Synergistic activation of PtdIns 3-kinase by tyrosine-phosphorylated peptide and beta gamma-subunits of GTP-binding proteins.
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ABSTRACT:
SUBMITTER: Okada T
PROVIDER: S-EPMC1217511 | biostudies-other | 1996 Jul
REPOSITORIES: biostudies-other
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Project description:AimTo evaluate the performance of urinary fibrinogen β-chain (FBC) - either alone or associated with urinary tyrosine-phosphorylated proteins (UPY) - as bladder cancer (BCa) diagnostic biomarker.Materials & methods164 subjects were tested.ResultsSignificantly different FBC and UPY levels were found between BCa patients and controls, as well as between low-grade and high-grade cancers. The diagnostic accuracy was 0.84 for FBC and 0.87 for UPY. The combination of FBC and UPY improved the accuracy to 0.91. The addition of clinical variables (age, gender, and smoking habit) to FBC and UPY into a model for BCa prediction significantly improved the accuracy to 0.99. The combination of FBC and UPY adjusted for clinical variables associates with the highest sensitivity and good specificity.ConclusionUrinary FBC and UPY could be used as biomarkers for BCa diagnosis.
| S-EPMC8558871 | biostudies-literature
Project description:Single-stranded DNA-binding proteins (SSBs) are required for repair, recombination and replication in all organisms. Eukaryotic SSBs are regulated by phosphorylation on serine and threonine residues. To our knowledge, phosphorylation of SSBs in bacteria has not been reported. A systematic search for phosphotyrosine-containing proteins in Streptomyces griseus by immunoaffinity chromatography identified bacterial SSBs as a novel target of bacterial tyrosine kinases. Since genes encoding protein-tyrosine kinases (PTKs) have not been recognized in streptomycetes, and SSBs from Streptomyces coelicolor (ScSSB) and Bacillus subtilis (BsSSB) share 38.7% identity, we used a B.subtilis protein-tyrosine kinase YwqD to phosphorylate two cognate SSBs (BsSSB and YwpH) in vitro. We demonstrate that in vivo phosphorylation of B.subtilis SSB occurs on tyrosine residue 82, and this reaction is affected antagonistically by kinase YwqD and phosphatase YwqE. Phosphorylation of B.subtilis SSB increased binding almost 200-fold to single-stranded DNA in vitro. Tyrosine phosphorylation of B.subtilis, S.coelicolor and Escherichia coli SSBs occured while they were expressed in E.coli, indicating that tyrosine phosphorylation of SSBs is a conserved process of post-translational modification in taxonomically distant bacteria.
| S-EPMC1405823 | biostudies-literature
Project description:Phosphorylation on tyrosine residues is a key signal transduction mechanism known to regulate intercellular and intracellular communication in multicellular organisms. Despite the lack of conventional tyrosine kinases in the genome of the single cell organism Trypanosoma brucei, phosphorylation on trypanosomal protein tyrosine residues has been reported for this parasite. However, the identities of most of the tyrosine-phosphorylated proteins and their precise site(s) of phosphorylation were unknown. Here, we have applied a phosphotyrosine-specific proteomics approach to identify 34 phosphotyrosine-containing proteins from whole-cell extracts of procyclic form T. brucei. A significant proportion of the phosphotyrosine-containing proteins identified in this study were protein kinases of the CMGC kinase group as well as some proteins of unknown function and proteins involved in energy metabolism, protein synthesis, and RNA metabolism. Interestingly, immunofluorescence microscopy using anti-phosphotyrosine antibodies suggests that there is a concentration of tyrosine-phosphorylated proteins associated with cytoskeletal structures (basal body and flagellum) and in the nucleolus of the parasite. This localization of tyrosine-phosphorylated proteins supports the idea that the function of signaling molecules is controlled by their precise location in T. brucei, a principle well known from higher eukaryotes.
