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J A Weatherbee

Publications and source records attributed to J A Weatherbee.

At least 19 recordsLinked to original sources
PubMed1996

Binding affinity of transforming growth factor-beta for its type II receptor is determined by the C-terminal region of the molecule.

Transforming growth factor-beta (TGF-beta) isoforms have differential binding affinities for the TGF-beta type II receptor (TbetaRII). In most cells, TGF-beta1 and TGF-beta3 bind to TbetaRII with much higher affinity than TGF-beta2. Here, we report an analysis of the effect of TGF-beta structure on its binding to TbetaRII by using TGF-beta mutants with domain deletions, amino acid replacements, and isoform chimeras. Examination of the binding of TGF-beta mutants to the recombinant extracellular domain of TbetaRII by a solid-phase TGF-beta/TbetaRII assay demonstrated that only those TGF-beta mutants containing the C terminus of TGF-beta1 (TGF-beta1-(Delta69-73), TGF-beta1-(Trp71), and TGF-beta2/beta1-(83-112)) bind with high affinity to TbetaRII, similar to native TGF-beta1. Moreover, replacement of only 6 amino acids in the C terminus of TGF-beta1 with the corresponding sequence of TGF-beta2 (TGF-beta1/beta2-(91-96)) completely eliminated the high affinity binding of TGF-beta1. Proliferation of fetal bovine heart endothelial (FBHE) cells was inhibited to a similar degree by all of the TGF-beta mutants. However, recombinant soluble TbetaRII blocked the inhibition of FBHE cell proliferation induced by TGF-beta mutants retaining the C terminus of TGF-beta1, consistent with the high binding affinity between these TGF-beta molecules and TbetaRII. It was further confirmed that the TGF-beta2 mutant with its C terminus replaced by that of TGF-beta1 (TGF-beta2/beta1-(83-112)) competed as effectively as TGF-beta1 with 125I-TGF-beta1 for binding to membrane TbetaRI and TbetaRII on FBHE cells. These observations clearly indicate that the domain in TGF-beta1 responsible for its high affinity binding to TbetaRII, both the soluble and membrane-bound forms, is located at C terminus of the molecule.

Amino Acid Sequence↗
PubMed1996

Transforming growth factor beta 1: three-dimensional structure in solution and comparison with the X-ray structure of transforming growth factor beta 2.

The three-dimensional solution structure of human transforming growth factor beta 1 (TGF-beta 1) has been determined using multinuclear magnetic resonance spectroscopy and a hybrid distance geometry/ simulated annealing algorithm. It represents one of the first examples of a mammalian protein structure that has been solved by isotopic labeling of the protein in a eukaryotic cell line and multinuclear NMR spectroscopy. The solution structure of the 25 kDa disulfide-linked TGF-beta 1 homodimer was calculated from over 3200 distance and dihedral angle restraints. The final ensemble of 33 accepted structures had no NOE or dihedral angle violations greater than 0.30 A and 5.0 degrees, respectively. The RMSD of backbone atoms for the ensemble of 33 structures relative to their mean structure was 1.1 A when all residues were used in the alignment and 0.7 A when loop regions were omitted. The solution structure of TGF-beta 1 follows two independently determined crystal structures of TGF-beta 2 (Daopin et al., 1992, 1993; Schlunegger & Grütter, 1992, 1993), providing the first opportunity to examine structural differences between the two isoforms at the molecular level. Although the structures are very similar, with an RMSD in backbone atom positions of 1.4 A when loop regions are omitted in the alignment and 1.9 A when all residues are considered, there are several notable differences in structure and flexibility which may be related to function. The clearest example of these is in the beta-turn from residues 69-72: the turn type found in the solution structure of TGF-beta 1 falls into the category of type II, whereas that present in the X-ray crystal structure of TGF-beta 2 is more consistent with a type I turn conformation. This may be of functional significance as studies using TGF-beta chimeras and deletion mutants indicate that this portion of the molecule may be important in receptor binding.

