scholarly journals Direct association of p110 beta phosphatidylinositol 3-kinase with p85 is mediated by an N-terminal fragment of p110 beta.

1994 ◽  
Vol 14 (4) ◽  
pp. 2577-2583 ◽  
Author(s):  
P Hu ◽  
J Schlessinger
Keyword(s):  
Amino Acids ◽  
Fusion Protein ◽  
Growth Factor Receptor ◽  
Sh2 Domain ◽  
Glutathione S Transferase ◽  
Intact Cells ◽  
Viral Oncoproteins ◽  
Terminal Fragment ◽  
Mitogenic Signal Transduction

Phosphatidylinositol (PI) 3-kinase is a heterodimeric enzyme of 85-kDa (p85) and 110-kDa (p110) subunits implicated in mitogenic signal transduction by virtue of its activation in cells transformed by diverse viral oncoproteins and treated with various growth factors. We have identified a domain in p110 that mediates association with p85 in vitro and in intact cells. A glutathione S-transferase fusion protein containing the N-terminal 171 amino-acids of p110 beta bound to free p85 in cell lysates. This fusion protein also bound directly to p85 immobilized on nitrocellulose filters. An epitope-tagged fragment containing amino acids 31 to 150 of p110 beta associated with p85 upon expression in intact cells. Expression of either an N-terminal fragment of p110 beta or the p85 inter-SH2 domain, which mediates association with p110, reduced the association of endogenous PI 3-kinase activity with the activated platelet-derived growth factor receptor in intact cells. Hence, these defined regions of p85 and p110 mediate the interaction between the two subunits of PI 3-kinase.

Direct association of p110 beta phosphatidylinositol 3-kinase with p85 is mediated by an N-terminal fragment of p110 beta

1994 ◽  
Vol 14 (4) ◽  
pp. 2577-2583
Author(s):  
P Hu ◽  
J Schlessinger
Keyword(s):  
Amino Acids ◽  
Fusion Protein ◽  
Growth Factor Receptor ◽  
Sh2 Domain ◽  
Glutathione S Transferase ◽  
Intact Cells ◽  
Viral Oncoproteins ◽  
Terminal Fragment ◽  
Mitogenic Signal Transduction

Phosphatidylinositol (PI) 3-kinase is a heterodimeric enzyme of 85-kDa (p85) and 110-kDa (p110) subunits implicated in mitogenic signal transduction by virtue of its activation in cells transformed by diverse viral oncoproteins and treated with various growth factors. We have identified a domain in p110 that mediates association with p85 in vitro and in intact cells. A glutathione S-transferase fusion protein containing the N-terminal 171 amino-acids of p110 beta bound to free p85 in cell lysates. This fusion protein also bound directly to p85 immobilized on nitrocellulose filters. An epitope-tagged fragment containing amino acids 31 to 150 of p110 beta associated with p85 upon expression in intact cells. Expression of either an N-terminal fragment of p110 beta or the p85 inter-SH2 domain, which mediates association with p110, reduced the association of endogenous PI 3-kinase activity with the activated platelet-derived growth factor receptor in intact cells. Hence, these defined regions of p85 and p110 mediate the interaction between the two subunits of PI 3-kinase.

scholarly journals Direct association of occludin with ZO-1 and its possible involvement in the localization of occludin at tight junctions.

1994 ◽  
Vol 127 (6) ◽  
pp. 1617-1626 ◽  
Author(s):  
M Furuse ◽  
M Itoh ◽  
T Hirase ◽  
A Nagafuchi ◽  
S Yonemura ◽  
...  
Keyword(s):  
Amino Acids ◽  
Fusion Protein ◽  
Tight Junctions ◽  
Integral Membrane Protein ◽  
Deletion Mutants ◽  
Glutathione S Transferase ◽  
E Coli ◽  
Vitro Binding ◽  
Peripheral Proteins

