The proportion of plasma Mg++ which was bound to plasma protein did not change significantly during entry into seawater, even though the in vitro addition of exogenous Mg++ to the plasma showed that additional binding was possible. 相似文献
9.
D.B. Moody 《Cellular and molecular life sciences : CMLS》2001,58(10):1461-1474
T cells are well known to recognize peptide antigens presented by major histocompatibility (MHC) class I or class II molecules.
More recently, the CD1 family of antigen-presenting molecules has been shown to present both mammalian and microbial glycolipid
antigens for specific recognition by T cells. Human CD1c proteins mediate T cell recognition of polyisoprenyl glycolipids,
evolutionarily conserved phosphoglycolipids, which function in glycan synthesis pathways. This family of antigenic molecules
is particularly attractive for the study of the molecular features that control T cell recognition of self and foreign glycolipids
because natural polyisoprenols from mammals, fungi, protozoa, mycobacteria and eubacteria differ in structure. Moreover, these
naturally occurring structural differences can influence their recognition by CD1c-restricted T cells. This review of the
structural diversity and evolutionary relationships of polyisoprenoid glycolipids emphasizes those features of polyisoprenyl
glycolipid biosynthesis that are relevant to their functions as targets of CD1-mediated T cell responses.
Received 16 March 2001; received after revision 19 April 2001; accepted 23 April 2001 相似文献
10.
Glass R Loesch A Bodin P Burnstock G 《Cellular and molecular life sciences : CMLS》2002,59(5):870-881
We investigated the expression of P2X4 and P2X6 receptors on human umbilical vein endothelial cells (HUVECs) and found that both P2X receptor subtypes on plasma membranes
are largely restricted to areas of cell-cell contact. Co-labelling experiments at the confocal and electron microscopy levels
revealed that P2X4 and P2X6 receptors are strongly co-localised with the cell adhesion molecule VE-cadherin. The P2X4 and P2X6 receptors on plasma membranes at cellular junctions are rapidly (within 5 min) internalised specifically after decreasing
extracellular [Ca2+]. Disruption of microfilaments, microtubules and integrin-mediated adhesion or stimulation of P2 receptors with ATP did not
alter P2X4 and P2X6 receptor expression on HUVEC plasma membranes. Membraneous P2X4 and P2X6 receptors resisted extraction with Triton-X 100, whereas cytoplasmic P2X receptors were Triton-X 100 soluble. P2X4 receptors, but not P2X6 receptors, could be co-immunoprecipitated with VE-cadherin and vice versa. We conclude that P2X4 and P2X6 receptors are associated with VE-cadherin at HUVEC adherens junctions.
Received 15 March 2002; revised 15 March 2002; accepted 19 March 2002 相似文献
11.
Kristi Baker Timo Rath Wayne I. Lencer Edda Fiebiger Richard S. Blumberg 《Cellular and molecular life sciences : CMLS》2013,70(8):1319-1334
IgG is a molecule that functionally combines facets of both innate and adaptive immunity and therefore bridges both arms of the immune system. On the one hand, IgG is created by adaptive immune cells, but can be generated by B cells independently of T cell help. On the other hand, once secreted, IgG can rapidly deliver antigens into intracellular processing pathways, which enable efficient priming of T cell responses towards epitopes from the cognate antigen initially bound by the IgG. While this process has long been known to participate in CD4+ T cell activation, IgG-mediated delivery of exogenous antigens into a major histocompatibility complex (MHC) class I processing pathway has received less attention. The coordinated engagement of IgG with IgG receptors expressed on the cell-surface (FcγR) and within the endolysosomal system (FcRn) is a highly potent means to deliver antigen into processing pathways that promote cross-presentation of MHC class I and presentation of MHC class II-restricted epitopes within the same dendritic cell. This review focuses on the mechanisms by which IgG-containing immune complexes mediate such cross-presentation and the implications that this understanding has for manipulation of immune-mediated diseases that depend upon or are due to the activities of CD8+ T cells. 相似文献
12.
