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1.
Sánchez-Margalet V González-Yanes C Santos-Alvarez J Najib S 《Cellular and molecular life sciences : CMLS》1999,55(1):142-147
Insulin action is initiated by binding to its cognate receptor, which then triggers multiple cellular responses by activating
different signaling pathways. There is evidence that insulin receptor signaling may involve G protein activation in different
target cells. We have studied the activation of G proteins in rat hepatoma (HTC) cells. We found that insulin stimulated binding
of guanosine 5′-O-(3-thiotriphosphate) (GTP-γ-35S) to plasma membrane proteins of HTC cells, in a dose-dependent manner. This effect was completely blocked by pertussis toxin
treatment of the membranes, suggesting the involvement of G proteins of the Gα
i/Gα
o family. The expression of these Gα proteins was checked by Western blotting. Next, we used blocking antibodies to sort out the specific Gα protein activated by insulin stimulation. Anti-Gα
il,2 antibodies completely prevented insulin-stimulated GTP binding, whereas anti-Gα
o,i3 did not modify this effect of insulin on GTP binding. Moreover, we found physical association of the insulin receptor with
Gα
i1,2 by copurification studies. These results further support the involvement of a pertussis toxin-sensitive G protein in insulin
receptor signaling and provides some evidence of specific association and activation of Gα
i1,2 protein by insulin. These findings suggest that Gα
i1,2 proteins might be involved in insulin action.
Received 23 September 1998; received after revision 23 November 1998; accepted 25 November 1998 相似文献
2.
3.
Trimeric guanine nucleotide-binding proteins (G proteins) function as the key regulatory elements in a number of transmembrane
signaling cascades where they convey information from agonist-activated receptors to effector molecules. The subcellular localization
of G proteins is directly related to their functional role, i.e., the dominant portion of the cellular pool of G proteins
resides in the plasma membrane. An intimate association of G protein subunits with the plasma membrane has been well known
for a long time. However, results of a number of independent studies published in the past decade have indicated clearly that
exposure of intact target cells to agonists results in subcellular redistribution of the cognate G proteins from plasma membranes
to the light-vesicular membrane fractions, in internalization from the cell surface into the cell interior and in transfer
from the membrane to the soluble cell fraction (high-speed supernatant), i.e., solubilization. Solubilization of G protein
α subunits as a consequence of stimulation of G protein-coupled receptors (GPCRs) with agonists has also been observed in
isolated membrane preparations. The membrane-cytosol shift of G proteins was detected even after direct activation of these
proteins by non-hydrolyzable analogues of GTP or by cholera toxin-induced ADP-ribosylation. In addition, prolonged stimulation
of GPCRs with agonists has been shown to lead to down-regulation of the relevant G proteins. Together, these data suggest
that G proteins might potentially participate in a highly complex set of events, which are generally termed desensitization
of the hormone response. Internalization, subcellular redistribution, solubilization, and down-regulation of trimeric G proteins
may thus provide an additional means (i.e., beside receptor-based mechanisms) to dampen the hormone or neurotransmitter response
after sustained (long-term) exposure.
Received 31 August 2001; received after revision 31 October 2001; accepted 7 November 2001 相似文献
4.
Gineitis A Treigyte G Savickiene J Shanbhag VP Stigbrand T 《Cellular and molecular life sciences : CMLS》1999,55(2):317-326
The two-dimensional electrophoretic patterns of nuclear proteins and their tyrosine phosphorylation were compared for HL-60
cells before and after differentiation induction to granulocytes by dimethyl sulfoxide, all-trans retinoic acid and N
6,O
2-dibutyryl adenosine 3′5′-cyclic monophosphate. Regardless of the inducer used, some nuclear proteins, which are tyrosine-phosphorylated
in proliferating HL-60 cells, undergo gradual dephosphorylation 12–72 h after induction of differentiation, followed by drastic
dephosphorylation during maturation to granulocytes. At least 13 nuclear proteins with a molecular mass of 35–110 kDa are
dephosphorylated, and 6 nuclear proteins undergo tyrosine phosphorylation. Analysis of the nuclear proteins differentially
extracted by salt and detergents indicates that changes in their tyrosine phosphorylation during the maturation stage of differentiating
granulocytes occur mainly in proteins which are abundant in nucleoplasm, chromatin and residual nuclear structures. The abundance
of these proteins, residing in the nuclear structures, and their long-term modification in phosphorylation during the maturation
stages of differentiation strongly suggest that tyrosine phosphorylation of these proteins is involved in reorganization of
the differentiating cell nucleus.
Received 21 September 1998; received after revision 24 November 1998; accepted 3 December 1998 相似文献
5.