Occludin is an integral membrane protein localizing at tight junctions (TJ) with four transmembrane domains and a long COOH-terminal cytoplasmic domain (domain E) consisting of 255 amino acids. Immunofluorescence and laser scan microscopy revealed that chick full-length occludin introduced into human and bovine epithelial cells was correctly delivered to and incorporated into preexisting TJ. Further transfection studies with various deletion mutants showed that the domain E, especially its COOH-terminal approximately 150 amino acids (domain E358/504), was necessary for the localization of occludin at TJ. Secondly, domain E was expressed in Escherichia coli as a fusion protein with glutathione-S-transferase, and this fusion protein was shown to be specifically bound to a complex of ZO-1 (220 kD) and ZO-2 (160 kD) among various membrane peripheral proteins. In vitro binding analyses using glutathione-S-transferase fusion proteins of various deletion mutants of domain E narrowed down the sequence necessary for the ZO-1/ZO-2 association into the domain E358/504. Furthermore, this region directly associated with the recombinant ZO-1 produced in E. coli. We concluded that occludin itself can localize at TJ and directly associate with ZO-1. The coincidence of the sequence necessary for the ZO-1 association with that for the TJ localization suggests that the association with underlying cytoskeletons through ZO-1 is required for occludin to be localized at TJ.

Cytosolic glutathione S-transferases of Oesophagostomum dentatum

Parasitology ◽  
2008 ◽  
Vol 135 (10) ◽  
pp. 1215-1223 ◽  
Author(s):  
A. JOACHIM ◽  
B. RUTTKOWSKI
Keyword(s):  
Amino Acids ◽  
Pcr Primers ◽  
Mrna Levels ◽  
Fourth Stage ◽  
Glutathione S Transferase ◽  
Cdna Sequences ◽  
Oesophagostomum Dentatum ◽  
Cytosolic Glutathione ◽  
Glutathione S Transferases

SUMMARYOesophagostomum dentatum stages were investigated for glutathione S-transferase (GST) expression at the protein and mRNA levels. GST activity was detected in all stages (infectious and parasitic stages including third- and fourth-stage larvae of different ages as well as males and females) and could be dose-dependently inhibited with sulfobromophthalein (SBP). Addition of SBP to in vitro larval cultures reversibly inhibited development from third- to fourth-stage larvae. Two glutathione-affinity purified proteins (23 and 25 kDa) were detected in lysates of exsheathed third-stage larvae by SDS-PAGE. PCR-primers were designed based on peptide sequences and conserved GST sequences of other nematodes for complete cDNA sequences (621 and 624 nt) of 2 isoforms, Od-GST1 and Od-GST2, with 72% nucleotide similarity and 75% for the deduced proteins. Genomic sequences consisted of 7 exons and 6 introns spanning 1296 bp for Od-GST1 and 1579 and 1606 bp for Od-GST2. Quantitative real-time-PCR revealed considerably elevated levels of Od-GST1 in the early parasitic stages and slightly reduced levels of Od-GST2 in male worms. Both Od-GSTs were most similar to GST of Ancylostoma caninum (nucleotides: 73 and 70%; amino acids: 80 and 73%). The first three exons (75 amino acids) corresponded to a synthetic prostaglandin D2 synthase (53% similarity). O. dentatum GSTs might be involved in intrinsic metabolic pathways which could play a role both in nematode physiology and in host-parasite interactions.

The sorting determinant guiding Hsp150 to the COPI-independent transport pathway in yeast

1999 ◽  
Vol 112 (22) ◽  
pp. 3889-3898 ◽  
Author(s):  
T. Suntio ◽  
A. Shmelev ◽  
M. Lund ◽  
M. Makarow
Keyword(s):  
Amino Acids ◽  
Growth Factor Receptor ◽  
Retrograde Transport ◽  
Temperature Sensitive ◽  
Beta Lactamase ◽  
Heterologous Proteins ◽  
Glycosylation Pattern ◽  
Transport Pathway ◽  
Amino Acid Peptide ◽  
Terminal Fragment