| S-EPMC2669198 | biostudies-literature
Project description:The interactions between guanine nucleotide regulatory proteins and the Ca(2+)-binding protein calmodulin were studied using calmodulin-Sepharose affinity chromatography. Purified bovine brain beta gamma subunits bound to calmodulin-Sepharose in a Ca(2+)-dependent manner. On the contrary, beta gamma subunits produced in an activated Go/Gi preparation did not bind to calmodulin-Sepharose. The effect was independent of the type of bovine brain G protein (Go/Gi, Gs), method of activation and the presence of magnesium. To distinguish whether the binding of purified beta gamma subunits to calmodulin was unique to brain beta gamma or to the method of purification, similar experiments were performed using transducin. In contrast to bovine brain G proteins, both purified transducin beta gamma subunits and beta gamma released from rhodopsin-activated transducin bound to calmodulin-Sepharose in a Ca(2+)-dependent manner. To assess the functional significance of the binding of bovine brain beta gamma subunits to calmodulin, the ability of purified beta gamma and of beta gamma in unactivated and activated Go/Gi to inhibit partially purified calmodulin-sensitive adenylate cyclase was determined. Purified beta gamma was highly effective in inhibiting calmodulin-stimulated adenylate cyclase activity. However, unactivated Go/Gi and preactivated Go/Gi inhibited calmodulin-stimulated adenylate cyclase activity to the same extent. This Go/Gi-mediated inhibition also occurred in the presence of a 500-fold molar excess of calmodulin over added G protein. These results demonstrate: (1) that beta gamma subunits may not be completely released upon G protein activation, and (2) that inhibition of calmodulin-stimulated adenylate cyclase by beta gamma subunits does not appear to be mediated by a direct beta gamma-calmodulin interaction. Differences in the binding properties of activated bovine brain G proteins versus those of transducin could be explained by differences in the gamma subunit between the proteins, or by differences in affinities of the alpha and beta gamma subunits for each other and for calmodulin. The different functional properties of purified beta gamma subunits and beta gamma subunits produced in situ by activation of G proteins indicates that extrapolation from the effects of purified subunits to events occurring in membranes should be done with caution.
| S-EPMC1130940 | biostudies-other
Project description:We examined the effects of G-protein beta and gamma subunit heterodimers on human alpha(1B) (N-type) Ca channels expressed in HEK293 cells. All of the known beta subunits (beta1-beta5) produced voltage-dependent inhibition of alpha(1B) Ca channels, depending on the gamma subunit found in the heterodimer. beta1-beta4 subunits inhibited Ca channels when paired with gamma1-gamma3. However, beta5 subunits only produced inhibition when paired with gamma2. In contrast, heterodimers between beta5 subunits and RGS (regulators of G-protein signaling) proteins containing GGL domains did not produce inhibition of Ca channels. However, GGL domain-containing RGS proteins (e.g., RGS6 and RGS11) did block the ability of Gbeta5/gamma2 heterodimers to inhibit Ca channels. Because all of the G-protein beta subunits are found in the nervous system, we conclude that they may all potentially participate in Ca channel inhibition. The interaction of GGL-containing RGS proteins with Gbeta5gamma2 suggests a novel way in which Ca channels can be regulated.
| S-EPMC6772774 | biostudies-literature
Project description:β-Catenin independent, non-canonical Wnt signaling pathways play a major role in the regulation of morphogenetic movements in vertebrates. The term non-canonical Wnt signaling comprises multiple, intracellularly divergent, Wnt-activated and β-Catenin independent signaling cascades including the Wnt/Planar Cell Polarity and the Wnt/Ca(2+) cascades. Wnt/Planar Cell Polarity and Wnt/Ca(2+) pathways share common effector proteins, including the Wnt ligand, Frizzled receptors and Dishevelled, with each other and with additional branches of Wnt signaling. Along with the aforementioned proteins, β-Arrestin has been identified as an essential effector protein in the Wnt/β-Catenin and the Wnt/Planar Cell Polarity pathway. Our results demonstrate that β-Arrestin is required in the Wnt/Ca(2+) signaling cascade upstream of Protein Kinase C (PKC) and Ca(2+)/Calmodulin-dependent Protein Kinase II (CamKII). We have further characterized the role of β-Arrestin in this branch of non-canonical Wnt signaling by knock-down and rescue experiments in Xenopus embryo explants and analyzed protein-protein interactions in 293T cells. Functional interaction of β-Arrestin, the β subunit of trimeric G-proteins and Dishevelled is required to induce PKC activation and membrane translocation. In Xenopus gastrulation, β-Arrestin function in Wnt/Ca(2+) signaling is essential for convergent extension movements. We further show that β-Arrestin physically interacts with the β subunit of trimeric G-proteins and Dishevelled, and that the interaction between β-Arrestin and Dishevelled is promoted by the beta/gamma subunits of trimeric G-proteins, indicating the formation of a multiprotein signaling complex.