Oka T Nishimoto Y Sasagawa T Kanouchi H Kawasaki Y Natori Y 《Cellular and molecular life sciences : CMLS》1999,55(1):131-134
An efficient Escherichia coli expression system for the production of a perchloric acid-soluble protein (PSP) has been constructed. Complementary DNA encoding
PSP was inserted into an inducible bacterial expression vector pGEX-4T-1. After the plasmid introduced into E. coli was expressed by isopropyl 1-thio-β-D-galactopyranoside (IPTG), the recombinant product was purified by glutathione-Sepharose 4B affinity chromatography. The
purified product showed the expected NH2-terminal sequence, but the translation inhibitory activity of this product was 10 times lower compared with that of authentic
PSP isolated from rat liver.
Received 8 October 1998; received after revision 6 November 1998; accepted 6 November 1998 相似文献
6.
M. Karpusas A. Whitty L. Runkel P. Hochman 《Cellular and molecular life sciences : CMLS》1998,54(11):1203-1216
Interferons (IFNs) are potent extracellular protein mediators of host defence and homoeostasis. This article reviews the
structure of human IFN-β (HuIFN-β), in particular in relation to its activity. The recently determined crystal structure of HuIFN-β provides a framework for understanding of the mechanism of differentiation of type I IFNs by their common receptor. Insights
are generated by comparison with the structures of other type I IFNs and from the interpretation of existing mutagenesis data.
The details of the observed carbohydrate structure, together with biochemical data, implicate the glycosylation of HuIFN-β, which is uncommon among type I IFNs, as an important factor in the solubility, stability and, consequently, activity of
the protein. Finally, these structural implications are discussed in the context of the clinical use of HuIFN-β.
Received 12 June 1998; received after revision 16 July 1998; accepted 16 July 1998 相似文献
7.
A possible new role for the anti-ageing peptide carnosine 总被引:5,自引:0,他引:5
The naturally occurring dipeptide carnosine (β-alanyl-L-histidine) is found in surprisingly large amounts in long-lived tissues and can delay ageing in cultured human fibroblasts.
Carnosine has been regarded largely as an anti-oxidant and free radical scavenger. More recently, an anti-glycating potential
has been discovered whereby carnosine can react with low-molecular-weight compounds that bear carbonyl groups (aldehydes and
ketones). Carbonyl groups, arising mostly from the attack of reactive oxygen species and ow-molecular-weight aldehydes and
ketones, accumulate on proteins during ageing. Here we propose, with supporting evidence, that carnosine can react with protein
carbonyl groups to produce protein-carbonyl-carnosine adducts (‘carnosinylated’ proteins). The various possible cellular fates
of the carnosinylated proteins are discussed. These proposals may help explain anti-ageing actions of carnosine and its presence
in non-mitotic cells of long-lived mammals.
Received 29 November 1999; accepted 27 December 1999 相似文献
8.
G. M. Rossolini S. Schippa M. L. Riccio F. Berlutti L. E. Macaskie M. C. Thaller 《Cellular and molecular life sciences : CMLS》1998,54(8):833-850
Bacterial nonspecific acid phosphohydrolases (NSAPs) are secreted enzymes, produced as soluble periplasmic proteins or as
membrane-bound lipoproteins, that are usually able to dephosphorylate a broad array of structurally unrelated substrates and
exhibit optimal catalytic activity at acidic to neutral pH values. Bacterial NSAPs are monomeric or oligomeric proteins containing
polypeptide components with an M
r of 25 – 30 kDa. On the basis of amino acid sequence relatedness, three different molecular families of NSAPs can be distinguished,
indicated as molecular class A, B and C, respectively. Members of each class share some common biophysical and functional
features, but may also exhibit functional differences. NSAPs have been detected in several microbial taxa, and enzymes of
different classes can be produced by the same bacterial species. Structural and phyletic relationships exist among the various
bacterial NSAPs and some other bacterial and eucaryotic phosphohydrolases. Current knowledge on bacterial NSAPs is reviewed,
together with analytical tools that may be useful for their characterization. An overview is also presented concerning the
use of bacterial NSAPs in biotechnology.
Received 21 November 1997; received after revision 10 March 1998; accepted 10 March 1998 相似文献
9.