The COPI coatomer is thought to be required in yeast directly for retrograde transport from the Golgi to the endoplasmic reticulum (ER), and directly or indirectly for ER-to-Golgi transport. Unexpectedly, the secretory glycoproteins Hsp150 and invertase have been found not to require COPI for ER exit. The features according to which cargo proteins are selected for the COPI-independent pathway are not known. The ER form of Hsp150 has three distinct domains: an N-terminal fragment of 54 amino acids (subunit I) is followed by 11 repeats of a 19 amino acid peptide plus a unique C-terminal fragment of 114 amino acids (subunit II). By fusing heterologous proteins to different Hsp150 domains and expressing them in sec21-1 and sec21-3 mutants with temperature-sensitive mutations in the gamma-COPI subunit, we show here that the repeats of subunit II function as sorting determinants for COPI-independent ER exit. The C-terminal fragment of Hsp150 could be replaced by E. coli beta-lactamase or rat nerve growth factor receptor ectodomain (NGFRe), and subunit I could be deleted, without inhibiting COPI-independent transport. However, when the repetitive region was omitted and beta-lactamase was fused directly to the C terminus of subunit I, COPI was required for efficient ER exit. Mass spectroscopic analysis demonstrated that both subunit I and II of Hsp150 were extensively O-glycosylated, suggesting that the O-glycosylation pattern was not decisive for cargo selection.

Binding of the Src SH2 domain to phosphopeptides is determined by residues in both the SH2 domain and the phosphopeptides

1993 ◽  
Vol 13 (12) ◽  
pp. 7278-7287
Author(s):  
K B Bibbins ◽  
H Boeuf ◽  
H E Varmus
Keyword(s):  
Intramolecular Interaction ◽  
Growth Factor Receptor ◽  
Sh2 Domain ◽  
Binding Properties ◽  
Vitro Assay ◽  
Sh2 Domains ◽  
Free Peptide ◽  
C Terminus

Src homology 2 (SH2) domains are found in a variety of signaling proteins and bind phosphotyrosine-containing peptide sequences. To explore the binding properties of the SH2 domain of the Src protein kinase, we used immobilized phosphopeptides to bind purified glutathione S-transferase-Src SH2 fusion proteins. With this assay, as well as a free-peptide competition assay, we have estimated the affinities of the Src SH2 domain for various phosphopeptides relative to a Src SH2-phosphopeptide interaction whose Kd has been determined previously (YEEI-P; Kd = 4 nM). Two Src-derived phosphopeptides, one containing the regulatory C-terminal Tyr-527 and another containing the autophosphorylation site Tyr-416, bind the Src SH2 domain in a specific though low-affinity manner (with about 10(4)-lower affinity than the YEEI-P peptide). A platelet-derived growth factor receptor (PDGF-R) phosphopeptide containing Tyr-857 does not bind appreciably to the Src SH2 domain, suggesting it is not the PDGF-R binding site for Src as previously reported. However, another PDGF-R-derived phosphopeptide containing Tyr-751 does bind the Src SH2 domain (with an affinity approximately 2 orders of magnitude lower than that of YEEI-P). All of the phosphopeptides which bind to the Src SH2 domain contain a glutamic acid at position -3 or -4 with respect to phosphotyrosine; changing this residue to alanine greatly diminishes binding. We have also tested Src SH2 mutants for their binding properties and have interpreted our results in light of the recent crystal structure solution for the Src SH2 domain. Mutations in various conserved and nonconserved residues (R155A, R155K, N198E, H201R, and H201L) cause slight reductions in binding, while two mutations cause severe reductions. The W148E mutant domain, which alters the invariant tryptophan that marks the N-terminal border of the SH2 domain, binds poorly to phosphopeptides. Inclusion of the SH3 domain in the fusion protein partially restores the binding by the W148E mutant. A change in the invariant arginine that coordinates twice with phosphotyrosine in the peptide (R175L) results in a nearly complete loss of binding. The R175L mutant does display high affinity for the PDGF-R peptide containing Tyr-751, via an interaction that is at least partly phosphotyrosine independent. We have used this interaction to show that the R175L mutation also disrupts the intramolecular interaction between the Src SH2 domain and the phosphorylated C terminus within the context of the entire Src protein; thus, the binding properties observed for mutant domains in an in vitro assay appear to mimic those that occur in vivo.

scholarly journals Expression and purification of functional recombinant epitopes for the platelet antigens, PlA1 and PlA2