Amides↗
PubMed1996

The recombinant proregion of transforming growth factor beta1 (latency-associated peptide) inhibits active transforming growth factor beta1 in transgenic mice.

All three isoforms of transforming growth factors beta (TGF-betal, TGF-beta2, and TGF-beta3) are secreted as latent complexes and activated extracellularly, leading to the release of the mature cytokines from their noncovalently associated proregions, also known as latency-associated peptides (LAPs). The LAP region of TGF-beta1 was expressed in a baculovirus expression system and purified to homogeneity. In vitro assays of growth inhibition and gene induction mediated by TGF-beta3 demonstrate that recombinant TGF-beta1 LAP is a potent inhibitor of the activities of TGF-betal, -beta2, and -beta3. Effective dosages of LAP for 50% neutralization of TGF-beta activities range from 4.7- to 80-fold molar excess depending on the TGF-beta isoform and activity examined. Using 125I-labeled LAP, we show that the intraperitoneal application route is effective for systemic administration of LAP. Comparison of concentrations of LAP in tissues shows a homogenous pattern in most organs with the exception of heart and muscle, in which levels of LAP are 4- to 8-fold lower. In transgenic mice with elevated hepatic levels of bioactive TGF-betal, treatment with recombinant LAP completely reverses suppression of the early proliferative response induced by TGF-beta1 in remnant livers after partial hepatectomy. The results suggest that recombinant LAP is a potent inhibitor of bioactive TGF-beta both in vitro and in vivo, after intraperitoneal administration. Recombinant LAP should be a useful tool for novel approaches to study and therapeutically modulate pathophysiological processes mediated by TGF-beta3.

Animals↗
PubMed1996

Heterodimers of placenta growth factor/vascular endothelial growth factor. Endothelial activity, tumor cell expression, and high affinity binding to Flk-1/KDR.

Here we show that the Escherichia coli expressed monomers of placenta growth factor (PLGF)129 and vascular endothelial growth factor (VEGF)165 can be re-folded in vitro to form PLGF/VEGF heterodimers. The purified recombinant PLGF/VEGF heterodimers and VEGF homodimers have potent mitogenic and chemotactic effects on endothelial cells. However, PLGF/VEGF heterodimers display 20-50-fold less mitogenic activity than VEGF165 homodimers. In contrast, PLGF129 homodimers have little or no effect in these in vitro assays. We also demonstrate the presence of natural PLGF/VEGF heterodimers in the conditioned media of various human tumor cell lines. While PLGF/VEGF heterodimers bind with high affinity to a soluble Flk-1/KDR receptor, PLGF129 homodimers fail to bind to this receptor. Cross-linking of 125I-ligands to human umbilical vein endothelial cells reveals that PLGF/VEGF heterodimers and VEGF165 homodimers, but not PLGF129 homodimers, form complexes with membrane receptors. VEGF165 homodimers and PLGF/VEGF heterodimers stimulate tyrosine phosphorylation of a 220-kDa protein, the expected size for the KDR receptor in human umbilical vein endothelial cells, whereas PLGF129 homodimers are unable to induce tyrosine phosphorylation of this protein. These data indicate that PLGF may modulate VEGF-induced angiogenesis by the formation of PLGF/VEGF heterodimers in cells producing both factors.

Angiogenesis Inducing Agents↗
PubMed1996

Cytokine assays and their limitations.

With the increasing popularity of the use of cytokine immunoassays in basic and clinical research, there is an urgent need for cytokine immunoassay reference preparations and standards in order that results published by various investigators can be directly compared. Until such standards are available, it is recommended that results obtained using immunoassays from different sources be compared with caution. Additionally, users of immunoassays should clearly understand the biology of the systems they are studying and the characteristics of their immunoassays with respect to cross-reactivities with cytokine isoforms, interferences by soluble receptors, and matrix effects on samples of interest. It is also recommended that immunoassay developers take special precautions in the selection of antibodies and only use antibodies that are not biased against one or the other of the recombinant forms.

