Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “effector”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,693 records · Page 94Linked to original sources
PubMed2001

GADD45gamma mediates the activation of the p38 and JNK MAP kinase pathways and cytokine production in effector TH1 cells.

The p38 and JNK stress-activated MAPK signal transduction pathways are activated by T cell receptor (TCR) signaling and are required for IFN-gamma production by TH1 effector cells. Here, we show that the expression of GADD45gamma is induced during T cell activation and that the level of expression is higher in TH1 cells than in TH2 cells. TH1 cells from GADD45gamma(-/-) mice are severely compromised in their abilities to activate p38 and JNK in response to TCR signaling, produce much less IFN-gamma upon restimulation, and are deficient in activation-induced cell death (AICD). Additionally, GADD45gamma deficiencies caused reduced contact hypersensitivity in mice. Thus, GADD45gamma mediates activation of the p38 and JNK pathways and effector function of TH1 cells.

Animals↗
PubMed2001

Constitutive CD27/CD70 interaction induces expansion of effector-type T cells and results in IFNgamma-mediated B cell depletion.

The interaction between the TNF receptor family member CD27 and its ligand CD70 provides a costimulatory signal for T cell expansion. Normally, tightly regulated expression of CD70 ensures the transient availability of this costimulatory signal. Mice expressing constitutive CD70 on B cells had higher peripheral T cell numbers that showed increased differentiation toward effector-type T cells. B cell numbers in CD70 transgenic (TG) mice progressively decreased in primary and secondary lymphoid organs. This B cell depletion was caused by CD27-induced production of IFNgamma in T cells. We conclude that apart from its role in controlling the size of the activated T cell pool, CD27 ligation contributes to immunity by facilitating effector T cell differentiation.

Animals↗
PubMed2003

The repertoires of circulating human CD8(+) central and effector memory T cell subsets are largely distinct.

Memory T cells are divided into central and effector subsets with distinct functions and homing capabilities. We analyzed the composition and dynamics of the CD8(+) T cell repertoire of these subsets within the peripheral blood of four healthy individuals. Both subsets had largely distinct and autonomous TCRbeta repertoires. Their composition remained stable over a 9 month period, during which no cell passage between these subsets was detected despite important size variation of several clones. In one donor, four out of six TCRbeta clonotypes specific for the influenza A virus were detected in the central subset only, while the two others were shared. Altogether, these observations suggest that most effector memory T cells may not have derived from the central memory subset.

Adult↗
PubMed2003

Not all effector CD8+ T cells are alike.

As naive CD8+ T cells circulate throughout the bloodstream and secondary lymphoid tissues (i.e. spleen and lymph nodes), they sample complexes of peptides and MHC class I molecules expressed on the surface of professional antigen presenting cells (APCs). A proper fit between lymphocyte and APCs sets into motion a complex series of events that result in the generation of activated cytotoxic T lymphocytes (CTLs) that are the principal immune effectors against infected and transformed cells. Owing to the severe immunopathology that can result from the aberrant stimulation of CTLs, the activation of naïve CD8(+) T cells is a tightly regulated process. A growing body of evidence suggests that the quality of stimulation naïve CD8+ T cells receive during the induction and maintenance of an immune response dictates the functional competency of the responding antigen-specific CTLs, and that CD8+ T cells and their progeny "effector cells" can exist long-term in vastly different activation states.

Animals↗
PubMed2003

SseA is required for translocation of Salmonella pathogenicity island-2 effectors into host cells.

The Salmonella pathogenicity island-2 (SPI2) is a virulence locus on the bacterial chromosome required for intracellular proliferation and systemic infection in mice. Cell culture models and a murine model of systemic infection were used to address the role of an uncharacterized SPI2 open reading frame, designated as sseA, in Salmonella virulence. A Salmonella strain with an unmarked internal deletion of sseA displayed a phenotype that was similar to an SPI2-encoded type III secretion system apparatus mutant. Moreover, SseA was required for survival and replication within epithelial cells and macrophages. Murine infection studies confirmed that the DeltasseA strain was severely attenuated for virulence. Using immunofluorescence microscopy, the virulence defect in the DeltasseA strain was attributed to an inability to translocate SPI2 effector proteins into host cells. These data demonstrate that SseA is essential for SPI2-mediated translocation of effector proteins.