Blood ◽  
1994 ◽  
Vol 84 (4) ◽  
pp. 1157-1163 ◽  
Author(s):  
EA Barron-Casella ◽  
TS Kickler ◽  
OC Rogers ◽  
JF Casella
Keyword(s):  
Amino Acids ◽  
Fusion Protein ◽  
Fusion Proteins ◽  
Disulfide Bonds ◽  
Affinity Purification ◽  
Platelet Glycoprotein ◽  
Enzyme Linked Immunosorbent Assay ◽  
Glutathione S Transferase ◽  
Amino Terminal ◽  
Posttransfusion Purpura

Abstract The platelet antigens, PlA1 and PlA2, are responsible for most cases of posttransfusion purpura (PTP) and neonatal alloimmune thrombocytopenia (NAIT) in the caucasian population and are determined by two allelic forms of the platelet glycoprotein GPIIIa gene. To study the interaction between these antigens and their respective antibodies, we inserted the sequence that encodes the signal peptide and the N- terminal 66 amino acids of the PlA1 form of GPIIIa into the expression vector pGEX1. To express the PlA2 antigen, nucleotide 196 of the PlA1 coding sequence was mutated to the PlA2 allelic form. When transformed and induced in Escherichia coli, the two constructs produce glutathione S-transferase (GST)/N-terminal GPIIIa fusion proteins, one containing leucine at position 33 (PlA1), the other proline (PlA2). These proteins are easily purified in milligram quantities using glutathione-Sepharose and react specifically with their respective antibodies by immunoblot and enzyme-linked immunosorbent assay. Antigenicity of the PlA1 fusion protein in reduced glutathione increases with time; moreover, the addition of oxidized glutathione accelerates this process, presumably because of formation of the native disulfide bonds. Neutralization assays indicate that the PlA1 fusion protein competes for all of the anti-PlA1 antibody in the serum of patients with PTP and NAIT that is capable of interacting with the surface of intact platelets. This study shows that the GST/N-terminal GPIIIa fusion proteins contain conformational epitopes that mimic those involved in alloimmunization, and that regions other than the amino terminal 66 amino acids of GPIIIa are not likely to contain or be required for the development of functional PlA1 epitopes. Furthermore, these recombinant proteins can be used for the affinity-purification of clinical anti-PlA1 antibodies and specific antibody identification by western blotting, making them useful in the diagnosis of patients alloimmunized to PlA1 alloantigens.

scholarly journals Specific activation of p85-p110 phosphatidylinositol 3'-kinase stimulates DNA synthesis by ras- and p70 S6 kinase-dependent pathways.

1997 ◽  
Vol 17 (1) ◽  
pp. 248-255 ◽  
Author(s):  
J McIlroy ◽  
D Chen ◽  
C Wjasow ◽  
T Michaeli ◽  
J M Backer
Keyword(s):  
Dna Synthesis ◽  
Affinity Purification ◽  
Specific Inhibitor ◽  
Brdu Incorporation ◽  
Glutathione S Transferase ◽  
Intact Cells ◽  
S6 Kinase ◽  
P70 S6 Kinase ◽  
Quiescent Cells

We have developed a polyclonal antibody that activates the heterodimeric p85-p110 phosphatidylinositol (PI) 3'-kinase in vitro and in microinjected cells. Affinity purification revealed that the activating antibody recognized the N-terminal SH2 (NSH2) domain of p85, and the antibody increased the catalytic activity of recombinant p85-p110 dimers threefold in vitro. To study the role of endogenous PI 3'-kinase in intact cells, the activating anti-NSH2 antibody was microinjected into GRC + LR73 cells, a CHO cell derivative selected for tight quiescence during serum withdrawal. Microinjection of anti-NSH2 antibodies increased bromodeoxyuridine (BrdU) incorporation fivefold in quiescent cells and enhanced the response to serum. These data reflect a specific activation of PI 3'-kinase, as the effect was blocked by coinjection of the appropriate antigen (glutathione S-transferase-NSH2 domains from p85 alpha), coinjection of inhibitory anti-p110 antibodies, or treatment of cells with wortmannin. We used the activating antibodies to study signals downstream from PI 3'-kinase. Although treatment of cells with 50 nM rapamycin only partially decreased anti-NSH2-stimulated BrdU incorporation, coinjection with an anti-p70 S6 kinase antibody effectively blocked anti-NSH2-stimulated DNA synthesis. We also found that coinjection of inhibitory anti-ras antibodies blocked both serum- and anti-NSH2-stimulated BrdU incorporation by approximately 60%, and treatment of cells with a specific inhibitor of MEK abolished antibody-stimulated BrdU incorporation. We conclude that selective activation of physiological levels of PI 3'-kinase is sufficient to stimulate DNA synthesis in quiescent cells. PI 3'-kinase-mediated DNA synthesis requires both p70 S6 kinase and the P21ras/MEK pathway.