| S-EPMC3906129 | biostudies-literature
Project description:BackgroundA noninvasive, highly sensitive and specific urine test is needed for bladder cancer (BC) diagnosis and surveillance in addition to the invasive cystoscopy. We previously described the diagnostic effectiveness of urinary tyrosine-phosphorylated proteins (UPY) and a new assay (UPY-A) for their measurement in a pilot study. The aim of this work was to evaluate the performances of the UPY-A using an independent cohort of 262 subjects.MethodsUrinary tyrosine-phosphorylated proteins were measured by UPY-A test. The area under ROC curve, cutoff, sensitivity, specificity and predictive values of UPY-A were determined. The association of UPY levels with tumour staging, grading, recurrence and progression risk was analysed by Kruskal-Wallis and Wilcoxon's test. To test the probability to be a case if positive at the UPY-A, a logistic test adjusted for possible confounding factor was used.ResultsResults showed a significant difference of UPY levels between patients with BC vs healthy controls. For the best cutoff value, 261.26 Standard Units (SU), the sensitivity of the assay was 80.43% and the specificity was 78.82%. A statistically significant difference was found in the levels of UPY at different BC stages and grades between Ta and T1 and with different risk of recurrence and progression. A statistically significant increased risk for BC at UPY-A ⩾261.26 SU was observed.ConclusionsThe present study supplies important information on the diagnostic characteristics of UPY-A revealing remarkable performances for early stages and allowing its potential use for different applications encompassing the screening of high-risk subjects, primary diagnosis and posttreatment surveillance.
| S-EPMC4522638 | biostudies-literature
Project description:Proteomic analysis of pervanadate-induced tyrosine-phosphorylated proteins in hepatocellular carcinoma WRL 68 cells Protein tyrosine phosphorylation plays critical roles in modulating biological processes such as cellular proliferation, differentiation, migration, apoptosis and metabolism. To profile tyrosine phosphorylated (pTyr) proteins as well as search novel pTyr proteins as cross-talk points among different cellular pathways, we developed a rapid and efficient approach to identify cellular pTyr proteins and their complexes by a combination of subcellular proteomics approach with signal transduction strategies. Human hepatocytic cells from WRL68 cell line were treated with pervanadate (POV), subfractionated into four fractions and then subjected to immunoaffinity purification with anti-pTyr antibody. The eluted mixtures of the anti-pTyr purification were identified by LC-MS/MS. Subcellular fractionation and affinity purification of tyrosine-phosphorylated proteins: WRL68 cells were first grown to 80% confluence in MEM complete medium and then the medium replaced with serum free media. After 15 h, the cells were either untreated or stimulated with 0.1 mM pervanadate (1 mM sodium orthovanadate, 3 mM H2O2) for 10 min. 150-mm cultures of WRL 68 cells were rinsed twice with 4? PBS and then scraped from the dish in 750?l of hypotonic buffer (10 mM Tris, 1 mM NaF, 10 mM IAA, pH 7.5) containing a cocktail of protein inhibitors. After a 20-min incubation on ice, the cells were passed about five times through a 25-g needle. The resulting lysate was subjected to a 15min centrifugation at 1000 rpm at 4?, after which the pellet was resuspended in 250?l of hypotonic buffer and re-extracted by a second round of the trituration and centrifugation. The supernatants of the first and second spins were combined, adjusted to 0.25 M NaCl, and separated into cytosolic (supernatant) and membrane (pellet) fractions bycentrifugation at 19,000 rpm (43,000 g) for 90 min at 4?. All the pellets and total cell lysate were resuspended in RIPA buffer (50 mM Tris-HCl, 150 mM NaCl, 1% Triton X-100, 0.1% SDS, 1% deoxycholic acid sodium) containing 1mM pervanadate with a cocktail of protein inhibitors with sonication aid. Cleared cell lysates were incubated overnight at 4? with 30?l monoclonal anti-phosphotyrosine-agrose (Sigma). Precipitated immune complexes were washed three times with 1×HNTG (20 mM HEPES, 150 mM NaCl, 0.1% Triton X-100, 10% Glycerol, pH 7.5) and then eluted with 100 mM phenyl phosphate (Sigma) in lysis buffer at 4?. Enzyme digestion, mass spectrometry and protein identification: The sample was digested according to the published method. Chromatography was performed using a surveyor LC system (Thermo Finnigan,SanJose,CA) on C18 reverse phase column(RP, 180 µm x 150 mm, BioBasic® C18, 5 µm, Thermo Hypersil-Keystone). The pump flow rate is split 1:100 for a colum flow rate of 1.5 µL/min.The column effluent is directly electrosprayed using the orthogonal metal needle source without further splitting.Mobile phase A is 0.1% formic acid in water,and the B mobile phase is 0.1% formic acid in acetonitrile. The separation of peptides obtained by enzymatic digest of bile sample was achieved with a gradient of 2-80% B over 360 min.The column effluent from the reverse phase column was analyzed by LCQ Deca XP ion-trap mass spectrometer.The micro-electrospray interface uses a 30 µm metal needle that is orthogonal to the inlet