Animals↗
PubMed1995

gro-beta, a -C-X-C- chemokine, is an angiogenesis inhibitor that suppresses the growth of Lewis lung carcinoma in mice.

We have found that two chemokines, recombinant gro-alpha and gro-beta, specifically inhibit growth factor-stimulated proliferation of capillary endothelial cells in a dose-dependent manner, whereas gro-gamma has no inhibitory effect. In vivo, gro-beta inhibits blood vessel formation in the chicken chorioallantoic membrane assay. It is sufficiently potent to effectively suppress basic fibroblast growth factor-induced corneal neovascularization after systemic administration in mice. Further, gro-beta significantly inhibits the growth of murine Lewis lung carcinoma in syngeneic C57B16/J and immunodeficient nude mice without toxicity. In vitro, Lewis lung carcinoma cells are completely insensitive to recombinant gro-beta at high concentrations that significantly inhibit endothelial cell proliferation. This finding supports the conclusion that gro-beta inhibits Lewis lung tumor growth by suppression of tumor-induced neovascularization.

Amino Acid Sequence↗
PubMed1995

Characterization of recombinant soluble human transforming growth factor-beta receptor type II (rhTGF-beta sRII).

Recombinant human transforming growth factor soluble receptor Type II (rhTGF-beta sRII) corresponding to the 159 amino acid extracellular domain of hTGF-beta RII has been expressed in insect cells using the baculovirus expression system or in a mouse myeloma cell line. N-terminal sequence analysis of the purified protein revealed the removal of the 23 amino acid signal peptide. In SDS-PAGE, the rhTGF-beta sRII resolves into multiple bands due to N-linked glycosylation. Recombinant hTGF-beta sRII is a TGF-beta antagonist and will inhibit the biological activities of TGF-beta 1, TGF-beta 3, and TGF-beta 5 on TGF-beta-responsive cell lines, such as murine HT-2 or human TF-1 with an ED50 of approximately 0.3 micrograms/mL. However, hTGF-beta sRII does not inhibit TGF-beta 2 bioactivities in these cell lines, suggesting that hTGF-beta RII has low affinity for TGF-beta 2. Polyclonal antibodies to hTGF-beta sRII have been produced in goats and purified on Protein-G affinity columns. This antibody can inhibit TGF-beta 1,2,3,5-dependent bioactivities on human cell lines such as TF-1. Additionally, this antibody has species cross-reactivity and will also inhibit TGF-beta-dependent bioactivities on murine cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

The role of shared receptor motifs and common Stat proteins in the generation of cytokine pleiotropy and redundancy by IL-2, IL-4, IL-7, IL-13, and IL-15.

To understand the molecular bases for cytokine redundancy and pleiotropy, we have compared the Stat proteins activated in peripheral blood lymphocytes (PBLs) by cytokines with shared and distinct actions. Interleukin-2 (IL-2) rapidly activated Stat5 in fresh PBL, and Stat3 and Stat5 in preactivated PBL. IL-7 and IL-15 induced the same complexes as IL-2, a feature explained by the existence of similar tyrosine-phosphorylated motifs in the cytoplasmic domains of IL-2R beta and IL-7R that can serve as docking sites for Stat proteins. IL-13 Induced the same complexes as IL-4, a finding explained by our studies implicating IL-4R as a shared component of the receptors. These studies demonstrate that a single cytokine can activate different combinations of Stat proteins under different physiological conditions, and also indicate two mechanisms by which distinct cytokines can activate the same Stat protein.

Amino Acid Sequence↗
PubMed1995

Circadian characteristics of circulating interleukin-6 in men.