Summary Lectins which bind sialic acid-containing receptors are present in the hemolymph of the scorpionParuroctonus mesaensis Stahnke. Glycoproteins like bovine submaxillary mucin, fetuin and human orosomucoid behave as strong inhibitors forParuroctonus lectins; desialylation of glycoproteins results in a drastic reduction of their inhibitory capabilities confirming that sialic acids are the terminal monosaccharides ofParuroctonus lectin receptors.We wish to thank Dr H. L. Stahnke, Arizona State University, Tempe, Arizona, for taxonomic assistance. This work received fellowship support from the Consejo Nacional de Investigaciones Cientificas y Técnicas de la República Argentina. 相似文献
13.
D. Chao G. Balboni L. H. Lazarus S. Salvadori Y. Xia 《Cellular and molecular life sciences : CMLS》2009,66(6):1105-1115
Activation of δ-opioid receptors (DOR) attenuates anoxic K+ leakage and protects cortical neurons from anoxic insults by inhibiting Na+ influx. It is unknown, however, which pathway(s) that mediates the Na+ influx is the target of DOR signal. In the present work, we found that, in the cortex, (1) DOR protection was largely dependent
on the inhibition of anoxic Na+ influxes mediated by voltage-gated Na+ channels; (2) DOR activation inhibited Na+ influx mediated by ionotropic glutamate N-methyl-D-aspartate (NMDA) receptors, but not that by non-NMDA receptors, although both played a role in anoxic K+ derangement; and (3) DOR activation had little effect on Na+/Ca2+ exchanger-based response to anoxia. We conclude that DOR activation attenuates anoxic K+ derangement by restricting Na+ influx mediated by Na+ channels and NMDA receptors, and that non-NMDA receptors and Na+/Ca2+ exchangers, although involved in anoxic K+ derangement in certain degrees, are less likely the targets of DOR signal.
Received 26 November 2008; received after revision 26 December 2008; accepted 13 January 2009 相似文献
14.
Davoli C Marconi A Serafino A Iannoni C Marcheggiano A Ravagnan G 《Cellular and molecular life sciences : CMLS》2002,59(3):527-539
Nerve growth factor (NGF) belongs by sequence homology to the neurotrophins, a family of proteins binding the same p75 receptor
and closely related members of the Trk family of receptor tyrosine kinases. Fundamental in the vertebrate nervous system,
neurotrophin signals have also been suggested as essential for relatively complex nervous systems occurring in invertebrate
species that live longer than Caenorhabditis elegans and Drosophila melanogaster. Mammalian neurotrophins have been found to influence invertebrate neuronal growth. However, there are only a few data on
the presence of molecules related to neurotrophin signalling components in invertebrates. Our studies provide evidence that
analogues of neurotrophins and neurotrophin receptors are expressed in Eisenia foetida earthworms. In particular, NGF-like and Trk-like immunoreactive proteins are both expressed in the nervous system, whereas
p75-like positivity identifies tubular structures associated with dorsal pores that are involved in the earthworm response
to mechanical irritation or stress.
Received 12 November 2001; received after revision 8 January 2002; accepted 8 January 2002 相似文献
15.
Large conductance, Ca2+-activated potassium (BK) channels are widely expressed throughout the animal kingdom and play important roles in many physiological
processes, such as muscle contraction, neural transmission and hearing. These physiological roles derive from the ability
of BK channels to be synergistically activated by membrane voltage, intracellular Ca2+ and other ligands. Similar to voltage-gated K+ channels, BK channels possess a pore-gate domain (S5–S6 transmembrane segments) and a voltage-sensor domain (S1–S4). In addition,
BK channels contain a large cytoplasmic C-terminal domain that serves as the primary ligand sensor. The voltage sensor and
the ligand sensor allosterically control K+ flux through the pore-gate domain in response to various stimuli, thereby linking cellular metabolism and membrane excitability.