of the LCQ.The mass spectrometer was set that one full MS scan was followed by three MS/MS scans on the three most intense ion from the MS spectrum with the following Dynamic Exclusion™ settings: repeat count, 1; repeat duration, 0.5 min; exclusion duration, 3.0 min. The acquired MS/MS spectra were automatically searched against protein database for human proteins (SWISS-PROT/TrEMBL) using the TurboSEQUEST program in the BioWorks™ 3.0 software suite. An accepted SEQUEST result had to have a ?Cn score of at least 0.1 (regardless of charge state) and Xcorr (one charge?1.5, two charges?2.0, three charges?2.5). Single peptides that alone identify a protein were manually validated after meeting the above criteria. Bioinformatics analysis: The pI and MW of the proteins were analyzed using ExPASy proteomics tools accessed from http://cn.expasy.org/tools/#proteome. The grand average hydropathicity (GRAVY) values were determined according to Kyte-Doolittle. The protein subcellular location annotation was from SwissProt &TrEMBL protein database (http://us.expasy.org/sprot/). The protein function family was categorized according to Gene Ontology (GO) annotation terms extracted by InterPro (http://www.ebi.ac.uk./interpro/). The annotation of protein phosphorylation was from SwissProt &TrEMBL protein database (http://us.expasy.org/sprot/) and PhosphoSite (http://www.phosphosite.org). The kinases were annotated according to human kinome. Keywords: other
2005-04-07 | GSE2408 | GEO
Project description:Although most heterotrimeric G proteins are thought to dissociate into G? and G?? subunits upon activation, the evidence in the Gi/o family has long been inconsistent and contradictory. The Gi/o protein family mediates inhibition of cAMP production and regulates the activity of ion channels. On the basis of experimental evidence, both heterotrimer dissociation and rearrangement have been postulated as crucial steps of Gi/o protein activation and signal transduction. We have now investigated the process of Gi/o activation in living cells directly by two-photon polarization microscopy and indirectly by observations of G protein-coupled receptor kinase-derived polypeptides. Our observations of existing fluorescently labeled and non-modified G?i/o constructs indicate that the molecular mechanism of G?i/o activation is affected by the presence and localization of the fluorescent label. All investigated non-labeled, non-modified Gi/o complexes dissociate extensively upon activation. The dissociated subunits can activate downstream effectors and are thus likely to be the major activated Gi/o form. Constructs of G?i/o subunits fluorescently labeled at the N terminus (GAP43-CFP-G?i/o) seem to faithfully reproduce the behavior of the non-modified G?i/o subunits. G?i constructs labeled within the helical domain (G?i-L91-YFP) largely do not dissociate upon activation, yet still activate downstream effectors, suggesting that the dissociation seen in non-modified G?i/o proteins is not required for downstream signaling. Our results appear to reconcile disparate published data and settle a long running dispute.
| S-EPMC3894313 | biostudies-literature
Project description:Phosphorylated proteins play important roles in the regulation of many different cell networks. However, unlike the preparation of proteins containing unmodified proteinogenic amino acids, which can be altered readily by site-directed mutagenesis and expressed in vitro and in vivo, the preparation of proteins phosphorylated at predetermined sites cannot be done easily and in acceptable yields. To enable the synthesis of phosphorylated proteins for in vitro studies, we have explored the use of phosphorylated amino acids in which the phosphate moiety bears a chemical protecting group, thus eliminating the negative charges that have been shown to have a negative effect on protein translation. Bis-o-nitrobenzyl protection of tyrosine phosphate enabled its incorporation into DHFR and I?B-? using wild-type ribosomes, and the elaborated proteins could subsequently be deprotected by photolysis. Also investigated in parallel was the re-engineering of the 23S rRNA of Escherichia coli, guided by the use of a phosphorylated puromycin, to identify modified ribosomes capable of incorporating unprotected phosphotyrosine into proteins from a phosphotyrosyl-tRNACUA by UAG codon suppression during in vitro translation. Selection of a library of modified ribosomal clones with phosphorylated puromycin identified six modified ribosome variants having mutations in nucleotides 2600-2605 of 23S rRNA; these had enhanced sensitivity to the phosphorylated puromycin. The six clones demonstrated some sequence homology in the region 2600-2605 and incorporated unprotected phosphotyrosine into I?B-? using a modified gene having a TAG codon in the position corresponding to amino acid 42 of the protein. The purified phosphorylated protein bound to a phosphotyrosine specific antibody and permitted NF-?B binding to a DNA duplex sequence corresponding to its binding site in the IL-2 gene promoter. Unexpectedly, phosphorylated I?B-? also mediated the exchange of exogenous DNA into an NF-?B-cellular DNA complex isolated from the nucleus of activated Jurkat cells.
| S-EPMC5901656 | biostudies-literature