K. J. Clemetson 《Cellular and molecular life sciences : CMLS》1998,54(6):499-501
Integrins are a family of adhesive receptors consisting of α- and β-subunits which attach cells together via adhesive protein ligands or bind cells to extracellular matrix. They are found on
virtually all cell types and link the external ligand to the cytoskeleton of the cell. Integrins also act as signal transducers
both from the outside of the cell to the interior and also inside-out. Their main functions are in recognition and in tight
but regulated binding. The series of reviews presented here cover both basic aspects of integrin function, including signal
transduction, snake disintegrins and structure and function of I-domains in some integrin α-subunits, as well as the role of integrins in diseases, cancer, inflammation and cardiovascular diseases. The search for suitable
inhibitors of integrins for treatment of these diseases and future prospects for their use are also discussed. 相似文献
10.
SNAREs and SNARE regulators in membrane fusion and exocytosis 总被引:21,自引:0,他引:21
J. E. Gerst 《Cellular and molecular life sciences : CMLS》1999,55(5):707-734
Eukaryotes have a remarkably well-conserved apparatus for the trafficking of proteins between intracellular compartments
and delivery to their target organelles. This apparatus comprises the secretory (or ‘protein export’) pathway, which is responsible
for the proper processing and delivery of proteins and lipids, and is essential for the derivation and maintenance of those
organelles. Protein transport between intracellular compartments is mediated by carrier vesicles that bud from one organelle
and fuse selectively with another. Therefore, organelle-specific trafficking of vesicles requires specialized proteins that
regulate vesicle transport, docking and fusion. These proteins are generically termed SNAREs and comprise evolutionarily conserved
families of membrane-associated proteins (i.e. the synaptobrevin/VAMP, syntaxin and SNAP-25 families) which mediate membrane
fusion. SNAREs act at all levels of the secretory pathway, but individual family members tend to be compartment-specific and,
thus, are thought to contribute to the specificity of docking and fusion events. In this review, we describe the different
SNARE families which function in exocytosis, as well as discuss the role of possible negative regulators (e.g. ‘SNARE-masters’)
in mediating events leading to membrane fusion. A model to illustrate the dynamic cycling of SNAREs between fusion-incompetent
and fusion-competent states, called the SNARE cycle, is presented.
Received 8 October 1998; received after revision 26 November 1998; accepted 26 November 1998 相似文献
11.
M. C. Marden L. Kiger C. Poyart S. J. Edelstein 《Cellular and molecular life sciences : CMLS》1998,54(12):1365-1384
While most researchers agree on the global features of cooperative ligand binding to haemoglobin (Hb), the internal mechanisms
remain open to debate. This is not due to inaccurate measurements, but is rather a consequence of the cooperative ligand binding
that decreases the equilibrium populations of the partially liganded states and makes observation of the transitions between
these substates more difficult. For example, the equilibrium population of the doubly liganded tetramers is typically less
than 5% of the total Hb. As a result many models with widely varying mechanisms may fit the oxygen equilibrium curve, but
may not be consistent with observations of other parameters, such as ligand-binding kinetics or subunit association equilibria.
The wide range of methods and models has led to divergent conclusions about the properties of specific substates. One notable
debate concerns the properties of the doubly liganded forms. The simple two-state model predicts a shift in the allosteric
equilibrium based on the number of ligands bound, but not on their distribution within the tetramer. From studies of dimer-tetramer
equilibria of various pure and hybrid forms, it was concluded that a tetramer with two ligands bound on the same α
β dimer (species 21, an asymmetric hybrid) shows an enhanced tetramer stability, similar to singly liganded Hb, relative to
the other three types of doubly liganded tetramers which resemble the triply liganded forms [Ackers et al. (1992), Science
255: 54–63]. The implications of this model and the relevant experiments will be reviewed here.
Received 27 April 1998; received after revision 17 July 1998; accepted 10 August 1998 相似文献
12.
Ligand recognition by the I domain-containing integrins 总被引:11,自引:0,他引:11
Seven of the integrin α subunits described to date, α
1 , α
2 , α
L , α
X , α
d , α
M and α
E , contain a highly conserved I (or A) domain of approximately 200 amino acid residues inserted near the amino-terminus of
the subunit. As the result of a variety of independent experimental approaches, a large body of data has recently accumulated
that indicates that the I domains are independent, autonomously folding domains capable of directly binding ligands that play
a necessary and important role in ligand binding by the intact integrins. Recent crystallographic studies have elucidated
the structures of recombinant α
M and α
L I domains and also delineated a novel divalent cation-binding motif within the I domains (metal ion-dependent adhesion site,
MIDAS) that appears to mediate the divalent cation binding of the I domains and the I domain-containing integrins to their
ligands. 相似文献
13.
