We have examined the ability of various forms of activin and inhibin, which are structurally related to transforming growth factor-beta (TGF-beta), to interact with various types of cell surface TGF-beta binding sites. Activin AB, inhibin A, and inhibin B were unable to compete with 125I-TGF-beta 1 for binding to the TGF-beta receptor types I, II, or III that coexist in human skin fibroblasts, rat liver epithelial cells, and mink lung epithelial cells. In contrast, activins and inhibins effectively competed for TGF-beta 1 binding to GH3 rat pituitary tumor cells. Binding of TGF-beta 1 to GH3 cells was mediated by about 2700 sites/cell with a Kd = 90 pM. Affinity labeling of these GH3 binding sites by cross-linking to 125I-TGF-beta 1 yielded 70-74-kDa labeled complexes distinct from previously identified TGF-beta binding components. Labeling of these 70-74-kDa components with 125I-TGF-beta 1 was inhibited by TGF-beta 1, TGF-beta 2, activin AB, and inhibin B at concentrations in the high picomolar to low nanomolar range, but it was not significantly affected by other polypeptide hormones and growth factors tested. The 70-74-kDa labeled GH3 components represent a novel type of cell surface TGF-beta binding protein that is unique in its ability to recognize various other members of the TGF-beta family of bioactive polypeptides. 相似文献
A radioimmunoassay (RIA) was developed to measure fibroblast growth factor (FGF) using antiserum generated against a synthetic replicate of [Tyr10]FGF(1–10). The antisera, previously shown to be capable of inhibiting the biological action of FGF on bovine aortic arch endothelial cells in vitro [1], are highly specific for the amino-terminus of FGF. In the RIA, the antisera recognize the decapeptide antigen [Tyr10]FGF(1–10) and the intact mitogen on an equimolar basis and show less than 0.01% cross-reactivity with N-acetyl-[Tyr10]FGF(1–10).
Bovine adenohypophysial cells maintained in primary monolayer culture release and ir-FGF which is indistinguishable from the intact mitogen in as much as it is retained on heparin-Sepharose affinity columns and shows a dose-dependent and parallel displacement in RIA. The release of ir-FGF by the bovine adenohypophysis can be increased with forskolin (10−5 M) or KCl (50 mM). Preincubation of pituitary cells with 17β-estradiol has no measurable effects on basal ir-FGF, but increases the release after KCl treatment 2–3-fold. These results show that ir-FGF can be released by the bovine adenohypophysis in vitro and lend credence to the hypothesis that FGF plays a physiological role in the homeostatic mechanisms regulating mesoderm-derived cell growth. 相似文献
The two major protein components of bovine seminal plasma, PDC-109 and BSP I, have been purified by gel filtration, partition chromatography and reverse-phase high performance liquid chromatography from an 86% ethanol precipitate of bovine seminal plasma ejaculate. The complete 109-residue amino acid sequence of PDC-109 has been established by automated Edman degradation of the intact peptide as well as its proteolytic digestion and cyanogen bromide cleavage fragments. The 12,774 dalton structure has two structurally similar domains of 38 and 41 amino acids, each containing two disulfide bonds. 相似文献
Immunocytofluorescence techniques with well characterized anti-sera to α-endorphin and β-endorphin show presence of these two peptides in all cellular elements of the pars intermedia of the rat hypophysis, and in discrete cells of the pars distalis (adenohypophysis) at the complete exclusion of the neurohypophysis (pars nervosa, posterior lobe). 相似文献
3-O-(2-Acetamido-3,4,6-tri-O-acetyl-2-deoxy-beta-D-glucopyranosyl)-N- (tert-butyloxycarbonyl)-L-serine was synthesized and condensed by the solid-phase procedure to give the sequence Gly-[beta-D-GlcpNAc-(1 leads to 3)-Ser]-Ala-OH and beta-D-GlcpNAc-(1 leads to 3)-Ser-13-somatostatin. The synthetic glycopeptides appeared homogeneous on t.l.c. and l.c. examination and showed the correct amino acid composition and 2-amino-2-deoxy-D-glucose content. The structure of Gly-[beta-D-GlcpNAc-(1 leads to 3)-Ser]-Ala-OH was further confirmed by mass spectrometry of the N-acetyl permethyl derivative, and by n.m.r. spectroscopy. 相似文献
The role of astrocytes in the production of the neurotoxin quinolinic acid (QUIN) and other products of the kynurenine pathway (KP) is controversial. Using cytokine-stimulated human astrocytes, we assayed key enzymes and products of the KP. We found that astrocytes lack kynurenine-hydroxylase so that large amounts of kynurenine (KYN) and kynurenic acid (KYNA) were produced, while minor amounts of QUIN were synthesised that were completely degraded. We then showed that kynurenine added to macrophages led to significant production of QUIN. These results suggest that astrocytes alone are neuroprotective by minimising QUIN production and maximising synthesis of KYNA. However, it is likely that, in the presence of macrophages and/or microglia, astrocytes are neurotoxic by producing large concentrations of KYN that can be metabolised by neighbouring monocytic cells to QUIN. 相似文献
Human obesity is characterized by chronic low-grade inflammation in white adipose tissue and is often associated with hypertension. The potential induction of indoleamine 2,3-dioxygenase-1 (IDO1), the rate-limiting enzyme in tryptophan/kynurenine degradation pathway, by proinflammatory cytokines, could be associated with these disorders but has remained unexplored in obesity. Using immunohistochemistry, we detected IDO1 expression in white adipose tissue of obese patients, and we focused on its contribution in the regulation of vascular tone and on its immunoregulatory effects. Concentrations of tryptophan and kynurenine were measured in sera of 36 obese and 15 lean women. The expression of IDO1 in corresponding omental and subcutaneous adipose tissues and liver was evaluated. Proinflammatory markers and T-cell subsets were analyzed in adipose tissue via the expression of CD14, IL-18, CD68, TNFα, CD3ε, FOXP3 [a regulatory T-cell (Treg) marker] and RORC (a Th17 marker). In obese subjects, the ratio of kynurenine to tryptophan, which reflects IDO1 activation, is higher than in lean subjects. Furthermore, IDO1 expression in both adipose tissues and liver is increased and is inversely correlated with arterial blood pressure. Inflammation is associated with a T-cell infiltration in obese adipose tissue, with predominance of Th17 in the omental compartment and of Treg in the subcutaneous depot. The Th17/Treg balance is decreased in subcutaneous fat and correlates with IDO1 activation. In contrast, in the omental compartment, despite IDO1 activation, the Th17/Treg balance control is impaired. Taken together, our results suggest that IDO1 activation represents a local compensatory mechanism to limit obesity-induced inflammation and hypertension. 相似文献