BACKGROUND: The cytokine interleukin-6 (IL-6) is a multifunctional small-peptide molecule that is produced by various types of lymphoid and nonlymphoid cells. It plays a central role in hematopoiesis, host defense mechanisms, and acute-phase reactions, including regulation of inflammatory and immune responses. METHODS: Because a circadian time structure has been shown to characterize nearly every biologic function tested in human beings, including some cytokines, we sought to investigate the 24-hour pattern of circulating IL-6 in a group of 11 clinically symptom-free men (median age, 50 years; range, 46 to 72 years). Blood samples were obtained every 3 hours for 24 hours (eight samples per subject), and serum was frozen until analysis for IL-6 with a solid-phase ELISA. RESULTS: Average IL-6 values ranged from 1.66 to 5.38 pg/ml, with lowest to highest values within 24 hours ranging from 1.20 to 7.58 pg/ml (120% to 531%) between subjects. On average, values were greater than the mean throughout the night, with a peak at 01:00 hours and less than the mean throughout the day, with a nadir at 10:00 hours. A significant time effect was found by analysis of variance; and a high-amplitude circadian rhythm was described by the least-squares fit of a 24-hour cosine (p < 0.001; amplitude, 41% +/- 5%; acrophase, 02:16 +/- 00:28 hours). In addition, a positive correlation between mean IL-6 levels and age was found (r = 0.63, p = 0.037). CONCLUSIONS: Because monitoring of endogenous cytokine levels is suggested for assessing immune function and pathologic condition, clinical decisions and immunotherapies may be significantly influenced by the large and predictable day-night variations in endogenous cytokine production and bioactivity.

Age Factors↗
PubMed1994

High-resolution solution structure of the beta chemokine hMIP-1 beta by multidimensional NMR.

The three-dimensional structure of a member of the beta subfamily of chemokines, human macrophage inflammatory protein-1 beta (hMIP-1 beta), has been determined with the use of solution multidimensional heteronuclear magnetic resonance spectroscopy. Human MIP-1 beta is a symmetric homodimer with a relative molecular mass of approximately 16 kilodaltons. The structure of the hMIP-1 beta monomer is similar to that of the related alpha chemokine interleukin-8 (IL-8). However, the quaternary structures of the two proteins are entirely distinct, and the dimer interface is formed by a completely different set of residues. Whereas the IL-8 dimer is globular, the hMIP-1 beta dimer is elongated and cylindrical. This provides a rational explanation for the absence of cross-binding and reactivity between the alpha and beta chemokine subfamilies. Calculation of the solvation free energies of dimerization suggests that the formation and stabilization of the two different types of dimers arise from the burial of hydrophobic residues.

Amino Acid Sequence↗
PubMed1994

Aggregation of the chemokine MIP-1 alpha is a dynamic and reversible phenomenon. Biochemical and biological analyses.

Macrophage inhibitory protein (MIP)-1 alpha is a potent inhibitor of hemopoietic stem cell proliferation and is a member of a family of pro-inflammatory mediators, the chemokine family. This molecule along with other members of the chemokine family exists as a peptide of 8 kDa but has a strong tendency for noncovalent extensive self-aggregation. As this aggregation may interfere with biological activity, we have produced nonaggregating variants of MIP-1 alpha which display a range of molecular sizes. The mutants, produced by sequential neutralization of carboxyl-terminal acidic residues, display native molecular masses representative of tetramers, dimers, and monomers. Intriguingly when these mutants are assessed in comparison with native MIP-1 alpha for bioactivity in vitro, they are seen to be equipotent in both stem cell assays and in monocyte shape-change assays, suggesting that there is no requirement for aggregation in either of these biological contexts. This indicates that the aggregated MIP-1 alpha and the aggregated mutants spontaneously disaggregate under assay conditions and ultimately function as monomers. We have further demonstrated the ability of MIP-1 alpha to disaggregate spontaneously in dilute solution by enzyme-linked immunosorbent assay analysis of fractions obtained from gel filtration of varying concentrations of MIP-1 alpha. The aggregation of MIP-1 alpha is therefore a dynamic and reversible phenomenon which has little, if any, impact on bioactivity in vitro.

Amino Acid Sequence↗
PubMed1994

Transforming growth factor-beta activation in irradiated murine mammary gland.