Animals↗
PubMed2002

Movement-related EEG potentials are force or end-effector dependent: evidence from a multi-finger experiment.

OBJECTIVES: This study examined behavioral and electrocortical responses in producing 3 levels of force (25, 50 and 75% of MVC) at a constant rate of force development with each of 4 fingers both during the achievement of the desired force (ramp phase) and its maintenance (static phase). We were particularly interested in describing in more detail the interaction between nominal force and finger on various components of movement-related potential (MRP) associated with preparation and execution of isometric force production tasks. METHODS: Our experimental design systematically controlled the rate of force development while nominal force level was experimentally manipulated during isometric force production tasks. We applied time-domain averaging of EEG single trials in order to extract 3 components of MRP (BP(-600 to -500); MP(-100 to 0); MMP) preceding and accompanying behavioral responses. RESULTS: Overall, as in our previous research the effect of force per se was not reflected in the EEG components. However, we did find an interaction between finger and force level in both the Bereitshaftspotential (BP) and motor potential (MP) components of the movement-related potentials. While the middle, ring and little finger produced no differences in EEG components at any of the 3 force levels, the index finger did. We further correlated the force trajectory and the EEG time series with the highest correlations found in the lowest force level with the index finger. As the force level was increased, the correlation was significantly reduced. CONCLUSIONS: Overall, the whole complex of MRP components and evolution of EEG time series during multi-finger isometric force production tasks reflect a combination of factors including the primary end-effector performing the task and interaction of end-effector and the amount of nominal force.

Adult↗
PubMed2006

Localization of the Rho GTPases and some Rho effector proteins in the sperm of several mammalian species.

The acrosome reaction is a fundamental event in the biology of the sperm and is a prerequisite to fertilization of the egg. Members of the Rho family of GTPases and their effectors are present in the cytoplasm and/or plasma membrane overlying the acrosome of porcine sperm. We have implicated the Rho family of GTPases and the Rho-activated kinase, ROCK-1, in mediating the zona-pellucida-induced acrosome reaction. Others have implicated the Rho GTPase in regulating the ionophore-induced acrosome reaction in the sperm of several mammalian species as well as in motility of bovine sperm. In this study, the localization of the Rho GTPases (RhoA, RhoB, Rac1 and Cdc42) as well as the effectors RhoGDI, PI(4)P5K and ROCK-1, was determined in boar, human, rat, ram, bull and elephant sperm. The four GTPases were each present in the sperm head of all species examined. RhoGDI was expressed in the head and tail of sperm from all species except pig, where it was present only in the head. PI(4)P5K was expressed in both head and tail of sperm from all species, but expression was typically weaker in the tail. Finally, ROCK-1 was expressed in the heads and tails of all sperm except that of the boar, where it was present only in the acrosomal region. These observations taken together suggest that the expression of Rho GTPases in sperm has been conserved throughout mammalian evolution, most likely due to the role of these GTPases in regulating acrosomal exocytosis.

Animals↗
PubMedDate not supplied

Synthesis and biodistribution of 211At-labeled, biotinylated, and charge-modified poly-L-lysine: evaluation for use as an effector molecule in pretargeted intraperitoneal tumor therapy.

Poly-L-lysine (7, 21, and 204 kDa) has been evaluated as an effector carrier for use in pretargeted intraperitoneal tumor therapy. For the synthesis, the epsilon-amino groups on the poly-L-lysine were modified in three steps utilizing conjugate biotinylation with biotin amidocaproate N-hydroxysuccinimide ester (BANHS), conjugate radiolabeling with (211)At using the intermediate reagent N-succinimidyl 3-(trimethylstannyl)benzoate (m-MeATE), and charge modification using succinic anhydride, resulting in an increase in the molecular weight of approximately 80% of the final product. The labeling of the m-MeATE reagent and subsequent conjugation of the polymer were highly efficient with overall radiochemical yields in the range of 60-70%. The in vitro avidin binding ability of the modified polymer was almost complete (90-95%), as determined by binding to avidin beads using a convenient filter tube assay. Following intraperitoneal (ip) injection in athymic mice, the 13 kDa polymer product was cleared mainly via the kidneys with fast kinetics (biological half-live T(b) approximately 2 h) and with low whole-body retention. The clearance of the 38 kDa polymer was distributed between kidneys and liver, and the 363 kDa polymer was mainly sequestered by the liver with a T(b) of 8 h. Increased tissue uptake in the thyroid, lungs, stomach, and spleen following the distribution of the large effector molecules (38 and 363 kDa) suggests that degradation of the polymers by the liver may release some of the label as free astatine/astatide.