This review summarizes the current understanding of these structural domains and their mutual interactions in voltage-, Ca2+ - and Mg2+ -dependent activation of the channel.
Received 25 September 2008; received after revision 23 October 2008; accepted 24 October 2008 相似文献
16.
17.
Summary The biological effects of lithium ions have been studied, using plant cytokinesis in onion root meristems as the experimental model. Lithium induces binucleate cells by inhibiting cell plate formation. Moreover, lithium and caffeine have additive effects on the induction of binucleate cells. Na+, K+, Ca++ and Mg++ antagonize lithium-induced inhibition of cytokinesis. 相似文献
18.
F. Reusser 《Cellular and molecular life sciences : CMLS》1966,22(5):309-310
Zusammenfassung Hochgereinigtes Rinderwachstumshormon besitzt ein ziemlich gutes Bindungsvermögen für Mg++-, Ca++- und Na+-Ionen. Andererseits wird K+ je nach Konzentration überhaupt nicht, oder nur in Spuren gebunden.
The performance of the elementary analyses by R. C.Anderson is gratefully acknowledged. Thanks are also due to B.Czuk and N. O.Milkovich for technical assistance. 相似文献
The performance of the elementary analyses by R. C.Anderson is gratefully acknowledged. Thanks are also due to B.Czuk and N. O.Milkovich for technical assistance. 相似文献
19.
Morphine 6 glucuronide stimulates nitric oxide release in mussel neural tissues: evidence for a morphine 6 glucuronide opiate receptor subtype 总被引:1,自引:0,他引:1
Mantione K Zhu W Rialas C Casares F Cadet P Franklin AL Tonnesen J Stefano GB 《Cellular and molecular life sciences : CMLS》2002,59(3):570-574
We have previously demonstrated that Mytilus edulis pedal ganglia contain opiate alkaloids, i.e., morphine and morphine 6 glucuronide (M6G), as well as mu opiate receptor subtype
fragments exhibiting high sequence similarity to those found in mammals. Now we demonstrate that M6G stimulates pedal ganglia
constitutive nitric oxide (NO) synthase (cNOS)-derived NO release at identical concentrations and to similar peak levels as
morphine. However, the classic opiate antagonist, naloxone, only blocked the ability of morphine to stimulate cNOS-derived
NO release and not that of M6G. CTOP, a mu-specific antagonist, blocked the ability of M6G to induce cNOS-derived NO release
as well as that of morphine, suggesting that a novel mu opiate receptor was present and selective toward M6G. In examining
a receptor displacement analysis, both opiate alkaloids displaced [3H]-dihydromorphine binding to the mu opiate receptor subtype. However, morphine exhibited a twofold higher affinity, again
suggesting that a novel mu opiate receptor may be present.
Received 1 November 2001; received after revision 1 February 2002; accepted 1 February 2002 相似文献
20.
Modification of ligand-gated receptor function at the postsynaptic domain is one of the most important mechanisms by which
the efficacy of synaptic transmission in the nervous system is regulated. Traditionally, these types of modifications have
been thought to be achieved mainly by altering the channel-gating properties or conductance of the receptors. However, recent
evidence suggests that AMPA (α-amino-3-hydroxyl-5-methyl-4-isoxayolepropionic acid)-type ligand-gated glutamate receptors are continuously recycling between
the plasma membrane and the intracellular compartments via vesicle-mediated plasma membrane insertion and clathrin-dependent
endocytosis. Regulation of either receptor insertion or endocytosis results in a rapid change in the number of these receptors
expressed on the plasma membrane surface and in the receptor-mediated responses, thereby playing an important role in mediating
certain forms of synaptic plasticity. Thus, controlling the number of postsynaptic receptors by regulating the intracellular
trafficking and plasma membrane expression of the postsynaptic receptors may be a common and important mechanism of synaptic
plasticity in the mammalian central nervous system. 相似文献