The biological activity of TGF-beta, an important modulator of cell proliferation and extracellular matrix formation, is governed by dissociation of mature TGF-beta from an inactive, latent TGF-beta complex in a process that is critical to its role in vivo. So far, it has not been possible to monitor activation in vivo since conventional immunohistochemical detection does not accurately discriminate latent versus active TGF-beta, nor have events associated with activation been defined well enough to serve as in situ markers of this process. We describe here a modified immunodetection method using differential antibody staining that allows the specific detection of active versus latent TGF-beta. Under these conditions, we report that an antibody raised to latency-associated peptide detects latent TGF-beta, and we demonstrate that LC(1-30) antibodies specifically recognize active TGF-beta 1 in tumor xenografts overproducing active TGF-beta 1, without cross-reactivity in tumors expressing similar levels of latent TGF-beta 1. We previously reported that TGF-beta immunoreactivity increases in murine mammary gland after whole-body 60Co-gamma radiation exposure. Using differential antibody staining we now show that radiation exposure specifically generates active TGF-beta 1. While latent TGF-beta 1 was widely distributed in unirradiated tissue, active TGF-beta 1 distribution was restricted. Active TGF-beta 1 increased significantly within 1 h of irradiation concomitant with decreased latent TGF-beta immunoreactivity. This rapid shift in immunoreactivity provides the first evidence for activation of TGF-beta in situ. This reciprocal pattern of expression persisted for 3 d and was accompanied by decreased recovery of latent TGF-beta 1 from irradiated tissue. Radiation-induced activation of TGF-beta may have profound implications for understanding tissue effects caused by radiation therapy.

Animals↗
PubMed1993

Transforming growth factor beta 1: NMR signal assignments of the recombinant protein expressed and isotopically enriched using Chinese hamster ovary cells.

The transforming growth factor beta s are a homologous family of multifunctional cytokines that regulate cell growth and differentiation. As a prelude to studies of the solution structure and dynamics of TGF-beta 1, we report virtually complete assignment of 1H and 15N resonances for this 25-kDa homodimeric protein. Recombinant TGF-beta 1 was expressed in Chinese hamster ovary cells. The cells were grown either in a completely 15N-enriched medium or in a medium containing selectively 13C, 15N-labeled amino acids to obtain either uniformly or specifically labeled protein, respectively. Two- and three-dimensional heteronuclear edited magnetic resonance spectra of the uniformly 15N-labeled protein and three samples selectively labeled with 13C and 15N yielded assignments for 96% of the backbone amide and C alpha protons and 87% of the side chain protons. To our knowledge, this is the first report of the use of an animal cell expression system to obtain extensive isotopic enrichment in order to sequentially assign a protein. The methodology described herein for the isotopic enrichment and resonance assignments of TGF-beta 1 should be generally applicable to other eukaryotic proteins expressed by animal cells.

Amino Acid Sequence↗
PubMed1993

Transforming growth factor beta 1: secondary structure as determined by heteronuclear magnetic resonance spectroscopy.

Virtually complete backbone NMR signal assignments have been reported for transforming growth factor beta 1 (TGF-beta 1) [Archer et al. (1993) Biochemistry (preceding paper in this issue)]. Herein we report the secondary structure of the protein in solution on the basis of these assignments and proton NOE's observed in a variety of 2D and 3D heteronuclear NMR spectra. Regular elements of secondary structure derived from the NOE data consist of (a) three helices spanning residues Y58-H68, F24-G29, and N5-F8 and (b) several pairs of two-stranded antiparallel beta-sheets. The longest two-stranded sheet runs from residue L83 to V106 with a type II reverse turn at G93-R94 and a chain twist at residue N103-M104. These elements of regular structure were confirmed by hydrogen exchange, chemical shift, and coupling constant data. With the exception of residues G46-S53, which exhibit relatively few and weak intraresidue NOE's, residues in the rest of the protein adopt an irregular but well-defined structure. All peptide bonds are trans except for a cis peptide bond between Glu35 and Pro36. The structural characteristics observed for TGF-beta 1 in solution generally agree closely with the recently derived crystal structures of TGF-beta 2 [Daopin et al. (1992) Science 257, 369-374; Schlunegger & Grütter (1992) Nature 358, 430-434]. Several noteworthy differences were observed that may be related to function.