Aminocaproates↗
PubMed1995

How allosteric effectors can bind to the same protein residue and produce opposite shifts in the allosteric equilibrium.

Monoaldehyde allosteric effectors of hemoglobin were designed, using molecular modeling software (GRID), to form a Schiff base adduct with the Val 1 alpha N-terminal nitrogens and interact via a salt bridge with Arg 141 alpha of the opposite subunit. The designed molecules were synthesized if not available. It was envisioned that the molecules, which are aldehyde acids, would produce a high-affinity hemoglobin with potential interest as antisickling agents similar to other aldehyde acids reported earlier. X-ray crystallographic analysis indicated that the aldehyde acids did bind as modeled de novo in symmetry-related pairs to the alpha subunit N-terminal nitrogens. However, oxygen equilibrium curves run on solutions obtained from T- (tense) state hemoglobin crystals of reacted effector molecules produced low-affinity hemoglobins. The shift in the allosteric equilibrium was opposite to that expected. We conclude that the observed shift in allosteric equilibrium was due to the acid group on the monoaldehyde aromatic ring that forms a salt bridge with the guanidinium ion of Arg 141 alpha on the opposite subunit. This added constraint to the T-state structure that ties two subunits across the molecular symmetry axis shifts the equilibrium further toward the T-state. We tested this idea by comparing aldehydes that form Schiff base interactions with the same Val 1 alpha residues but do not interact across the dimer subunit symmetry axis (a new one in this study with no acid group and others that have had determined crystal structures). The latter aldehydes shift the allosteric equilibrium toward the R-state. A hypothesis to predict the direction in shift of the allosteric equilibrium is made and indicates that it is not exclusively where the molecule binds but how it interacts with the protein to stabilize or destabilize the T- (tense) allosteric state.

Aldehydes↗
PubMed1995

Bisaldehyde allosteric effectors as molecular ratchets and probes.

Four new series of monoaldehyde bisacids and bisaldehyde bisacids with varying chain lengths have been synthesized and evaluated as allosteric effectors of hemoglobin. Molecular modeling, oxygen equilibrium, and crystallographic studies were combined for structure/function studies. Crystallographic analyses of the bisaldehydes reveal that Schiff base interaction occurred exclusively between Val 1 alpha and Lys 99 alpha of the opposite alpha chain even though the two terminal Val 1 alpha nitrogens are ideally spaced to also form cross-links. The reason for the observed mode of binding appears to be the influence of chain direction set by key substitutions on the bisaldehyde molecule. Even longer chain derivatives that could overcome the direction set by the key functional groups bind in the same manner. These studies support the general conclusion that long flexible molecules prefer to bind along cavity walls, like double-sided molecular sticky tape, rather than span large open spaces with few chances for interaction. The cross-linked bisaldehydes bind at the same site when incubated under both allosteric states and exhibit reduced cooperativity with a significant decrease in oxygen affinity. The chain length acts as a molecular ratchet and dictates the degree of allosteric effect observed. The tighter the cross-link, the greater the constraint on the tense- (T-) state and the stronger the allosteric effect that is produced. The monoaldehyde bisacids bind in the same fashion with Schiff base formation at Val 1 alpha while the acid that replaces the second aldehyde moiety forms a salt bridge with Lys 99 alpha of the opposite subunit. This class of molecules has weaker allosteric effector activity as would be expected with replacement of one covalent bond by a salt bridge. The importance of Lys 99 alpha on the allosteric equilibrium is confirmed.

Aldehydes↗
PubMed2001

An increase in side chain entropy facilitates effector binding: NMR characterization of the side chain methyl group dynamics in Cdc42Hs.