ROPs in the spotlight of plant signal transduction 总被引:7,自引:0,他引:7
Berken A 《Cellular and molecular life sciences : CMLS》2006,63(21):2446-2459
Small guanine nucleotide binding proteins of the Rho family called ROP play a crucial role as regulators of signal transduction
in plants. They participate in pathways that influence growth and development, and the adaptation of plants to various environmental
situations. As members of the Ras superfamily, ROPs function as molecular switches cycling between a GDP-bound ‘off’ and a
GTP-bound ‘on’ state in a strictly regulated manner. Latest research provided fascinating new insights into ROP regulation
by novel guanine nucleotide exchange factors, unconventional GTPase activating proteins, and guanine nucleotide dissociation
inhibitors, which apparently organize localized ROP activation. Important progress has also been made concerning signaling
components upstream and downstream of the ROP cycle involving receptor-like serine/threonine kinases and effectors that can
manipulate cytoskeletal dynamics, intracellular calcium levels, H2O2 production and further cellular targets. This review outlines the fast developing knowledge on ROP GTPases highlighting their
specific features, regulation and roles in a cellular signaling context.
Received 28 April 2006; received after revision 2 June 2006; accepted 29 June 2006 相似文献
14.
Evidence of undiscovered cell regulatory mechanisms: phosphoproteins and protein kinases in mitochondria 总被引:3,自引:0,他引:3
Thomson M 《Cellular and molecular life sciences : CMLS》2002,59(2):213-219
The finding that mitochondria contain substrates for protein kinases lead to the discovery that protein kinases are located
in the mitochondria of certain tissues and species. These include pyruvate dyhydrogenase kinase, branched-chain α-ketoacid dehydrogenase kinase, protein kinase A, protein kinase Cδ, stress-activated kinase and A-Raf as well as unidentified kinases. Recent evidence suggests that mitochondrial protein kinases
may be involved in physiological processes such as apoptosis and steroidogenesis. Additionally, the novel finding of low-molecular-weight
GTP-binding proteins in mitochondria suggests the possibility that these may interact with mitochondrial protein kinases to
regulate the activity of mitochondrial effector proteins. The fact that there are components of cellular regulatory systems
in mitochondria indicates the exciting possibility of undiscovered systems regulating mitochondrial physiology.
Received 19 June 2001; received after revision 7 August 2001; accepted 8 August 2001 相似文献
15.
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
16.
T. Matsuoka T. Nishizaki Y. Ikeuchi Y. Okada K. Sumino 《Cellular and molecular life sciences : CMLS》1997,53(3):233-236
Effects of serotonin (5-HT) on cerebral cortical neurons were examined by patch clamp techniques. 5-HT produced a variety
of responses such as outward (19/73 patches/neurons), slow inward (15/73 patches/neurons), fast inward (8/73 patches/neurons),
and mixed currents (initially fast inward deflection followed by an outward response: 2/73 patches/neurons), with a latency
of 12 sec, 15 sec, 0 sec, and 0 sec respectively, at a holding potential of −60 mV in whole-cell patches. The fast inward
currents were again evoked by a selective 5-HT3 receptor agonist, 1-(m-chlorophenyl)-biguanide hydrochloride (CPBG). In the
cell-attached patch clamp configuration, 5-HT inside the patch pipette elicited single channel currents with slope conductances
of 42 pS and 132 pS (4/42 patches/neurons). CPBG inside the patch pipette evoked inward single channel currents with a lower
slope conductance of 41 pS (3/23 patches/neurons). In contrast, application of 5-HT or a 5-HT2 receptor agonist, α-methyl-5-hydroxytryptamine-maleate, outside the patch pipette induced outward single channel currents with a major slope
conductance of 140 pS (8/30 patches/neurons) or 135 pS (6/20 patches/neurons), respectively. These results indicate that the
outward and fast inward currents may be mediated respectively by the 5-HT2 receptor, which is coupled to a G-protein, and by the 5-HT3 receptor, which contains the non-selective cation channel, and that the mixed type may be caused by both the 5-HT2 and 5-HT3 receptors.
Received 27 September 1996; received after revision 4 November 1996; accepted 7 November 1996 相似文献
17.
F. E. Weber J. H. Dyer F. López García M. Werder T. Szyperski K. Wüthrich H. Hauser 《Cellular and molecular life sciences : CMLS》1998,54(7):751-759
The preform of the rabbit sterol carrier protein 2 (pre-rSCP2) was cloned, the uniformly 15N-labelled protein expressed in Escherichia coli and studied by three-dimensional 15N-resolved nuclear magnetic resonance spectroscopy. In spite of its low solubility in aqueous solution of only ∼0.3 mM, sequential
15N and 1H backbone resonance assignments were obtained for 105 out of the 143 residues. From comparison of the sequential and medium-range
nuclear Overhauser effects (NOEs) in the two proteins, all regular secondary structures previously determined in mature human
SCP2 (hSCP2) [Szyperski et al. (1993) FEBS Lett. 335: 18–26] were also identified in pre-rSCP2. Near-identity of the backbone 15N and 1H chemical shifts and 1 : 1 correspondence of 24 long-range NOEs to backbone amide groups in the two proteins show that the
residues 21 – 143 adopt the same globular fold in pre-rSCP2 and mature hSCP2. The N-terminal 20-residue leader peptide of pre-rSCP2 is flexibly disordered in solution and does not observably affect the conformation of the polypeptide segment 21 – 143.