Amino Acid Sequence↗
PubMed1993

Characterization of a receptor for macrophage inflammatory protein 1 alpha and related proteins on human and murine cells.

Macrophage inflammatory protein 1 alpha (MIP-1 alpha) is a potent stem cell inhibitor and a member of a large and expanding family of related cytokines. In an effort to understand the molecular basis of the activities of MIP-1 alpha, we have sought to characterize the cellular receptors for this molecule. Our results demonstrate the presence of abundant MIP-1 alpha receptors on both human and murine cells. The receptor on K562 cells can bind a range of members of the MIP-1 alpha family and may thus be a general MIP-1 alpha family receptor. Murine FDCPmix cells also bind a range of members of this peptide family, although the receptor(s) that they express appear somewhat more selective for peptides capable of displaying stem cell inhibitory properties. The human and murine receptors do not bind members of the related interleukin 8 family of peptides and are thus distinct from the recently cloned interleukin 8 receptor. We suggest that the receptor on the murine cell is a candidate for the receptor responsible for articulating stem cell inhibitory signals following MIP-1 alpha binding.

Amino Acid Sequence↗
PubMed1991

Binding and internalization of transforming growth factor-beta 1 by human hepatoma cells: evidence for receptor recycling.

Cellular processing of 125I-labeled transforming growth factor-beta 1 was investigated in the human hepatoma cell lines Hep G2 and Hep 3B. Binding of 125I-transforming growth factor-beta 1 to cell surface receptors was specific, saturable and calcium-independent. Both cell lines exhibited a single class of high-affinity (Kd = 2.2 x 10(-10) mol/L) binding sites (4.5 x 10(3) for the Hep G2 cell; 1.5 x 10(3) for the Hep 3B cell) for both human and porcine transforming growth factor-beta 1. Binding was temperature dependent, time dependent and pH dependent. Cell-bound 125I-transforming growth factor-beta 1 was removed by brief exposure to acidic medium (pH less than 4) but was converted into an acid-resistant state rapidly after shifting the cells to 37 degrees C. Spontaneous dissociation of bound ligand over a 6 hr period at 4 degrees C was less than 10%. Disuccinimidyl suberate was used to covalently label 125I-transforming growth factor-beta 1 to cell-surface binding sites. Labeling of the ligand/receptor complexes was inhibited by unlabeled transforming growth factor-beta 1 but was unaffected by other growth factors. The radiolabeled complexes showed approximate molecular weights of 280,000, 85,000 and 65,000 when run on reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Cell-bound 125I-transforming growth factor-beta 1 was internalized and degraded at 37 degrees C, and the products were released into the medium as trichloroacetic acid-nonprecipitable radioactivity. The lysosomotropic base chloroquine and the carboxylic ionphore monensin inhibited degradation and release of 125I-labeled products from the cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding, Competitive↗
PubMed1989

Transient production and secretion of human transforming growth factor TGF-beta 2.

Transient transfection of simian COS cells with a recombinant plasmid encoding the human transforming growth factor TGF-beta 2 precursor protein results in the production of a latent, biologically inactive protein. Upon acidification, recombinant TGF-beta 2 exhibits full biological activity, including inhibition of mink lung epithelial cell growth, stimulation of anchorage-independent growth of murine embryonic fibroblasts, and competition for TGF-beta receptor binding. Further analysis of conditioned media with antiserum to either a pro- [amino acid (aa) residues 1-220] or mature [aa 297-414] peptide of the TGF-beta 2 precursor suggests that TGF-beta 2, similar to TGF-beta 1 production in Chinese hamster ovary cells [Gentry et al., Mol. Cell. Biol. 7 (1987) 3418-3427], is initially synthesized as a larger precursor protein which is proteolytically cleaved to yield the mature 112-aa transforming growth factor.

Animals↗