Cdc42Hs is a signal transduction protein that is involved in cytoskeletal growth and organization. We describe here the methyl side chain dynamics of three forms of (2)H,(13)C,(15)N-Cdc42Hs [GDP-bound (inactive), GMPPCP-bound (active), and GMPPCP/PBD46-bound (effector-bound)] from (13)C-(1)H NMR measurements of deuterium T(1) and T(1 rho) relaxation times. A wide variation in flexibility was observed throughout the protein, with methyl axis order parameters (S(2)(axis)) ranging from 0.2 to 0.4 (highly disordered) in regions near the PBD46 binding site to 0.8--1.0 (highly ordered) in some helices. The side chain dynamics of the GDP and GMPPCP forms are similar, with methyl groups on the PBD46 binding surface experiencing significantly greater mobility (lower S(2)(axis)) than those not on the binding surface. Binding of PBD46 results in a significant increase in the disorder and a corresponding increase in entropy for the majority of methyl groups. Many of the methyl groups that experience an increase in mobility are found in residues that are not part of the PBD46 binding interface. This entropy gain represents a favorable contribution to the overall entropy of effector binding and partially offsets unfavorable entropy losses such as those that occur in the backbone.

Amino Acid Sequence↗
PubMed1994

Splicing of effector cell protease receptor-1 mRNA is modulated by an unusual retained intron.

Effector cell protease receptor-1 (EPR-1) is a transmembrane glycoprotein receptor for factor Xa that contributes to cell surface assembly of proteolytic activities and leukocyte mitogenesis. It is now shown that membrane expression of EPR-1 is dynamically modulated by mRNA splicing. Northern hybridization analysis of EPR-1-expressing cells and genetically engineered transfectants demonstrates that this mechanism involves removal of a 451 bp intervening sequence retained in 70-90% of mature mRNA, as quantitated by polymerase chain reaction amplification and ribonuclease protection studies. Splicing of the intervening sequence occurs in a cell type-specific fashion, as judged by the constitutive membrane overexpression of EPR-1 in certain leukemic B lymphocytes and monocytic cells. Furthermore, phenotypic analysis of cell lines stably transfected with functionally spliced or unspliced EPR-1 constructs suggests a potential role of intron cis-acting sequence(s) in splicing regulation. Instead of a transmembrane receptor for factor Xa (EPR-1a), the most prevalent unspliced EPR-1 transcript generates a novel truncated protein of 110 amino acids (EPR-1b), in which a unique intron-encoded -COOH terminus carries a potential nuclear targeting signal PPQHRAKS. An antibody generated against the intron-encoded sequence of EPR-1b demonstrates prominent nuclear localization of this variant isoform in indirect immunofluorescence staining of permeabilized cells. These findings provide evidence for a novel mechanism based on high efficiency intron retention modulating factor Xa-dependent cellular effector functions.

Amino Acid Sequence↗
PubMed1982

Allosteric transitions associated with the binding of substrate and effector ligands to T2 phage induced deoxycytidylate deaminase.

The binding characteristics of T2 phage induced deoxycytidylate deaminase were examined through the use of ultrafiltration and equilibrium dialysis. The positive effectors, 5-(hydroxymethyl)deoxycytidine 5'-triphosphate and deoxycytidine 5'-triphosphate, were bound in a highly cooperative manner, which is consistent with the allosteric effects promoted by these compounds. Their respective S0.5 values were 8 and 2 microM. A similar degree of cooperativity was associated with the binding of such competitive inhibitors of deoxycytidylate deaminase as dGMP, 4-N-hydroxydeoxycytidine 5'-monophosphate, and tetrahydrodeoxyuridylate. The negative effector, dTTP, also inhibited the binding of dCTP in a pH-dependent manner, which is consistent with its previously demonstrated inhibition of catalysis [Maley, G. F., Guarino, D. U., & Maley, F. (1972) J. Biol. Chem. 247, 931-939]. The binding of dTTP could be demonstrated only at low phosphate concentrations and did not appear to be cooperative. The number of binding sites for the allosteric ligands, substrate, and substrate inhibitors was shown to be six, which coincides with the number of enzyme subunits. It was established by CD difference spectroscopy that dCTP, at concentrations normally employed to demonstrate enzyme activation, effects a dramatic conformation transition in the deaminase, as indicated by a sharp decrease in ellipticity at about 280 nm. The nature of this response suggests that the microenvironment of some of the enzyme's tyrosyl residues had been perturbed by the presence of this allosteric nucleotide.