Received 11 May 1998; accepted 15 May 1998 相似文献
18.
Recent discoveries revealing that carbohydrate modifications play critical roles in a wide variety of biological processes
have brought wide recognition to the field of glycobiology. Growing attention has focused on the function of unusual O-linked carbohydrate modifications such as O-fucose. O-fucose modifications have been described in several different protein contexts, including epidermal growth factor-like repeats
and thrombospondin type 1 repeats. The O-fucose modifications on thrombospondin type 1 repeats have only recently been described, but the site of modification occurs
in a region proposed to play a role in cell adhesion. O-fucose modifications on epidermal growth factor-like repeats have been described as important players in several signal transduction
systems. For instance, Notch, a cell-surface signaling receptor required for many developmental events, bears multiple O-fucose saccharides on the epidermal growth factor-like repeat of its extracellular domain. The O-fucose moieties serve as a substrate for the β1,3 N-acetylglucosaminyltransferase activity of Fringe, a known modifier of Notch function. The alteration of O-fucose structures by Fringe influences the ability of Notch ligands to activate the receptor and provides a means to regulate
Notch signaling. Thus, O-fucose and Fringe provide a clear example of how carbohydrate modifications can have direct functional consequences on the
proteins they modify.
RID="*"
ID="*"Corresponding author. 相似文献
19.
Kirkpatrick DT 《Cellular and molecular life sciences : CMLS》1999,55(3):437-449
Numerous proteins are involved in the nucleotide excision repair (NER) and DNA mismatch repair (MMR) pathways. The function
and specificity of these proteins during the mitotic cell cycle has been actively investigated, in large part due to the involvement
of these systems in human diseases. In contrast, comparatively little is known about their functioning during meiosis. At
least three repair pathways operate during meiosis in the yeast Saccharomyces cerevisiae to repair mismatches that occur as a consequence of heteroduplex formation in recombination. The first pathway is similar
to the one acting during postreplicative mismatch repair in mitotically dividing cells, while two pathways are responsible
for the repair of large loops during meiosis, using proteins from MMR and NER systems. Some MMR proteins also help prevent
recombination between diverged sequences during meiosis, and act late in recombination to affect the resolution of crossovers.
This review will discuss the current status of DNA mismatch repair and nucleotide excision repair proteins during meiosis,
especially in the yeast S. cerevisiae.
Received 21 September 1998; received after revision 23 November 1998; accepted 23 November 1998 相似文献
20.
V. Bellotti P. Mangione M. Stoppini 《Cellular and molecular life sciences : CMLS》1999,55(6-7):977-991
The physiological metabolism of proteins guarantees that different cellular compartments contain the appropriate concentration
of proteins to perform their biological functions and, after a variable period of wear and tear, mediates their natural catabolism.
The equilibrium between protein synthesis and catabolism ensures an effective turnover, but hereditary or acquired abnormalities
of protein structure can provoke a premature loss of biological function, an accelerated catabolism and diseases caused by
the loss of an irreplaceable function. In certain proteins, abnormal structure and metabolism are associated with a strong
tendency to self-aggregation into a polymeric fibrillar structure, and in these cases the disease is not principally caused
by the loss of an irreplaceable function but by the action of this new biological entity. Amyloid fibrils are an apparently
inert, insoluble, mainly extracellular protein polymer that kills the cell without tissue necrosis but by activation of the
apoptotic mechanism. We analyzed the data reported so far on the structural and functional properties of four prototypic proteins
with well-known biological functions (lysozyme, transthyretin, β2-microglobulin and apolipoprotein AI) that are able to create
amyloid fibrils under certain conditions, with the perspective of evaluating whether the achievement of biological function
favors or inhibits the process of fibril formation. Furthermore, studying the biological functions carried out by amyloid
fibrils reveals new types of protein-protein interactions in the transmission of messages to cells and may provide new ideas
for effective therapeutic strategies.
Received 9 November 1998; received after revision 15 January 1999; accepted 15 January 1999 相似文献