DIRECTED MUTAGENESIS IN THE STUDY OF THE REQUIREMENTS FOR FACTOR VIII ACTIVITY IN VITRO AND IN VIVO

1987 ◽  
Author(s):  
Randal J Kaufman ◽  
Debra D Pittman ◽  
Louise C Wasley ◽  
W Barry Foster ◽  
Godfrey W Amphlett ◽  
...  
Keyword(s):  
Amino Acids ◽  
Factor Viii ◽  
Cleavage Site ◽  
Factor Xa ◽  
Cleavage Sites ◽  
Thrombin Cleavage ◽  
Terminal Fragment ◽  
Cofactor Activity

Factor VIII is a high molecular weight plasma glycoprotein that functions in the blood clotting cascade as the cofactor for factor DCa proteolytic activation of factor X. Factor VIII does not function proteolytically in this reaction hut itself can be proteolytically activated by other coagulation enzymes such as factor Xa and thrombin. In the plasma, factor VIII exists as a 200 kDa amino-terminal fragment in a metal ion stabilized complex with a 76 kDa carboxy-terminal fragment. The isolation of the cENA for human factor VIII provided the deduced primary amino acid sequence of factor VIIT and revealed three distinct structural domains: 1) a triplicated A domain of 330 amino acids which has homology to ceruloplasmin, a plasma copper binding protein, 2) a duplicated C domain of 150 amino acids, and 3) a unique B domain of 980 amino acids. These domains are arranged as shown below. We have previously reported the B domain is dispensible far cofactor activity in vitro (Toole et al. 1986 Proc. Natl. Acad 5939). The in vivo efficacy of factor VIII molecules harboring the B domain deletion was tested by purification of the wildtype and modified forms and infusion into factor VIII deficient, hemophilic, dogs. The wildtype and the deleted forms of recombinant derived factor VIII exhibited very similar survival curves (Tl/2 = 13 hrs) and the cuticle bleeding times suggested that both preparations appeared functionally equivalent. Sepharose 4B chromatography indicated that both factor VIII molecules were capable of binding canine plasma vWF.Further studies have addressed what cleavages are necessary for activation of factor VIII. The position of the thrombin, factor Xa, and activated protein C (AFC) cleavage sites within factor VIII are presented below, site-directed ENA medicated mutagenesis has been performed to modify the arginine at the amino side of each cleavagesite to an soleucine. In all cases this modification resulted in molecules that were resistant to cleavage by thrombin at the modified site. Modification of the thrombin cleavage sites at 336 and 740 and modification of the factor Xa cleavage site at 1721 resulted in no loss of cofactor activity. Modification of the thrombin cleavage site at either 372 or 1689 destroyed oofactor activity. Modification of the thrombin cleavage site at 336 resulted in a factor VIII having an increased activity, possibly due to resistance to inactivation. These results suggest the requirement of cleavage at residues 372 and 1689 for cofactor activity.

Characterisation of the paxillin-binding site and the C-terminal focal adhesion targeting sequence in vinculin

1994 ◽  
Vol 107 (2) ◽  
pp. 709-717 ◽  
Author(s):  
C.K. Wood ◽  
C.E. Turner ◽  
P. Jackson ◽  
D.R. Critchley
Keyword(s):  
Amino Acids ◽  
Fusion Protein ◽  
Binding Site ◽  
Focal Adhesion ◽  
Focal Adhesions ◽  
Cytoskeletal Proteins ◽  
Terminal Region ◽  
Nih3t3 Cells ◽  
Cell Biol