Circular Dichroism↗
PubMed1989

Regulation of oxidation-reduction potentials of anthranilate hydroxylase from Trichosporon cutaneum by substrate and effector binding.

The pH dependence of the redox behavior of anthranilate hydroxylase from Trichosporon cutaneum in its uncomplexed and anthranilate-complexed forms, as well as the effects on the reduction potential, at pH 7.4, of enzyme in complex with 3-methylanthranilate, salicylate, 3-acetylpyridine adenine dinucleotide phosphates, and azide plus anthranilate, is described. At pH 7.4 the midpoint potential of uncomplexed enzyme (EFlox/EFlredH-) is -0.229 V vs SHE, close to that of free flavin. The aromatic substrates and effector all shift the midpoint potential value in a positive direction by 0.068-0.100 V. This shift results in thermodynamically more favorable reduction of the substrate/effector-complexed enzyme by NADPH. Consistent with thermodynamic considerations, the aromatic substrates (or effector) are bound to the reduced enzyme 2-4 orders of magnitude more tightly than to the oxidized enzyme. The tighter binding of the substrate to the two-electron-reduced enzyme may be related to the double hydroxylation reaction performed by this enzyme, which is a more complex reaction than is carried out by typical flavoprotein hydroxylases. The acetylpyridine nucleotides appear to have no significant regulatory role.

Azides↗
PubMed1990

New effectors of human hemoglobin: structure and function.

We describe the actions of two new allosteric effectors of hemoglobin, 2-[4-(3,5-dichlorophenylureido)phenoxy]-2-methylpropionic acid (L35) and 2-[4-(3,4,5-trichlorophenylureido)phenoxy]-2-methylpropionic acid (L345). Each of them binds to two pairs of symmetry-related sites in the central cavity of human deoxyhemoglobin. One pair of sites overlaps with that occupied by bezafibrate [Perutz et al. (1986) J. Am. Chem. Soc. 108, 1064-1078]. The other sites are new, and the pair occupied by L35 is different from that occupied by L345. All the sites are at least 20 A from the site where organic phosphates are bound. L345 is by far the most potent allosteric effector of hemoglobin ever described. At a concentration of 0.1 mM, it raises the P50 of a suspension of red cells by 50%; at 0.2 mM it raises the P50 2.5-fold. At acid pH, it reduces Hill's coefficient to near unity and prevents complete oxygen saturation even under 1 atm of pure oxygen. In azidemethemoglobin at pH 6, it induces a transition to higher spin. These properties are reminiscent of those of teleost fish hemoglobins that exhibit a Root effect. The influence of L35 and L345 and that of organic phosphates on the oxygen affinity are additive, but they compete with chloride. L35 acts more weakly than L345, but can be made to induce the same effects as L345 alone by adding inositol hexaphosphate. Both compounds increase the alkaline and acid Bohr effects. They alter the bimolecular kinetics of CO recombination after a flash by increasing the slowly reacting fraction of hemoglobin in the T state at the expense of the fast-reacting fraction in the R state.(ABSTRACT TRUNCATED AT 250 WORDS)

Allosteric Regulation↗
PubMed1976

The effect of opposing effectors on activation level of succinate dehydrogenase: equilibrium and kinetic studies.

The activation of mitochondrial succinate dehydrogenase by various activators is a result of dissociation of oxaloacetate tightly bound to the nonactive enzyme. But, quantitative correlation between the effector concentrations and the active fraction of the enzyme was not at hand. In this study we measured the level of active succinate dehydrogenase equilibrated with a wide range of opposing effectors: oxaloacetate (1-500 muM) and activator (0.02-1.5 M NaBr). The results are compatible with a model assuming two stable forms of the enzyme: a nonactive enzyme-oxaloacetate complex and an active enzyme free of oxaloacetate. The active form is stabilized by binding two Br- and one H+. The rate of activation (ka) and exchange between enzyme bound and free oxaloacetate k(ex) were measured. Both ka and kex are hyperbolically dependent on Br- concentration but differ in magnitude and pH dependence. kex at infinite Br- concentration is pH dependent but ka is not. The two reactions, activation and exchange, also differ in their activation energy bein 32 and 21.5 kcal/mol, respectively. It is concluded that, in the course of activation, Br- interacts at two distinct steps. First to produce a ternary, nonactive [enzyme-oxaloacetate-Br-] complex. From this complex, oxaloacetate dissociates and the oxaloacetate-free enzyme assumes its active form. Finally, the active enzyme is stabilized by binding another Br-. The rate-limiting step in deactivation is binding of oxaloacetate to active enzyme. The complex formed undergoes a very rapid transformation to the stable nonactive form. This pathway, under certain conditions, can reverse its direction and contribute to the overall rate of activation. It is suggested that the equilibrium between the two stable forms of the enzyme can be reached by two parallel pathways, each contributing independently to the observed rate of activation, while the final equilibrium is determined by the free energy between the products and the reactants.

Animals↗
PubMed2005

Conformational states of Ras complexed with the GTP analogue GppNHp or GppCH2p: implications for the interaction with effector proteins.

The guanine nucleotide-binding protein Ras occurs in solution in two different states, state 1 and state 2, when the GTP analogue GppNHp is bound to the active center as detected by (31)P NMR spectroscopy. Here we show that Ras(wt).Mg(2+).GppCH(2)p also exists in two conformational states in dynamic equilibrium. The activation enthalpy DeltaH(++)(12) and the activation entropy DeltaS(++)(12) for the transition from state 1 to state 2 are 70 kJ mol(-1) and 102 J mol(-1) K(-1), within the limits of error identical to those determined for the Ras(wt).Mg(2+).GppNHp complex. The same is true for the equilibrium constants K(12) = [2]/[1] of 2.0 and the corresponding DeltaG(12) of -1.7 kJ mol(-1) at 278 K. This excludes a suggested specific effect of the NH group of GppNHp on the equilibrium. The assignment of the phosphorus resonance lines of the bound analogues has been done by two-dimensional (31)P-(31)P NOESY experiments which lead to a correction of the already reported assignments of bound GppNHp. Mutation of Thr35 in Ras.Mg(2+).GppCH(2)p to serine leads to a shift of the conformational equilibrium toward state 1. Interaction of the Ras binding domain (RBD) of Raf kinase or RalGDS with Ras(wt) or Ras(T35S) shifts the equilibrium completely to state 2. The (31)P NMR experiments suggest that, besides the type of the side chain of residue 35, a main contribution to the conformational equilibrium in Ras complexes with GTP and GTP analogues is the effective acidity of the gamma-phosphate group of the bound nucleotide. A reaction scheme for the Ras-effector interaction is presented which includes the existence of two conformations of the effector loop and a weak binding state.

Amino Acid Substitution↗
PubMed2005

Allosteric models for multimeric proteins: oxygen-linked effector binding in hemocyanin.

In many crustaceans, changing concentrations of several low molecular weight compounds modulates hemocyanin oxygen binding, resulting in lower or higher oxygen affinities of the pigment. The nonphysiological effector caffeine and the physiological modulator urate, the latter accumulating in the hemolymph of the lobster Homarus vulgaris during hypoxia, increase hemocyanin oxygen affinity and decrease cooperativity of oxygen binding. To derive a model that describes the mechanism of allosteric interaction between hemocyanin and oxygen in the presence of urate or caffeine, studies of oxygen, urate, and caffeine binding to hemocyanin were performed. Exposure of lobster hemocyanin to various pH values between 7.25 and 8.15 resulted in a decrease of p50. In this pH interval, p50 decreases from 95 to 11 Torr without effectors and from 49 to 6 Torr and from 34 to 5 Torr in the presence of 1 mM urate or caffeine, respectively. Thus, the allosteric effects induced by protons and urate or caffeine are coupled. In contrast, isothermal titration calorimetry did not reveal any differences in binding enthalpy (DeltaH degrees ) for urate or caffeine under either normoxic or hypoxic conditions at different pH values. Despite these apparently conflicting results, they can be explained by the nested MWC model if two different types of modulator binding sites are assumed, an allosteric and a nonallosteric type of site. Simulations of in vivo conditions with this model indicate that the naturally occurring modulator urate is physiologically relevant in H. vulgaris only during hypoxic conditions, i.e., either during environmental oxygen limitation or extensive exercise.

Allosteric Regulation↗