Paxillin and vinculin are cytoskeletal proteins that colocalise to focal adhesions, specialised regions of the cell involved in attachment to the extracellular matrix. These two molecules form part of a complex of proteins that link the actin network to the plasma membrane. Paxillin has been shown to bind directly in vitro to the C-terminal region of vinculin (Turner et al. (1990). J. Cell Biol. 111, 1059–1068), which also contains a focal adhesion targeting sequence (Bendori et al. (1989). J. Cell Biol. 108, 2383–2393). In the present study, we have used a series of vinculin deletion mutants to map more precisely the sites in vinculin responsible for paxillin binding and focal adhesion localisation. A glutathione-S-transferase fusion protein spanning vinculin residues 881–1000 was sufficient to support 125I-paxillin binding in a gel-blot assay while no detectable binding was observed to a fusion protein spanning residues 881–978. Transfection experiments using cDNAs encoding chick vinculin residues 398–1066 and 398–1028 demonstrated that amino acids C-terminal to residue 1028 were not necessary for targeting to focal adhesions. In contrast, a vinculin polypeptide expressed from a cDNA encoding residues 398–1000 failed to localise to focal adhesions in stably transfected NIH3T3 cells. We have therefore identified a region of 50 amino acids (residues 979–1028) within the C-terminal region of vinculin that contains both the paxillin-binding site and the focal adhesion targeting sequence. This region is highly conserved in human and chicken vinculin and is likely to be important in regulation of the assembly of focal adhesions.

Identification and characterization of a high-affinity interaction between v-Crk and tyrosine-phosphorylated paxillin in CT10-transformed fibroblasts

1993 ◽  
Vol 13 (8) ◽  
pp. 4648-4656
Author(s):  
R B Birge ◽  
J E Fajardo ◽  
C Reichman ◽  
S E Shoelson ◽  
Z Songyang ◽  
...  
Keyword(s):  
Fusion Protein ◽  
Tyrosine Phosphorylation ◽  
Cell Transformation ◽  
Tyrosine Phosphatase ◽  
State Level ◽  
Sh2 Domain ◽  
Sequence Specificity ◽  
Src Homology

The genome of avian sarcoma virus CT10 encodes a fusion protein in which viral Gag sequences are fused to cellular Crk sequences containing primarily Src homology 2 (SH2) and Src homology 3 (SH3) domains. Transformation of chicken embryo fibroblasts (CEF) with the Gag-Crk fusion protein results in the elevation of tyrosine phosphorylation on specific cellular proteins with molecular weights of 130,000, 110,000, and 70,000 (p130, p110, and p70, respectively), an event which has been correlated with cell transformation. In this study, we have identified the 70-kDa tyrosine-phosphorylated protein in CT10-transformed CEF (CT10-CEF) as paxillin, a cytoskeletal protein suggested to be important for organizing the focal adhesion. Tyrosine-phosphorylated paxillin was found to be complexed with v-Crk in vivo as evident from coimmunoprecipitation studies. Moreover, a bacterially expressed recombinant glutathione S-transferase (GST)-CrkSH2 fragment bound paxillin in vitro with a subnanomolar affinity, suggesting that the SH2 domain of v-Crk is sufficient for binding. Mapping of the sequence specificity of a GST-CrkSH2 fusion protein with a partially degenerate phosphopeptide library determined a motif consisting of pYDXP, and in competitive coprecipitation studies, an acetylated A(p)YDAPA hexapeptide was able to quantitatively inhibit the binding of GST-CrkSH2 to paxillin and p130, suggesting that it meets the minimal structural requirements necessary for the interaction of CrkSH2 with physiological targets. To investigate the mechanism by which v-Crk elevates the tyrosine phosphorylation of paxillin in vivo, we have treated normal CEF and CT10-CEF with sodium vanadate to inhibit protein tyrosine phosphatase activity. These data suggest that paxillin is involved in a highly dynamic kinase-phosphatase interplay in normal CEF and that v-Crk binding may interrupt this balance to increase the steady-state level of tyrosine phosphorylation. By contrast, the 130-kDa protein was not tyrosine phosphorylated upon vanadate treatment of normal CEF and only weakly affected in the CT10-CEF, suggesting that a different mechanism may be involved in its phosphorylation.

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